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Book Chapter

DEPOSITION, DIAGENESIS, AND RESERVOIR PROPERTIES OF HONDO SULFATES IN THE GROSMONT CARBONATE–EVAPORITE SYSTEM—UPPER DEVONIAN, CANADA

By
Hans G. Machel
Hans G. Machel
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2E3 Canada
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Mary Luz Borrero
Mary Luz Borrero
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2E3 Canada
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B. Charlotte Schreiber
B. Charlotte Schreiber
Department of Earth and Space Sciences, University of Washington, Seattle, Washington, 98195-1310 USA
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Published:
January 01, 2017
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ABSTRACT:

The Upper Devonian Grosmont reservoir in Alberta, Canada, is the world’s largest heavy oil/bitumen reservoir hosted in carbonates, with an estimated 400 to 500 billion barrels of “Initial Oil In Place” at average depths of about 250 to 400 m. Our study is part of a more comprehensive effort to evaluate the Grosmont reservoir through geological, geophysical, and petrophysical methods in order to determine the most advantageous method(s) of exploitation.

The reservoir is a carbonate–evaporite system. The carbonates of the Grosmont were deposited during the Late Devonian on an extensive platform and/or a ramp in five or six cycles. Evaporites are interbedded with the carbonates at several stratigraphic levels. These evaporites, informally referred to as the “Hondo Formation,” have received scant attention or were ignored in most earlier studies. However, they may play a crucial role regarding the distribution of the most porous and/or permeable reservoir intervals via dissolution, as permeability barriers to compartmentalize the reservoir during or after hydrocarbon migration, and as a source of dissolved sulfate for microbial hydrocarbon degradation.

Most Hondo primary evaporites are anhydrite that formed subaqueously as well as displacively and/or replacively very close to the depositional surface. Secondary/diagenetic sulfates were formed from primary sulfates much later and under considerable burial. The locations of primary evaporite deposition were controlled by a shift from carbonate platform or ramp deposition over time. At present the primary sulfates occur in a number of relatively small areas of about 10 by 20 km to 20 by 30 km, with thicknesses of a few meters each. If these areas represent the depositional distribution, the primary evaporites were deposited in a series of large, shallow subaqueous ponds (salinas). Alternatively, the primary evaporites were deposited in a more extensive lagoon, and their present distribution represents the remnants after postdepositional, mainly karstic dissolution. The evaporites would have acted as intraformational flow barriers up until the time of dissolution, which may be a factor in the development of compositional differences of the bitumens contained at various stratigraphic levels. In the eastern part of the Grosmont reservoir the evaporites appear to be dissolved and replaced by solution-collapse breccias and bitumen-supported intervals of dolomite powder. In the western part of the reservoir the sulfates may form effective reservoir seals on the scale of the sizes of former brine ponds. However, it is likely that hydrocarbons bypassed them wherever the carbonates had sufficient permeability and/or where the marls were breached by faults and/or karstification.

INTRODUCTION

Beneath the Cretaceous oil sand deposits in Alberta, Canada, Upper Devonian carbonates form the Grosmont reservoir in a huge carbonate platform or ramp (Fig. 1) that hosts at least 400 billion barrels of “Initial Oil In Place” (IOIP) in the form of low-gravity (American Petroleum Institute gravity = API gravity of ~5° to ~9°) bitumen (Hein et al. 2008, Wo et al. 2011), by some estimates up to ~500 billion barrels (MacNeil et al. 2013). This renders the Grosmont the world’s largest unconventional oil reservoir hosted in carbonates (Alvarez et al. 2006, 2008). The reservoir is located within the often-cited but ill-defined “carbonate triangle” that contains heavy oil reserves in carbonates at four stratigraphic levels: the Devonian Grosmont and Nisku and the Mississippian Shunda and Debolt (AEUB 2007, ERCB 2010).

Fig. 1.

—Simplified subsurface map showing the outlines of Upper Devonian Woodbend carbonate platforms and reefs in Alberta. At this scale, the various outlines are only approximate. The Hondo study was conducted in the trapezoid area. Cross section A-Aʹ is shown schematically in Figure 3. The Grosmont platform was delineated seismically except along its eastern limit, which is erosional against the Canadian Shield. LDB = Limit of the Disturbed Belt.

Fig. 1.

—Simplified subsurface map showing the outlines of Upper Devonian Woodbend carbonate platforms and reefs in Alberta. At this scale, the various outlines are only approximate. The Hondo study was conducted in the trapezoid area. Cross section A-Aʹ is shown schematically in Figure 3. The Grosmont platform was delineated seismically except along its eastern limit, which is erosional against the Canadian Shield. LDB = Limit of the Disturbed Belt.

At this time the Grosmont reservoir is not yet commercial. Past pilot activity in the Grosmont reservoir between 1975 and 1987, mainly with “huff and puff” technology, had variable success, and the reservoir was deemed uneconomical at the time. More advanced thermal recovery technologies, such as variants of steam-assisted gravity drive (SAGD) and electrical and in situ retorting schemes, together with elevated world market prices for oil that hit a high spot near $US 140/bbl in 2008, spurred a boom of research into the reservoir properties that peaked between 2007 and 2011. A SAGD pilot site was started by Laricina Energy in 2010. Despite the more recent and dramatic drop in world market oil prices, several companies are currently investigating the Grosmont reservoir with the aim of future commercial production.

Several previous studies (Cutler 1983; Harrison 1987; Luo et al. 1994; Luo and Machel 1995; Dembicki and Machel 1996; Machel and Huebscher 2000; Zhao and Machel 2011, 2012; Machel et al. 2012; Russel-Houston and Gray 2014) discussed most of the important geological and geophysical characteristics of the Grosmont reservoir. Accordingly, the sedimentary stratigraphy consists of five or six stacked carbonate units interbedded with marls and some evaporites that formed regionally extensive aquitards very soon after deposition (through compaction and cementation), effectively forming “seals” that compartmentalized the future reservoir into subhorizontal units that were hydrologically isolated from one another. In addition, the Grosmont platform or ramp underwent a complex diagenetic history, as represented by features that formed from near-surface to burial environments at about 2000 m of depth, including dolomites, calcites, pyrite and sulfur, fractures, and dissolution voids of various sizes. Diagenetic processes also shaped the reservoir quality, including the creation of many breaches in the formerly contiguous marl and evaporite “seals” via four phases of fracturing and up to four phases of karstification (Machel et al. 2012).

None of the previous studies listed above dealt in any detail with the evaporite units in the reservoir. However, the Grosmont is a carbonate–evaporite system, the reservoir properties of which are determined by an interplay of carbonates and evaporites both depositionally and postdepositionally. This study is focused on the sedimentary characteristics, distribution, and postdepositional alteration of the evaporite units within the reservoir, commonly referred to as the “Hondo Formation,” with five specific objectives: (1) delineation of the spatial distribution of Hondo evaporites; (2) better definition of the western margin of the Grosmont reservoir; (3) investigation of the sedimentological and diagenetic characteristics of the Hondo; (4) determination of the depositional and sedimentological evolution of the Hondo evaporites, and application of possible recent analogs for the Hondo; and (5) determination of the role of the Hondo evaporites as potential reservoir seals.

GEOLOGIC FRAMEWORK

The Devonian section in the Western Canada Sedimentary Basin was deposited on the passive margin of the ancestral North American continent during a second-order eustatic sea-level cycle that was punctuated by several higher-order sea-level fluctuations, while the Alberta region was moving northward but was still fairly close to the paleoequator of the time (Mossop and Shetsen 1994, Blakey 2010). Four orogenies affected the region: Antler (Devonian–Carboniferous), Sonoma (Late Permian), Columbian (Jurassic–Early Cretaceous), and Laramide (Mid–Late Cretaceous–Tertiary). The Antler and the Laramide orogenies were most significant in shaping the size, depth, accommodation space, subsidence, and uplift of the Western Canada Sedimentary Basin (Mossop and Shetsen 1994). Today, the Alberta Basin constitutes the foreland basin of the Canadian Rocky Mountains (note: Miall et al. [2008] refer to the Alberta Basin as the northern part of the “Western Interior Basin”). As a result of the asymmetry of the Alberta Basin, the Devonian strata form a basin-wide, structural homocline that gently dips from outcrops in northeastern Alberta to nearly 7 km in southwestern Alberta next to the Rocky Mountain fold and thrust belt. For comprehensive overviews of the geologic history of western Canada see Mossop and Shetsen (1994) and Miall et al. (2008), while Machel (2010) provides a summary of the Devonian petroleum system in this basin.

Magnetic, gravimetric, and seismic surveys have identified a number of structural highs and two prominent lineament/fault systems that strike about NW–SE and SSE–NNW in the Precambrian basement (Edwards and Brown 1995, Lyatsky and Pana 2003, Lyatsky et al. 2005). These structural features controlled deposition of the Devonian sedimentary strata to some, albeit debatable, degree (Jones 1980). At least some of the many basement faults that are located in the region of the Grosmont platform or ramp appear to have been active during the Paleozoic and Mesozoic, influencing fluid flow and petroleum migration. Geothermal gradients and heat flow in the Alberta Basin appear to have been near-normal from the late Paleozoic to the Laramide orogeny, and then again after the orogeny, with oil and gas maturation and migration starting during the Middle Cretaceous and peaking in the Late Cretaceous to early Tertiary (Stoakes and Creaney 1984, Dawson and Kalkreuth 1994, Selby and Creaser 2005, Higley et al. 2009).

Geologically and physiographically the Grosmont reservoir is commonly referred to as a platform or shelf or complex, approximately 150 km wide and at least 600 km in length. Seismic data define its depositional limits toward the west and the south, whereas the eastern limit is erosional, and the northern limits are almost unknown as a result of structural tilting, erosion, and lack of data. The region studied by our group encompasses approximately 24,700 km2 from Townships 60 to 90 and Ranges 19W4 to 12W5, which stretches from ~50 km north of Edmonton in the south to the erosional edge near Fort McMurray in the north, and crosses the reservoir in its southern part (Fig. 1). Several strike and dip sections across these areas cover all stratigraphic levels and facies types.

STRATIGRAPHY AND DEPOSITION

Stratigraphically the strata of the Grosmont reservoir belong to the Upper Devonian Woodbend and Winterburn groups (Fig. 1). Woodbend deposition began with increased input of marls and shales of the lower Ireton Formation. Marl and shale sedimentation caused a gradual shallowing of the area and eventually the termination of Leduc reef growth. Carbonate production resumed on this shallow shelf, resulting in the deposition of the Grosmont strata, which consist of the Grosmont Formation at the base, interbedded with several marl layers and some evaporites, and overlain by the Upper Ireton (UIRE) Formation and the Nisku Formation (Figs. 2, 3). Sequence-stratigraphically the Grosmont as a whole and the package of the overlying strata likely represent deposition in response to third- and/or fourth-order eustatic sea-level fluctuations (Switzer et al. 1994).

Fig. 2.

—Schematic stratigraphy in the study area. Not to scale.

Fig. 2.

—Schematic stratigraphy in the study area. Not to scale.

Fig. 3.

—Schematic structural SW–NW cross section across the study area, as identified in Figure 1. Vertical exaggeration roughly 1:100. Relative thicknesses are not to scale.

Fig. 3.

—Schematic structural SW–NW cross section across the study area, as identified in Figure 1. Vertical exaggeration roughly 1:100. Relative thicknesses are not to scale.

Traditionally, the Grosmont units carry the following stratigraphic terminology in ascending order (from oldest to youngest): LGM (Lower Grosmont) and UGM1, UGM2, and UGM3 (Upper Grosmont 1, 2, and 3, respectively) (e.g., Theriault 1988). Some oil companies refer to the Grosmont A, B, C, and D in lieu of LGM, UGM1, UGM2, and UGM3, respectively (e.g., Russel-Houston and Gray 2014). Each of these stratigraphic units has shallowing-upward facies characteristics, commonly with biostromal, open marine facies (tabular stromatoporoid floatstone to rudstone) at the base, followed by marginal marine, lagoonal, and shoal deposits (Amphipora floatstone to rudstone; peloid, intraclast and/or bioclast packstone to grainstone), and then peritidal carbonate facies (laminated, algal-laminated, and massive dolomudstone) (Cutler 1983, Machel and Hunter 1994, Huebscher 1996). Brecciated and reworked dolomud-stone facies, indicative of short-lived supratidal conditions in parts of the carbonate strata, and/or interbedded carbonate mudstones and anhydrites cap some of the cycles. Thin, regionally extensive marl layers, commonly referred to as “shale breaks” (Harrison 1987) SB1, SB2, and SB3, mark relatively short-lived flooding events at the beginning of each overlying cycle. In some parts of the study area there is evidence of higher (fourth- or fifth-order) cyclicity in the form of additional thin marly layers, which has prompted some workers to further subdivide the above stratigraphic units (for example, the UGM3 divided into UGM3a and UGM3b). Layers of anhydrite, solution-collapse breccias, and occasional halite pseudomorphs or molds suggestive of the former presence of evaporites are present at the stratigraphic levels of the UGM1 and UGM3/Upper Ireton. The evaporites are commonly referred to as the Hondo Formation or “Member.” The entire stratigraphic succession is now tilted toward the southwest and truncated by the regional sub-Cretaceous unconformity (Fig. 3), which is an erosional surface that resulted from prolonged subaerial exposure and complete erosion of all pre-Cretaceous strata down to and including the uppermost layers of the Devonian section. As a result, the Devonian strata are overlain by the Lower Cretaceous Mannville Group, which hosts the Athabasca oil sands deposit.

The Hondo evaporites were first described by Belyea (1952, 1956) as the Hondo “Member” and as stratigraphically equivalent to the upper part of the Grosmont Formation. Local studies of the Hondo were undertaken by Cutler (1983), and a sketch of the possible areal distribution of the Hondo is shown in chapter 12 of the Geological Atlas of the Western Canada Sedimentary Basin, by Mossop and Shetsen (1994). However, no data were provided to support the extent of the current or past (depositional) Hondo distribution. Moreover, the Hondo is not formally defined in the Stratigraphic Code, likely because data from the region are sparse and evaporite facies had been observed in only five cores. Thus, the depositional nature and areal distribution of the Hondo evaporites remain somewhat enigmatic, which has important ramifications for reservoir development: areas or regions of evaporites may form aquitards; thus, their distribution should be known as best as possible where SAGD or other thermal recovery schemes are contemplated.

METHODS

Well Control

Well density is variable across the study area, commonly only one to two wells per township, yet this density increases toward the eastern limit of the reservoir approaching the erosional edge. An important issue is posed by age: most wells used for this study were drilled during the 1950s, 1960s, and 1970s. Consequently, wireline logging data are antiquated and often poor, and cores have deteriorated, mainly as a result of the bleeding out and subsequent desiccation of bitumen, which renders facies recognition impossible in many core intervals. While modern two-dimensional and three-dimensional (3D) seismic was acquired by several companies over the past 5 years (e.g., Russel-Houston and Gray 2014), seismic information was not available at the time during which this study was undertaken.

Core and Cuttings Description

Data were collected from several hundred meters of drill core from 32 wells (Table 1) and from approximately 25,000 m of cuttings from 105 additional wells. Some wells have poor recovery, which is attributed to loss of circulation when drilling. An additional problem is contamination from overlying intervals (cavings). Nevertheless, cuttings were useful to identify the marl–shale layers within the Grosmont units that were calibrated against wireline logs, where available.

Table 1.

—Locations, depth intervals, and formations of the wells investigated for this study.

Well ID Core Depth (m) Formation 
02-29-68-01W5 1127.7-1139.05 UIRE -UGM3 
02/15-23-68-01W5 1096.0-1127.0 UGM3, UGM2? 
08-28-69-04W5 1305.0-1337.0 Nisku-UIRE 
01-12-69-01W5 964.80-1043.0 UIRE-Nisku 
05-25-69-20W5 626.0-738.24 UGM3, UGM2, UGM1 
04-15-69-24W4 1005.8-1019.6 L1RE-LGM 
03-28-70-24W4 740.7-751.9 854.7-868.4 Nisku, UGM3, UGM2 
11-35-70-25W4 893.1-901.1 Nisku-UIRE 
02-23-70-01W5 879.3-880.9 Nisku 
06-03-70-02W5 1215.0-1253.7 UGM3 
01-09-70-03W5 1155.4-1161.5 GM3 
15-17-71-25W4 888.5-918.21012.0-1047.9 UIRE UGM3. LGM 
10-01-71-26W4 928.1-932.4 UGM3 
05-09-72-01W4 881.5-1026.0 Nisku, UGM3, UGM2 
10-35-73-04W5 1012.9-1121.7 Nisku-UGM2 
10-18-76-25W4 1043.7-1066.8 UGM3 
06-10-77-25W4 1052.5-1057.4 LGM 
02-30-79-04W5 1065.0-1076.7 UGM3 
11-34-80-03W5 831.2-976.6 UGM3, UGM2 
11-14-81-20W4 380.0-389.0449.0-455.0 UGM3, UGM1 
16-24-81-20W4 430.0-433.1 Grosmont 
06-24-83-18W4 295.7-300.8 UIRE 
10-17-83-18W4 370.3-460.5 UGM3-LGM 
10-09-83-19W4 371.0-438.4 UGM2, UGM1, LGM 
13-22-83-22W4 555.0-584.3 UGM3, UGM2 
08-05-83-25W4 416.0-419.0 Nisku 
13-24-84-02W5 856.0-860.0 UGM1 
10-17-84-19W4 371.5-521.0 Grosmont 
06-34-85-19W4 322.0-406.5 UIRE?, UGM3, UGM2 
08-16-87-01W5 652.0-900.0 Calmar to UGM2 
10-14-88-02W5 672.8-725.5 Nisku - UIRE 
06-11-89-25W4 529.0-585.5624.0-638.0 UGM2, UGM1, LGM, 
Well ID Core Depth (m) Formation 
02-29-68-01W5 1127.7-1139.05 UIRE -UGM3 
02/15-23-68-01W5 1096.0-1127.0 UGM3, UGM2? 
08-28-69-04W5 1305.0-1337.0 Nisku-UIRE 
01-12-69-01W5 964.80-1043.0 UIRE-Nisku 
05-25-69-20W5 626.0-738.24 UGM3, UGM2, UGM1 
04-15-69-24W4 1005.8-1019.6 L1RE-LGM 
03-28-70-24W4 740.7-751.9 854.7-868.4 Nisku, UGM3, UGM2 
11-35-70-25W4 893.1-901.1 Nisku-UIRE 
02-23-70-01W5 879.3-880.9 Nisku 
06-03-70-02W5 1215.0-1253.7 UGM3 
01-09-70-03W5 1155.4-1161.5 GM3 
15-17-71-25W4 888.5-918.21012.0-1047.9 UIRE UGM3. LGM 
10-01-71-26W4 928.1-932.4 UGM3 
05-09-72-01W4 881.5-1026.0 Nisku, UGM3, UGM2 
10-35-73-04W5 1012.9-1121.7 Nisku-UGM2 
10-18-76-25W4 1043.7-1066.8 UGM3 
06-10-77-25W4 1052.5-1057.4 LGM 
02-30-79-04W5 1065.0-1076.7 UGM3 
11-34-80-03W5 831.2-976.6 UGM3, UGM2 
11-14-81-20W4 380.0-389.0449.0-455.0 UGM3, UGM1 
16-24-81-20W4 430.0-433.1 Grosmont 
06-24-83-18W4 295.7-300.8 UIRE 
10-17-83-18W4 370.3-460.5 UGM3-LGM 
10-09-83-19W4 371.0-438.4 UGM2, UGM1, LGM 
13-22-83-22W4 555.0-584.3 UGM3, UGM2 
08-05-83-25W4 416.0-419.0 Nisku 
13-24-84-02W5 856.0-860.0 UGM1 
10-17-84-19W4 371.5-521.0 Grosmont 
06-34-85-19W4 322.0-406.5 UIRE?, UGM3, UGM2 
08-16-87-01W5 652.0-900.0 Calmar to UGM2 
10-14-88-02W5 672.8-725.5 Nisku - UIRE 
06-11-89-25W4 529.0-585.5624.0-638.0 UGM2, UGM1, LGM, 

A total of five wells contain evaporite facies, four of them within the Upper Grosmont, and one of them within the Lower Grosmont. Well 15-17-71-25W4 is here informally considered the “type section well” of the Hondo because it contains the most complete evaporite succession (25 m) in the study area. An additional 27 wells with core contain intervals of the Nisku, Ireton, and Grosmont formations, but no evaporites were found. Stratigraphic identification of the Grosmont units is based on Union Oil, as refined by Cutler (1983) for the Grosmont type section well 10-17-84-19W4.

Cuttings are available generally in about 3-m (10-foot) spacings. The main purpose for examining the cuttings was the identification of the sulfate minerals anhydrite and gypsum. Part of the coarse fraction (1–2 mm) of the cuttings was dipped into a 10% HCl solution, and parts of the fraction were dipped into an Alizarin Red-S solution to identify calcite or dolomite, which were examined under a binocular microscope.

Well Log Analysis

A total of 140 wells with geophysical wireline logs were available for the Grosmont–Hondo intervals from the data repository in AccuMap®. The main well logs used for identification of the carbonates and evaporites in the area are gamma ray, density, resistivity, and neutron. However, for most of the wells only spontaneous potential (SP) and gamma ray and now-outdated electrical logs had been run. For the identification of the Hondo evaporites the best logs are density and sonic, but these are rarely available. For these reasons, lithologic interpretations are based mainly on cores and cuttings.

The information from logs, cores, and cuttings was used to produce several dip-oriented and two strike-oriented stratigraphic and structural cross sections. In addition, isopach and structural maps were produced using the contouring software SURFER®. Contours were then edited by hand to interpret geological features not captured by computer contouring and were then redrawn using graphics software.

Petrography

Petrographic analyses were performed on all available core intervals and on 75 thin sections cut from selected core samples. Most sections were impregnated with blue epoxy and stained with Alizarin Red-S. Eighteen samples were finely powdered for mineral identification by X-ray diffraction (XRD) in the XRD laboratory at the Earth and Atmospheric Sciences Department at the University of Alberta using standard procedures.

Isotope Analyses

δ18O, δ13C, and δ34S isotopic compositions for dolomites, calcite, and sulfates (n = 19) from the Upper Grosmont units were obtained in the Isotope Science Laboratory of the University of Calgary. Radiogenic strontium isotopes 87Sr/86Sr of 15 samples of anhydrite/gypsum, calcite, and dolomite were determined in the radiogenic isotope facility in the Earth and Atmospheric Sciences Department at the University of Alberta using standard procedures.

DEPOSITIONAL LITHOFACIES

The carbonate lithofacies types in the Grosmont reservoir are addressed following the method of Machel and Hunter (1994). These authors used their own observations from various Devonian carbonate platforms and reefs, those of two seminal earlier studies of the Grosmont (Cutler 1983, Theriault 1988), and modern analogs to establish facies models for Middle to Late Devonian carbonates in platform and ramp settings. An idealized shallowing-upward cycle begins with a shallow subtidal bioclastic packstone–grainstone facies and ends with a barren dolomudstone facies with scant evidence of evaporation, as shown in Figure 4.

Fig. 4.

—Lithofacies in an idealized shallowing-upward cycle of the Grosmont platform. A) Subtidal skeletal grainstone facies; B–D) shallow(er) shelf facies; E) intertidal algal/cyanobacterial mat facies; F) primary anhydrite–dolomite brine pond/salina facies (this sample represents various subaqueous lithofacies types, further illustrated in Fig. 5); G) supratidal mud facies with mold and reaction halo from dissolution of anhydrite nodule; and H) supratidal mud facies with mold of deformed halite hopper crystal.

Fig. 4.

—Lithofacies in an idealized shallowing-upward cycle of the Grosmont platform. A) Subtidal skeletal grainstone facies; B–D) shallow(er) shelf facies; E) intertidal algal/cyanobacterial mat facies; F) primary anhydrite–dolomite brine pond/salina facies (this sample represents various subaqueous lithofacies types, further illustrated in Fig. 5); G) supratidal mud facies with mold and reaction halo from dissolution of anhydrite nodule; and H) supratidal mud facies with mold of deformed halite hopper crystal.

The evaporite facies types are addressed using the classifications of Murray (1964) and Maiklem et al. (1969), supplemented with observations from regionally extensive evaporite deposits in the Permian Basin (Sarg 1977, 1989) and elsewhere (Shearman 1971, 1978; Schreiber and Kinsman 1975; Schreiber 1978; Schreiber and El Tabakh 2000). The main facies types are shown in Figures 5 and 6. More detailed petrographic descriptions and photographic representations of the various Hondo lithotypes can be found in Borrero (2010). Drill cuttings were not used to identify facies but served to delineate the current subsurface extent and distribution of the Hondo.

Fig. 5.

—Summary of the most important evaporite lithofacies types of the Hondo. The rock type shown in Figure 4F can occur in either Lithofacies B or Lithofacies C, as defined herein.

Fig. 5.

—Summary of the most important evaporite lithofacies types of the Hondo. The rock type shown in Figure 4F can occur in either Lithofacies B or Lithofacies C, as defined herein.

Fig. 6.

—Spontaneous potential and short normal (SN) logs of the Hondo type well Imperial Smith 15-17-71-24W4 from about 820 to 1050 m, also showing stratigraphic boundaries and a core photograph representing one of the thickest evaporite intervals within the UGM3. The well contains two cored intervals within the depth interval shown here, both containing Hondo evaporites, with the upper one straddling the UGM3–UIRE boundary. The well contains several more cored intervals above and below the depth interval shown here. The stratigraphic boundaries in the uncored intervals are based on electric logs, cuttings, and/or correlation to neighboring wells. See Figure 2 and text for stratigraphic nomenclature.

Fig. 6.

—Spontaneous potential and short normal (SN) logs of the Hondo type well Imperial Smith 15-17-71-24W4 from about 820 to 1050 m, also showing stratigraphic boundaries and a core photograph representing one of the thickest evaporite intervals within the UGM3. The well contains two cored intervals within the depth interval shown here, both containing Hondo evaporites, with the upper one straddling the UGM3–UIRE boundary. The well contains several more cored intervals above and below the depth interval shown here. The stratigraphic boundaries in the uncored intervals are based on electric logs, cuttings, and/or correlation to neighboring wells. See Figure 2 and text for stratigraphic nomenclature.

The carbonate and evaporite facies types can be integrated into a depositional model for the Grosmont carbonate–evaporite system as a modification of the facies model(s) developed by Machel and Hunter (1994). One of their models is modified to accommodate deposition of Hondo-type evaporites (Fig. 7). To infer a depositional model specifically for the evaporites would require comparisons with similar evaporite settings elsewhere and at additional stratigraphic levels (Schreiber 1978; Schreiber and El Tabakh 2000). However, in the current context it appears more sensible to consider the Hondo evaporites only in the context of the carbonate–evaporite system that the Grosmont represents. Accordingly, the primary sulfates form(ed) subaqueously in subtle depressions on a ramp at relatively low sea level, with displacive/replacive primary sulfates forming at the same time within the uppermost layers of the sediments that are permeated by the same evaporative fluids.

Fig. 7.

—Carbonate–evaporite depositional model representing the Grosmont–Hondo system (modified from Fig. 3 in Machel and Hunter [1994]). The letter designations “Ib” through “If” refer to the carbonate facies identified by these authors, as follows: Zone Ib: fenestral laminites; Zone IIb: sparsely fossiliferous packstones and wackestones; Zone IIIb: Amphipora floatstones and grainstones; Zone IVb: Stachyodes rudstones, bafflestones, and floatstones; Zone V: stromatoporoid framestones and bindstones; Zone IV/V: stromatoporoid–coral bindstones and rudstones; Zone IVf: Stachyodes–coral–stromatoporoid bafflestones and rudstones; Zone IIIf: crinoid–stromatoporoid floatstones and rudstones; Zone IIf: crinoid–stromatoporoid floatstones, grainstones, and packstones; and Zone If: poorly fossiliferous wackestones and mudstones. These facies are roughly equivalent to the facies depicted in Figure 4 of this study during relatively high sea levels, here labeled “Carbonate sea level.” Numbers 4A–F, 5, and 6 refer to the photos shown in the figures with the same numbers from this article. Evaporite deposition took place during lower sea levels and/or when the ramp fell dry, here labeled “Evaporite level high” and “Evaporite level low,” respectively. The depression on the ramp is the site of a salina or brine pond on a sabkha where subaqueous evaporites would have formed. Displacive as well as replacive evaporites would have formed in the sediments immediately below the sediment–water or sediment–air interface.

Fig. 7.

—Carbonate–evaporite depositional model representing the Grosmont–Hondo system (modified from Fig. 3 in Machel and Hunter [1994]). The letter designations “Ib” through “If” refer to the carbonate facies identified by these authors, as follows: Zone Ib: fenestral laminites; Zone IIb: sparsely fossiliferous packstones and wackestones; Zone IIIb: Amphipora floatstones and grainstones; Zone IVb: Stachyodes rudstones, bafflestones, and floatstones; Zone V: stromatoporoid framestones and bindstones; Zone IV/V: stromatoporoid–coral bindstones and rudstones; Zone IVf: Stachyodes–coral–stromatoporoid bafflestones and rudstones; Zone IIIf: crinoid–stromatoporoid floatstones and rudstones; Zone IIf: crinoid–stromatoporoid floatstones, grainstones, and packstones; and Zone If: poorly fossiliferous wackestones and mudstones. These facies are roughly equivalent to the facies depicted in Figure 4 of this study during relatively high sea levels, here labeled “Carbonate sea level.” Numbers 4A–F, 5, and 6 refer to the photos shown in the figures with the same numbers from this article. Evaporite deposition took place during lower sea levels and/or when the ramp fell dry, here labeled “Evaporite level high” and “Evaporite level low,” respectively. The depression on the ramp is the site of a salina or brine pond on a sabkha where subaqueous evaporites would have formed. Displacive as well as replacive evaporites would have formed in the sediments immediately below the sediment–water or sediment–air interface.

In this study, the term “Hondo sulfates” includes both anhydrite and gypsum. The term “Hondo primary sulfates” refers to sulfates that formed syndepositionally, either subaqueously or displacively/replacively near the sediment–water interface and/or at the sediment–air interface in the case of supratidal sabkha deposition. Based on the textures present in core, almost all primary sulfates in the study area probably formed originally as gypsum but are anhydrite today. Thus, most anhydrite formed by dehydration of primary gypsum, often with good to excellent fabric retention. “Hondo secondary sulfates” corresponds to diagenetically altered primary sulfates in which syndepositional features have been partially to completely altered. “Diagenetic anhydrite” refers to anhydrite that was precipitated from diagenetic solution, most commonly in secondary voids or in fractures.

Hondo primary sulfates are present in four cores in the upper portion of the Grosmont reservoir and also in lower reservoir units (Figs. 2, 3). Well 15-17-71-25W4 is herein informally designated to be the “type well” for the Hondo. This well contains most of the Hondo lithofacies and thus is the most instructive for facies analysis, and with 25 m of evaporites it has the longest cored continuous section of the Hondo (Fig. 6). Interpreted individually, most of the Hondo primary sulfates point to a semiarid to arid shallow marine to coastal (sabkha) setting. Most of the microtextures suggest formation of sulfates originally as gypsum, with subsequent recrystallization to anhydrite during burial.

Lithofacies A: Laminated Anhydrite and Laminated Dolomudstone

Facies A is characterized by finely laminated (lamina thickness = 2 mm to ~1 cm) gray anhydrite and cream to brownish dolomudstones. The laminae are planar to wavy and continuous. Contacts with underlying laminae are mainly sharp. There is no evidence of bioclasts, and it appears that the laminae were not affected by bioturbation. In thin sections, lenticular–microcrystalline anhydrite is oriented more or less horizontally, and dolomite is very fine-grained (dolomicrite). Some anhydrite shows corrotopic textures indicative of gypsum–anhydrite transformation (Machel 2013, his fig. 7). Disseminated rounded grains of pyrite are observed in the dolomudstone layers.

The dominance of laminated sulfates implies precipitation and deposition in a water body whose bottom received little or no influence from wave action, currents, and/or burrowing. Evaporitic laminites commonly form in relatively deep, quiet waters (Warren 2006), but also in shallow stratified water bodies, such as solar salt ponds (Schreiber 1978, Schreiber and El Tabakh 2000). Generally, laminar carbonates and sulfates, especially the ones formed in deep waters, have a broad lateral continuity. For example, in the modern Black Sea such laminae may be correlated over an approximated distance of 1000 km (Davies and Ludlam 1973), and calcite–anhydrite laminae can be correlated over thousands of square kilometers in the Permian Basin of west Texas and New Mexico (Anderson et al. 1971, Sarg 1977). In the case of the Hondo, however, a correlation between laminated units across the study area is unreasonable because of the relatively wide spacing of core. Facies A contains some sporadic wavy parallel laminations that are interpreted to be formed by slight currents. Depth of sulfate formation has to be interpreted from other facies. Although the main mineral in this lithofacies is currently anhydrite, gypsum likely was the first mineral precipitated. Gypsum then dehydrated when temperatures reached >50° C, mainly during burial (Hardie 1967), or under mixing of seawater with mesohaline water below gypsum saturation.

Gypsum crystals have been observed growing in salina ponds in two forms: the mineral forms on the floor of the brine pond as grasslike “meadows,” with the crystal axes perpendicular to bedding, and as acicular crystals formed at the air–water interface or at the pycnocline (Schreiber 1978, Schreiber and El Tabakh 2000). When such crystals become too heavy to float, they sink and align horizontally on the bottom, creating laminae. Interlamination of sulfates and dolomudstones likely forms as a result of episodic variations in temperature or changes in evaporation rates. Dolomudstones in the Hondo are interpreted as having formed nearly syndepositionally, that is, lime muds (the penultimate origin of which is speculative) were dolomitized during or very soon after deposition by evaporative reflux and/or in a sabkha (further discussed below). Salinities in gypsum-forming ponds commonly have salinities of 150 to 320 g/l (Schreiber and El Tabakh 2000). The lack of bioturbation is attributed to the relatively high salinity of the brine. In modern evaporitic environments, marine fauna may live in salinities up to 55 g/l, but as soon as salinity increases to >35 g/l fauna becomes restricted (Schreiber and El Tabakh 2000). Low energy at the bottom of the water body also promotes anoxic conditions that inhibit development of benthic fauna. Taking all evidence together, Facies A is interpreted as deposits formed predominantly in low-energy and high-salinity shallow pools.

Lithofacies B: Mosaic Anhydrite with Microbial Mats

Facies B, as found in type well 15-17-71-24W4 from 910.15 m to 911.4 m, contains centimeter-sized “nodules” of milky-white to gray anhydrite that are aligned subhorizontally within a thin-bedded, cream-colored dolomite matrix, here classified as mosaic anhydrite (Maiklem et al. 1969). Dolomicritic laminae have sharp contacts with the mosaic areas. These commonly are very thin (few centimeters) in comparison with the sulfate layers, which commonly have thicknesses in the decimeter range, up to about 3 m in total thickness. Under the microscope, the nodules appear as felted anhydrite laths, with the long axes diverging into radial sprays or with crystals parallel to each other. The microbial laminae consist of clusters of a granular dolomite–anhydrite mix in the nucleus, surrounded by dolomicrite and micrite. This type of anhydrite nodule was likely formed displacively by nucleation within carbonate mud and then coalesced to the mosaic texture with continued growth. It is likely that gypsum crystals originally precipitated and then transformed to a mass of tiny laths plus liquid water (“crystal mush”), which, by weight of the overlying sediments, dewatered and compacted further to spherical or ovoid nodules (Hardie 2003). Mosaic anhydrite is also considered a transitional texture between laminar and nodular anhydrite (Friedman 1973).

Facies B is herein interpreted as having been formed under subaqueous to intertidal conditions within shallow hypersaline lagoons/pools in arid conditions. The microbial laminae mats represent deposition in a mesohaline to hypersaline intertidal environment.

Lithofacies C: Enterolithic Anhydrite/Contorted Bedded Anhydrite

Facies C is made up of cream-colored dolomudstone and gray anhydrite layers. There are deformed beds with a ropey structure. The anhydrite displaces the sediment around it, causing deformation of the horizontal layers. As in the case of Lithofacies B, individual beds commonly have thicknesses in the decimeter range and reach up to about 3 m in total thickness.

The contorted layers are interpreted to represent a product of deformation caused by differences in density of semifluid gypsum and consolidated or semiconsolidated nonevaporitic sediments formed during or shortly after deposition (Maiklem et al. 1969). When the sediments are still unlithified, brines may sink into the underlying sediments and facilitate the reaction and alteration of evaporite beds (Warren 2006). Thus, nodules grow by displacement in the soft sediment within the dolomudstone matrix as the first stage to form enterolithic, contorted fold and mosaic anhydrite (Loucks and Longman 1982, Rouchy et al. 1985, Shearman 1985).

Lithofacies D: Displacive-Nodular Anhydrite

Facies D is characterized by nodular anhydrite. Nodules of this facies are 2 mm to 5 mm in size and are embedded in brown dolomudstone. They form displacively within the matrix and can coalesce to layers. In thin section, anhydrite is blocky to lath-shaped.

Nodular anhydrite of this type has been interpreted to be formed in a sabkha setting under subaerial exposure (e.g., Shearman 1963, 1978; Dean and Anderson 1982). However, in the Hondo, such nodules of anhydrite are interpreted to be primary and secondary sulfates formed in a subaqueous setting and/or within the soft, unlithified sediments right below the brine pools. The geometry of the layers can also be attributed to the growth of anhydrite within dolomitic sediments or to the replacement of gypsum crusts (Shearman 1970). Sporadic currents could also have deformed the laminae horizontally.

Lithofacies E: Disrupted Bedding and Breccias

Facies E is made up of breccias with subangular to subrounded intraclasts of brown dolomudstones and small anhydrite nodules less than 1 mm in size in a green-colored mud matrix. Some of the dolomudstone lithoclasts show internal lamination, which corresponds to Facies A.

This facies is interpreted as synsedimentary breccias, being the product of reworking during storms or minor transgressions with concomitant plastic deformation. The development of this lithofacies thus requires at least a moderate degree of synsedimentary lithification.

Halite Lithofacies

One may expect a halite lithofacies to follow the above sequence of Lithofacies A through E. However, bedded “primary” halite is not present in any of the Hondo cores. However, a handful of samples were found to contain displacively grown halite hopper molds (Fig. 4H) and/or pseudomorphs of anhydrite after halite crystals “floating” in a dolomudstone facies. While these textures indicate that episodically the depositional environment reached halite saturation in a marine-marginal sabkha or salina (Handford 1991), there is not enough evidence to describe or establish any halite lithofacies.

SYNDEPOSITIONAL AND POSTDEPOSTIONAL DIAGENESIS

The overall paragenetic sequence, supporting petrographic and geochemical evidence, and impact on reservoir quality have been discussed in considerable detail elsewhere (Luo et al 1994; Luo and Machel 1995; Dembicki and Machel 1996; Zhao 2009; Zhao and Machel 2011, 2012; Machel et al. 2012; Russel-Houston and Gray 2014), and only a brief summary is provided here, except in the case of dolomitization and sulfate diagenesis, which are discussed in some detail further below.

Diagenetic processes affected the Grosmont and overlying strata from the time of deposition to sub-Recent times. The earliest pervasive diagenetic process was dolomitization by density-driven reflux. Most dolostones are finely crystalline and tight, however, and the only notable porosity caused by and/or related to dolomitization is scattered molds and vugs. A dense fracture network is present and apparently was created in three or four phases. Most fractures likely originated from collapse following subsurface salt dissolution and/or from Laramide tectonics far to the west, whereby pulsed crustal loading in the fold-and-thrust belt created a dynamic forebulge in the Grosmont region via multiple pulses of basin-wide crustal flexing, each followed by relaxation. The fracture network likely was reactivated and/or expanded by glacial loading and postglacial isostatic rebound in the Pleistocene and Holocene.

In addition, the region experienced three or four prolonged periods of epigene (top-down) karstification, although there is tangible evidence for only two of them in the Grosmont reservoir. The first of these episodes was a “warm epigene karstification” during the Jurassic–Cretaceous, and the second was/is a “cold epigene karstification” that started sometime in the Cenozoic and continues to this day. In addition, there is circumstantial evidence for hypogene (bottom-up) “karstification” (= dissolution) throughout much of the geologic history of the Grosmont since the Late Devonian, with two possible maxima around the time of hydrocarbon emplacement; i.e., Early–Middle Cretaceous and Early Tertiary, respectively. Karstification was accompanied by and/or followed by extensive biodegradation. Present bitumen in situ viscosities are >1 million Cp, and API gravities range from 5 to 9°. The last pervasive process was the incursion of subglacial meltwater that accompanied and followed the melting of the most recent Holocene ice sheet about 14,000 and 6000 years ago.

Replacement Dolomitization

Although mainly affecting the carbonate sediments and rocks, replacement dolomitization cannot be separated from the diagenesis of the Hondo because of the intimate spatial and genetic relationships between primary anhydrites and lime- or dolomudstones. In addition, the reservoir contains a peculiar diagenetic facies in the form of a dolomite powder, which likely originated from diagenesis of primary sulfates, as discussed further below.

Huebscher (1996) and Huebscher and Machel (2004) discriminated between two major types of dolomite in the Grosmont Formation. Type 1 dolomite (R1) pervasively replaced lime mud and lime sand and is present in all depositional facies of the Grosmont reservoir. Regionally, the extent of R1 increases toward the eastern part of the Grosmont and toward the upper members of the Grosmont Formation, especially in the Upper Grosmont 2 and 3, while parts of the LGM remain limestone. In cores, R1 dolomite commonly is light gray to light brown. R1 dolomite preferentially replaced matrix of the original limestones, while primary fabrics are preserved in many cases. Most dolomite crystals are planar-e to planar-s, with diameters of commonly 20 to 50 µm.

Type 2 replacement dolomite (R2) was recognized in the southern part of the study area, where the Grosmont Formation overlies reefs of the Leduc and Cooking Lake formations. R2 dolomite shows clear evidence of recrystallization (Huebscher and Machel 2004). In core, this type of dolomite is gray or light brown; it occurs as a pervasive replacement phase including calcitic fossils and commonly has visible intercrystal porosity. In thin section, it is coarser crystalline than R1 dolomite, and the crystals are planar-s to nonplanar-a.

Dolomite types R1 and R2 also occur in the Hondo, with a clear predominance of R1. In core, dolomite associated with the Hondo primary sulfates is generally cream to light gray in color, as present in the Hondo type well 15-17-71-25W4. In microscopic view, R1 dolomite is cryptocrystalline to fine-crystalline, with diameters of up to ~50 m, mainly planar-s to nonplanar-a. Replacement dolomite type R1 likely formed syndepositionally or during shallow burial. Reflux of sulfate-saturated brines containing elevated Mg2+ levels could have formed the majority of the dolomite in the Grosmont Formation (Jones et al. 2003, Huebscher and Machel 2004). In this type of dolomitization, seawater evaporates at or beyond gypsum saturation and seeps and/or flows seaward within the topmost few meters of the carbonate sediments via density-drive. Dolomite type R2 was interpreted to have been formed during burial via warm fluids that migrated from the reef aquifers into the Grosmont (Huebscher and Machel 2004) and/or via recrystallization of R1.

A rock type that is highly unusual in general yet relatively common in the Grosmont is dolomite powder cemented with bitumen. In core this material is black to dark brown, depending on the color of the bitumen (Fig. 8A). It is sticky and commonly malleable, like pottery clay, which led to various fanciful names, including “dolofudge” and “dologunk.” When the bitumen is dissolved (using organic solvents such as carbon disulfide), all that remains is a nearly white to gray dolomite powder (Fig. 8B). Some core intervals with dolomite powder can be correlated over relatively large distances and appear to be stratiform in at least a part of the Grosmont.

Fig. 8.

—Images of powdered dolomite (A–C) and breccias (D–F). A) Core interval with dolomite powder held together by bitumen. Bags contain white dolomite powder after bitumen extraction with organic solvent. B) Dolomite powder. C) Thin section, transmitted light: dolomite crystals floating in bedded anhydrite. This kind of rock is a possible, if not the most likely, precursor of dolomite powder in the Grosmont reservoir. The sample is from Nisku anhydrites in southeastern Alberta (Machel 1985). No such rocks or textures were found in the Grosmont reservoir. D–F) Fractured and brecciated core intervals due to evaporite dissolution. Samples are from well 7-29-84-18W4M, UGM2, 356.0 m, with the exception of C, which is from the overlying Nisku Formation from well 14-9-35-20W4, 1622.5 m.

Fig. 8.

—Images of powdered dolomite (A–C) and breccias (D–F). A) Core interval with dolomite powder held together by bitumen. Bags contain white dolomite powder after bitumen extraction with organic solvent. B) Dolomite powder. C) Thin section, transmitted light: dolomite crystals floating in bedded anhydrite. This kind of rock is a possible, if not the most likely, precursor of dolomite powder in the Grosmont reservoir. The sample is from Nisku anhydrites in southeastern Alberta (Machel 1985). No such rocks or textures were found in the Grosmont reservoir. D–F) Fractured and brecciated core intervals due to evaporite dissolution. Samples are from well 7-29-84-18W4M, UGM2, 356.0 m, with the exception of C, which is from the overlying Nisku Formation from well 14-9-35-20W4, 1622.5 m.

Speculations as to the origin of this dolomite powder range from syndepositional or very early diagenetic calcite or dolomite dissolution, via syndepositional or postdepositional evaporite dissolution, to cryogenic mechanical weathering during Pleistocene interglacial periods (Machel et al. 2012, MacNeil 2015). The latter interpretation, surely the oddest and thus least likely one, at least for the Grosmont reservoir, is well supported by data from powderized dolostones in Triassic dolostones of the Buda Hills, Hungary (Poros et al. 2013). At present, we have no conclusive interpretation for the origin of the dolomite powder in the Grosmont reservoir. On the balance of all data, we favor dissolution of gypsum or anhydrite layers, which are known to contain countless “floating” dolomite crystals in some evaporite deposits elsewhere (Fig. 8C). Upon dissolution of the sulfates, these crystals would form a residue of dolomite powder. A cryogenic origin appears unlikely in the case of the Grosmont, considering that the dolomite powder is bitumen-saturated and that there were no cold climatic periods in the Grosmont region preceding oil migration. On the other hand, if the powdered dolomite in the Grosmont were indeed of cryogenic origin, it would have been created during the Pleistocene, which would require that the bitumen invaded the dolomite powder intervals sometime in a Pleistocene interglacial or even in the Holocene. This is not impossible, considering that oil/bitumen can remigrate at any time after its original migration and emplacement.

Dissolution

Dissolution in Grosmont–Hondo cores is represented by (1) bioclast-selective dissolution that created moldic porosity (Fig. 4D); (2) vugs and cavities formed without specific shape(s) (Fig. 4G); (3) microscopic intercrystal porosity; (4) halite dissolution, as shown by molds of halite hoppers (Fig. 4H); (5) dissolution of calcium sulfate “matrix” to yield dolomite powder (see previous section); (6) dissolution of calcium sulfate and/or halite beds to yield dissolution collapse breccias (Fig. 8D–F) that are stratiform and regionally extensive; and (7) sinkholes and caves.

One of the most important advances in the understanding of the Grosmont reservoir over the past 10 years is that postdepositional dissolution was perhaps the most important process shaping the reservoir properties. Dissolution is interpreted to have affected the Grosmont reservoir multiple times during its evolution and in a “fractal” manner, that is, at scales that range from submicroscopic to regionally extensive (Luo et al. 1994, Luo and Machel 1995, Machel et al. 2012).

While dissolution features are nearly unpredictable on the scale of individual wells, they were mapped out with the aid of modern 3D seismic by Russel-Houston and Gray (2014) in at least one small part of the reservoir. These authors could also show that the volumetrically most important and pervasive dissolution event likely was Karstification Phase K3 (sensu Machel et al. 2012), which affected the region from the Late-Jurassic to the Early Cretaceous and dissolved both carbonates and evaporites on a grand scale. In addition, it is safe to suggest that a first dissolution event may have taken place much earlier (i.e., soon after deposition of the Hondo primary sulfates), either from replenishment of the “lagoons” by normal seawater or by rainfall and the temporary creation of fresh to brackish water lakes, which is common in and/or near supratidal settings such as sabkhas (e.g., Warren 2006). Molds, vugs, and small cavities are interpreted to have formed as a result of calcite, dolomite and/or sulfate dissolution. Dissolution of halite apparently occurred during physical compaction but after partial cementation, as shown by the curved faces of halite hopper molds. Brecciated zones, sinkholes, and collapsed caves are common, especially in the updip portions of the reservoir (Russel-Houston and Gray 2014), schematically indicated as karst in Figure 3. Earlier studies identified karsted intervals as “caves” from well logs in Townships 85 to 93 and Ranges 16W4 to 25W4 (Dembicki 1994, Dembicki and Machel 1996), and Huebscher (1996) identified two levels of enhanced “cave” formation that appear to be subhorizontal and regionally correlatable. However, none of these studies could properly map out these features without the aid of seismic tools at the time.

Secondary Anhydritization

Anhydrite is the main mineral recognized as a secondary sulfate in the Hondo and Grosmont. Some samples contain a mixture of anhydrite and gypsum, with anhydrite as the main component. Anhydritization affected the Grosmont and Hondo in three different ways: replacement of primary gypsum via dewatering during burial; replacement of remnant calcite or dolomite; and cementation/infill of molds or vugs.

Based on the regional burial history, dewatering of primary gypsum occurred during relatively rapid burial in the Late Devonian and Early Mississippian (Machel et al. 2012). The dewatering of gypsum to anhydrite commonly takes place at depths of 700 to 800 m, but at elevated pore pressures and/or low geothermal gradients down to depths of ~1200 m (e.g., Mossop and Shearman 1973). In the Hondo cores this transformation preserved many of the primary textures on the scale of drill core. However, at the microscale the primary textures were almost obliterated, and the primary sulfates now consist of felted and corrotopic anhydrite (Fig. 9), the latter of which are thought to be indicative of the replacement of gypsum by anhydrite, with subsequent anhydrite recrystallization (Machel 2014).

Fig. 9.

—Thin-section photomicrographs of secondary anhydrites, A and C) Plane polarized light; B and D) crossed polarized light. Both samples contain corrotopic anhydrite, in which corroded porphyrotopes of anhydrite are embedded in a finer-crystalline anhydrite matrix. These textures are indicative of original deposition as gypsum with subsequent transformation to anhydrite during dewatering and recrystallization during increasing burial. Well 02-30-79-04W5, 1066.5 m; UGM3.

Fig. 9.

—Thin-section photomicrographs of secondary anhydrites, A and C) Plane polarized light; B and D) crossed polarized light. Both samples contain corrotopic anhydrite, in which corroded porphyrotopes of anhydrite are embedded in a finer-crystalline anhydrite matrix. These textures are indicative of original deposition as gypsum with subsequent transformation to anhydrite during dewatering and recrystallization during increasing burial. Well 02-30-79-04W5, 1066.5 m; UGM3.

Some core intervals contain large (up to several centimeters), irregularly shaped nodules or domains of milky-white anhydrite that appear to be replacive (Fig. 10). The source of calcium sulfate for these features likely was dissolution of primary sulfates. In addition, although clearly postdepositional, even these features originally formed as gypsum and later transformed to anhydrite during burial, as suggested by corrotopic microfabrics.

Fig. 10.

—Secondary anhydrite filling fractures or replacing limestone and/or dolostone matrix. A) Well 16-13-89-23W4, 329.5 m, UGM3. B) Well 15-17-71-25W4, 908.0 m, UGM3–Hondo interval. Coin for scale (diameter 1.85 cm).

Fig. 10.

—Secondary anhydrite filling fractures or replacing limestone and/or dolostone matrix. A) Well 16-13-89-23W4, 329.5 m, UGM3. B) Well 15-17-71-25W4, 908.0 m, UGM3–Hondo interval. Coin for scale (diameter 1.85 cm).

Ca-Sulfate Cementation of Molds and/or Vugs

In some intervals within the Grosmont units, especially in the UGM3, UGM1, and LGM, Amphipora molds in floatstones are cemented by anhydrite. Most of this type of anhydrite does not appear to have had a gypsum precursor, as suggested by its microtexture, which commonly falls into the category of “cement” and/or “pile-of-brick” (Carozzi 1960).

Rehydration to Gypsum

Some microfabrics suggest that anhydrite was rehydrated to gypsum and later dehydrated again to anhydrite (Fig. 11). Rehydration to gypsum likely took place during one or several of the noted phases of meteoric karstification.

Fig. 11.

–Secondary gypsum. A) Core sample of gypsum nodule in dolomudstone, well 10-18-76-25W4, 1062.10 m, UGM3. B) Replacive gypsum rosettes in mosaic anhydrite formed during uplift and partial rehydration; well 10-17-84-19W4, 501.00 m, LGM.

Fig. 11.

–Secondary gypsum. A) Core sample of gypsum nodule in dolomudstone, well 10-18-76-25W4, 1062.10 m, UGM3. B) Replacive gypsum rosettes in mosaic anhydrite formed during uplift and partial rehydration; well 10-17-84-19W4, 501.00 m, LGM.

GEOCHEMISTRY

This section provides a brief discussion of the sulfur, oxygen, and strontium (Sr) isotope values of Hondo anhydrites. The analytical procedures and results of the full data set of all Hondo samples (carbon and oxygen isotopes for calcites and dolomites; sulfur and oxygen isotopes for anhydrites; strontium isotopes for all three phases) are documented in Borrero (2010).

Late Devonian seawater is reported to have had a δ34S average of 25% Vienna Cañon Diablo troilite (VCDT) (Claypool et al. 1980). Primary anhydrite samples from the Hondo (n = 8) have δ34S values between 23.7 and 27.4‰ VCDT, whereas their δ18O values range from 14.3 to 16.6‰ Standard Mean Ocean Water (SMOW). These numbers are typical for brines that originated from Late Devonian seawater that was evaporated to or beyond gypsum saturation and was also modified by bacterial sulfate reduction syndepositionally and/or early postdepositionally. Bacterial sulfate reduction is common in evaporitic, sulfate-rich environments and is evident in Grosmont cores via fine-crystalline, disseminated pyrite.

The 87Sr/86Sr ratios for primary and secondary anhydrites from the Hondo, UGM3, UGM2, and Upper Ireton yielded a range of 0.7081 to 0.7087 (n = 8), with an average of 0.7087, plus one outlier at 0.7096. These values are consistent with a parentage from Upper Devonian seawater (Denison et al. 1997, Veizer et al. 1999). A single value of 0.7096 is from a secondary anhydrite nodule within an argillaceous, partially dolomitized limestone in the Upper Ireton. The moderate 87Sr-enrichment of this sample can be attributed to an admixture of Sr from the siltstones in the overlying Calmar Formation.

In summary, the sulfur, oxygen, and strontium isotope data support and confirm that the primary and secondary anhydrites in the Hondo all originated from evaporation of Late Devonian seawater. Extra-formational sources of calcium sulfate are not evident from these geochemical data.

REGIONAL DISTRIBUTION

The spatial distribution of Hondo sulfates and the margin of what is now the Grosmont reservoir were reconstructed using 32 wells with core, 105 wells with cuttings, and a total of 140 wells with logs. Structural maps were constructed for the Upper Ireton, Upper Grosmont 3, and Upper Grosmont 2, isopach maps were constructed for the Upper Grosmont 3, 2, and 1, and also five cross sections. Descriptions of cuttings were matched with log interpretations to better define the presence of gypsum and/or anhydrite and to identify and locate the so-called shale breaks. A sulfate content of 25 to 35% classified an interval as part of the Hondo. A sedimentological interpretation for the Hondo is proposed based on lithofacies, distribution, integration of geochemical results, and comparison with modern examples of evaporitic basins.

The Upper Ireton Formation displays a regional strike of 160° in the northeast to 150° in the southwest. The dip is approximately 0.3° to the southwest. The structural map shows elevation ranging from ~800 m below sea level in the southwest to ~250 m above sea level close to the erosional edge in the northeast (Fig. 12; this map can be viewed to represent the structure for the Grosmont 3 and 2 as well, for which the structural maps look almost identical).

Fig. 12.

—Structure contour map of the top of the Upper Ireton.

Fig. 12.

—Structure contour map of the top of the Upper Ireton.

The Upper Grosmont 2 shows a regional strike of 160°, which varies locally from 130 to 150° in the northwest. The dip of the formation is 0.3° southwest in the north and central parts and in the southwest increases to 0.5°. Elevation varies from 900 m below sea level in the southwest to 200 m above sea level in the northeast. The Upper Grosmont 3 shows a regional strike of 150 to 160° and a dip of 0.3° in the southwest. The elevation of the UGM3 top varies from ~700 m below sea level to ~250 m close to the erosional edge.

The distribution of the Hondo primary sulfates can be contoured across the study area in pods with average sizes of two by two or two by three townships, equivalent to 20 by 20 km to 20 by 30 km (Fig. 13). Unfortunately, the poor well control noted earlier does not permit a unique solution for contouring the current limits of the primary sulfates. As a best-guess solution, anhydrites were assigned to a neighboring pod (rather than to the same one) if the spacing between the wells is more than 15 km.

Fig. 13.

—Map of the Hondo area with well control. Cross section B-Bʹ – Figures 14 + 15. Note westward-migrating platform edge. See text for further explanation.

Fig. 13.

—Map of the Hondo area with well control. Cross section B-Bʹ – Figures 14 + 15. Note westward-migrating platform edge. See text for further explanation.

Several cross sections were constructed as traverses parallel and perpendicular to the long axis of the Grosmont reservoir, roughly corresponding to strike and dip sections, to illustrate the regional distribution of the Hondo sulfates and the Grosmont Formation. The stratigraphic boundaries can be considered as timelines in these sections, considering that the depositional relief was nearly flat before structural tilting. One of these sections, Section B-Bʹ, is presented here in the form of a structural and a stratigraphic cross section (Figs. 14, 15; the section line is shown in Fig. 13). Cross section line B-Bʹ was constructed from 10 wells over a distance of 186.00 km; i.e., from well 04-27-73-07W5 to well 10-17-84-19W4. These wells were chosen based on availability of core and cuttings and on the quality of the available wireline logs. Sections B-Bʹ are considered representative of the main findings regarding the distribution of the Hondo across the entire study area, except for the fact that Hondo evaporites in this part of the reservoir occur both in the LGM and, more massively, in the UGM3–UIRE, where evaporites straddle this boundary. Elsewhere in the reservoir Hondo evaporites are largely restricted to the UGM3, with sporadic occurrences in the UGM1 and UGM2 that are too small to be mappable (however, their presence is indicated in the schematic stratigraphic chart and cross section of Figs. 2 and 3, respectively). Furthermore, sulfates similar to those of the Hondo also occur higher in the Devonian section, most notably in the Nisku Formation of the Hondo type well. This discovery, while irrelevant for Grosmont reservoir analysis, is in keeping with findings elsewhere in the Alberta Basin, where evaporites were deposited during deposition of the Nisku Formation, and also in the overlying Blue Ridge Member (e.g., Mossop and Shetsen 1994).

Fig. 14.

—Structural SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Hondo evaporite deposition was recognized at two stratigraphic levels: UGM1 (two thin units) and in a series of thicker beds in the UGM3–UIRE. The platform or ramp margin migrated from east to west over time. See text for further explanation.

Fig. 14.

—Structural SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Hondo evaporite deposition was recognized at two stratigraphic levels: UGM1 (two thin units) and in a series of thicker beds in the UGM3–UIRE. The platform or ramp margin migrated from east to west over time. See text for further explanation.

Fig. 15.

–Stratigraphic SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Timelines can be inferred from the boundaries between individual stratigraphic members. See Figure 14 for further explanation.

Fig. 15.

–Stratigraphic SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Timelines can be inferred from the boundaries between individual stratigraphic members. See Figure 14 for further explanation.

In all dip sections, the Grosmont units thin basinward, and the “shale” content within them increases westward toward the reservoir edge, as shown in gamma logs, suggesting that the depositional environment was a ramp with a rather steadily westward-increasing water depth, as opposed to a platform with a flat top and an abrupt edge or cliff along its current western limit. However, there remains a degree of uncertainty in delineating the extent of the Grosmont units in the west as a result of the lack of good-quality logs in this part of the study area. Thus, for the sake of simplicity and for historical reasons, we shall continue to refer to the Grosmont depositional environment as a platform.

Another interesting finding is the discovery of syndepositional faulting, which happened at least once between deposition of the UGM1 and the UGM3 near the western limit of the reservoir (Figs. 1315: note the “dropping-off” and/or increased thicknesses of strata older than the UGM2 west of the inferred reverse fault marked as “UGM3 ramp margin,” best seen in Fig. 15). Reverse faulting in the area is herein inferred to be a factor in the change of the Grosmont from a platform to a ramp, the latter being established latest during deposition of the UGM3. Supporting evidence for faulting is the presence of saddle dolomite in well 01-09-71-03W5, located laterally correlative to the location of the inferred fault in Section B-Bʹ a few kilometers father south. Saddle dolomite is generally recognized as a high-temperature type of dolomite that often forms from “hot” (greater than 80° C) aqueous fluids (Radke and Mathis 1980, Machel 1987). Thus, it is likely that the saddle dolomite found in well 01-09-71-03W5 formed from fluids that ascended from a fault nearby, albeit most likely relatively late in the diagenetic history. In addition, there are isolated occurrences of sparry calcite cements that may also have formed from hydrothermal fluids. Last but not least, it is well known that the entire region is dissected by an orthogonal fault system (Lyatsky and Pana 2003; Wagner et al. 2010, 2011). Despite all of this circumstantial evidence, the interpretation of faulting is somewhat tenuous, considering the relatively wide well spacing, the vertical exaggeration of the cross sections, and the absence of reliable seismic information.

If correct, syndepositional faulting in this geographic and stratigraphic location also provides a ready explanation for the deposition of Hondo primary sulfates. The area west of the inferred fault would have been slightly raised relative to the east, largely evening out the depositional relief across the region. In combination with the generally falling sea level that is represented by the Grosmont Formation, this likely provided the environmental conditions favorable for evaporite deposition. The inferred fault thus marks the location of the Grosmont “ramp margin” at UGM3 time. Considering further that the LGM, UGM1, UGM2, and UGM3 all appear to be forming a slight “bulge” in the region of the platform or ramp margins, it appears that the fault was reactivated postdepositionally with the opposite sense of throw (down-thrown on the west).

These findings further suggest that the Grosmont platform or ramp margin migrated westward between LGM and UGM3 times. Thus, the platform margin during deposition of the Lower Grosmont was not controlled by faulting, unless there is an unrecognized fault immediately west of and along the Rimbey–Meadowbrook reef trend (basement-controlled faulting has been suspected as the reason for the location and extent of the Rimbey–Meadowbrook reef trend for many decades; e.g., Switzer et al. 1994, Edwards and Brown 1995). The reefs themselves are thereby recognized as the chief factor that provided accommodation as well as restricted water circulation for the deposition of Hondo primary sulfates farther east during LGM times. Well 10-17-19-84W4 contains two narrow intervals with primary sulfates in the LGM, whereas primary sulfates can be inferred from log signatures in well 11-14-81-20W4.

The regional trend of westward progradation had already been recognized by Switzer et al. (1994), who provided contours for a platform margin also for earlier Upper Devonian Duvernay and Majeau Lake times located farther northeast. Switzer et al. (1994) also showed that the western edge of the Grosmont coincides with reduced thickness of the UGM2 and even more so of the UGM3. However, previous studies failed to identify two crucial aspects: the role of syndepositional faulting and the fact that the Grosmont changed over time in depositional character from that of a true platform with a distinct, reef-rimmed margin to that of a ramp.

DEPOSITIONAL ENVIRONMENTS

Based in an integration of core logging, petrography, isotopic geochemistry, and stratigraphic correlations and on limited comparisons with modern examples of evaporitic basins, the Hondo primary sulfates embedded in the UGM3 and LGM are interpreted to have been deposited in subaqueous salinas or lagoons (Warren and Kendall 1985); i.e., either in a series of relatively small salinas or in a large lagoon striking with an orientation of about 15 to 30° NW. Evaporite deposition was possible because depressions had formed near the platform or ramp margin, at least during LGM time and again during UGM3 time. Furthermore, the current distribution of the Hondo primary sulfates is consistent with two depositional scenarios (Fig. 13): in salinas with an average size of two by two or three townships and/or in a “lagoon” that includes these salinas.

In a first scenario, the salinas are represented by the current distribution of Hondo primary sulfates. In a second scenario, the current distribution of the primary sulfates may not correspond to the original distribution at the time of deposition. Evaporite dissolution in one or several phases, ranging from the time of deposition to the present, may have reduced the geometry of the Hondo such that the current distribution represents merely the remnants of originally more extensive layers of evaporites. Supporting this possibility, outside of the inferred “Hondo lagoon” in the UGM3 in the northeastern part of the study area, many cores contain brecciated and bitumen-supported intervals. Such intervals may well represent sulfate removal by postdepositional dissolution. In addition, these intervals appear to be correlatable over tens of kilometers outside of the study area to the north and northeast, where much better core control is available (Dembicki 1994, Barrett and Hopkins 2010). At least some bitumen-supported intervals within the UGM3 are likely dissolved parts of the Hondo, now saturated with bitumen.

Based on strontium, sulfur, oxygen, and carbon isotope data (Borrero 2010), the Hondo brines were of marine parentage, and the sulfates were precipitated from Late Devonian evaporated seawater. Salinities in the Hondo brines appear to have been between mesohaline (one to three times the salinity of seawater) and less than halite saturation (about 10 times the salinity of seawater), providing for the widespread formation of dolomite and calcium sulfate (gypsum and/or anhydrite). Most Hondo primary sulfates likely were deposited subaqueously as gypsum layers. At times the brines must have exceeded halite saturation, as shown by the scattered presence of halite hoppers. Halite that was previously precipitated is now completely dissolved. No evidence of a shoreline was found in the cores described.

The main lithofacies in the Hondo primary sulfates corresponds to laminated anhydrite and dolomudstone, interpreted to have been deposited in quiet waters below wave base within the photic zone.

Intervals at which many fine dolomitic layers are interbedded with comparatively few gypsum–anhydrite layers may have been formed during periods of increased rainfall or during a temporary decrease in salinity. Some distorted and synsedimentary breccias could have been formed during seasonal storms or by an enhanced inflow of normal marine water.

The rate of deposition of the Hondo primary sulfates can be estimated by comparison with modern evaporite environments. Using the rates published in Schreiber and Hsü (1980), deposition of the Hondo primary sulfates might have taken place within periods as short as a few hundreds to a few thousands of years.

MODERN ANALOGS

In terms of scale there are no recent evaporite depositional environments analogous to the Hondo primary evaporites. However, limited comparisons can be made using the southern part of the Arabian (aka Persian) Gulf region and the Great Bahama Bank as end members.

In the southern part of the Arabian (aka Persian) Gulf, the Abu Dhabi region has been recognized as a coastal “sabkha” (e.g., Alsharhan and Kendall 1994, Warren 2006). Sabkha conditions are common in near-equatorial regions that are generally dry but may have short wet seasons. Such terrains may constitute large areas of formation of present and ancient evaporites (Curtis et al. 1963, Evans et al. 1969, Butler et al. 1982, Sonnenfeld 1984, Evans 1995, Steinhoff and Strohmenger 1999). During the Middle to Late Devonian (Givetian–Famennian), Alberta was located close to the equator, and climatic conditions were likely very similar to those in the Middle East today. However, the bulk of the Hondo primary sulfates surely were not formed in sabkha environments, as shown by the various evaporite facies recognized in core and based on their spatial distribution.

On the other hand, the Great Bahama Bank can be considered a viable analog for the Grosmont with regard to scale (Fig. 16). However, no evaporites analogous to those in the Hondo are forming or have formed in the Great Bahama Bank. One reason for the absence of evaporite deposition on the Great Bahama Bank is the absence of a “sill,” or raised platform edge, which could restrict inflow and outflow of seawater sufficiently for evaporation to create mesohaline or haline brines. Other factors likely involved are (1) whether a platform is “isolated” and surrounded by ocean or attached to a landmass and (2) climate.

Fig.16.

—The Great Bahama Bank represents a modern analog, with regard to size, to the Grosmont platform, including the depositional region of the Hondo. Photograph taken from www. maps.google.ca.

Fig.16.

—The Great Bahama Bank represents a modern analog, with regard to size, to the Grosmont platform, including the depositional region of the Hondo. Photograph taken from www. maps.google.ca.

IMPLICATIONS FOR RESERVOIR EVALUATION

The implications of depositional cyclicity, diagenesis, structure, and bitumen properties with regard to the reservoir properties have been discussed in several previous studies (Cutler 1983, Harrison 1987, Luo et al. 1994, Luo and Machel 1995, Dembicki and Machel 1996, Machel et al. 2012, Russel-Houston and Gray 2014) and are not repeated here. The role of the Hondo sulfates has been elusive so far but potentially is crucial with regard to (1) the distribution of the best, most porous, and/or permeable reservoir intervals via dissolution; (2) their ability to serve as a permeability barrier (“seal”) to compartmentalize the reservoir during or after hydrocarbon migration; and (3) their ability to serve as a source of dissolved sulfate for microbial hydrocarbon degradation.

As discussed earlier, the original distribution of the evaporites corresponds to one of two scenarios: salinas with an average size of two by two or three townships (10 by 20 km to 20 by 30 km) and/or in a “lagoon,” which included the areas that currently contain the sulfates. In the second case the evaporites would have served to compartmentalize the reservoir for water and hydrocarbon migration and entrapment soon after deposition, but this would not be the case in the first instance. In addition, compartmentalization would have been facilitated by the “shale breaks.” Thus, on the basis of simple probability, it seems likely that the reservoir was compartmentalized “hydrologically” soon after deposition once both the evaporites and the marls lithified to aquitards.

Currently, however, it appears that both aquitards, and certainly the evaporites (if they ever formed a laterally contiguous layer that would have enveloped all the possible “salinas” shown in Fig. 13), fail to form effective permeability barriers. This is shown by the patchy distribution of the sulfates, by downhole well log signatures, by drillbit drops, and by brecciated core intervals that correspond to evaporites and/or shale breaks in many wells. Clearly, postdepositional dissolution of sulfates and/or calcite (in the marls of the “shale breaks”) created many breaches in the aquitards. Whether this dissolution was karstic (sensu meteoric water infiltration from above), and during which karstification phase it happened (of which there were four of five; Machel et al. 2012), remains speculative. It is possible that at least some evaporite dissolution was facilitated by basin-derived brines, which are known to have escaped to the basin margin for many millions of years (e.g., Grasby and Chen 2006). In addition, it remains to be decided by reservoir engineers whether the breaching of the aquitards is “good” or “bad” in terms of bitumen recovery. This judgment call depends on whether the bitumen is to be liquefied by steam or electrical heating layer by layer or in several layers at the same time, or whether liquefied bitumen from one stratigraphic level is to be extracted from the same or from another stratigraphic level.

In addition, dissolution of sulfates likely was instrumental in forming the now-infamous layers of bitumen-saturated dolomite powder (“dolofudge”), which arguably are the best reservoir facies, in the sense that they consist of nothing but bitumen with dolomite crystals floating therein. Had these layers been sulfate to begin with, hydrocarbon migration must have postdated evaporite dissolution, as it is unthinkable that the sulfates were dissolved after being coated and infiltrated by hydrocarbons. Based on this fact alone it appears likely that significant dissolution, be it karstic (as defined above) or not, created the best reservoir facies and also the cross-formational permeability pathways prior to hydrocarbon migration and emplacement.

On a regional scale, in the eastern part of the Grosmont platform or ramp the Hondo evaporites appear to have been dissolved entirely and replaced by solution-collapse breccias and “dolofudge” intervals. On the other hand, in the western part of the reservoir the areas with bedded primary sulfates may now form effective reservoir seals, but only on the scale of the sizes of the former inferred salinas. Hydrocarbons likely bypassed them wherever the carbonates had sufficient permeability and/or where the marls were breached by faults and/or karstification. Bennet et al. (2012) made similar arguments for the “shale breaks.” Based on biomarker studies of the trapped bitumen, Bennet et al. (2012) could show that karstification had created a network of passageways for bitumen migration sideways and even downwards in parts of the reservoir, yet subsequently the oils underwent biodegradation in the UGM2 and UGM3 as hydrologically isolated compartments in some areas.

Lastly, the Hondo sulfates likely play a role in biodegradation as well. Up until the 1980s to 1990s, unconventional reservoir bitumen was generally thought to be the result of aerobic biodegradation of oil that had migrated as conventional oil (e.g., Hunt 1979, Connan 1984). However, following the pioneering work by Kartsev et al. (1959), it has been shown that bitumens in reservoirs with low concentrations of aqueous sulfate were likely formed via anaerobic biodegradation facilitated predominantly by methanogens (Head et al. 2003, Larter et al. 2003, Aitken et al. 2004). This appears to be true for the Cretaceous oil–tar sands deposits that overlie the Grosmont reservoir as well. Similarly, it is likely that methanogens are or were the major biodegraders in the Grosmont as well, considering the composition of the bitumens (e.g., Zhao and Machel 2011, Bennet et al. 2012) and the fact that there are several shallow biogenic gas (methane) pools on/in the Grosmont platform. However, although recognized in principle (Larter et al. 2006), the potential role of sulfate-reducing microbes has been either ignored or not recognized in the Grosmont.

Sulfate reduction by bacteria (and some other types of microbes) is known to be an anaerobic process that generates hydrogen sulfide gas as the main inorganic reaction product, enriches the reservoir bitumen in sulfur (in form of various organo–sulfur compounds), and forms several common byproducts, notably iron sulfides and elemental sulfur, under certain circumstances (Machel 2001, and references therein). Scattered traces of pyrite and elemental sulfur have been found in Grosmont cores, and it is well known that the reservoir bitumens—both in the Grosmont and in the overlying Cretaceous oil–tar sands—have relatively high sulfur contents on theorder of 4 to 10% (e.g., Strausz and Lown 2003). Elevated sulfur contents in the bitumens of the oil–tar sands have been related to sulfur-rich source kerogens (Mehay et al. 2009, Adams et al. 2010). However, it stands to reason that the bitumen in the Grosmont reservoir contains at least some sulfur that originated as a byproduct of microbial sulfate reduction, considering that this process undoubtedly took place while the Hondo sulfates underwent dissolution, and probably later on as well. The implications of this process for reservoir evaluation are not clear. One may speculate that enhanced sulfur extraction may be required in the updip portions of the reservoir, where the sulfates were dissolved preferentially by meteoric waters, with concomitant sulfur enrichment of the bitumen.

CONCLUSIONS

The Hondo evaporites occur mainly as “primary sulfates” that formed syndepositionally as gypsum or anhydrite, either subaqueously or displacively–replacively near the sediment–water interface and/or the sediment–air interface in the case of supratidal sabkha deposition. “Secondary sulfates” are diagenetically altered sulfates, mostly anhydrite, in which syndepositional features have been partially to completely altered. “Diagenetic anhydrite” refers to anhydrite that was precipitated from diagenetic solution, most commonly in secondary voids or in fractures.

The primary sulfates can be grouped into several lithofacies with distinct characteristics, indicating that Hondo deposition took place under semiarid to arid conditions. A possible modern analog with respect to climatic conditions is the Abu Dhabi coast in the Arabian/Persian Gulf. In terms of the size of the carbonate platform, the Great Bahama Bank provides a recent analog, albeit without evaporite deposition.

The primary sulfates presently occur in a number of relatively small areas of about 10 by 20 km to 20 by 30 km, with thicknesses of a few meters each. If these areas represent the depositional distribution, the Hondo primary evaporites were deposited in a series of small, shallow subaqueous ponds (salinas). Alternatively, the Hondo primary evaporites were deposited in a more extensive lagoon, and their present distribution represents the remnants after postdepositional (mainly karstic) dissolution.

The distribution of the Hondo sulfates is linked to the deposition of the carbonates that make up the bulk of the Grosmont reservoir, which evolved from a platform to a ramp over time. Furthermore, the Grosmont platform–ramp margin migrated from east to west through time. During the deposition of the Lower Grosmont Formation the platform margin was defined by the underlying Leduc reef trend, which facilitated evaporite deposition on the landward side to the east. Several depositional cycles later during deposition of the Upper Grosmont 3 the carbonates formed a ramp with a margin that was defined by syndepositional faulting farther west. At that time evaporite deposition was facilitated by a combination of faulting with minor drops in sea level and the formation of shallow depressions on the ramp.

The findings of this study have several implications for reservoir development. First, it is clear that an evaporitic climate paired with a platform–ramp paleotopography favors the development of a layered carbonate–evaporite system such as the Grosmont. Second, compart-mentalization, which can also be considered as “seal integrity,” depends on both depositional and postdepositional factors. In the case of the Grosmont, both the evaporites and the shale breaks that mark cycle boundaries had and/or have the potential to compartmentalize the reservoir. In the eastern townships the Hondo evaporites appear to be dissolved, which effectively removed them as “seals.” However, the same process created solution-collapse breccias and bitumen-supported intervals of dolomite powder (“dolofudge”), both excellent reservoir facies with very high levels of bitumen saturation.

In the western part of the reservoir the Hondo may form effective reservoir seals on the scale of the sizes of inferred former brine pools. However, it is likely that hydrocarbons bypassed them wherever the carbonates had sufficient permeability and/or where the marls were breached by faults and/or karstification. Third, it remains to be decided by reservoir engineers whether the breaching of the aquitards is “good” or “bad” for bitumen recovery. This judgment call depends on the type of recovery method. There are no satisfactory answers for several additional questions: How can saline-type depositional settings be predicted farther downdip? Can such evaporites and their lateral continuity be predicted from logs or cores? The best hope for mapping out the evaporites and/or their postdepositional alteration products surely is a combination of investigative techniques that involve high-resolution 3D seismic, as demonstrated for the mapping out of various karst phenomena by Russell-Houston and Gray (2014).

ACKNOWLEDGMENTS

This article is based on the MSc thesis of Mary Luz Borrero, completed under the supervision of the senior author at the University of Alberta in 2010. Funding was provided by Shell International (Houston, Texas) and the Natural Sciences and Engineering Council of Canada. Constructive comments on the manuscript by Art Saller, Alan Kendall (who was not always in agreement with our approach or interpretations), Paul Montgomery, and especially Ted Playton improved our article significantly.

REFERENCES

Aitken
CM
,
Jones
DM
,
Larter
SR
.
2004
.
Anaerobic hydrocarbon biodegradation in deep subsurface reservoirs
.
Nature
 
431
:
291
294
.
Alberta Energy Utilities Board (AEUB)
.
2007
.
Alberta’s energy reserves 2006 and supply/demand outlook 2007-216: Report ST98-2007
,
Alberta Energy and Utilities Board
,
Calgary, Alberta
.
218
p.
Alsharhan
AS
,
Kendall
C
.
1994
.
Depositional setting of the Upper Jurassic Hith anhydrite of the Arabian Gulf: An analog to Holocene evaporites of the United Arab Emirates and Lake MacLeod of Western Australia
.
American Association of Petroleum Geologists Bulletin
 
78
:
1075
1096
.
Alvarez
JM
,
Escoba
E
,
Ivory
J
.
2006
.
Bibliographic review of carbonate reservoirs: Alberta Research Council
.
Heavy Oil & Oil Sands Internal Report
.
Alvarez
JM
,
Sawatzki
RP
,
Forster
LM
,
Coates
RM
.
2008
.
Alberta’s bitumen carbonate reservoirs—Moving orward with advanced R&D: World Heavy Oil Congress, Edmonton
,
Canada
. Paper 2008-467,
14
p.
Anderson
RY
,
Dean
W
,
Kirkland
D
,
Snider
HI
.
1971
.
Permian Castile Varved Evaporite Sequence, West Texas and New Mexico
.
Geological Society America Bulletin
 
77
:
241
256
.
Barrett
K
,
Hopkins
J
.
2010
.
Stratiform carbonate breccias of the Grosmont Formation, Alberta
.
AAPG Search and Discovery Article 90108
 .
AAPG International Convention and Exhibition
, September 12–15, 2010;
Calgary, Alberta, Canada
.
Belyea
HR
.
1952
.
Notes on the Devonian System of the north-central plains of Alberta
:
Geological Survey of Canada
.
Ottawa
. Paper 52-27.
Belyea
HR
.
1956
.
Grosmont Formation in the Loon Lake area
.
Journals of Alberta Society of Petroleum Geologists
 
4
:
66
69
.
Bennet
B
,
Marcano
N
,
Larter
S
.
2012
.
Geochemical insights into the oil charging and degradation systematics of the Grosmont bitumen accumulation: AAPG Datapages/Search and Discovery Article 90174
.
GeoConvention 2012 (Vision)
 , May 14–18, 2012;
Calgary, Alberta, Canada
.
Borrero
ML
.
2010
.
Hondo evaporites within the Grosmont heavy oil carbonate platform, Alberta, Canada
[unpublished MSc thesis]:
University of Alberta
,
Edmonton, Canada
, 190 p.
Blakey
R
.
2010
.
Middle Devonian
. In
Paleogeography and Geologic Evolution of North America
 . Retrieved from https://deeptimemaps.com/map-room-individual/.
Butler
GP
,
Kendall
CGStC
,
Harris
PM
.
1982
.
Recent evaporites from the Abu Dhabi coastal flats
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
33
64
.
Carozzi
AV
.
1960
.
Microscopic Sedimentary Petrography
 :
Wiley & Sons
,
New York
.
485
p.
Claypool
E
,
Holser
WT
,
Kaplan
IR
,
Sakai
H
,
Zak
T
.
1980
.
The age curves of sulfur and oxygen isotopes in marine sulfate and their mutual interpretation
.
Chemical Geology
 
28
:
199
260
.
Connan
J
.
1984
.
Biodegradation of crude oils in reservoirs
. In
Brooks
J
,
Welte
D
(Editors).
Advances in Petroleum Geochemistry
 , Vol.
1
:
Academic Press
,
London
. p.
299
335
.
Curtis
R
,
Evans
G
,
Kinsman
D
,
Shearman
D
.
1963
.
Association of dolomite and anhydrite in the recent sediments of the Persian Gulf
.
Nature
 
197
:
679
680
.
Cutler
WG
.
1983
.
Stratigraphy and sedimentology of the Upper Devonian Grosmont Formation, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
31
:
282
325
.
Davies
GR
,
Ludlam
SD
.
1973
.
Origin of laminated and graded sediments, Middle Devonian of western Canada
.
Geological Society of America Bulletin
 
84
:
3527
3546
.
Dawson
FM
,
Kalkreuth
W
.
1994
.
Coal rank and coalbed methane potential of Cretaceous/Tertiary coals in the Canadian Rocky Mountain foothills and adjacent foreland: 1
.
Hinton and Grande Cache areas, Alberta. Bulletin of Canadian Petroleum Geology
 
42
:
544
561
.
Dean
WE
,
Anderson
RY
.
1982
.
Continuous subaqueous deposition of the Permian Castile Evaporites, Delaware Basin, Texas and New Mexico
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
324
353
.
Dembicki
E
.
1994
.
The Upper Devonian Grosmont Formation: Well log evaluation and regional mapping of heavy oil carbonate reservoir in northeastern Alberta
[unpublished MSc thesis]:
University of Alberta
,
Edmonton, Canada
,
221
p.
Dembicki
EA
,
Machel
HG
.
1996
.
Recognition and delineation of paleokarst zones by the use of wireline logs in the bitumen-saturated Upper Devonian Grosmont Formation of northeastern Alberta, Canada
.
American Association of Petroleum Geologists Bulletin
 
80
:
695
712
.
Denison
RE
,
Koepnick
RB
,
Burke
WH
,
Hetherington
EA
,
Fletcher
A
.
1997
.
Construction of the Silurian and Devonian seawater 87Sr/86Sr curve
.
Chemical Geology
 
140
:
109
121
.
Edwards
DJ
,
Brown
RJ
.
1995
.
A geophysical perspective on the question of basement involvement with the distribution of Upper Devonian carbonates in central Alberta
. In
Ross
GM
(Compiler).
Alberta Basement Transects Workshop, Lithoprobe Report 51, Lithoprobe Secretariat
 ,
University of British Columbia
,
Canada
. p.
225
233
.
Energy Resources Conservation Board (ERCB)
.
2010
.
Energy Reserves 2009 and Supply/Demand Outlook 2010-2019
,
Statistical Series, ST98-2010
 .
Calgary
.
Evans
G
.
1995
.
The Arabian Gulf: A modern carbonate–evaporite factory; A review
.
Cuadernaos de Geologia Iberica
 
19
:
61
96
.
Evans
G
,
Schmidt
V
,
Bush
P
,
Nelson
H
.
1969
.
Stratigraphy and geologic history of the sabkha, Abu Dhabi, Persian Gulf
.
Sedimentology
 
12
:
145
159
.
Friedman
GM
.
1973
.
Petrographic data and comments on the depositional environment of the Miocene sulfates and dolomites at Sites 124, 132 and 134, western Mediterranean Sea
. In
Ryan
WBF
,
Hsü
KJ
,
Cita
MB
,
Dumitrica
P
,
Lort
J
,
Maync
W
,
Nesteroff
WD
,
Pautot
G
,
Stradner
H
,
Wezel
FC
(Editors).
Initial Reports of the Deep Sea Drilling Project
 , Vol.
13
, Part 2:
US Government Office
,
Washington, DC
. p.
695
708
.
Grasby
SE
,
Chen
Z
.
2006
.
Subglacial recharge into the Western Canada Sedimentary Basin—Impact of Pleistocene glaciation on basin hydrodynamics
.
Geological Society of America Bulletin
 
117
:
500
514
.
Handford
CR
.
1991
.
Marginal marine halite: Sabkhas and salinas
. In
Melvin
L
(Editor).
Evaporites, Petroleum, and Mineral Resources, Developments in Sedimentology 50
 :
Elsevier
,
Amsterdam
. p.
1
66
.
Hardie
LA
.
1967
.
The gypsum–anhydrite equilibrium at one atmosphere pressure
.
American Mineralogist Journal
 
52
:
172
200
.
Hardie
LA
.
2003
.
Anhydrite and gypsum
. In
Middleton
G
(Editor).
Encyclopedia of Sediments and Sedimentary Rocks
 :
Kluwer Academic Publishers
,
Dordrecht, The Netherlands
. p.
16
18
.
Harrison
R
.
1987
.
Bitumen-bearing Paleozoic carbonate trend of Northern Alberta: Section III. Geologic environments and migration
. In
Meyer
RF
(Editor).
Exploration for Heavy Crude Oil and Natural Bitumen, Studies in Geology 25
 :
American Association of Petroleum Geologists
,
Tulsa, Oklahoma
. p.
319
326
.
Head
IM
,
Jones
DM
,
Larter
SR
.
2003
.
Biological activity in the deep subsurface and the origin of heavy oil
.
Nature
 
426
:
344
352
.
Hein
F
,
Marsh
RA
,
Boddy
M
.
2008
.
Overview of the oil sands and carbonate bitumen of Alberta: Regional Geologic Framework and influence of salt-dissolution effects
.
American Association of Petroleum Geologists Search and Discovery Article 10145
.
Higley
DK
,
Lewan
MD
,
Roberts
LNR
,
Henry
M
.
2009
.
Timing and petroleum sources for the Lower Cretaceous Manville Group oil sands of northern Alberta based on 4-D modeling
.
American Association of Petroleum Geologists Bulletin
93
:
203
230
.
Huebscher
H
.
1996
.
Regional controls on stratigraphic and diagenetic evolution of Woodbend Group carbonates, North-central Alberta, Canada
[unpublished PhD thesis]:
University of Alberta
,
Edmonton, Canada
,
231
p.
Huebscher
H
,
Machel
HG
.
2004
.
Reflux and burial dolomitization in the Upper Devonian Woodbend Group of orth-central Alberta, Canada: Extended Abstract
,
Dolomite Conference, CSPG
,
Calgary, Canada
.
Jones
GD
,
Smart
PL
,
Whitaker
FF
,
Rostron
BJ
,
Machel
HG
.
2003
.
Numerical modeling of reflux dolomitization in the Grosmont platform complex (Upper Devonian), Western Canada Sedimentary Basin
.
American Association of Petroleum Geologists Bulletin
 
87
:
1273
1298
.
Jones
RMP
.
1980
.
Basinal isostatic adjustment faults and their petroleum significance
.
Bulletin of Canadian Petroleum Geology
 
28
:
211
251
.
Kartsev
AA
,
Tabasaranskii
ZA
,
Subbota
MI
,
Mogilevski
GA
.
1959
.
Geochemical methods of prospecting and exploration for petroleum and natural gas
. In
Witherspoon
PA
,
Romey
WD
(Editors).
English Translation
 .
University of California Press
,
Berkeley, California
.
349
p.
Larter
SR
,
Huang
H
,
Adams
J
,
Bennett
B
,
Jokanola
O
,
Olldenburg
T
,
Jones
M
,
Head
I
,
Riediger
C
,
Fowler
M
.
2006
.
The controls on the composition of biodegraded oils in the deep subsurface: Part II—Geological controls on subsurface biodegradation fluxes and constraints on reservoir-fluid property prediction
.
American Association of Petroleum Geologists Bulletin
 
90
:
921
938
.
Larter
S
,
Wilhelms
A
,
Head
I
,
Koopmans
M
,
Aplin
A
,
Di Primio
R
,
Zwach
C
,
Erdmann
M
,
Telnaes
N
.
2003
.
The controls on the composition of biodegraded oils in the deep subsurfacepart 1: biodegradation rates in petroleum reservoirs
.
Organic Geochemistry
 
34
:
601
613
.
Loucks
RG
,
Longman
MW
.
1982
.
Lower Cretaceous Ferry Lake anhydrite, Fairway Field, east Texas, product of shallow-subtidal deposition
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
130
173
.
Luo
P
,
Machel
HG
.
1995
.
Pore size and pore throat types in a heterogeneous dolostone reservoir, Devonian Grosmont Formation, Western Canada Sedimentary Basin
.
American Association of Petroleum Geologists Bulletin
 
79
:
1698
1720
.
Luo
P
,
Machel
HG
,
Shaw
J
.
1994
.
Petrophysical properties of matrix blocks of a heterogeneous dolostone reservoir—The Upper Devonian Grosmont Formation, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
42
:
465
481
.
Lyatsky
H
,
Pana
D
.
2003
.
Catalogue of selected regional gravity and magnetic maps of Northern Alberta: The Alberta Energy and Utilities Board/Alberta Geological Survey (EUB/AGS)
.
Edmonton
, Report 56.
40
p.
Lyatsky
HV
,
Pana
DI
,
Grobe
M
.
2005
.
Basement structure in central and southern Alberta: Insights from gravity and magnetic maps
.
The Alberta Energy and Utilities Board/Alberta Geological Survey (EUB/AGS)
 .
Edmonton, Report
72
,
83
p.
Machel
HG
.
1985
.
Facies and diagenesis of the Upper Devonian Nisku Formation in the subsurface of central Alberta
. [unpublished Ph.D. Thesis],
McGill University
,
Montreal
,
392
p.
Machel
HG
.
1987
.
Saddle dolomite as a by-product of chemical compaction and thermochemical sulfate reduction
.
Geology
 
15
:
936
940
.
Machel
HG
.
2001
.
Bacterial and thermochemical sulfate reduction in diagenetic settings
.
Sedimentary Geology
 
140
:
143
175
.
Machel
HG
.
2010
.
The Devonian petroleum system of the Western Canada Sedimentary Basin—With implications for heavy-oil reservoir geology
. In
Chopra
S
,
Lines
LR
,
Schmitt
DR
,
Batzle
ML
(Editors).
Heavy Oils: Reservoir Characterization and Production Monitoring, Geophysical Developments 13
 :
SEG Society of Exploration Geophysicists
,
Tulsa, Oklahoma
. p.
131
154
.
Machel
HG
.
2013
.
Secondary anhydrites in deeply buried Devonian carbonates of the Alberta Basin, Canada
.
Carbonates and Evaporites
 
28
(
3
):
267
280
.
Machel
HG
,
Borrero
ML
,
Dembicki
E
,
Huebscher
E
,
Luo
P
,
Zhao
Y
.
2012
.
The Grosmont: The world’s largest unconventional oil reservoir hosted in carbonate rocks
. In
Garland
J
,
Neilson
JE
,
Laubach
SE
,
Whidden
KJ
(Editors).
Advances in Carbonate Exploration and Reservoir Analysis, Special Publication 370
 :
Geological Society
,
London
. p.
49
82
.
Machel
HG
,
Huebscher
H
.
2000
.
The Devonian Grosmont heavy oil reservoir in Alberta, Canada
.
Zentralblatt für Geologie und Paläontologie, Teil I, Heft
 
1/2
:
55
84
.
Machel
HG
,
Hunter
I
.
1994
.
Facies models for Middle to Late Devonian shallow marine carbonates with comparisons to modern reefs—A guide for facies analysis
.
Facies
 
30
:
155
176
.
MacNeil
A
.
2015
.
Dolomite diagenesis and the origin of “Dolofudge”—An intriguing reservoir facies
.
15th Bathurst Meeting, July 13–16, 2015
;
University of Edinburgh, UK Technical Program with Abstracts
, p.
80
.
MacNeil
AJ
,
Russel-Houston
J
,
Gray
KA
.
2013
.
Recognizing potential in the bitumen saturated dolostones of the Upper Devonian Nsiku Formation through comparison with the Grosmont Formation
.
GeoConvention 2013: Integration
 ,
7
pages. http://cseg.ca/assets/files/resources/abstracts/2013/core/052_GC2013_Recognizing_Potential_in_Bitumen_Saturated_Dolostones.pdf
Maiklem
W
,
Bedout
D
,
Glaister
R
.
1969
.
Classification of anhydrite: A practical approach
.
Bulletin of Canadian Petroleum Geology
 
17
:
194
233
.
Mehay
S
,
Adam
P
,
Kowalewski
I
,
Albrecht
P
.
2009
.
Evaluating the sulfur isotopic composition of biodegraded petroleum: The case of the Western Canada Sedimentary Basin
.
Organic Geochemistry
 
40
:
531
545
.
Mossop
G
,
Shearman
D
.
1973
.
Origins of secondary gypsum rock
.
Institute of Mining and Metallurgy Transactions Section B
 
82
:
147
154
.
Mossop
G
,
Shetsen
I
(Compilers).
1994
.
Geological Atlas of the Western Canada Sedimentary Basin
 :
Canadian Society of Petroleum Geologists and Alberta Research Council
.
504
p.
Murray
RC
.
1964
.
Origin and diagenesis of gypsum and anhydrite
.
Journal of Sedimentary Petrology
 
34
:
512
523
.
Poros
Z
,
Machel
HG
,
Mindszenty
A
,
Molnar
F
.
2013
.
Cryogenic powderization of Triassic dolostones in the Buda Hills, Hungary
.
International Journal of Earth Sciences
 
102
:
1513
1539
.
Radke
BM
,
Mathis
RL
.
1980
.
On the formation and occurrence of saddle dolomite
.
Journal of Sedimentary Petrology
 
50
:
1149
1168
.
Rouchy
J
,
Monty
P
,
Bernet-Rollande
M
,
Maurin
A
,
Perthuisot
J
.
1985
.
Genese de Corps Carbonatés Diagénétiques par Réduction de Sulfates dans le Miocène Evaporitique du Golfe de Suez et de la Mer Rouge
:
C.R. Academic Science
,
Paris
. p.
1193
1198
.
Russell-Houston
J
,
Gray
K
.
2014
.
Paleokarst in the Grosmont Formation and reservoir implications, Saleski, Alberta, Canada
.
Interpretation
 
2
(
3
):
SF29
SF50
.
Sarg
JF
.
1977
.
Sedimentology of the carbonate-evaporite facies transition of the Seven Rivers Formation (Guadalupian, Permian) in southeast New Mexico
. In
Hileman
ME
,
Mazzullo
SJ
(Editors).
Upper Guadalupian Facies, Permian Reef Complex, Guadalupe Mountains, New Mexico and West Texas, Publication 77-16
 :
SEPM Permian Basin Section
,
Midland, Texas
. P.
451
478
.
Sarg
JF
.
1989
.
Stratigraphy and sedimentology of the back-reef upper Queen–lower Seven Rivers strata, Goat-Seep-Capitan reef complexes (Middle–Late Guadalupian, Permian), southeast New Mexico
. In
Harris
PM
,
Grover
GA
(Editors).
Subsurface and Outcrop Examination of the Capitan Shelf Margin, Northern Delaware Basin, Core Workshop Notes 13: SEPM (Society for Sedimentary Geology)
 ,
Tulsa, Oklahoma
. p.
347
352
.
Schreiber
BC
.
1978
.
Environments of subaqueous gypsum deposition
. In
Dean
W
,
Schreiber
BC
(Editors).
Marine Evaporites, Short Course Notes 4
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
43
73
.
Schreiber
BC
,
Hsü
KJ
.
1980
.
Evaporites
, Vol.
2
,
Developments in Petroleum Geology
 :
Applied Science
,
London UK
. p.
87
138
.
Schreiber
BC
,
Kinsman
D
.
1975
.
New observations in the Pleistocene evaporites of Montallegro, Sicily and a modern analog
.
Journal of Sedimentary Petrology
 
45
:
469
479
.
Schreiber
BC
,
El Tabakh
M
.
2000
.
Deposition and early alteration of evaporates
.
Sedimentology
 
47
:
215
238
.
Selby
D
,
Creaser
RA
.
2005
.
Direct radiometric dating of hydrocarbon deposits using Rhenium–Osmium isotopes
.
Science
 
308
:
1293
1295
.
Shearman
DJ
.
1963
.
Recent anhydrite, gypsum, dolomite, and halite from the coastal flats in the Arabian shore of the Persian Gulf
.
Proceedings of the Geological Society of London
1607
:
63
65
.
Shearman
DJ
.
1971
.
Marine evaporites: The calcium sulfate facies
 :
Alberta Society Petroleum Geology Seminar
,
University Calgary
,
65
p.
Shearman
DJ
.
1978
.
Evaporites of coastal sabkhas
. In
Dean
WE
,
Schreiber
BC
(Editors).
Marine Evaporites, Short Course Notes 4
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
6
42
.
Shearman
DJ
.
1985
.
Syndepositional and late diagenetic alteration of primary gypsum to anhydrite
. In
Schreiber
BC
(Editor).
Sixth International Symposium on Salt. Salt Institute
,
Alexandria, Virginia
. p.
41
50
.
Sonnenfeld
P
.
1984
.
Brines and Evaporites
 :
Academic Press
,
New York
.
631
p.
Steinhoff
I
,
Strohmenger
C
.
1999
.
Facies differentiation and sequence stratigraphy in ancient evaporite basins—An example from the basal Zechstein (Upper Permian of Germany)
.
Carbonates and Evaporites
 
14
:
146
181
.
Stoakes
FA
,
Creaney
S
.
1984
.
Sedimentology of a carbonate source rock: The Duvernay Formation of Central Alberta
. In
Eliuk
L
(Editor).
Carbonates in Subsurface and Outcrop
 :
Canadian Society Petroleum Geology Core Conference 1984
,
Calgary, Alberta
. p.
132
147
.
Strausz
OP
,
Lown
EM
.
2003
.
The Chemistry of Alberta Oil Sands Bitumens and Heavy Oils
 :
The Alberta Energy Research Institute
,
Calgary, Canada
.
695
p.
Switzer
S
,
Holland
W
,
Christie
D
,
Graf
G
,
Hedinger
A
,
McCauley
R
,
Wierzbicki
R
,
Packard
J
.
1994
.
Devonian Woodbend–Winterburn strata of the Western Canada Sedimentary Basin
. In
Mossop
G
,
Shetsen
I
(Editors).
Geologic Atlas of the Western Canada Sedimentary Basin
 :
Canadian Society of Petroleum Geologists and Alberta Research Council
,
Calgary, Alberta
. p.
165
195
.
Theriault
F
.
1988
.
Lithofacies, diagenesis, and related reservoir properties of the Upper Devonian Grosmont Formation, northern Alberta
.
Bulletin of Canadian Petroleum Geology
 
36
:
52
69
.
Veizer
J
,
Ala
D
,
Azmy
K
,
Bruckshen
P
,
Buhl
D
,
Strauss
H
.
1999
.
87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater
.
Chemical Geology
 
161
:
59
88
.
Wagner
P
,
Nelson
R
,
Lonnee
J
,
Costello
M
,
Whale
R
,
McKinzie
W
,
Jennings
J
,
Balzarini
M
,
Reed
D
,
Al Bahry
A
,
Watson
R
.
2010
.
Fracture Characterization of a Giant Unconventional Carbonate Reservoir, Alberta, Canada
.
Abstract, AAPG Conference
,
Calgary
.
Wagner
P
,
Nelson
R
,
Lonnee
J
,
Costello
M
,
Whale
R
,
McKinzie
W
,
Jennings
J
,
Balzarini
M
,
Reed
D
,
Al Bahry
A
,
Watson
R
,
Ortega
O
.
2011
.
Natural fracture characterization of a giant unconventional carbonate reservoir, Grosmont Venture, Alberta, Canada: Implications for recovery
.
14th Bathurst Meeting Abstracts, International Conference of Carbonate Sedimentologists
,
Bristol, UK
.
Warren
JK
.
2006
.
Evaporites; Sediments, Resources and Hydrocarbons
 :
Springer
,
Berlin
.
1035
p.
Warren
JK
,
Kendall
C
.
1985
.
Comparison of sequences formed in marine sabkha (subaerial) and salina (subaqueous) settings—Modern and ancient
.
American Association of Petroleum Geologists Bulletin
 
69
:
1013
1023
.
Zhao
Y
.
2009
.
Petrophysical Properties of Bitumen from the Upper Devonian Grosmont Reservoir, Alberta, Canada
. [Unpublished M.Sc. Thesis],
University of Alberta
,
189
p.
Zhao
Y
,
Machel
HG
.
2011
.
Biodegradation characteristics of bitumen from the Upper Devonian Grosmont Reservoir, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
59
(
2
):
112
130
.
Zhao
Y
,
Machel
HG
.
2012
.
Viscosity and other rheological properties from the Upper Devonian Grosmont reservoir, Alberta, Canada
.
American Association of Petroleum Geologists Bulletin
 
96
(
1
):
133
153
.

Figures & Tables

Fig. 1.

—Simplified subsurface map showing the outlines of Upper Devonian Woodbend carbonate platforms and reefs in Alberta. At this scale, the various outlines are only approximate. The Hondo study was conducted in the trapezoid area. Cross section A-Aʹ is shown schematically in Figure 3. The Grosmont platform was delineated seismically except along its eastern limit, which is erosional against the Canadian Shield. LDB = Limit of the Disturbed Belt.

Fig. 1.

—Simplified subsurface map showing the outlines of Upper Devonian Woodbend carbonate platforms and reefs in Alberta. At this scale, the various outlines are only approximate. The Hondo study was conducted in the trapezoid area. Cross section A-Aʹ is shown schematically in Figure 3. The Grosmont platform was delineated seismically except along its eastern limit, which is erosional against the Canadian Shield. LDB = Limit of the Disturbed Belt.

Fig. 2.

—Schematic stratigraphy in the study area. Not to scale.

Fig. 2.

—Schematic stratigraphy in the study area. Not to scale.

Fig. 3.

—Schematic structural SW–NW cross section across the study area, as identified in Figure 1. Vertical exaggeration roughly 1:100. Relative thicknesses are not to scale.

Fig. 3.

—Schematic structural SW–NW cross section across the study area, as identified in Figure 1. Vertical exaggeration roughly 1:100. Relative thicknesses are not to scale.

Fig. 4.

—Lithofacies in an idealized shallowing-upward cycle of the Grosmont platform. A) Subtidal skeletal grainstone facies; B–D) shallow(er) shelf facies; E) intertidal algal/cyanobacterial mat facies; F) primary anhydrite–dolomite brine pond/salina facies (this sample represents various subaqueous lithofacies types, further illustrated in Fig. 5); G) supratidal mud facies with mold and reaction halo from dissolution of anhydrite nodule; and H) supratidal mud facies with mold of deformed halite hopper crystal.

Fig. 4.

—Lithofacies in an idealized shallowing-upward cycle of the Grosmont platform. A) Subtidal skeletal grainstone facies; B–D) shallow(er) shelf facies; E) intertidal algal/cyanobacterial mat facies; F) primary anhydrite–dolomite brine pond/salina facies (this sample represents various subaqueous lithofacies types, further illustrated in Fig. 5); G) supratidal mud facies with mold and reaction halo from dissolution of anhydrite nodule; and H) supratidal mud facies with mold of deformed halite hopper crystal.

Fig. 5.

—Summary of the most important evaporite lithofacies types of the Hondo. The rock type shown in Figure 4F can occur in either Lithofacies B or Lithofacies C, as defined herein.

Fig. 5.

—Summary of the most important evaporite lithofacies types of the Hondo. The rock type shown in Figure 4F can occur in either Lithofacies B or Lithofacies C, as defined herein.

Fig. 6.

—Spontaneous potential and short normal (SN) logs of the Hondo type well Imperial Smith 15-17-71-24W4 from about 820 to 1050 m, also showing stratigraphic boundaries and a core photograph representing one of the thickest evaporite intervals within the UGM3. The well contains two cored intervals within the depth interval shown here, both containing Hondo evaporites, with the upper one straddling the UGM3–UIRE boundary. The well contains several more cored intervals above and below the depth interval shown here. The stratigraphic boundaries in the uncored intervals are based on electric logs, cuttings, and/or correlation to neighboring wells. See Figure 2 and text for stratigraphic nomenclature.

Fig. 6.

—Spontaneous potential and short normal (SN) logs of the Hondo type well Imperial Smith 15-17-71-24W4 from about 820 to 1050 m, also showing stratigraphic boundaries and a core photograph representing one of the thickest evaporite intervals within the UGM3. The well contains two cored intervals within the depth interval shown here, both containing Hondo evaporites, with the upper one straddling the UGM3–UIRE boundary. The well contains several more cored intervals above and below the depth interval shown here. The stratigraphic boundaries in the uncored intervals are based on electric logs, cuttings, and/or correlation to neighboring wells. See Figure 2 and text for stratigraphic nomenclature.

Fig. 7.

—Carbonate–evaporite depositional model representing the Grosmont–Hondo system (modified from Fig. 3 in Machel and Hunter [1994]). The letter designations “Ib” through “If” refer to the carbonate facies identified by these authors, as follows: Zone Ib: fenestral laminites; Zone IIb: sparsely fossiliferous packstones and wackestones; Zone IIIb: Amphipora floatstones and grainstones; Zone IVb: Stachyodes rudstones, bafflestones, and floatstones; Zone V: stromatoporoid framestones and bindstones; Zone IV/V: stromatoporoid–coral bindstones and rudstones; Zone IVf: Stachyodes–coral–stromatoporoid bafflestones and rudstones; Zone IIIf: crinoid–stromatoporoid floatstones and rudstones; Zone IIf: crinoid–stromatoporoid floatstones, grainstones, and packstones; and Zone If: poorly fossiliferous wackestones and mudstones. These facies are roughly equivalent to the facies depicted in Figure 4 of this study during relatively high sea levels, here labeled “Carbonate sea level.” Numbers 4A–F, 5, and 6 refer to the photos shown in the figures with the same numbers from this article. Evaporite deposition took place during lower sea levels and/or when the ramp fell dry, here labeled “Evaporite level high” and “Evaporite level low,” respectively. The depression on the ramp is the site of a salina or brine pond on a sabkha where subaqueous evaporites would have formed. Displacive as well as replacive evaporites would have formed in the sediments immediately below the sediment–water or sediment–air interface.

Fig. 7.

—Carbonate–evaporite depositional model representing the Grosmont–Hondo system (modified from Fig. 3 in Machel and Hunter [1994]). The letter designations “Ib” through “If” refer to the carbonate facies identified by these authors, as follows: Zone Ib: fenestral laminites; Zone IIb: sparsely fossiliferous packstones and wackestones; Zone IIIb: Amphipora floatstones and grainstones; Zone IVb: Stachyodes rudstones, bafflestones, and floatstones; Zone V: stromatoporoid framestones and bindstones; Zone IV/V: stromatoporoid–coral bindstones and rudstones; Zone IVf: Stachyodes–coral–stromatoporoid bafflestones and rudstones; Zone IIIf: crinoid–stromatoporoid floatstones and rudstones; Zone IIf: crinoid–stromatoporoid floatstones, grainstones, and packstones; and Zone If: poorly fossiliferous wackestones and mudstones. These facies are roughly equivalent to the facies depicted in Figure 4 of this study during relatively high sea levels, here labeled “Carbonate sea level.” Numbers 4A–F, 5, and 6 refer to the photos shown in the figures with the same numbers from this article. Evaporite deposition took place during lower sea levels and/or when the ramp fell dry, here labeled “Evaporite level high” and “Evaporite level low,” respectively. The depression on the ramp is the site of a salina or brine pond on a sabkha where subaqueous evaporites would have formed. Displacive as well as replacive evaporites would have formed in the sediments immediately below the sediment–water or sediment–air interface.

Fig. 8.

—Images of powdered dolomite (A–C) and breccias (D–F). A) Core interval with dolomite powder held together by bitumen. Bags contain white dolomite powder after bitumen extraction with organic solvent. B) Dolomite powder. C) Thin section, transmitted light: dolomite crystals floating in bedded anhydrite. This kind of rock is a possible, if not the most likely, precursor of dolomite powder in the Grosmont reservoir. The sample is from Nisku anhydrites in southeastern Alberta (Machel 1985). No such rocks or textures were found in the Grosmont reservoir. D–F) Fractured and brecciated core intervals due to evaporite dissolution. Samples are from well 7-29-84-18W4M, UGM2, 356.0 m, with the exception of C, which is from the overlying Nisku Formation from well 14-9-35-20W4, 1622.5 m.

Fig. 8.

—Images of powdered dolomite (A–C) and breccias (D–F). A) Core interval with dolomite powder held together by bitumen. Bags contain white dolomite powder after bitumen extraction with organic solvent. B) Dolomite powder. C) Thin section, transmitted light: dolomite crystals floating in bedded anhydrite. This kind of rock is a possible, if not the most likely, precursor of dolomite powder in the Grosmont reservoir. The sample is from Nisku anhydrites in southeastern Alberta (Machel 1985). No such rocks or textures were found in the Grosmont reservoir. D–F) Fractured and brecciated core intervals due to evaporite dissolution. Samples are from well 7-29-84-18W4M, UGM2, 356.0 m, with the exception of C, which is from the overlying Nisku Formation from well 14-9-35-20W4, 1622.5 m.

Fig. 9.

—Thin-section photomicrographs of secondary anhydrites, A and C) Plane polarized light; B and D) crossed polarized light. Both samples contain corrotopic anhydrite, in which corroded porphyrotopes of anhydrite are embedded in a finer-crystalline anhydrite matrix. These textures are indicative of original deposition as gypsum with subsequent transformation to anhydrite during dewatering and recrystallization during increasing burial. Well 02-30-79-04W5, 1066.5 m; UGM3.

Fig. 9.

—Thin-section photomicrographs of secondary anhydrites, A and C) Plane polarized light; B and D) crossed polarized light. Both samples contain corrotopic anhydrite, in which corroded porphyrotopes of anhydrite are embedded in a finer-crystalline anhydrite matrix. These textures are indicative of original deposition as gypsum with subsequent transformation to anhydrite during dewatering and recrystallization during increasing burial. Well 02-30-79-04W5, 1066.5 m; UGM3.

Fig. 10.

—Secondary anhydrite filling fractures or replacing limestone and/or dolostone matrix. A) Well 16-13-89-23W4, 329.5 m, UGM3. B) Well 15-17-71-25W4, 908.0 m, UGM3–Hondo interval. Coin for scale (diameter 1.85 cm).

Fig. 10.

—Secondary anhydrite filling fractures or replacing limestone and/or dolostone matrix. A) Well 16-13-89-23W4, 329.5 m, UGM3. B) Well 15-17-71-25W4, 908.0 m, UGM3–Hondo interval. Coin for scale (diameter 1.85 cm).

Fig. 11.

–Secondary gypsum. A) Core sample of gypsum nodule in dolomudstone, well 10-18-76-25W4, 1062.10 m, UGM3. B) Replacive gypsum rosettes in mosaic anhydrite formed during uplift and partial rehydration; well 10-17-84-19W4, 501.00 m, LGM.

Fig. 11.

–Secondary gypsum. A) Core sample of gypsum nodule in dolomudstone, well 10-18-76-25W4, 1062.10 m, UGM3. B) Replacive gypsum rosettes in mosaic anhydrite formed during uplift and partial rehydration; well 10-17-84-19W4, 501.00 m, LGM.

Fig. 12.

—Structure contour map of the top of the Upper Ireton.

Fig. 12.

—Structure contour map of the top of the Upper Ireton.

Fig. 13.

—Map of the Hondo area with well control. Cross section B-Bʹ – Figures 14 + 15. Note westward-migrating platform edge. See text for further explanation.

Fig. 13.

—Map of the Hondo area with well control. Cross section B-Bʹ – Figures 14 + 15. Note westward-migrating platform edge. See text for further explanation.

Fig. 14.

—Structural SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Hondo evaporite deposition was recognized at two stratigraphic levels: UGM1 (two thin units) and in a series of thicker beds in the UGM3–UIRE. The platform or ramp margin migrated from east to west over time. See text for further explanation.

Fig. 14.

—Structural SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Hondo evaporite deposition was recognized at two stratigraphic levels: UGM1 (two thin units) and in a series of thicker beds in the UGM3–UIRE. The platform or ramp margin migrated from east to west over time. See text for further explanation.

Fig. 15.

–Stratigraphic SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Timelines can be inferred from the boundaries between individual stratigraphic members. See Figure 14 for further explanation.

Fig. 15.

–Stratigraphic SW–NE cross section (see Fig. 13 for location) about midway through the Hondo area. Timelines can be inferred from the boundaries between individual stratigraphic members. See Figure 14 for further explanation.

Fig.16.

—The Great Bahama Bank represents a modern analog, with regard to size, to the Grosmont platform, including the depositional region of the Hondo. Photograph taken from www. maps.google.ca.

Fig.16.

—The Great Bahama Bank represents a modern analog, with regard to size, to the Grosmont platform, including the depositional region of the Hondo. Photograph taken from www. maps.google.ca.

Table 1.

—Locations, depth intervals, and formations of the wells investigated for this study.

Well ID Core Depth (m) Formation 
02-29-68-01W5 1127.7-1139.05 UIRE -UGM3 
02/15-23-68-01W5 1096.0-1127.0 UGM3, UGM2? 
08-28-69-04W5 1305.0-1337.0 Nisku-UIRE 
01-12-69-01W5 964.80-1043.0 UIRE-Nisku 
05-25-69-20W5 626.0-738.24 UGM3, UGM2, UGM1 
04-15-69-24W4 1005.8-1019.6 L1RE-LGM 
03-28-70-24W4 740.7-751.9 854.7-868.4 Nisku, UGM3, UGM2 
11-35-70-25W4 893.1-901.1 Nisku-UIRE 
02-23-70-01W5 879.3-880.9 Nisku 
06-03-70-02W5 1215.0-1253.7 UGM3 
01-09-70-03W5 1155.4-1161.5 GM3 
15-17-71-25W4 888.5-918.21012.0-1047.9 UIRE UGM3. LGM 
10-01-71-26W4 928.1-932.4 UGM3 
05-09-72-01W4 881.5-1026.0 Nisku, UGM3, UGM2 
10-35-73-04W5 1012.9-1121.7 Nisku-UGM2 
10-18-76-25W4 1043.7-1066.8 UGM3 
06-10-77-25W4 1052.5-1057.4 LGM 
02-30-79-04W5 1065.0-1076.7 UGM3 
11-34-80-03W5 831.2-976.6 UGM3, UGM2 
11-14-81-20W4 380.0-389.0449.0-455.0 UGM3, UGM1 
16-24-81-20W4 430.0-433.1 Grosmont 
06-24-83-18W4 295.7-300.8 UIRE 
10-17-83-18W4 370.3-460.5 UGM3-LGM 
10-09-83-19W4 371.0-438.4 UGM2, UGM1, LGM 
13-22-83-22W4 555.0-584.3 UGM3, UGM2 
08-05-83-25W4 416.0-419.0 Nisku 
13-24-84-02W5 856.0-860.0 UGM1 
10-17-84-19W4 371.5-521.0 Grosmont 
06-34-85-19W4 322.0-406.5 UIRE?, UGM3, UGM2 
08-16-87-01W5 652.0-900.0 Calmar to UGM2 
10-14-88-02W5 672.8-725.5 Nisku - UIRE 
06-11-89-25W4 529.0-585.5624.0-638.0 UGM2, UGM1, LGM, 
Well ID Core Depth (m) Formation 
02-29-68-01W5 1127.7-1139.05 UIRE -UGM3 
02/15-23-68-01W5 1096.0-1127.0 UGM3, UGM2? 
08-28-69-04W5 1305.0-1337.0 Nisku-UIRE 
01-12-69-01W5 964.80-1043.0 UIRE-Nisku 
05-25-69-20W5 626.0-738.24 UGM3, UGM2, UGM1 
04-15-69-24W4 1005.8-1019.6 L1RE-LGM 
03-28-70-24W4 740.7-751.9 854.7-868.4 Nisku, UGM3, UGM2 
11-35-70-25W4 893.1-901.1 Nisku-UIRE 
02-23-70-01W5 879.3-880.9 Nisku 
06-03-70-02W5 1215.0-1253.7 UGM3 
01-09-70-03W5 1155.4-1161.5 GM3 
15-17-71-25W4 888.5-918.21012.0-1047.9 UIRE UGM3. LGM 
10-01-71-26W4 928.1-932.4 UGM3 
05-09-72-01W4 881.5-1026.0 Nisku, UGM3, UGM2 
10-35-73-04W5 1012.9-1121.7 Nisku-UGM2 
10-18-76-25W4 1043.7-1066.8 UGM3 
06-10-77-25W4 1052.5-1057.4 LGM 
02-30-79-04W5 1065.0-1076.7 UGM3 
11-34-80-03W5 831.2-976.6 UGM3, UGM2 
11-14-81-20W4 380.0-389.0449.0-455.0 UGM3, UGM1 
16-24-81-20W4 430.0-433.1 Grosmont 
06-24-83-18W4 295.7-300.8 UIRE 
10-17-83-18W4 370.3-460.5 UGM3-LGM 
10-09-83-19W4 371.0-438.4 UGM2, UGM1, LGM 
13-22-83-22W4 555.0-584.3 UGM3, UGM2 
08-05-83-25W4 416.0-419.0 Nisku 
13-24-84-02W5 856.0-860.0 UGM1 
10-17-84-19W4 371.5-521.0 Grosmont 
06-34-85-19W4 322.0-406.5 UIRE?, UGM3, UGM2 
08-16-87-01W5 652.0-900.0 Calmar to UGM2 
10-14-88-02W5 672.8-725.5 Nisku - UIRE 
06-11-89-25W4 529.0-585.5624.0-638.0 UGM2, UGM1, LGM, 

Contents

Society for Sedimentary Geology

NEWADVANCES IN DEVONIAN CARBONATES: OUTCROP ANALOGS, RESERVOIRS AND CHRONOSTRATIGRAPHY

Ted E. Playton
Ted E. Playton
Tengizchevroil, Atyrau 060011, Kazakhstan
Search for other works by this author on:
Charles Kerans
Charles Kerans
Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
Search for other works by this author on:
John A.W. Weissenberger
John A.W. Weissenberger
ATW Associates, Calgary, Alberta, T3E 7M8, Canada
Search for other works by this author on:
Society for Sedimentary Geology
Volume
107
ISBN electronic:
9781565763456
Publication date:
January 01, 2017

GeoRef

References

REFERENCES

Aitken
CM
,
Jones
DM
,
Larter
SR
.
2004
.
Anaerobic hydrocarbon biodegradation in deep subsurface reservoirs
.
Nature
 
431
:
291
294
.
Alberta Energy Utilities Board (AEUB)
.
2007
.
Alberta’s energy reserves 2006 and supply/demand outlook 2007-216: Report ST98-2007
,
Alberta Energy and Utilities Board
,
Calgary, Alberta
.
218
p.
Alsharhan
AS
,
Kendall
C
.
1994
.
Depositional setting of the Upper Jurassic Hith anhydrite of the Arabian Gulf: An analog to Holocene evaporites of the United Arab Emirates and Lake MacLeod of Western Australia
.
American Association of Petroleum Geologists Bulletin
 
78
:
1075
1096
.
Alvarez
JM
,
Escoba
E
,
Ivory
J
.
2006
.
Bibliographic review of carbonate reservoirs: Alberta Research Council
.
Heavy Oil & Oil Sands Internal Report
.
Alvarez
JM
,
Sawatzki
RP
,
Forster
LM
,
Coates
RM
.
2008
.
Alberta’s bitumen carbonate reservoirs—Moving orward with advanced R&D: World Heavy Oil Congress, Edmonton
,
Canada
. Paper 2008-467,
14
p.
Anderson
RY
,
Dean
W
,
Kirkland
D
,
Snider
HI
.
1971
.
Permian Castile Varved Evaporite Sequence, West Texas and New Mexico
.
Geological Society America Bulletin
 
77
:
241
256
.
Barrett
K
,
Hopkins
J
.
2010
.
Stratiform carbonate breccias of the Grosmont Formation, Alberta
.
AAPG Search and Discovery Article 90108
 .
AAPG International Convention and Exhibition
, September 12–15, 2010;
Calgary, Alberta, Canada
.
Belyea
HR
.
1952
.
Notes on the Devonian System of the north-central plains of Alberta
:
Geological Survey of Canada
.
Ottawa
. Paper 52-27.
Belyea
HR
.
1956
.
Grosmont Formation in the Loon Lake area
.
Journals of Alberta Society of Petroleum Geologists
 
4
:
66
69
.
Bennet
B
,
Marcano
N
,
Larter
S
.
2012
.
Geochemical insights into the oil charging and degradation systematics of the Grosmont bitumen accumulation: AAPG Datapages/Search and Discovery Article 90174
.
GeoConvention 2012 (Vision)
 , May 14–18, 2012;
Calgary, Alberta, Canada
.
Borrero
ML
.
2010
.
Hondo evaporites within the Grosmont heavy oil carbonate platform, Alberta, Canada
[unpublished MSc thesis]:
University of Alberta
,
Edmonton, Canada
, 190 p.
Blakey
R
.
2010
.
Middle Devonian
. In
Paleogeography and Geologic Evolution of North America
 . Retrieved from https://deeptimemaps.com/map-room-individual/.
Butler
GP
,
Kendall
CGStC
,
Harris
PM
.
1982
.
Recent evaporites from the Abu Dhabi coastal flats
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
33
64
.
Carozzi
AV
.
1960
.
Microscopic Sedimentary Petrography
 :
Wiley & Sons
,
New York
.
485
p.
Claypool
E
,
Holser
WT
,
Kaplan
IR
,
Sakai
H
,
Zak
T
.
1980
.
The age curves of sulfur and oxygen isotopes in marine sulfate and their mutual interpretation
.
Chemical Geology
 
28
:
199
260
.
Connan
J
.
1984
.
Biodegradation of crude oils in reservoirs
. In
Brooks
J
,
Welte
D
(Editors).
Advances in Petroleum Geochemistry
 , Vol.
1
:
Academic Press
,
London
. p.
299
335
.
Curtis
R
,
Evans
G
,
Kinsman
D
,
Shearman
D
.
1963
.
Association of dolomite and anhydrite in the recent sediments of the Persian Gulf
.
Nature
 
197
:
679
680
.
Cutler
WG
.
1983
.
Stratigraphy and sedimentology of the Upper Devonian Grosmont Formation, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
31
:
282
325
.
Davies
GR
,
Ludlam
SD
.
1973
.
Origin of laminated and graded sediments, Middle Devonian of western Canada
.
Geological Society of America Bulletin
 
84
:
3527
3546
.
Dawson
FM
,
Kalkreuth
W
.
1994
.
Coal rank and coalbed methane potential of Cretaceous/Tertiary coals in the Canadian Rocky Mountain foothills and adjacent foreland: 1
.
Hinton and Grande Cache areas, Alberta. Bulletin of Canadian Petroleum Geology
 
42
:
544
561
.
Dean
WE
,
Anderson
RY
.
1982
.
Continuous subaqueous deposition of the Permian Castile Evaporites, Delaware Basin, Texas and New Mexico
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
324
353
.
Dembicki
E
.
1994
.
The Upper Devonian Grosmont Formation: Well log evaluation and regional mapping of heavy oil carbonate reservoir in northeastern Alberta
[unpublished MSc thesis]:
University of Alberta
,
Edmonton, Canada
,
221
p.
Dembicki
EA
,
Machel
HG
.
1996
.
Recognition and delineation of paleokarst zones by the use of wireline logs in the bitumen-saturated Upper Devonian Grosmont Formation of northeastern Alberta, Canada
.
American Association of Petroleum Geologists Bulletin
 
80
:
695
712
.
Denison
RE
,
Koepnick
RB
,
Burke
WH
,
Hetherington
EA
,
Fletcher
A
.
1997
.
Construction of the Silurian and Devonian seawater 87Sr/86Sr curve
.
Chemical Geology
 
140
:
109
121
.
Edwards
DJ
,
Brown
RJ
.
1995
.
A geophysical perspective on the question of basement involvement with the distribution of Upper Devonian carbonates in central Alberta
. In
Ross
GM
(Compiler).
Alberta Basement Transects Workshop, Lithoprobe Report 51, Lithoprobe Secretariat
 ,
University of British Columbia
,
Canada
. p.
225
233
.
Energy Resources Conservation Board (ERCB)
.
2010
.
Energy Reserves 2009 and Supply/Demand Outlook 2010-2019
,
Statistical Series, ST98-2010
 .
Calgary
.
Evans
G
.
1995
.
The Arabian Gulf: A modern carbonate–evaporite factory; A review
.
Cuadernaos de Geologia Iberica
 
19
:
61
96
.
Evans
G
,
Schmidt
V
,
Bush
P
,
Nelson
H
.
1969
.
Stratigraphy and geologic history of the sabkha, Abu Dhabi, Persian Gulf
.
Sedimentology
 
12
:
145
159
.
Friedman
GM
.
1973
.
Petrographic data and comments on the depositional environment of the Miocene sulfates and dolomites at Sites 124, 132 and 134, western Mediterranean Sea
. In
Ryan
WBF
,
Hsü
KJ
,
Cita
MB
,
Dumitrica
P
,
Lort
J
,
Maync
W
,
Nesteroff
WD
,
Pautot
G
,
Stradner
H
,
Wezel
FC
(Editors).
Initial Reports of the Deep Sea Drilling Project
 , Vol.
13
, Part 2:
US Government Office
,
Washington, DC
. p.
695
708
.
Grasby
SE
,
Chen
Z
.
2006
.
Subglacial recharge into the Western Canada Sedimentary Basin—Impact of Pleistocene glaciation on basin hydrodynamics
.
Geological Society of America Bulletin
 
117
:
500
514
.
Handford
CR
.
1991
.
Marginal marine halite: Sabkhas and salinas
. In
Melvin
L
(Editor).
Evaporites, Petroleum, and Mineral Resources, Developments in Sedimentology 50
 :
Elsevier
,
Amsterdam
. p.
1
66
.
Hardie
LA
.
1967
.
The gypsum–anhydrite equilibrium at one atmosphere pressure
.
American Mineralogist Journal
 
52
:
172
200
.
Hardie
LA
.
2003
.
Anhydrite and gypsum
. In
Middleton
G
(Editor).
Encyclopedia of Sediments and Sedimentary Rocks
 :
Kluwer Academic Publishers
,
Dordrecht, The Netherlands
. p.
16
18
.
Harrison
R
.
1987
.
Bitumen-bearing Paleozoic carbonate trend of Northern Alberta: Section III. Geologic environments and migration
. In
Meyer
RF
(Editor).
Exploration for Heavy Crude Oil and Natural Bitumen, Studies in Geology 25
 :
American Association of Petroleum Geologists
,
Tulsa, Oklahoma
. p.
319
326
.
Head
IM
,
Jones
DM
,
Larter
SR
.
2003
.
Biological activity in the deep subsurface and the origin of heavy oil
.
Nature
 
426
:
344
352
.
Hein
F
,
Marsh
RA
,
Boddy
M
.
2008
.
Overview of the oil sands and carbonate bitumen of Alberta: Regional Geologic Framework and influence of salt-dissolution effects
.
American Association of Petroleum Geologists Search and Discovery Article 10145
.
Higley
DK
,
Lewan
MD
,
Roberts
LNR
,
Henry
M
.
2009
.
Timing and petroleum sources for the Lower Cretaceous Manville Group oil sands of northern Alberta based on 4-D modeling
.
American Association of Petroleum Geologists Bulletin
93
:
203
230
.
Huebscher
H
.
1996
.
Regional controls on stratigraphic and diagenetic evolution of Woodbend Group carbonates, North-central Alberta, Canada
[unpublished PhD thesis]:
University of Alberta
,
Edmonton, Canada
,
231
p.
Huebscher
H
,
Machel
HG
.
2004
.
Reflux and burial dolomitization in the Upper Devonian Woodbend Group of orth-central Alberta, Canada: Extended Abstract
,
Dolomite Conference, CSPG
,
Calgary, Canada
.
Jones
GD
,
Smart
PL
,
Whitaker
FF
,
Rostron
BJ
,
Machel
HG
.
2003
.
Numerical modeling of reflux dolomitization in the Grosmont platform complex (Upper Devonian), Western Canada Sedimentary Basin
.
American Association of Petroleum Geologists Bulletin
 
87
:
1273
1298
.
Jones
RMP
.
1980
.
Basinal isostatic adjustment faults and their petroleum significance
.
Bulletin of Canadian Petroleum Geology
 
28
:
211
251
.
Kartsev
AA
,
Tabasaranskii
ZA
,
Subbota
MI
,
Mogilevski
GA
.
1959
.
Geochemical methods of prospecting and exploration for petroleum and natural gas
. In
Witherspoon
PA
,
Romey
WD
(Editors).
English Translation
 .
University of California Press
,
Berkeley, California
.
349
p.
Larter
SR
,
Huang
H
,
Adams
J
,
Bennett
B
,
Jokanola
O
,
Olldenburg
T
,
Jones
M
,
Head
I
,
Riediger
C
,
Fowler
M
.
2006
.
The controls on the composition of biodegraded oils in the deep subsurface: Part II—Geological controls on subsurface biodegradation fluxes and constraints on reservoir-fluid property prediction
.
American Association of Petroleum Geologists Bulletin
 
90
:
921
938
.
Larter
S
,
Wilhelms
A
,
Head
I
,
Koopmans
M
,
Aplin
A
,
Di Primio
R
,
Zwach
C
,
Erdmann
M
,
Telnaes
N
.
2003
.
The controls on the composition of biodegraded oils in the deep subsurfacepart 1: biodegradation rates in petroleum reservoirs
.
Organic Geochemistry
 
34
:
601
613
.
Loucks
RG
,
Longman
MW
.
1982
.
Lower Cretaceous Ferry Lake anhydrite, Fairway Field, east Texas, product of shallow-subtidal deposition
. In
Handford
GR
,
Loucks
RG
,
Davies
GR
(Editors).
Depositional and Diagenetic Spectra of Evaporites, Core Workshop Notes 3
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
130
173
.
Luo
P
,
Machel
HG
.
1995
.
Pore size and pore throat types in a heterogeneous dolostone reservoir, Devonian Grosmont Formation, Western Canada Sedimentary Basin
.
American Association of Petroleum Geologists Bulletin
 
79
:
1698
1720
.
Luo
P
,
Machel
HG
,
Shaw
J
.
1994
.
Petrophysical properties of matrix blocks of a heterogeneous dolostone reservoir—The Upper Devonian Grosmont Formation, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
42
:
465
481
.
Lyatsky
H
,
Pana
D
.
2003
.
Catalogue of selected regional gravity and magnetic maps of Northern Alberta: The Alberta Energy and Utilities Board/Alberta Geological Survey (EUB/AGS)
.
Edmonton
, Report 56.
40
p.
Lyatsky
HV
,
Pana
DI
,
Grobe
M
.
2005
.
Basement structure in central and southern Alberta: Insights from gravity and magnetic maps
.
The Alberta Energy and Utilities Board/Alberta Geological Survey (EUB/AGS)
 .
Edmonton, Report
72
,
83
p.
Machel
HG
.
1985
.
Facies and diagenesis of the Upper Devonian Nisku Formation in the subsurface of central Alberta
. [unpublished Ph.D. Thesis],
McGill University
,
Montreal
,
392
p.
Machel
HG
.
1987
.
Saddle dolomite as a by-product of chemical compaction and thermochemical sulfate reduction
.
Geology
 
15
:
936
940
.
Machel
HG
.
2001
.
Bacterial and thermochemical sulfate reduction in diagenetic settings
.
Sedimentary Geology
 
140
:
143
175
.
Machel
HG
.
2010
.
The Devonian petroleum system of the Western Canada Sedimentary Basin—With implications for heavy-oil reservoir geology
. In
Chopra
S
,
Lines
LR
,
Schmitt
DR
,
Batzle
ML
(Editors).
Heavy Oils: Reservoir Characterization and Production Monitoring, Geophysical Developments 13
 :
SEG Society of Exploration Geophysicists
,
Tulsa, Oklahoma
. p.
131
154
.
Machel
HG
.
2013
.
Secondary anhydrites in deeply buried Devonian carbonates of the Alberta Basin, Canada
.
Carbonates and Evaporites
 
28
(
3
):
267
280
.
Machel
HG
,
Borrero
ML
,
Dembicki
E
,
Huebscher
E
,
Luo
P
,
Zhao
Y
.
2012
.
The Grosmont: The world’s largest unconventional oil reservoir hosted in carbonate rocks
. In
Garland
J
,
Neilson
JE
,
Laubach
SE
,
Whidden
KJ
(Editors).
Advances in Carbonate Exploration and Reservoir Analysis, Special Publication 370
 :
Geological Society
,
London
. p.
49
82
.
Machel
HG
,
Huebscher
H
.
2000
.
The Devonian Grosmont heavy oil reservoir in Alberta, Canada
.
Zentralblatt für Geologie und Paläontologie, Teil I, Heft
 
1/2
:
55
84
.
Machel
HG
,
Hunter
I
.
1994
.
Facies models for Middle to Late Devonian shallow marine carbonates with comparisons to modern reefs—A guide for facies analysis
.
Facies
 
30
:
155
176
.
MacNeil
A
.
2015
.
Dolomite diagenesis and the origin of “Dolofudge”—An intriguing reservoir facies
.
15th Bathurst Meeting, July 13–16, 2015
;
University of Edinburgh, UK Technical Program with Abstracts
, p.
80
.
MacNeil
AJ
,
Russel-Houston
J
,
Gray
KA
.
2013
.
Recognizing potential in the bitumen saturated dolostones of the Upper Devonian Nsiku Formation through comparison with the Grosmont Formation
.
GeoConvention 2013: Integration
 ,
7
pages. http://cseg.ca/assets/files/resources/abstracts/2013/core/052_GC2013_Recognizing_Potential_in_Bitumen_Saturated_Dolostones.pdf
Maiklem
W
,
Bedout
D
,
Glaister
R
.
1969
.
Classification of anhydrite: A practical approach
.
Bulletin of Canadian Petroleum Geology
 
17
:
194
233
.
Mehay
S
,
Adam
P
,
Kowalewski
I
,
Albrecht
P
.
2009
.
Evaluating the sulfur isotopic composition of biodegraded petroleum: The case of the Western Canada Sedimentary Basin
.
Organic Geochemistry
 
40
:
531
545
.
Mossop
G
,
Shearman
D
.
1973
.
Origins of secondary gypsum rock
.
Institute of Mining and Metallurgy Transactions Section B
 
82
:
147
154
.
Mossop
G
,
Shetsen
I
(Compilers).
1994
.
Geological Atlas of the Western Canada Sedimentary Basin
 :
Canadian Society of Petroleum Geologists and Alberta Research Council
.
504
p.
Murray
RC
.
1964
.
Origin and diagenesis of gypsum and anhydrite
.
Journal of Sedimentary Petrology
 
34
:
512
523
.
Poros
Z
,
Machel
HG
,
Mindszenty
A
,
Molnar
F
.
2013
.
Cryogenic powderization of Triassic dolostones in the Buda Hills, Hungary
.
International Journal of Earth Sciences
 
102
:
1513
1539
.
Radke
BM
,
Mathis
RL
.
1980
.
On the formation and occurrence of saddle dolomite
.
Journal of Sedimentary Petrology
 
50
:
1149
1168
.
Rouchy
J
,
Monty
P
,
Bernet-Rollande
M
,
Maurin
A
,
Perthuisot
J
.
1985
.
Genese de Corps Carbonatés Diagénétiques par Réduction de Sulfates dans le Miocène Evaporitique du Golfe de Suez et de la Mer Rouge
:
C.R. Academic Science
,
Paris
. p.
1193
1198
.
Russell-Houston
J
,
Gray
K
.
2014
.
Paleokarst in the Grosmont Formation and reservoir implications, Saleski, Alberta, Canada
.
Interpretation
 
2
(
3
):
SF29
SF50
.
Sarg
JF
.
1977
.
Sedimentology of the carbonate-evaporite facies transition of the Seven Rivers Formation (Guadalupian, Permian) in southeast New Mexico
. In
Hileman
ME
,
Mazzullo
SJ
(Editors).
Upper Guadalupian Facies, Permian Reef Complex, Guadalupe Mountains, New Mexico and West Texas, Publication 77-16
 :
SEPM Permian Basin Section
,
Midland, Texas
. P.
451
478
.
Sarg
JF
.
1989
.
Stratigraphy and sedimentology of the back-reef upper Queen–lower Seven Rivers strata, Goat-Seep-Capitan reef complexes (Middle–Late Guadalupian, Permian), southeast New Mexico
. In
Harris
PM
,
Grover
GA
(Editors).
Subsurface and Outcrop Examination of the Capitan Shelf Margin, Northern Delaware Basin, Core Workshop Notes 13: SEPM (Society for Sedimentary Geology)
 ,
Tulsa, Oklahoma
. p.
347
352
.
Schreiber
BC
.
1978
.
Environments of subaqueous gypsum deposition
. In
Dean
W
,
Schreiber
BC
(Editors).
Marine Evaporites, Short Course Notes 4
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
43
73
.
Schreiber
BC
,
Hsü
KJ
.
1980
.
Evaporites
, Vol.
2
,
Developments in Petroleum Geology
 :
Applied Science
,
London UK
. p.
87
138
.
Schreiber
BC
,
Kinsman
D
.
1975
.
New observations in the Pleistocene evaporites of Montallegro, Sicily and a modern analog
.
Journal of Sedimentary Petrology
 
45
:
469
479
.
Schreiber
BC
,
El Tabakh
M
.
2000
.
Deposition and early alteration of evaporates
.
Sedimentology
 
47
:
215
238
.
Selby
D
,
Creaser
RA
.
2005
.
Direct radiometric dating of hydrocarbon deposits using Rhenium–Osmium isotopes
.
Science
 
308
:
1293
1295
.
Shearman
DJ
.
1963
.
Recent anhydrite, gypsum, dolomite, and halite from the coastal flats in the Arabian shore of the Persian Gulf
.
Proceedings of the Geological Society of London
1607
:
63
65
.
Shearman
DJ
.
1971
.
Marine evaporites: The calcium sulfate facies
 :
Alberta Society Petroleum Geology Seminar
,
University Calgary
,
65
p.
Shearman
DJ
.
1978
.
Evaporites of coastal sabkhas
. In
Dean
WE
,
Schreiber
BC
(Editors).
Marine Evaporites, Short Course Notes 4
 :
SEPM (Society for Sedimentary Geology)
,
Tulsa, Oklahoma
. p.
6
42
.
Shearman
DJ
.
1985
.
Syndepositional and late diagenetic alteration of primary gypsum to anhydrite
. In
Schreiber
BC
(Editor).
Sixth International Symposium on Salt. Salt Institute
,
Alexandria, Virginia
. p.
41
50
.
Sonnenfeld
P
.
1984
.
Brines and Evaporites
 :
Academic Press
,
New York
.
631
p.
Steinhoff
I
,
Strohmenger
C
.
1999
.
Facies differentiation and sequence stratigraphy in ancient evaporite basins—An example from the basal Zechstein (Upper Permian of Germany)
.
Carbonates and Evaporites
 
14
:
146
181
.
Stoakes
FA
,
Creaney
S
.
1984
.
Sedimentology of a carbonate source rock: The Duvernay Formation of Central Alberta
. In
Eliuk
L
(Editor).
Carbonates in Subsurface and Outcrop
 :
Canadian Society Petroleum Geology Core Conference 1984
,
Calgary, Alberta
. p.
132
147
.
Strausz
OP
,
Lown
EM
.
2003
.
The Chemistry of Alberta Oil Sands Bitumens and Heavy Oils
 :
The Alberta Energy Research Institute
,
Calgary, Canada
.
695
p.
Switzer
S
,
Holland
W
,
Christie
D
,
Graf
G
,
Hedinger
A
,
McCauley
R
,
Wierzbicki
R
,
Packard
J
.
1994
.
Devonian Woodbend–Winterburn strata of the Western Canada Sedimentary Basin
. In
Mossop
G
,
Shetsen
I
(Editors).
Geologic Atlas of the Western Canada Sedimentary Basin
 :
Canadian Society of Petroleum Geologists and Alberta Research Council
,
Calgary, Alberta
. p.
165
195
.
Theriault
F
.
1988
.
Lithofacies, diagenesis, and related reservoir properties of the Upper Devonian Grosmont Formation, northern Alberta
.
Bulletin of Canadian Petroleum Geology
 
36
:
52
69
.
Veizer
J
,
Ala
D
,
Azmy
K
,
Bruckshen
P
,
Buhl
D
,
Strauss
H
.
1999
.
87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater
.
Chemical Geology
 
161
:
59
88
.
Wagner
P
,
Nelson
R
,
Lonnee
J
,
Costello
M
,
Whale
R
,
McKinzie
W
,
Jennings
J
,
Balzarini
M
,
Reed
D
,
Al Bahry
A
,
Watson
R
.
2010
.
Fracture Characterization of a Giant Unconventional Carbonate Reservoir, Alberta, Canada
.
Abstract, AAPG Conference
,
Calgary
.
Wagner
P
,
Nelson
R
,
Lonnee
J
,
Costello
M
,
Whale
R
,
McKinzie
W
,
Jennings
J
,
Balzarini
M
,
Reed
D
,
Al Bahry
A
,
Watson
R
,
Ortega
O
.
2011
.
Natural fracture characterization of a giant unconventional carbonate reservoir, Grosmont Venture, Alberta, Canada: Implications for recovery
.
14th Bathurst Meeting Abstracts, International Conference of Carbonate Sedimentologists
,
Bristol, UK
.
Warren
JK
.
2006
.
Evaporites; Sediments, Resources and Hydrocarbons
 :
Springer
,
Berlin
.
1035
p.
Warren
JK
,
Kendall
C
.
1985
.
Comparison of sequences formed in marine sabkha (subaerial) and salina (subaqueous) settings—Modern and ancient
.
American Association of Petroleum Geologists Bulletin
 
69
:
1013
1023
.
Zhao
Y
.
2009
.
Petrophysical Properties of Bitumen from the Upper Devonian Grosmont Reservoir, Alberta, Canada
. [Unpublished M.Sc. Thesis],
University of Alberta
,
189
p.
Zhao
Y
,
Machel
HG
.
2011
.
Biodegradation characteristics of bitumen from the Upper Devonian Grosmont Reservoir, Alberta, Canada
.
Bulletin of Canadian Petroleum Geology
 
59
(
2
):
112
130
.
Zhao
Y
,
Machel
HG
.
2012
.
Viscosity and other rheological properties from the Upper Devonian Grosmont reservoir, Alberta, Canada
.
American Association of Petroleum Geologists Bulletin
 
96
(
1
):
133
153
.

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