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Abstract

The giant Pinedale gas field in the Green River Basin of Wyoming produces from up to 6000 ft (1800 m) of the Upper Cretaceous fluvial sandstones of the Lance Formation, the Upper Mesaverde Group, and the Paleocene Wagon Wheel Formation. The Wagon Wheel Formation is approximately 1300 ft (400 m) thick and differs in character from the underlying Lance and Mesaverde Formations in having conglomerates and significant feldspathic components. This lithologic change has previously been attributed to the unroofing of the crystalline core of the Wind River Mountains. The distinct lithology and mineralogy causes different log and rock property relationships than those seen in the Lance and Mesaverde.

A recent core in the Wagon Wheel Formation has allowed modern core analysis techniques to be applied, increasing our understanding of the reservoir characteristics for this interval. Porosity and permeability are higher in sandstones and conglomerates of the Wagon Wheel Formation as compared to the sandstones of the Lance Formation. Upper and lower intervals within the Wagon Wheel Formation have distinct lithologies and are separated by an unconformity. A distinct gamma-ray log shift, the “gamma-ray marker,” is present at the unconformity and is caused by an increase in potassium and thorium related to increases in feldspar and chlorite above the unconformity. The lower interval contains both lithic sandstones similar to the Lance and also feldspathic conglomerates. The upper interval contains feldspathic coarse sandstones and conglomerates but is dominated by greenish-gray debrites containing poorly sorted mixtures of chlorite-rich clay, sand, and pebbles. The upper interval is water bearing, whereas the lower interval contains and can produce gas, albeit with higher water saturation than that found in the Lance Formation.

Introduction

The Tertiary Wagon Wheel Formation immediately above the Lance Formation has been named by Law and Spencer (see Chapter 3) and was previously called the Tertiary unnamed unit (Law and Johnson, 1989). This chapter describes detailed evaluation of the Wagon Wheel Formation at Pinedale field in terms of seismic and log character, core lithology, and facies. We also characterize the influence of lithology and facies on log response and routine petrophysical properties and provide interpretations of the stratigraphic details impacting the overall geologic and depositional setting.

We suggest lower and upper intervals of the Wagon Wheel Formation are distinguishable based on core, log, and seismic data. Lower and upper intervals within the Wagon Wheel Formation have distinct lithologies and are also separated by an unconformity.

Previous Work

The location and geologic setting for the Pinedale field have been described by Law and Johnson (1989) and Meyer et al. (see Chapter 4). Law and Johnson (1989) defined the “unnamed” Tertiary interval in the Wagon Wheel well at Pinedale, based on its distinctive, arkosic lithology occurring above the Cretaceous/Tertiary (“K/T”) boundary interpreted from palynological evidence. Law and Spencer (see Chapter 3) have dubbed this previously unnamed interval the “Wagon Wheel Formation.” It is present only in the subsurface in the northern Green River Basin and is especially distinctive in the Pinedale field area.

Prensky (1989) documented the gamma-ray well log anomaly associated with this interval in the northern Green River Basin, especially in wells in and around Pinedale field. The interval above this gamma-ray marker has higher gamma-ray values whereas the interval below has lower values. Pollastro (1989) described some of the unique characteristics of the Wagon Wheel interval from a petrographic point of view, including the arkosic nature of the sandstones and conglomerates, some unusual clay mineralogy, for example mixed-layer smectite/chlorite, and the presence of glaucophane zeolite in some samples. This interval was interpreted by the above authors to represent the uplift and exposure of the granitic core of the Wind River range, eroding the feldspathic plutonic and metamorphic basement rocks that were incorporated as clasts into the Wagon Wheel Formation.

Dubois et al. (2004) and Hanson et al. (2004) described the nature of the Fort Union to Upper Lance transition, including the unnamed Tertiary interval, with respect to well log and seismic markers in the Jonah field. The Fort Union Formation in Jonah contains thicker, quartzose sandstones and coals in the Fort Union Formation compared to the Pinedale area.

Chapin et al. (see Chapter 6) described in detail the sedimentology and reservoir characteristics of the Lance and Mesaverde Formations at Pinedale. A similar approach will be applied here to the particular aspects of the Wagon Wheel Formation.

Dataset

The overall core dataset available to Shell was described by Chapin et al. (see Chapter 6). There are fewer wells having Wagon Wheel Formation cores (Table 1), including one recent core obtained by Shell from the Riverside 12c-3D well (NW SE Section 3, T31N, R108W, Sublette County, Wyoming), and several older cores available at the USGS core facility in Denver (Figure 1, Table 1). We have used core analyses from the recent Shell well. Older cores were obtained before modern tight gas analysis techniques and were used for facies description only. We will also show selected lines and images from the CGG-Veritas 3-D seismic survey covering part of the Pinedale anticline.

Figure 1.

Base map of the central and southern parts of the Pinedale anticline showing wells referenced in this paper. Structure contours are on the gamma-ray marker with a 200 ft (61 m) contour interval. Major reverse faults are indicated by heavy black lines with teeth on upthrown side. Thin red lines indicate minor faults. Cored wells are indicated by red circles. Seismic line in Figure 3 is noted by the dashed line. Abbreviations for the wells are explained in Table 1.

Figure 1.

Base map of the central and southern parts of the Pinedale anticline showing wells referenced in this paper. Structure contours are on the gamma-ray marker with a 200 ft (61 m) contour interval. Major reverse faults are indicated by heavy black lines with teeth on upthrown side. Thin red lines indicate minor faults. Cored wells are indicated by red circles. Seismic line in Figure 3 is noted by the dashed line. Abbreviations for the wells are explained in Table 1.

List of wells noted in text or shown in figures. Bold underlined wells have cores.

Table 1.
List of wells noted in text or shown in figures. Bold underlined wells have cores.
AbbreviationWellLocation
Rv12c-3dShell Riverside 12c-3DSec 3, T31N, R109W
NF 4El Paso New Fork 4Sec 35, T31N, R109W
EP-WW#1El Paso Wagon Wheel 1Sec 5, T30N, R108W
Wb 7d-6Shell Warbonnet 7d-6Sec 6, T30N, R108W
Wb 3-3Ultra Resources Warbonnet 3-3Sec 3, T30N, R108W
NF 2American Hunter New Fork 2Sec 2, T30N, R108W
NF 1American Hunter New Fork 1Sec 25, T30N, R108W
AbbreviationWellLocation
Rv12c-3dShell Riverside 12c-3DSec 3, T31N, R109W
NF 4El Paso New Fork 4Sec 35, T31N, R109W
EP-WW#1El Paso Wagon Wheel 1Sec 5, T30N, R108W
Wb 7d-6Shell Warbonnet 7d-6Sec 6, T30N, R108W
Wb 3-3Ultra Resources Warbonnet 3-3Sec 3, T30N, R108W
NF 2American Hunter New Fork 2Sec 2, T30N, R108W
NF 1American Hunter New Fork 1Sec 25, T30N, R108W

Character of the Wagon Wheel Formation in Logs and Seismic Data

A log cross section through the Wagon Wheel well illustrates key characteristics of the Wagon Wheel Formation and also shows the core coverage available (Figure 2). In the Wagon Wheel well, the top of the formation was described by Law and Spencer (see Chapter 3) at 6215 ft (1894 m) and the base at 7520 ft (2292 m; arrows in Figure 2). The distinctive gamma-ray shift occurs 265 ft (80 m) above the T/K boundary. One hundred feet (30 m) below Law and Spencer’s top of the Wagon Wheel Formation is a distinctive, low-resistivity interval, approximately 150 ft (46 m) thick, that can be correlated across much of the Pinedale field area.

Figure 2.

Well logs and core coverage (red bars) in the Wagon Wheel Formation The gamma-ray curve is shaded yellow where <75 API, and deep resistivity is shaded red where >16 Ω-m. Yellow arrows indicate the top and base of the Wagon Wheel Formation as defined by Law and Spencer (see Chapter 3). The Upper WW marker label indicates a low-resistivity well log and seismic marker near the top of the Wagon Wheel Formation that can be picked over much of the Pinedale anticline (see also Figure 3). The blue line indicates the base of the Fort Union and the top of the Wagon Wheel Formation. The red line indicates the gamma-ray marker and represents the top of the Lance pool for development purposes. The black dashed line represents the estimated Cretaceous–Tertiary boundary. The gold line labeled (UL5) is Shell’s top Lance pick, as defined via correlations consistent with the base of arkosic sediments.

Figure 2.

Well logs and core coverage (red bars) in the Wagon Wheel Formation The gamma-ray curve is shaded yellow where <75 API, and deep resistivity is shaded red where >16 Ω-m. Yellow arrows indicate the top and base of the Wagon Wheel Formation as defined by Law and Spencer (see Chapter 3). The Upper WW marker label indicates a low-resistivity well log and seismic marker near the top of the Wagon Wheel Formation that can be picked over much of the Pinedale anticline (see also Figure 3). The blue line indicates the base of the Fort Union and the top of the Wagon Wheel Formation. The red line indicates the gamma-ray marker and represents the top of the Lance pool for development purposes. The black dashed line represents the estimated Cretaceous–Tertiary boundary. The gold line labeled (UL5) is Shell’s top Lance pick, as defined via correlations consistent with the base of arkosic sediments.

A seismic cross section through the Wagon Wheel well illustrates some key features of the Wagon Wheel Formation stratigraphic relationships (Figure 3). The low-resistivity interval noted above is seen as a distinctive seismic reflector. The gamma-ray marker can also be seen to correspond to a good seismic marker and seismic unconformity, having an eastward-thickening wedge base-lapping upon it.

Figure 3.

Depth-converted seismic line through the Wagon Wheel well and three offset wells showing the nature of the Wagon Wheel Formation Line location is shown in Figure 1. Seismic data are displayed in depth (ft TVDSS); horizontal and vertical scales are in feet. The white arrow indicates the position of the Cretaceous–Tertiary boundary as documented by Law and Spencer (see Chapter 3) at 7535 ft MD, or −433 ft TVDSS. The yellow arrow indicates the top of the Wagon Wheel Formation as defined by Law and Spencer (see Chapter 3) in the Wagon Wheel well at 6220 ft MD (1896 m); it corresponds to a well-defined seismic and well log marker throughout much of the Pinedale anticline (green line). The gamma-ray marker (light blue line) corresponds to a strong reflector, and an apparent unconformity, with strata wedging both above and below it. Seismic data courtesy of CGG-Veritas.

Figure 3.

Depth-converted seismic line through the Wagon Wheel well and three offset wells showing the nature of the Wagon Wheel Formation Line location is shown in Figure 1. Seismic data are displayed in depth (ft TVDSS); horizontal and vertical scales are in feet. The white arrow indicates the position of the Cretaceous–Tertiary boundary as documented by Law and Spencer (see Chapter 3) at 7535 ft MD, or −433 ft TVDSS. The yellow arrow indicates the top of the Wagon Wheel Formation as defined by Law and Spencer (see Chapter 3) in the Wagon Wheel well at 6220 ft MD (1896 m); it corresponds to a well-defined seismic and well log marker throughout much of the Pinedale anticline (green line). The gamma-ray marker (light blue line) corresponds to a strong reflector, and an apparent unconformity, with strata wedging both above and below it. Seismic data courtesy of CGG-Veritas.

These relationships suggest a relatively complex sequence of events occurring within this thin interval. In this chapter we will call the interval below the gamma-ray marker (and unconformity) and above the T/K boundary the lower Wagon Wheel interval and the interval above the gamma-ray marker the upper Wagon Wheel interval. Next we will look in detail at aspects of log and core data to understand how lithology, mineralogy, and facies are represented in the different parts of the Wagon Wheel Formation and will show the lithologies above and below to be distinctive.

Character of the Wagon Wheel Formation in Core

Cores of the Wagon Wheel Formation are important to calibrate lithology interpretation from logs. Because some of the sandstones and conglomerates are arkosic and have high gamma-ray counts, they can be mistaken for shales if only the gamma-ray log is observed. Other logs are more diagnostic for differentiating facies.

The general descriptive methodology we used has been described by Chapin et al. (see Chapter 6, Figure 5 for an explanation of core codes).

Key Lithologies and Sedimentary Features

A continuous, 90-ft (27 m) core from the Riverside 12c-3D well provides the basis for much of the following discussion. Core photos of the section are displayed in Figure 4. Most of the lithology types and sedimentary structures in the fine sandstones and mudrocks are very similar to those described for the Lance Formation by Chapin et al. (see Chapter 6). The difference is in a population of arkosic conglomerates and coarse sandstones, which are unlike anything in the Lance and Upper Mesaverde intervals (e.g., Figure 4A, interval 7216.5 to 7233 ft [2200 to 2204 m]).

Figure 4.

Core slab photos of Riverside 12c-3D core from lower Wagon Wheel interval. A) Section from 7196 to 7241 ft (2193 to 2207 m). B) Section from 7241 to 7285.8 ft (2207 to 2220 m). A few key features are noted on the core photos. A detailed graphic description is included in Figure 5.

Figure 4.

Core slab photos of Riverside 12c-3D core from lower Wagon Wheel interval. A) Section from 7196 to 7241 ft (2193 to 2207 m). B) Section from 7241 to 7285.8 ft (2207 to 2220 m). A few key features are noted on the core photos. A detailed graphic description is included in Figure 5.

Description

The Riverside 12c-3D core contains arkosic conglomerate but also has arkosic sandstone, quartz-lithic sandstone (chert-rich litharenite), and gray mudrocks. Figure 5 shows a detailed core description, with logs and XRD data, which can be examined together with the core photographs.

Figure 5.

Core description of the lower Wagon Wheel interval in the Riverside 12c-3D well with XRD data, wireline logs, and interpreted petrophysics.

Figure 5.

Core description of the lower Wagon Wheel interval in the Riverside 12c-3D well with XRD data, wireline logs, and interpreted petrophysics.

The sandstones and conglomerates are mostly cross-bedded, with some soft-sediment deformation and thin concentrations of large, intraformational mudstone clasts. The arkosic sandstones are coarse-grained to conglomeratic, whereas the quartz-lithic sandstones are fine-grained. The mudrocks are gray, silty mudstone and siltstone and contain abundant root traces, clay skins, and burrows. The quartz-lithic sandstones and the gray mudrocks appear similar to those in the underlying Lance Formation. Roots, burrows, and intervals enriched and depleted in calcite are apparent in the overbank deposits, similar to what was observed in the Lance Formation. The arkosic sandstones and conglomerates are not present in the Lance Formation. It is important to note that the arkosic sandstones and conglomerates observed in the Riverside 12c-3D core occur below the gamma-ray marker.

Thin-section photomicrographs illustrate the nature of the arkosic conglomerates in contrast to the quartz-lithic sandstones (Figures 6 to 8). The conglomerates contain grains of potassium feldspar and plagioclase and also carbonate and metamorphic rock fragments. Grain breakage due to compaction is evident, especially around point contacts (Figure 7). Various generations and varieties of cement are present. Kaolinite and ferroan calcite cements postdate grain breakage as seen in Figure 7. Figure 8 shows a photomicrograph of the quartz-lithic sandstone present in the lower Wagon Wheel section. It is similar to the fine-grained sandstones present in the underlying Lance Formation (see Chapter 6 and Govert, 2009). XRD data from sandstones and conglomerates are compared in Figure 9. The XRD mineral composition of the quartz-lithic sandstones in the Wagon Wheel Formation is similar to that in the underlying Lance Formation. Note the XRD quartz percent also includes chert and other rock fragments. The arkosic conglomerate and sandstone contain much more feldspar. The sandstones and conglomerates in this core also contain an unusual mixed-layer chlorite/smectite, according to Core Lab XRD and SEM interpretation (Figure 10; see Figure 15, Chapter 6). The clay mineralogy is discussed further below.

Figure 6.

Thin-section photomicrograph showing feldspathic conglomerate with carbonate rock fragments. The left half of the slide is stained for potassium feldspar (yellow), and the right half of the slide is stained for carbonate (red). The yellow outlined box in the lower right corner is enlarged in Figure 7. Riverside 12c-3D core, 7230.4 ft.

Figure 6.

Thin-section photomicrograph showing feldspathic conglomerate with carbonate rock fragments. The left half of the slide is stained for potassium feldspar (yellow), and the right half of the slide is stained for carbonate (red). The yellow outlined box in the lower right corner is enlarged in Figure 7. Riverside 12c-3D core, 7230.4 ft.

Figure 7.

Thin-section photomicrograph showing carbonate (CRF) and metamorphic (MRF) rock fragments in conglomerate, with authigenic kaolinite infilling most primary pore space. Note the abundant grain breakage and microfractures, some of which are filled with kaolinite; others are filled with ferroan calcite (Fe-CC), and some remain open. Riverside 12c-3D core, 7230.4 ft. Ksp=potassium feldspar, Rx=recrystallization, Qtz=quartz; image from Core Laboratories, interpretation by Mary Nelis.

Figure 7.

Thin-section photomicrograph showing carbonate (CRF) and metamorphic (MRF) rock fragments in conglomerate, with authigenic kaolinite infilling most primary pore space. Note the abundant grain breakage and microfractures, some of which are filled with kaolinite; others are filled with ferroan calcite (Fe-CC), and some remain open. Riverside 12c-3D core, 7230.4 ft. Ksp=potassium feldspar, Rx=recrystallization, Qtz=quartz; image from Core Laboratories, interpretation by Mary Nelis.

Figure 8.

Thin-section photomicrograph showing fine-grained, quartz- and chert-rich litharenite, similar to that found in the underlying Lance Formation. The portion of the slide shown here was stained for calcite; calcareous rock fragments are reddish. Riverside 12c-3D core, 7243.6 ft (2207 m).

Figure 8.

Thin-section photomicrograph showing fine-grained, quartz- and chert-rich litharenite, similar to that found in the underlying Lance Formation. The portion of the slide shown here was stained for calcite; calcareous rock fragments are reddish. Riverside 12c-3D core, 7243.6 ft (2207 m).

Figure 9.

Histograms of mineral proportions from XRD of sandstones and conglomerates in the Wagon Wheel Formation (“WW”) and Lance Formation (Riverside 12c-3D core, analysis by Core Laboratories). Note similarity of composition of Wagon Wheel Formation quartz-lithic sandstones and Lance sandstones, contrasting with Wagon Wheel Formation arkosic sandstone and conglomerate.

Figure 9.

Histograms of mineral proportions from XRD of sandstones and conglomerates in the Wagon Wheel Formation (“WW”) and Lance Formation (Riverside 12c-3D core, analysis by Core Laboratories). Note similarity of composition of Wagon Wheel Formation quartz-lithic sandstones and Lance sandstones, contrasting with Wagon Wheel Formation arkosic sandstone and conglomerate.

Figure 10.

SEM image showing kaolinite replacement of a feldspar grain on left, with corrensite/chlorite clay (Cor/Chl) filling previous pore space on right. The lighter band of corrrensite marks the previous grain boundary. mP = micropores with the authigenic kaolinite. (Image from Core Laboratories, interpretation by Mary Nelis.)

Figure 10.

SEM image showing kaolinite replacement of a feldspar grain on left, with corrensite/chlorite clay (Cor/Chl) filling previous pore space on right. The lighter band of corrrensite marks the previous grain boundary. mP = micropores with the authigenic kaolinite. (Image from Core Laboratories, interpretation by Mary Nelis.)

Very different lithologies are observed above the gamma-ray marker. Figures 11 and 12 show core photos from the Wagon Wheel #1 well above the gamma-ray marker. The sandstone and conglomerate are dominantly coarse and arkosic, with little litharenitic sandstone. The clean sandstone–conglomeratic intervals are very thin, only rarely greater than 10 ft (3 m) thick. There is abundant, poorly sorted, greenish-gray, muddy siltstone and sandstone containing varying proportions of admixed coarse sand to pebble grains of quartz, feldspar, and carbonate. This material commonly contains abundant root traces (some greater than 1 cm wide), large burrows (some several centimeters wide), and carbonaceous material. The texture is chaotic with evidence of soft-sediment deformation.

Figure 11.

Core photos of the upper Wagon Wheel Formation in the Wagon Wheel #1 well. A) Box photo showing both thin, crossbedded feldspathic conglomerate channel fill (depth 7043–7047 ft) and also the greenish-gray debris facies, containing abundant, large root marks (yellow arrows). B) Close up of large root traces (or possibly burrows) on left side around 7049 ft (2148 m) (yellow arrows). Thinner root traces are marked with yellow arrows on the right side above 7052 ft (2150 m).

Figure 11.

Core photos of the upper Wagon Wheel Formation in the Wagon Wheel #1 well. A) Box photo showing both thin, crossbedded feldspathic conglomerate channel fill (depth 7043–7047 ft) and also the greenish-gray debris facies, containing abundant, large root marks (yellow arrows). B) Close up of large root traces (or possibly burrows) on left side around 7049 ft (2148 m) (yellow arrows). Thinner root traces are marked with yellow arrows on the right side above 7052 ft (2150 m).

Figure 12.

Core photo of the upper Wagon Wheel Formation in the Wagon Wheel #1 well showing mixing of coarser sediment into finer sediment by burrowing.

Figure 12.

Core photo of the upper Wagon Wheel Formation in the Wagon Wheel #1 well showing mixing of coarser sediment into finer sediment by burrowing.

Core Laboratories interpreted mixed-layer chlorite/smectite to be present within the conglomeratic facies of the Riverside 12c-3D core (Figures 9, 10, and 13). Pollastro (1989) also noted mixed-layer chlorite/smectite in XRD and SEM interpretation of some conglomerate and shale samples in this interval in the Wagon Wheel #1 well. Both Core Laboratories and Pollastro (1989) interpreted this clay mineral as corrensite. Corrensite is an iron–magnesium clay species having layers of chlorite alternating with layers of smectite or vermiculite. Macaulay Analytical of Aberdeen, Scotland, interpreted XRD data of two samples of this material as containing tosudite. Tosudite is a similar, mixed-layer chlorite/smectite having a different crystal form than corrensite and is less soluble in HCl. Figure 13 shows a plot of the whole rock weight percent of the sum of chlorite and mixed-layer chlorite/smectite from the Wagon Wheel #1 well (data from Pollastro, 1989). Note the increase of these clay species in the Wagon Wheel Formation compared to the underlying Lance Formation.

Figure 13.

Chart showing weight percent (whole rock) of chlorite plus mixed-layer chlorite/smectite from XRD. Data from Wagon Wheel #1 well as reported by Pollastro, 1989.

Figure 13.

Chart showing weight percent (whole rock) of chlorite plus mixed-layer chlorite/smectite from XRD. Data from Wagon Wheel #1 well as reported by Pollastro, 1989.

The origin of corrensite in the literature has been attributed to weathering of chlorite-rich or biotite-rich sediments, hydrothermal alteration, or precipitation in association with evaporates or carbonates (Johnson, 1964; Furbish, 1975; Jiang and Peacor, 1994). Of these options, the most likely would appear to be weathering of the metamorphic and igneous ferro-magnesian minerals contained in the sediment clasts in debris-dominated soils. Pollastro (1989) interpreted the corrensite as a later-stage diagenetic alteration of chlorite, coincident with the high-iron calcite precipitation and dissolution. Additional work on the clay mineralogy and diagenetic process might shed more light on the paleoenvironment of these alterations.

Interpretation

The sedimentary structures, their vertical sequence, and the presence of scours and lags indicate that the sandy intervals were deposited by fluvial channels somewhat similar to those described for the Lance Formation by Chapin et al. (see Chapter 6). The main difference is the presence of the coarser, arkosic material, which is also interpreted as gravel bar, point bar, and channel deposits sourced from a different provenance. The gray mudrocks of the lower Wagon Wheel interval are interpreted as overbank deposits, paleosols, and crevasse splays similar to those described for the Lance Formation.

The greenish-gray, poorly sorted sediment above the gamma-ray marker is interpreted to have been deposited by debris flows, with significant postdepositional churning by roots and burrows. Judging by the width of the root marks, some of the plants in the upper interval were significantly larger than those below the gamma-ray marker. It is possible some of the mixed material is due only to bioturbation and soil processes without a precursor debris flow. The thin, intercalated, cleaner sandstones and conglomerates above the gamma-ray marker are interpreted as very thin fluvial and flood deposits, as indicated by crossbedding and scours. The dominance of debris flow material and the thin channels suggest the upper Wagon Wheel Formation may have been deposited in an alluvial fan setting more dominated by the emerging mountain front compared to the lower Wagon Wheel Formation.

Based on the observations described above, five gross facies associations are distinguished to help understand the differences between the upper and lower Wagon Wheel Formation. These are (1) quartz-lithic, fine sandstone; (2) feldspathic, coarse sandstone and conglomerate; (3) feldspathic, fine sandstone; (4) gray mudstone; and (5) greenish-gray debrite. Placing these core facies associations on a log section helps illustrate their distribution (Figure 14). The interval below the gamma-ray marker has a mixture of feldspathic and quartz-lithic sandstone, and mostly gray mudstone. The interval above the gamma-ray marker contains no quartz-lithic sandstone and has abundant greenish-gray debrite. Figure 15 shows a sketch interpretation of the stratigraphic relationships seen in the seismic cross section shown in Figure 3, with the lithologic associations from core noted in their appropriate intervals.

Figure 14.

Gross lithology from core in the Wagon Wheel Formation, with reference to the gamma-ray marker. The arrow in the Wagon Wheel well indicates the K/T boundary from Law and Spencer (see Chapter 3).

Figure 14.

Gross lithology from core in the Wagon Wheel Formation, with reference to the gamma-ray marker. The arrow in the Wagon Wheel well indicates the K/T boundary from Law and Spencer (see Chapter 3).

The unconformity at the gamma-ray marker records erosion related to movement on the Pinedale thrust fault and Pinedale anticline growth, as indicated by onlap onto the unconformity. This unconformity in the Pinedale area is estimated to span approximately 3 m.y. and represent 100 m (330 ft) of erosion at the Wagon Wheel #1 well by Dickinson (1989, his Figure 2). Figure 15B shows the famous cross section by Law and Johnson (1989) and indicates by the red box the interval represented by Figure 15A. The seismic data (Figure 3) indicates less erosional truncation on this surface to the east. Erosional truncation increases to the west and south, and eventually this unconformity merges with other unconformities, cutting out the Wagon Wheel and Lance Formations entirely (e.g., west part of Figure 15B).

A seismic opacity slice centered 6 ms below the gamma-ray marker unconformity can be interpreted to show trunk stream and tributary geometries that can explain the mixture of lithologies in the lower Wagon Wheel Formation (Figure 16). Seismic opacity is a visualization of amplitude strength through a narrow window, where higher amplitudes are orange-yellow in this case, and lower amplitudes fade to black. The main trunk stream is oriented NW–SE, parallel to the mountain front, and is interpreted to carry the fine-grain, texturally mature, quartz lithic sands from far to the northwest, similar to the channels in the underlying Lance Formation. The NE–SW to N–S oriented tributaries are interpreted to carry the feldspathic gravel and coarse sand away from the emerging Wind River Mountains to the northeast. These sediment sources mix where there is confluence and also can be stacked vertically as the streams move.

Figure 15.

A) Sketch of major stratigraphic relationships of the Wagon Wheel Formation, as interpreted from seismic relationships shown in Figure 3 and from core lithologies. B) Cross section through the northern Green River Basin from Law and Spencer (1989) for comparison. Red box indicates the section represented in A. The unconformities indicated as wavy lines in B correspond to the “Top Wagon Wheel Formation” and “Unconformity=Gamma-Ray Marker” in A.

Figure 15.

A) Sketch of major stratigraphic relationships of the Wagon Wheel Formation, as interpreted from seismic relationships shown in Figure 3 and from core lithologies. B) Cross section through the northern Green River Basin from Law and Spencer (1989) for comparison. Red box indicates the section represented in A. The unconformities indicated as wavy lines in B correspond to the “Top Wagon Wheel Formation” and “Unconformity=Gamma-Ray Marker” in A.

Figure 16.

Seismic opacity slice centered 6 ms below the gamma-ray marker unconformity (20 ms window). Original seismic data from CGG-Veritas.

Figure 16.

Seismic opacity slice centered 6 ms below the gamma-ray marker unconformity (20 ms window). Original seismic data from CGG-Veritas.

Above the unconformity, the quartz-lithic trunk streams have been shifted west of the Pinedale anticline, if they existed at all during this time. The upper Wagon Wheel Formation is dominated by debris flows and small conglomeratic channels reflecting a higher-gradient, possibly alluvial fan environment closer to the now-emergent mountain front. Figure 17 illustrates these interpretations in a sketch.

Figure 17.

Diagrams illustrating environments of the Wagon Wheel Formation. The top figure represents the lower Wagon Wheel Formation with intermingling quartzose and feldspathic clastics over the future Pinedale area. The lower figure represents the upper Wagon Wheel Formation, which has debris-dominated alluvial fans with small feldspathic channels over the Pinedale anticline.

Figure 17.

Diagrams illustrating environments of the Wagon Wheel Formation. The top figure represents the lower Wagon Wheel Formation with intermingling quartzose and feldspathic clastics over the future Pinedale area. The lower figure represents the upper Wagon Wheel Formation, which has debris-dominated alluvial fans with small feldspathic channels over the Pinedale anticline.

Quantitative Analysis of Facies, Grain Size, and Sedimentary Structure Proportions within Channels

Channel facies classes were defined according to the process described for the Lance Formation in Chapin et al. (Chapter 6). In addition, feldspathic versus quartz-lithic facies were differentiated, and feldspathic conglomerate was separated as a unique class for the sake of analysis of facies proportions and rock quality. The definition of these classes is summarized in Table 2.

Channel facies classes and abbreviations.

Table 2.
Channel facies classes and abbreviations.
Abbreviations
Quartz-lithic SandstoneFeldspathic sandstone
Soil-modified bar top/abandonmentQcu
Upper barQcbFcb
Basal channel/barQcaFca
Channel lag (mud clasts)QclFcl
Conglomerate, gravel barFcg
Abbreviations
Quartz-lithic SandstoneFeldspathic sandstone
Soil-modified bar top/abandonmentQcu
Upper barQcbFcb
Basal channel/barQcaFca
Channel lag (mud clasts)QclFcl
Conglomerate, gravel barFcg

Figure 18 shows grain size for quartz-lithic and feldspathic channel deposits from core samples. The feldspathic channels contain much coarser material, whereas the quartz-lithic channels are dominantly fine-grained. Figure 19 further describes grain size according to facies. There is little very fine sand size or finer material in the feldspathic category. Therefore, the finer grained facies such as bar tops and overbank sandstones are mainly quartz-lithic dominated. This is consistent with the mineralogical and textural immaturity and interpreted proximal nature of the feldspathic material as described earlier.

Figure 18.

Grain size distribution in quartz-lithic (Qtz-yellow) versus feldspathic (Felds-red) channels.

Figure 18.

Grain size distribution in quartz-lithic (Qtz-yellow) versus feldspathic (Felds-red) channels.

Figure 19.

Grain size distribution broken out by facies within A) quartz-lithic and B) feldspathic channels.

Figure 19.

Grain size distribution broken out by facies within A) quartz-lithic and B) feldspathic channels.

Figure 20 illustrates how sedimentary structures are distributed proportionately in the various facies. (Facies abbreviations are explained in Figure 5 and Table 2 of Chapin et al., Chapter 6.) Qca facies are dominated by cross-bedded sandstone, with significant unstructured, convolute, and wavy-laminated sandstones. Fca facies are also dominated by cross-bedded sandstone, with some unstructured sandstone. Conglomeratic Fcl facies are mostly unstructured, with some cross-bedding. Qcb and Qcu facies are dominated by ripple lamination, wavy and diffuse lamination, and convolute lamination.

Figure 20.

Proportions of sedimentary structures present in channel facies: A) quartz-lithic and B) feldspathic. See Figure 5 in Chapin et al. (Chapter 6) for an explanation of abbreviations.

Figure 20.

Proportions of sedimentary structures present in channel facies: A) quartz-lithic and B) feldspathic. See Figure 5 in Chapin et al. (Chapter 6) for an explanation of abbreviations.

We catalogued the thickness distribution of channels and channel facies from core in a similar manner as described for the Lance and Mesaverde channels in Chapin et al., Chapter 6 (Table 3). These data can be used as input to stochastic reservoir models.

Summary of channel thickness data.

Table 3.
Summary of channel thickness data.
Thickness (ft)
Unnamed FormationMinAverageMaxCount
Sand Intervals6.528.8655
Individual Sands6.415.421.73
Multistory Sands3345652
“Complete” Stories
Best Estimate Story6.514.421.75
Minimum Story6.514.421.75
Facies
CuUpper Poor00.615
CbBar Upper01.92.75
CaActive Basal04.512.35
LLag/Conglomerate07.2175
Thickness (ft)
Unnamed FormationMinAverageMaxCount
Sand Intervals6.528.8655
Individual Sands6.415.421.73
Multistory Sands3345652
“Complete” Stories
Best Estimate Story6.514.421.75
Minimum Story6.514.421.75
Facies
CuUpper Poor00.615
CbBar Upper01.92.75
CaActive Basal04.512.35
LLag/Conglomerate07.2175

Porosity and Permeability Characterization by Facies

The ability to characterize porosity and permeability by facies can be an important enabler in static modeling for dynamic simulation. The facies described above were used to characterize the porosity and permeability of the lower Wagon Wheel Formation (Figure 21). We have no modern core analysis of the upper Wagon Wheel Formation. However, as noted earlier, we believe the upper Wagon Wheel Formation to be mostly water bearing, and it is not completed. We would expect the conglomeratic and arkosic sandstones present in the upper Wagon Wheel to have similar porosity–permeability relationships to those lithologies in the lower Wagon Wheel Formation.

Figure 21.

Permeability–porosity crossplot showing character of different facies types.

Figure 21.

Permeability–porosity crossplot showing character of different facies types.

The overall sandstone and conglomerate porosity and permeability are higher for the Wagon Wheel Formation compared to the Lance and Upper Mesaverde intervals (see Figure 36, Chapter 6). The procedures for determining porosity and permeability according to facies were described in detail by Chapin et al. in Chapter 6.

The arkosic conglomerates and coarse-grained sandstone have a very similar porosity–permeability character. They have a higher permeability than the finer-grained quartz-lithic sandstones. The Qca and Qcb facies described previous are similar to those in the Lance Formation, with the finer grained Qcb facies having slightly lower permeability for a given porosity compared to the Qca facies. Siltstones are approximately 10 to 15 times lower permeability than sandstones having similar porosity. Measurements on mudstones are unreliable due to core drying leading to clay dehydration.

Despite the complexity of the facies described earlier and their diagenetic overprint, there is good correspondence between facies, porosity, and permeability. This finding is similar to what was observed in the Lance and Upper Mesaverde intervals. The same caveats regarding core plug analysis apply as noted by Chapin et al. (Chapter 6), especially related to drying and stress correction.

Core-Log Integration

Figure 5 illustrates the Riverside 12c-3D core as compared to log response. The coarser sandstone and conglomerate intervals also have elevated gamma ray, and correspondingly higher potassium feldspar content. The finer, more quartz-rich sandstone has a lower gamma-ray response. The entire sandstone-conglomerate interval has elevated resistivity, and decreased neutron-density separation. Therefore, sandstone-conglomerate versus mudstone intervals can be diagnosed by log data but not by gamma-ray response alone. The more permeable sandstone and conglomerate-rich intervals can also be distinguished via the SP log if the well was drilled with water-based mud, as is shown in the Wagon Wheel well (Figure 22).

Figure 22.

Logs of Wagon Wheel #1 well showing how SP log distinguishes more-permeable sandstones in this well drilled with water-based mud. Two key fluid tests are also noted on the diagram, as reported by Shaughnessy and Butcher (1974).

Figure 22.

Logs of Wagon Wheel #1 well showing how SP log distinguishes more-permeable sandstones in this well drilled with water-based mud. Two key fluid tests are also noted on the diagram, as reported by Shaughnessy and Butcher (1974).

Note in Figure 5 how calcite-cemented nodules are indicated by XRD data as elevated calcite and elevated acid reactivity and are also indicated by neutron and density logs as lower porosity (e.g., at 7247 core depth = 7243 log depth). Core plug porosity matches very well with log-derived porosity after calibration to grain density. A permeability log is also shown to match well against core plug measurements. The permeability to porosity transform used to generate the permeability curve comes from the crossplot shown in Figure 21.

The curve in the right-most track of Figure 5 indicates water saturation. Water saturation in the lower Wagon Wheel Formation is high, typically greater than 50%. Nevertheless, some gas is produced from this interval. Figure 22 includes data from swabbing and a drill-stem test (DST) in the Wagon Wheel #1 well indicating the sandstones and conglomerates above the unconformity yielded water, but gas was produced to surface on a DST over the sandstones below the unconformity.

A spectral gamma-ray log was also run in the Riverside 12c-3D well (Figure 23). These logs illuminate some of the aspects of the different lithologies above and below the unconformity discussed previously. The total gamma-ray response is elevated above the gamma-ray marker. There is a modest increase in potassium above the marker, due to the increased feldspar content, but there is a more dramatic increase in thorium, with thorium/potassium ratios commonly greater than 8 ppm/pct. The shale baseline increases as well as the sand baseline, reflecting different clay as well as more arkosic sandstone. Logging company crossplots of Th/K indicate the higher thorium is consistent with more abundant chlorite and smectite.

Figure 23.

Logs from the Riverside 12c-3D well, highlighting the various spectral gamma-ray responses. Note the distinct increase in thorium above the gamma-ray marker. Right track is porosity, shaded above 8%. Note the consistently higher porosity above the gamma-ray marker.

Figure 23.

Logs from the Riverside 12c-3D well, highlighting the various spectral gamma-ray responses. Note the distinct increase in thorium above the gamma-ray marker. Right track is porosity, shaded above 8%. Note the consistently higher porosity above the gamma-ray marker.

Discussion

Much has been published regarding the explanation for the trap and pressure profile observed at Pinedale and Jonah fields (Cluff and Cluff, 2004; Law and Spencer, Chapter 3; Shanley et al., 2004; Dubois et al., 2004). Spencer (1989) described how the pressure gradient in Pinedale field increases with depth from around the top Lance Formation, based on mud weights in the Wagon Wheel #1 well. Quint et al. (2006) described the placement of permanent pressure gauges outside of casing in monitor wells to understand long-term pressure response due to depletion. From these data we know that the pressure gradient in the lower Wagon Wheel Formation is slightly elevated compared to fresh water, having values of 0.46 to 0.54 psi/ft (mostly above 0.5 psi/ft). The pressure gradient increases downward to over 0.8 psi/ft at the base of the Upper Mesaverde interval. Although we had no pressure gauges in the upper Wagon Wheel or Fort Union Formations, we believe the gradient becomes hydropressured above the gamma-ray marker, as indicated by fluid levels in hydrological tests reported by Shaughnessy and Butcher (1974), down to a depth of 7140 ft (2176 m; interval noted in Figure 22). From these pressure data we infer the upper Wagon Wheel Formation is nonsealing to gas over geologic time, likely due to the mixture of coarser grains leading to higher permeability.

The right-hand log curve on Figure 23 shows how density porosity varies above and below the gamma-ray marker. Porosity above the marker is consistently higher than below the marker. The shale intervals below the gamma-ray marker have especially low porosity. Figure 24 shows a permeability–porosity cross plot of core data from the Wagon Wheel #1 well from both above and below the gamma-ray marker. On the same figure we have also plotted for comparison purposes some core data from the Riverside 12c-3D well from the Upper Lance. The Wagon Wheel #1 well measurements are from 1969 and 1970, and originally unstressed and dried, so they are inherently too high compared to in situ conditions. The permeability has been corrected using Byrnes (2005) equation for routine core analysis: logK(corrected)=0.0588(log[Kair])3−0.187(log[Kair])2+1.154 (log[Kair])−0.159. Porosity values from the Wagon Wheel #1 cores were corrected using a comparison factor to Shell’s Riverside 12c-3D Upper Lance core (*0.911). The corrections are likely not perfect but may be comparable relative to each other, and the trends seem clear.

Figure 24.

Semi-log plot of permeability versus porosity for Upper Lance through Fort Union cores from the Wagon Wheel #1 well, and the upper Lance core from the Riverside 12c-3D well for comparison. The blue oval outlines the debrites from the Wagon Wheel Formation, the orange oval outlines the debrites from the Fort Union Formation, and the black oval outlines core measurements of mudstones from the Upper Lance.

Figure 24.

Semi-log plot of permeability versus porosity for Upper Lance through Fort Union cores from the Wagon Wheel #1 well, and the upper Lance core from the Riverside 12c-3D well for comparison. The blue oval outlines the debrites from the Wagon Wheel Formation, the orange oval outlines the debrites from the Fort Union Formation, and the black oval outlines core measurements of mudstones from the Upper Lance.

The muddy debrites of the Wagon Wheel and Fort Union Formations have similar permeability to the reservoir sandstones in the Upper Lance, and the sandstones in the Wagon Wheel and Fort Union Formations have higher permeability than the Lance sandstone. The blue oval in Figure 24 outlines the debrites from the Wagon Wheel Formation, the orange oval outlines the debrites from the Fort Union Formation, and the black oval outlines core measurements of mudstones from the Upper Lance. The debris-rich muddy sandstones and mudstones in the upper Wagon Wheel and Fort Union Formations appear to have higher permeability for a given porosity than the laminated illitic mudrocks within the Lance Formation.

The combination of pressure data, log porosity, imperfect core data, and gas versus water production leads us to believe the shales in the Lance and lower Wagon Wheel Formations are more effective baffles to gas than the rocks in the upper Wagon Wheel and Fort Union Formations. In this respect, our view of the lack of a top seal is very similar to the interpretation of Dubois et al. (2004) regarding Jonah field.

In this chapter we do not intend to delve further into the lively debate around ultimate origin and preservation of the gas accumulation and pressure anomalies at Pinedale and Jonah fields. Instead our intention has been to characterize the reservoirs as they are for the purpose of development exploitation.

Conclusions

An unconformity separates the lower and upper parts of the Wagon Wheel Formation. It can be observed in seismic data and also corresponds to the gamma-ray shift described by Prensky (1989). The gamma-ray shift is due to changes in both the sandstone composition and clay mineralogy above the unconformity where sandstones are more consistently arkosic, and where there is an increase in mixed-layer chlorite/smectite, resulting in higher thorium counts. The lower Wagon Wheel Formation is transitional with the Lance Formation. It includes fine-grained, litharenite sediment derived from texturally and mineralogically mature, Lance-like northwesterly sources, which are intermixed with coarser arkosic sediment derived from the emerging Wind River Mountains to the east.

The unconformity between the lower and upper parts of the Wagon Wheel Formation marks the onset of a prominent period of Pinedale anticline growth and movement of the Pinedale thrust, as indicated by prominent axial thinning and onlap above the unconformity. The upper Wagon Wheel Formation on the Pinedale anticline lacks the quartz-lithic sediment input. All the coarse sediment is arkosic, and the mud-rich facies appear to be mostly debris flows with significant amounts of included coarse grains and having abundant root and animal bioturbation.

Channel facies in the lower Wagon Wheel Formation can be distinguished and characterized in a similar manner to the Lance Formation, with the added dimension of the feldspathic sandstones and conglomerates. Porosity and permeability are higher than in the Lance Formation due to less burial and larger grain size. Similar reservoir characterization techniques can be applied to both the lower Wagon Wheel Formation and the Lance Formation. There is good correspondence between core and log properties and also core facies and log properties.

Gas is produced from the lower Wagon Wheel Formation, but the upper Wagon Wheel Formation is water bearing. The pressure gradient starts to deviate above hydrostatic below the unconformity separating the upper and lower Wagon Wheel intervals. We believe the upper Wagon Wheel Formation becomes leaky to gas due to higher permeability, whereas gas is trapped with the Upper Mesaverde, Lance, and lower Wagon Wheel intervals due to intercalated, less permeable shale layers.

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Byrnes
,
A.J.
2005
, Gas in low-permeability reservoirs of the Rocky Mountain region, in
Bishop
,
M. G.
Cumella
,
S.P.
Robinson
,
J.W.
Silverman
,
M.R.
, eds.,
Rocky Mountain Association of Geologists 2005 Guidebook CD
 , p.
69
108
.
Chapin
,
M.A.
Govert
,
A.
Brandon
,
N.
Uguetto
,
G.
,
2014
, Sedimentology and reservoir characterization of the Late Cretaceous Lance and Upper Mesaverde intervals from core data in Pinedale field, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
175
245
.
Cluff
,
S.G.
Cluff
,
R. M.
,
2004
, Petrophysics of the Lance sandstone reservoirs in Jonah field, Sublette County, Wyoming, in
Robinson
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J. W.
Shanley
,
K.W.
, eds.,
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 , p.
215
242
.
Dickinson
,
1989
, Analysis of vitrinite maturation and Tertiary burial history, northern Green River Basin, Wyoming, in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
, Chapter F.
DuBois
,
D.P.
Wynne
,
P.J.
Smagala
,
T.M.
Johnson
,
J.L.
Engler
,
K.D.
McBride
,
B.C.
,
2004
, Geology of the Jonah Field, Sublette County Wyoming, in
Robinson
,
J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52 and Rocky Mountain Association of Geologists 2004 Guidebook
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37
59
.
Furbish
,
W. J.
1975
,
Corrensite of deuteric origin, The American Minerologist
, v.
60
, p.
928
930
.
Govert
,
A.
2009
, Petrogenetic Controls on the Porosity of Tight-gas Sandstones in the Lance Formation, Pinedale Anticline, Sublette County, Wyoming,
M.S. Thesis, Colorado School of Mines
,
Golden, Colorado
,
131
p.
Hanson
,
W. B.
Vega
,
V.
Cox
,
D.
,
2004
, Chapter 6, Structural geology, seismic imaging, and genesis of the giant Jonah Gas Field, Wyoming, U.S.A., in
Robinson
,
J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52
 , p.
61
92
.
Jiang
,
Wei-The
Peacor
,
D. R.
,
1994
,
Formation of corrensite, chlorite and chlorite-mica stacks by replacement of biotite in low-grade politic rocks
,
Journal of Metamorphic Geology
 , v.
12
, p.
867
884
.
Johnson
,
L.J.
1964
,
Occurrence of regularly inter-stratified chlorite-vermiculite as a weathering product of chlorite in soil
,
American Mineralogist
 , v.
49
, p.
566
572
.
Law
,
B.E.
Johnson
,
R. C.
,
1989
, Chapter B, Structural and stratigraphic framework of the Pinedale Anticline, Wyoming, and the Multiwell Experiment Site, Colorado in
Law
,
B. E.
Spencer
,
C.W.
eds., Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site, Colorado,
U.S. Geological Survey Bulletin 1886
 .
Law
,
B. E.
Spencer
,
C. W.
,
2014
, The Pinedale Gas field: A sweet spot in a regionally pervasive basin-centered gas accumulation, Green River and Hoback Basins, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
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37
59
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Martin
,
T.S.
McDermott
,
R.W.
Kneller
,
S.R.
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,
M.W.
,
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, Geologic overview of Pinedale field, Sublette County, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
321
349
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Pollastro
,
R. M.
1989
, Chapter D, Mineral composition, petrography, and diagenetic modifications of the Lower Tertiary and Upper Cretaceous sandstones and shales, Northern Green River Basin, Wyoming in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
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Prensky
,
S.E.
1989
, Chapter H, Gamma-ray well-log anomaly in the northern Green River Basin of Wyoming, in
Law
,
B. E.
Spencer
,
C. W.
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Colorado
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U.S. Geological Survey Bulletin 1886
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Quint
,
E.
Singh
,
M.
Huckabee
,
P.
Brown
,
D.
Beck Brake
,
C.
Bickley
,
J.
Johnston
,
B.
,
2006
, 4D pressure pilot to steer well spacing in tight gas, Society of Petroleum Engineers Annual Technical Conference,
San Antonio, TX
, SPE Paper 102745,
14
p.
Shanley
,
K.W.
Cluff
,
R.M.
Robinson
,
J.W.
,
2004
,
Factors controlling prolific gas production from low-permeability sandstone reservoirs: Implications for resource assessment, prospect development, and risk analysis
:
AAPG Bulletin
 , v.
88
, p.
1083
1121
.
Shaughnessy
,
J.
Butcher
,
R. H.
,
1974
,
Geology of the Wagon Wheel nuclear stimulation project, Pinedale Field, Wyoming
,
AAPG Bulletin
 , v.
58
, p.
2250
2259
.
Spencer
,
C.W.
1989
, Comparison of overpressuring at the Pinedale anticline area, Wyoming and the Multiwell Experiment site, Colorado, in
Law
,
B. E.
Spencer
,
C.W.
, eds.,
Geology of tight gas reservoirs in the Pinedale anticline area, Wyoming and at the Multiwell Experiment site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
,
16
p.

Acknowledgments

Acknowledgments

The authors wish to thank Shell Western E&P, Inc. for permission to publish this chapter. Ultra Petroleum is a joint venturer in many of the Shell-operated wells on the Pinedale anticline. Mary Nelis of Core Laboratories provided the thin section photomicrographs, SEM image and interpretations. Core Laboratories also provided the stressed porosity and permeability and water saturation from the Riverside 12c-3D core. Nick Brandon and Gustavo Ugueto provided the interpreted log curves for the Riverside 12c-3D well. J.A. (Tony) Robertson created the seismic opacity slice. CGG-Veritas acquired the seismic data and granted permission for us to publish the data shown. The USGS Core Research Laboratory allowed us to access the Wagon Wheel #1 and New Fork cores in their facility. Mark Longman and Tom Meyer reviewed this chapter and provided many helpful suggestions. We are grateful to and appreciate the support of all these contributors. We are also grateful for the support of the many Shell staff and managers who have worked on the Pinedale field, without whom this work would not have been possible.

The authors wish to thank Shell Western E&P, Inc. for permission to publish this chapter. Ultra Petroleum is a joint venturer in many of the Shell-operated wells on the Pinedale anticline. Mary Nelis of Core Laboratories provided the thin section photomicrographs, SEM image and interpretations. Core Laboratories also provided the stressed porosity and permeability and water saturation from the Riverside 12c-3D core. Nick Brandon and Gustavo Ugueto provided the interpreted log curves for the Riverside 12c-3D well. J.A. (Tony) Robertson created the seismic opacity slice. CGG-Veritas acquired the seismic data and granted permission for us to publish the data shown. The USGS Core Research Laboratory allowed us to access the Wagon Wheel #1 and New Fork cores in their facility. Mark Longman and Tom Meyer reviewed this chapter and provided many helpful suggestions. We are grateful to and appreciate the support of all these contributors. We are also grateful for the support of the many Shell staff and managers who have worked on the Pinedale field, without whom this work would not have been possible.

Figures & Tables

List of wells noted in text or shown in figures. Bold underlined wells have cores.

Table 1.
List of wells noted in text or shown in figures. Bold underlined wells have cores.
AbbreviationWellLocation
Rv12c-3dShell Riverside 12c-3DSec 3, T31N, R109W
NF 4El Paso New Fork 4Sec 35, T31N, R109W
EP-WW#1El Paso Wagon Wheel 1Sec 5, T30N, R108W
Wb 7d-6Shell Warbonnet 7d-6Sec 6, T30N, R108W
Wb 3-3Ultra Resources Warbonnet 3-3Sec 3, T30N, R108W
NF 2American Hunter New Fork 2Sec 2, T30N, R108W
NF 1American Hunter New Fork 1Sec 25, T30N, R108W
AbbreviationWellLocation
Rv12c-3dShell Riverside 12c-3DSec 3, T31N, R109W
NF 4El Paso New Fork 4Sec 35, T31N, R109W
EP-WW#1El Paso Wagon Wheel 1Sec 5, T30N, R108W
Wb 7d-6Shell Warbonnet 7d-6Sec 6, T30N, R108W
Wb 3-3Ultra Resources Warbonnet 3-3Sec 3, T30N, R108W
NF 2American Hunter New Fork 2Sec 2, T30N, R108W
NF 1American Hunter New Fork 1Sec 25, T30N, R108W

Channel facies classes and abbreviations.

Table 2.
Channel facies classes and abbreviations.
Abbreviations
Quartz-lithic SandstoneFeldspathic sandstone
Soil-modified bar top/abandonmentQcu
Upper barQcbFcb
Basal channel/barQcaFca
Channel lag (mud clasts)QclFcl
Conglomerate, gravel barFcg
Abbreviations
Quartz-lithic SandstoneFeldspathic sandstone
Soil-modified bar top/abandonmentQcu
Upper barQcbFcb
Basal channel/barQcaFca
Channel lag (mud clasts)QclFcl
Conglomerate, gravel barFcg

Summary of channel thickness data.

Table 3.
Summary of channel thickness data.
Thickness (ft)
Unnamed FormationMinAverageMaxCount
Sand Intervals6.528.8655
Individual Sands6.415.421.73
Multistory Sands3345652
“Complete” Stories
Best Estimate Story6.514.421.75
Minimum Story6.514.421.75
Facies
CuUpper Poor00.615
CbBar Upper01.92.75
CaActive Basal04.512.35
LLag/Conglomerate07.2175
Thickness (ft)
Unnamed FormationMinAverageMaxCount
Sand Intervals6.528.8655
Individual Sands6.415.421.73
Multistory Sands3345652
“Complete” Stories
Best Estimate Story6.514.421.75
Minimum Story6.514.421.75
Facies
CuUpper Poor00.615
CbBar Upper01.92.75
CaActive Basal04.512.35
LLag/Conglomerate07.2175

Contents

GeoRef

References

References Cited

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A.J.
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M. G.
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J.W.
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M.R.
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M. W.
Kneller
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S. R.
Meyer
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M. A.
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Cluff
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R. M.
,
2004
, Petrophysics of the Lance sandstone reservoirs in Jonah field, Sublette County, Wyoming, in
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J. W.
Shanley
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K.W.
, eds.,
Jonah Field: Case Study of a Tight-Gas Fluvial Reservoir and AAPG Studies in Geology 52 and Rocky Mountain Association of Geologists 2004 Guidebook
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Dickinson
,
1989
, Analysis of vitrinite maturation and Tertiary burial history, northern Green River Basin, Wyoming, in
Law
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Spencer
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C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
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Colorado
,
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, Chapter F.
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Wynne
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Smagala
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J.L.
Engler
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K.D.
McBride
,
B.C.
,
2004
, Geology of the Jonah Field, Sublette County Wyoming, in
Robinson
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J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52 and Rocky Mountain Association of Geologists 2004 Guidebook
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Govert
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A.
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, Petrogenetic Controls on the Porosity of Tight-gas Sandstones in the Lance Formation, Pinedale Anticline, Sublette County, Wyoming,
M.S. Thesis, Colorado School of Mines
,
Golden, Colorado
,
131
p.
Hanson
,
W. B.
Vega
,
V.
Cox
,
D.
,
2004
, Chapter 6, Structural geology, seismic imaging, and genesis of the giant Jonah Gas Field, Wyoming, U.S.A., in
Robinson
,
J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52
 , p.
61
92
.
Jiang
,
Wei-The
Peacor
,
D. R.
,
1994
,
Formation of corrensite, chlorite and chlorite-mica stacks by replacement of biotite in low-grade politic rocks
,
Journal of Metamorphic Geology
 , v.
12
, p.
867
884
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Johnson
,
L.J.
1964
,
Occurrence of regularly inter-stratified chlorite-vermiculite as a weathering product of chlorite in soil
,
American Mineralogist
 , v.
49
, p.
566
572
.
Law
,
B.E.
Johnson
,
R. C.
,
1989
, Chapter B, Structural and stratigraphic framework of the Pinedale Anticline, Wyoming, and the Multiwell Experiment Site, Colorado in
Law
,
B. E.
Spencer
,
C.W.
eds., Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site, Colorado,
U.S. Geological Survey Bulletin 1886
 .
Law
,
B. E.
Spencer
,
C. W.
,
2014
, The Pinedale Gas field: A sweet spot in a regionally pervasive basin-centered gas accumulation, Green River and Hoback Basins, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
37
59
.
Martin
,
T.S.
McDermott
,
R.W.
Kneller
,
S.R.
Longman
,
M.W.
,
2014
, Geologic overview of Pinedale field, Sublette County, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
321
349
.
Pollastro
,
R. M.
1989
, Chapter D, Mineral composition, petrography, and diagenetic modifications of the Lower Tertiary and Upper Cretaceous sandstones and shales, Northern Green River Basin, Wyoming in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
.
Prensky
,
S.E.
1989
, Chapter H, Gamma-ray well-log anomaly in the northern Green River Basin of Wyoming, in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
.
Quint
,
E.
Singh
,
M.
Huckabee
,
P.
Brown
,
D.
Beck Brake
,
C.
Bickley
,
J.
Johnston
,
B.
,
2006
, 4D pressure pilot to steer well spacing in tight gas, Society of Petroleum Engineers Annual Technical Conference,
San Antonio, TX
, SPE Paper 102745,
14
p.
Shanley
,
K.W.
Cluff
,
R.M.
Robinson
,
J.W.
,
2004
,
Factors controlling prolific gas production from low-permeability sandstone reservoirs: Implications for resource assessment, prospect development, and risk analysis
:
AAPG Bulletin
 , v.
88
, p.
1083
1121
.
Shaughnessy
,
J.
Butcher
,
R. H.
,
1974
,
Geology of the Wagon Wheel nuclear stimulation project, Pinedale Field, Wyoming
,
AAPG Bulletin
 , v.
58
, p.
2250
2259
.
Spencer
,
C.W.
1989
, Comparison of overpressuring at the Pinedale anticline area, Wyoming and the Multiwell Experiment site, Colorado, in
Law
,
B. E.
Spencer
,
C.W.
, eds.,
Geology of tight gas reservoirs in the Pinedale anticline area, Wyoming and at the Multiwell Experiment site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
,
16
p.

References Cited

Byrnes
,
A.J.
2005
, Gas in low-permeability reservoirs of the Rocky Mountain region, in
Bishop
,
M. G.
Cumella
,
S.P.
Robinson
,
J.W.
Silverman
,
M.R.
, eds.,
Rocky Mountain Association of Geologists 2005 Guidebook CD
 , p.
69
108
.
Chapin
,
M.A.
Govert
,
A.
Brandon
,
N.
Uguetto
,
G.
,
2014
, Sedimentology and reservoir characterization of the Late Cretaceous Lance and Upper Mesaverde intervals from core data in Pinedale field, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
175
245
.
Cluff
,
S.G.
Cluff
,
R. M.
,
2004
, Petrophysics of the Lance sandstone reservoirs in Jonah field, Sublette County, Wyoming, in
Robinson
,
J. W.
Shanley
,
K.W.
, eds.,
Jonah Field: Case Study of a Tight-Gas Fluvial Reservoir and AAPG Studies in Geology 52 and Rocky Mountain Association of Geologists 2004 Guidebook
 , p.
215
242
.
Dickinson
,
1989
, Analysis of vitrinite maturation and Tertiary burial history, northern Green River Basin, Wyoming, in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
, Chapter F.
DuBois
,
D.P.
Wynne
,
P.J.
Smagala
,
T.M.
Johnson
,
J.L.
Engler
,
K.D.
McBride
,
B.C.
,
2004
, Geology of the Jonah Field, Sublette County Wyoming, in
Robinson
,
J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52 and Rocky Mountain Association of Geologists 2004 Guidebook
 , p.
37
59
.
Furbish
,
W. J.
1975
,
Corrensite of deuteric origin, The American Minerologist
, v.
60
, p.
928
930
.
Govert
,
A.
2009
, Petrogenetic Controls on the Porosity of Tight-gas Sandstones in the Lance Formation, Pinedale Anticline, Sublette County, Wyoming,
M.S. Thesis, Colorado School of Mines
,
Golden, Colorado
,
131
p.
Hanson
,
W. B.
Vega
,
V.
Cox
,
D.
,
2004
, Chapter 6, Structural geology, seismic imaging, and genesis of the giant Jonah Gas Field, Wyoming, U.S.A., in
Robinson
,
J. W.
Shanley
,
K. W.
, eds.,
Jonah Field: Case Study of a Giant Tight-Gas Fluvial Reservoir, AAPG Studies in Geology 52
 , p.
61
92
.
Jiang
,
Wei-The
Peacor
,
D. R.
,
1994
,
Formation of corrensite, chlorite and chlorite-mica stacks by replacement of biotite in low-grade politic rocks
,
Journal of Metamorphic Geology
 , v.
12
, p.
867
884
.
Johnson
,
L.J.
1964
,
Occurrence of regularly inter-stratified chlorite-vermiculite as a weathering product of chlorite in soil
,
American Mineralogist
 , v.
49
, p.
566
572
.
Law
,
B.E.
Johnson
,
R. C.
,
1989
, Chapter B, Structural and stratigraphic framework of the Pinedale Anticline, Wyoming, and the Multiwell Experiment Site, Colorado in
Law
,
B. E.
Spencer
,
C.W.
eds., Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site, Colorado,
U.S. Geological Survey Bulletin 1886
 .
Law
,
B. E.
Spencer
,
C. W.
,
2014
, The Pinedale Gas field: A sweet spot in a regionally pervasive basin-centered gas accumulation, Green River and Hoback Basins, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
37
59
.
Martin
,
T.S.
McDermott
,
R.W.
Kneller
,
S.R.
Longman
,
M.W.
,
2014
, Geologic overview of Pinedale field, Sublette County, Wyoming, in
Longman
,
M. W.
Kneller
,
S. R.
Meyer
,
T. S.
Chapin
,
M. A.
, eds.,
Pinedale field: Case study of a giant tight gas sandstone reservoir: AAPG Memoir 107
 , p.
321
349
.
Pollastro
,
R. M.
1989
, Chapter D, Mineral composition, petrography, and diagenetic modifications of the Lower Tertiary and Upper Cretaceous sandstones and shales, Northern Green River Basin, Wyoming in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
.
Prensky
,
S.E.
1989
, Chapter H, Gamma-ray well-log anomaly in the northern Green River Basin of Wyoming, in
Law
,
B. E.
Spencer
,
C. W.
, eds.,
Geology of Tight Gas Reservoirs in the Pinedale Anticline Area, Wyoming, and at the Multiwell Experiment Site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
.
Quint
,
E.
Singh
,
M.
Huckabee
,
P.
Brown
,
D.
Beck Brake
,
C.
Bickley
,
J.
Johnston
,
B.
,
2006
, 4D pressure pilot to steer well spacing in tight gas, Society of Petroleum Engineers Annual Technical Conference,
San Antonio, TX
, SPE Paper 102745,
14
p.
Shanley
,
K.W.
Cluff
,
R.M.
Robinson
,
J.W.
,
2004
,
Factors controlling prolific gas production from low-permeability sandstone reservoirs: Implications for resource assessment, prospect development, and risk analysis
:
AAPG Bulletin
 , v.
88
, p.
1083
1121
.
Shaughnessy
,
J.
Butcher
,
R. H.
,
1974
,
Geology of the Wagon Wheel nuclear stimulation project, Pinedale Field, Wyoming
,
AAPG Bulletin
 , v.
58
, p.
2250
2259
.
Spencer
,
C.W.
1989
, Comparison of overpressuring at the Pinedale anticline area, Wyoming and the Multiwell Experiment site, Colorado, in
Law
,
B. E.
Spencer
,
C.W.
, eds.,
Geology of tight gas reservoirs in the Pinedale anticline area, Wyoming and at the Multiwell Experiment site
 ,
Colorado
,
U.S. Geological Survey Bulletin 1886
,
16
p.

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