Abstract The Cretaceous Ferron Sandstone is a fluvial-deltaic system that is superbly exposed along the western flank of the San Rafael Swell in east-central Utah. The Ferron consists of fluvial, near shorezone, and shallow-marine strata that were deposited along the active margin of an evolving foreland basin. The 180-m-thick (590-ft) Ferron Sandstone forms an east- to northeast-thinning clastic wedge that is bounded by marine strata and pinches out over the distance of 40 km (25 mi). Numerous local transgressive intervals further subdivide the Ferron into 10-20-m (30-60-ft) thick successions of fluvial and shallow-marine strata that are similar to the commonly used ‘parasequence.’ Along the Molen Reef escarpment, cliffs of 100 m (300 ft) in height and 20 km (12 mi) in length provide a nearly complete dip view through the entire thickness of the Ferron Sandstone. A detailed stratigraphic framework is constructed for the exposure by tracing beds between closely spaced measured sections in the field and from photomosaics. The stratigraphic framework documents abrupt lateral facies changes across five surfaces interpreted as unconformities. The surfaces are characterized by incision (up to 30 m [90 ft]) of fluvial and estuarine strata into shallow-marine strata and an abrupt basinward shift of coastal-plain and nearshorezone strata. The unconformities are onlapped by coastal-plain and near-shorezone strata associated with sets of aggradational-to-retrogradational parasequences. Accompanying the change in parasequence stacking pattern are distinct changes in the facies of near-shorezone strata. Those associated with the abrupt basinward shifts are relatively mud-rich, display rapid lateral changes in facies, and are dominated by sediment-gravity-flow processes. In contrast, near-shorezone strata associated with the aggradational and retrogradational parasequences are relatively sand-rich, display minimal changes in facies laterally, and are dominated by wave and storm processes. The incision of fluvial strata and abrupt basinward shifts in environments are interpreted to reflect falls in relative sea level related to minor tectonic and/or eustatic events. Variations in near-shorezone deposits, between those dominated by sediment gravity flows and those dominated by wave or storm reworking, are interpreted to reflect changes in the ratio of sediment supply and accommodation.

Abstract Exposures of the Ferron Sandstone Member of the Cretaceous Mancos Shale formation, east-central Utah provide large-scale cross-sectional views of valley-fill sandstone bodies within a well-constrained sequence stratigraphic framework. Quantitative data collected from these outcrops help constrain the modeling of interwell volumes of analogous valley-fill reservoirs and permit a better evaluation of reservoir potential. The study has implications for how heterogeneities should be modeled in analogous reservoirs. Differences in net-to-gross, connectivity, and petrophysical property structure of valley-fill deposits can be related to stratigraphic stacking pattern (progradational versus aggradational) and position along depositional profile (proximal versus distal). Valley-fill deposits display a general decrease in net-to-gross and sand body connectivity when stacking patterns of delta-front sandstone bodies change from strongly progradational to aggradational or from proximal to distal positions within a valley fill. Valley-fill deposits associated with strongly progradational delta-front sandstone bodies are preserved as relatively homogenous, sand-rich bodies that have a narrow shoestring-like geometry. Sandstone beds are highly amalgamated and mudstone interbeds are generally rare. The principal heterogeneity within these deposits are caused by relatively low-permeability sandstones containing abundant clay clasts that occur along the base and margins of individual channel-form bodies. In contrast, valley fills associated with aggradational delta-front units are preserved as relatively heterogeneous, mud-rich bodies that have a broad ribbon like geometry. Internal heterogeneities result from mudstone drapes that line the base and margin of individual channel-form bodies and from the interbedding of sandstone dominated channel-form bodies with mud-stone-dominated channel fills. In going from a proximal to distal position within a valley-fill deposit the frequency and continuity of mudstone drapes and frequency of mudstone-dominated channel fills increases. Vertical and horizontal variograms indicate permeability is correlated over a distance of about 4-8 m (13-26 ft) vertically and approximately 40-60 m (130-200 ft) laterally. The vertical and lateral correlation ranges are similar to the average channel-form width and thickness.

Abstract Development of the 330-billion-bairel oil resource remaining in United States reservoirs after conventional primary and secondary recovery will be dependent on the advanced understanding of facies relations and compartmentalization inherent in reservoir depositional systems. Style of deposition, as reflected in internal reservoir architecture, defines flow units that determine how a reservoir drains, where hydrocarbons remain unrecovered at the interwell (macroscopic) scale, and what approaches will be effective in accessing unrecovered oil. A substantial part of the unrecovered oil resource is nonresidual oil that, although mobile in the reservoir, remains unrecovered owing to poor contact by existing wells and vertical or areal bypassing by the waterflood front. Because heterogeneity style is a product of depositional system, it is predictable and can be characterized in terms from low to high in a lateral and vertical sense. For sandstones, the wave-dominated deltas, barrier cores, and sand-rich strand plains show a low degree of heterogeneity in both dimensions, whereas the highly aggradational backbarrier fans, fluvially dominated deltas, and fine-grained meander belts show a higher intensity of heterogeneity. Other systems can be similarly classified. The resulting matrix leads to delineation of targeted approaches to incremental oil recovery specifically tailored to the distribution of remaining oil saturation. Such approaches, optimized to the character of the depositional system, may include geologically targeted infill drilling, selective recompletion, horizontal drilling, and strategic cross-reservoir flooding involving flood redesign and profile modification. Such techniques are herein termed Advanced Secondary Recovery (ASR) and represent advancements in technology that will lead to near- and mid-term improvements in efficiency that set the stage for later approaches to Enhanced Oil Recovery (EOR). Abstract Sedimentation rates vary by eleven Orders of magnitude and the physical scale of depositional units varies by fourteen orders of magnitude. These variations suggest a hierarchical ordering of depositional units in clastic sedimentary deposits. A tentative grouping of architectural units has been constructed, based primaril on the recurrence interval of the depositional events: Group 1 deposits are the product of events taking tens of seconds to a few minutes, such as the burst-and-sweep activitiy of a fluid boundary layer. Group 2 deposits are those formed in a few minutes to a few hours, and include ripples and dune depositional increaments. Group 3 deposits are those forming in a few hours to a day or two, including diurnal tidal bundles. Group 4 deposits form in days to a few months, and include such processes as neap-spring tidal cycles:group 4 deposits also encompasse the spacing of many storm events. Group 5 deposits represent one to a few years, such as seasonal events (spring runoff, glacial varves), and occasional violent storrms. Group 6 is for sedimentary processes of a hundred to thousands of years duration, including the evolution of fluvial macroforms, eolian dunes and tidal sand-wave fields. Group 7 represents longterm geomorphic processes, over thousands to tens of thousands of years, such as channel and draa migration. Group 8 processes extend over tens to hundreds of thousands of years, and represent such depositional elements as channel belts, ergs and sand-ridge fields. Fifth-order stratigraphic sequences, many generated by Milankovitch causes, are also of this rank. Group 9 processes are of hundreds of thousands to a few million years duration, such as fourth-order stratigraphic cycles (e.g., major cyclothems, shelf coarsening-upward cycles driven by thrust-loading events, etc). Deposits assigned to group 10 are those taking a few millions to tens of millions of years, including third-order stratigraphic cycles. Instantaneous sedimentation rates are of a similar order of magnitude within each group, ranging from 10 5 m/ka for the smallest scale of deposit, to 10 -1 m/ka for groups 9 and 10. Deposits of each group may be defined, in some cases, by enclosing bounding surfaces. Hierarchiesof such surfaces have been erected for fluvial and eolian deposits and for some suites of estuarine and shelf bedforms. Investigations of each group require different techniques. Deposits up to group 7 and possibly 8 may be documented in expectionalyy good outcrop. Studies of moderm deposits of groups 6 to 8 may be carried out using high-resolution geophysical techniques. Groups 7 to 10 require investigation and reconstructio using basin-mapping techniques based on careful correlation. Subsurface well and seimic data may be employed. Abstract An enormous mobile-oil resource (35 Bbbl in Texas and 80–100 Bbbl in the United States) is trapped in inefficiently drained, mature reservoirs. Much of this oil can be recovered at low cost through conventional infield exploration and development strategies that target untapped compartments in these reservoirs. Three-dimensional facies architecture exerts the primary control over the distribution and continuity of reservoir compartments. Reservoirs with complex internal architecture contain large volumes of remaining mobile oil; those with a simpler internal architecture are efficiently drained. Three Texas reservoirs, representing differences in internal architecture, illustrate variations in reservoir-pay continuity: barrier-island (41-A reservoir in West Ranch field in south-central Texas), fluvial (Jim Wells and Brooks reservoirs in La Gloria field in South Texas), and submarine fan (reservoirs in the Spraberry Trend in the Midland Basin). Methods of estimating pay continuity based on facies geometry and variations in permeability between wells can be used to describe reservoir heterogeneity and indicate areas for infield exploration in each of these reservoirs. Although most barrier-island reservoirs are considered to be relatively homogeneous, the 41-A barrier-island reservoir in West Ranch field contains wide, dip-oriented belts of lenticular tidal-inlet facies that disrupt reservoir continuity in the main barrier-core facies. Additionally, the tidal-inlet facies are internally less continuous than the barrier-core facies. Other reservoir compartments that exhibit low continuity in the 41-A reservoir occur in flood-tidal-delta sandstones partly encased in lagoonal mudstones updip of the barrier core. Infill wells drilled into the lower-continuity facies in the 41 - A reservoir at well spacings less than the conventional 20-acre spacing can contact additional oil, resulting in substantial reserve additions. Fluvial reservoirs have a higher degree of internal complexity than do barrier-island reservoirs, and they exhibit significant heterogeneity in the form of numerous sandstone stringers bounded vertically and laterally by thin mudstone layers. Successful infill wells in La Gloria field contact partly drained reservoir compartments in splay deposits that pinch out laterally into floodplain mudstones. Recompletions in bypassed stringers in La Gloria field contact channel-fill sandstone compartments that are isolated vertically by floodplain mudstones. Mud-rich submarine-fan deposits are extremely heterogeneous and may have the greatest potential for infill drilling to tap isolated compartments in clastic reserviors. The Spraberry Trend in West Texas contains thin, discontinuous reservoir sandstones deposited in a complex midfan channel- and levee-system. Although facies relationships in Spraberry reservoirs are similar to those in fluvial resevoirs in La Gloria field, individual pay stringers are thinner and more completely encased in low-permeability mudstone facies. Abstract Photomosaics can be useful tools for understanding and communicating geologic features expressed on outcrop faces. In order to utilize photomosaics properly, maximum resolution and minimum geometric distortion of the features is necessary. Maximum resolution is best obtained by using quality equipment and by attending to proper technique. In some cases increasing contrast will improve resolution; various methods can be utilized. Sufficient overlap of photographs in the construction of photomosaics will remove distortion in most situations. A common problem is perspective distortion, the convergence of vertical lines. This occurs when the film plane and outcrop face are not parallel and results in curved or "smiling" mosaics. When it is not feasible to obtain parallelism, several methods can be used to help correct this problem. In many situations fitting a 35-mm camera with a perspective control lens is the simplest and most economical strategy for reducing or eliminating the problem.

Abstract In order to understand how an eolian sequence was generated, a 45-m-high, 54,000-m 2 outcrop of Middle Jurassic Page Sandstone near Page, Arizona, was mapped and reconstructed within the context of a 9.5-km-long lateral traverse. Recognition of prominent bounding surfaces and distinctive sequences of cross-strata between surfaces allows the identification of nine complexes. The 'A' complex consists primarily of coarser grained, low- to moderate-angle wind-ripple laminae arranged in sets, but also shows a single set of high-angle grainflow strata. The complex is situated in a depression on the 3-2 unconformity at the top of the Navajo Sandstone, and is interpreted to represent deposits of isolated barchan dunes. slipfaceless bedforms, and ‘wedges’ of sand filling the depression. The ‘A’ complex may be part of the J-2 ‘event’, predating the Page per se and representing local deposition in an overall deflationary period, or it may herald widespread renewed deposition immediately preceding the Page system. The B' and 'C complexes are separated by a prominent surface, but both consist of large sets of trough cross-strata in which the directional spreads of the foresets define crescentic shapes, and the dominance of grainflow strata indicates deposition by transverse dunes. Complex ‘B’ also contains sets that are interpreted as the result of secondary air flow along flanks of crescentic draas. A wavy-laminated, silty, fine-grained, red standstone rests on a prominent surface that truncates the ‘C’ complex. Cross-strata above this surface are distinctly different from those of the underlying complexes. Complexes ‘D’ to T, each of which is separated by a surface with polygonal fractures, are similar to one another and consist of sets dominated by wind-ripple laminae with strongly developed cyclic stratifications, and are interpreted as oblique-dune deposits. The complexes differ, however, in interpreted dune size and whether the bedforms were simple dunes or draas. All complexes on the outcrop show a mean transport direction to the south, which corresponds to predominant northerly summer winds. Dunes represented by complexes ‘B’ and ‘C’ appear to have been little affected by winter winds from the northeast, but dunes in the overlying complexes were moderately modified by more variable winter winds. Radically different interpretations of the complexes and prominent surfaces can be reasonably proposed. Interpretation of the surfaces as first-order surfaces envisions that the vertical and lateral Page sequence results from uninterrupted accumulation of a widespread erg, albeit under changing conditions with evolving dune types. Interpretations of the surfaces as super surfaces and the complexes as deposits of separate dune fields and ergs forces the Page sequence to be viewed as a complex amalgamation of overlapping segments of ergs and dune fields formed in a dynamic-basin setting with varying times, sites, and degrees of deposition and erosion. These alternate views are fundamental to the understanding of the genesis of eolian sequences at the basin level, and are presently best addressed at the regional and not outcrop scale.

Abstract Auk field is located in the central North Sea and produces oil from Permian Zechstein carbonates and the underlying Rotliegend sandstones. The Rotliegend is 150 to 500 m thick and can be divided into five discrete episodes of desert sedimentation. Deposits of the upper three episodes are oil bearing, with eolian slipface sands forming the main producing intervals. The earliest deposits (unit 5) are localized waterlain conglomerates, which possibly infill topography on the unconformity with the Devonian. They are overlain by a large wedge-shaped mass of eolian slipface sands (unit 4) that onlaps the Devonian. Unit 3 represents a change in eolian deposition with a marked increase in wind-ripple laminated strata. Their abundance probably indicates more variable winds, and thin conglomerates of interdunal dolomite clasts suggest periodically wet conditions. This depositional unit varies in thickness by about 100%, with thick areas corresponding to the stacked deposits of slipfaceless draa and thin areas to stacked interdunes. Dune slipface sands within the draa accumulations are orientated toward the east and cannot be correlated over hundreds of meters between wells in a cross-wind direction. Unit 2 contains a still greater proportion of wind-ripple laminated sands and waterlain deposits. Its geometry is dominated by a large depositional mound -7 km across wind, 87 m thick, and thinning to 10 m in its adjacent interdunes. The mound is located above an interdunal thin of unit 3. Several intervals of dune and probably draa slipface sands occur where the mound is thickest, and a distinctive body of fine-grained eolian sands mantles its northern flank. The uppermost unit (1; Weissliegend) comprises waterlain mass-flow sands that partially infill interdunal lows and appear to represent reworking of a largely abandoned erg by rain water. Intercalated organic-rich shales and dolomites contain indications of evaporitic conditions, desiccation, and deflation and yield no evidence of marine faunas. The succeeding marine Zechstein gently inundated remaining topography.

Abstract The geometries of nonmarine-sandstone reservoirs of the subsurface Mesaverde Group in northwestern Colorado were estimated on the basis of sedimentologic studies. The accuracy of the estimates was subsequently assessed by geophysical tests and reservoir-engineering studies, such as vertical seismic profiles, hydraulic-fracture diagnostics, pressure tests (drawdown/buildup, production, and interference tests), and tracer tests. After the effects of natural fractures on these subsurface tests are accounted for, the tests provide indications of reservoir boundaries, internal heterogeneity, and continuity that are compatible with sedimentologic predictions.

Abstract The Westwater Canyon Member of the Morrison Formation (Upper Jurassic) has previously been interpreted as consisting of fluvial “channel systems” tens of kilometers wide and tens of meters thick. Reinvestigation of the member indicates that these “channel systems” actually represent post-depositional aquifer conduits, defined instead by differing sandstone colors, rather than primary depositional features. The member is composed of amalgamated, individual fining-up sandstone sheets each about 5-10 m thick. The absolute widths of these sheet sandstone bodies are at least 1 km and possibly exceed several kilometers. The width.thickness range of the sandstone sheets are well within the typical values of sandstone body dimensions reported from other fluvial sandstones, and are interpreted to represent aggradational channel-belts. Sandstone bodies thicker than about 12 m are the result of amalgamation of these individual unit sandstone bodies, and do not represent individual channel belts as interpreted previously. Internally, the sheets contain abundant concave-up troughs typically 30 m wide and 5 m thick, filled both laterally and vertically with inclined parallel- to low-angle cross-stratified sandstone, in places exhibiting parting lineation. The laterally-limited extent of these large troughs and nature of their internal fills suggest that they represent short-lived scour fills rather than confined elongated channels. The concave-up erosional base, a negative feature, was most likely formed due to large-scale flow separation within a wider and shallower channel. Physical conditions similar to stream-flow convergence at channel confluences may be responsible for their formation. The abundant preservation of these troughs in the Westwater Canyon Member is consistent with the expected poor preservation of positive barforms in a sweeping, sandy-braided channel belt. Review of the literature indicates that inferred channelbelt sandstone bodies mostly fall within the thickness range of 1 to 12 m, irrespective of their interpreted fluvial style. Post-depositional large-scale reservoir conduits are also expected to fall within this range for sandy fluvial systems-. Deviations from this range are due to amalgamation of the sandstone bodies or increased grain-size heterogeneity, resulting in an increase and decrease, respectively, of the conduit size.

Abstract Architectural studies in the Kayenta Formation (Lower Jurassic) of the Colorado Plateau reveal the characteristics of two types of sandstone body, that reflect both ephemeral and perennial fluvial processes. The first type is composed of high-regime horizontally-laminated sandstone, forming multiple-event Storys up to 8 m thick, deposited by flash floods. The second type is composed of planar cross-beds, deformed parabolic cross-beds and massive sandstone formed under low-regime flow from a perennial river during high stage. The style of deposition is dependent upon the degree of confinement within the boundaries of the channel system in question. Where confinement was dominant, sedimentary fill often reflects the geometry of the containing channel. Paleocurrent distribution reflects the depositing flow conditions in confined bodies. Horizontally-laminated units show strongly unimodal currents, whereas the heterolithic confined units show a wider scatter. Where flow was unconfined (during high stage, when thalwegs were inundated), the resulting deposits are broad sheets interfingering with underlying confined sandbodies. A zone of interdigitation displays sharp changes in paleoflow direction within the same stratigraphic horizon, resulting from the simultaneous action of confined and unconfined depositional processes. The interdigitation records the incremental abandonment of channels, as large unconfined barforms encroached on them during high stage. Discharge variability is inferred from lithofacies composition; variable but perennial discharge shows a wide range of lithofacies, including clay drapes resulting from minimum, sluggish flow. Flashy discharge shows only two lithofacies types, those representing low-regime waxing and waning flow and those representing high-regime peak flow. Clay drapes are absent

Abstract The Upper Triassic Chinle Formation in southeastern Utah is a sequence of continental strata deposited in a back-arc cratonic basin. Archi tectural-faries analysis of exposures in sub-parallel canyons and in cliffs surrounding structural uplifts reveals an intricately interbedded fluvial-deltaic-lacustrine system characterized by: 1. mobile fluvial-channel belts consisting of stacked, high- and low-sinuosity channel complexes; 2. overbank deposits, including levees, paleosols, marshes, and small floodplain lakes interiingered with crevasse splays and lacustrine deltas; and 3. extensive lacustrine-basin, lacustrine-mudflat, and eolian sandsheet strata deposited throughout the entire study area. Stratigraphic panels of closely-spaced measured sections oriented both perpendicular and parallel to depositional dip depict the facies architecture both within the extra-channel strata and the relations of the extra-channel deposits to adjacent channel complexes. In the Shinarump and Monitor Butte Members in the lower part of the Chinle Formation, fluvial-channel complexes interfinger with extra-channel facies. These extra-channel facies include levees, crevasse splays, and wetland complexes consisting of lacustrine deltas, lakes, and marshes. In the Moss Back and Petrified Forest Members in the middle part of the Chinle, fluvial-channel complexes interfinger with floodplain strata characterized by paleosols and crevasse splays. Locally, paleosol horizons and lake and marsh deposits serve as marker beds in three dimensions. The Owl Rock and Church Rock Members in the upper part of the Chinle are dominated by laterally extensive lacustrine-basin, lacustrine-mudflat, and minor eolian sandsheet strata that extended throughout the study area.

Abstract The Huesca System is interpreted as a terminal, distributive fluvial system. Flow across this ‘fluvial fan’ was largely through a network of well-defined channels and the deposits typically consist of channel-sandstone bodies enclosed within floodplain fines. Amalgamation of the sandstone units varies depending on the location within the system. Lateral profiles are used to show that there are systematic and broadly quantifiable variations in the alluvial architecture across the system. A precise apex for this distributive system cannot be determined, and thus a datum line has been constructed within the proximal region. This datum has enabled plots to be constructed showing medial to distal variations. The results indicate 1. the proportion of in-channel sediment decreased distally; 2. the sandstone bodies thin distally and thus the paleochannels were becoming shallower, and 3. sheet sandstones deposited by laterally unstable channels are prevalent medially, whereas more stable channels, indicated by ribbon sandstones, were more common distally. The decrease in channel depth and in-channel component are probably the result of evaporative water loss, channel bifurcation and gradient decrease. The increased channel stability distally is interpreted to be the result of reduced ability to erode the banks, more frequent avulsion and ephemeral flow. The alluvial architecture of the ‘peripheral areas’ of the system, adjacent to the thrust front that defines the northern margin of the basin, differs slightly from the main part of the system. The main difference is the higher frequency of ribbon sandstones in the peripheral areas. This may be due to the tectonic instability of the area near the thrust front and periodic inundation by the marginal alluvial fans. Also, these marginal fans would have increased the flow paths of streams into the peripheral parts of the main system. The study has applications to hydrocarbon exploration in analogous sequences. Radial variations in reservoir potential are indicated and the extents of sandstone bodies in the subsurface may be estimated from the width-thickness relationship determined from the medial part of the system.

Abstract The Late Devonian Rockfields Member of the Bulgeri Formation in northeast Queensland, Australia, was deposited in a tectonically active alluvial basin. The source area was an uplifted igneous and metamorphic terrain to the south of a major oblique-slip fault zone, forming the basin margin. The member is characterized by relatively uniform, very fine- to medium-grained, soft-sediment-deformed sandstones, interbedded predominantly with slightly reddened siltstones. Detailed mapping of sediment body geometries and internal structures has resulted in the recognition of eight architectural elements. Channel-fill elements include laminated sand sheets, dune complexes, scour fills, laterally-and downstream-accreting macroforms, and linguoid barforms. Floodplain elements include levees, crevasse splays, and overbank fines. The abundant soft-sediment deformation structures (mainly convolute lamination) were produced by liquefaction of sandy bedforms, during or immediately after rapid deposition. Larger scale structures, however, deform multiple erosion surfaces. These may be due to liquefaction of saturated unconsolidated sands during earthquakes of magnitude >5, with inferred epicenters along the fault zone 20 km to the south. The proposed depositional model comprises a broad, sandy braidplain with marked discharge variation, resulting in widespread seasonal flooding. Channel-avulsion events, combined with a relatively high subsidence rate associated with tectonic activity, resulted in the accumulation of laterally extensive, sheet-like, channel sandbodies and fine-grained floodplain deposits. A modem analog is the seasonally inundated low-sinuosity channel system of the alluvial plains and fans surrounding the Gulf of Carpentaria, north Queensland. This model bears some resemblance to published models for low-sinuosity streams, but sufficient differences warrant recognition as a distinct fluvial style. The unit represents an example of a strongly layered sequence with laterally extensive (>1,500 m) channel sandstone bodies 3-10 m thick, separated by floodplain deposits 0.3-2 m thick of comparable lateral extent (1,500 to >4,000 m). Hydrocarbon reservoirs with similar architecture, uniform grain size, and a general lack of internal fine partings could be considered to behave isotropically with respect to fluid flow within individual bodies.

Abstract In the Middle Jurassic series of the Cleveland basin (Northeastern England), the Scalby Formation comprises two main members, interpreted as a valley-fill complex overlain by a deltaic aggradational series. The valley was incised during a relative sea-level drop and infilled during a stepped relative sea-level rise by a retrogradational fluvial to estuarine complex. The valley fill is composed of three superposed sandsheet prisms showing, respectively, 1. fluvially dominated straight channels, 2. tidally influenced meander belts, and 3. a mixed fluvial-tidal meander belt The deltaic aggradational member corresponds to highstand deposits. Small ribbons or meandering channels are isolated in shaly floodplain and lacustrine facies. A precise three-dimensional reservoir reconstruction has been carried out on a 1-km 2 area using cliff sections, drill cores, wireline logs and petrophysical measurements. Accurate reservoir reconstructions are presented here as large cross sections in terms of lithology, porosity and permeability. At Cloughton, the valley-fill member consists of a lower and upper prism. Each corresponds to a channel-fill stage with a basal aggradational fluvial unit overlain by an estuarine or paralic transgressive unit The basal prism displays a fluvial stacked-chaanel unit with side bars and sand or clay plugs, the tops of which are truncated by a transgressive surface. The unit is overlain by an estuarine sand-flat complex. The upper prism corresponds to tidally-influenced meander belts with hectometric point bars composed of argillaceous sandstone and siltstone. It is capped by shaly marsh deposits, corresponding to the period of maximum flooding of the valley fill. The aggradational deltaic member consists mainly of delta-plain shales with multistory ribbon channels and wide meander belts. The best potential reservoirs are located in the basal fluvial sucked channels of the valley fill. Reservoir qualities decrease in the estuarine sand-flat complex and are very poor in the mixed fluvial-tidal meander belts. The small ribbon channels generally constitute good but small disconnected reservoirs. The sequence stratigraphy of the Scalby Formation shows that reservoir geometry and architecture could be controlled by minor relative sea-level variations.

Abstract A three-dimensional facies analysis of Cenozoic fluvial deposits in the vicinity of a federal Superfund site near Oroville, California, was conducted to characterize aquifer heterogeneity and to provide a basis for accurate modeling of the complex groundwater system. A network of 29 boreholes in the 6.5-km 2 study area penetrated four distinctive fluvial units, including the Laguna Formation (upper Pliocene-Holocene), Nomlaki Tuff (upper Pliocene), Mehrten Formation (Miocene-upper Pliocene), and lone Formation (Eocene). All four formations consist of pebble-cobble gravel, sand, and clay deposited by the Feather and ancestral Feather River systems at the margin of the Sacramento Basin near the western Sierra Nevada mountain front. Sediment gravity flows and waterlain andesitic and pumice-rich volcaniclastic facies derived from the southernmost Cascade volcanic centers episodically choked the ancestral Feather River system during late Pliocene upper Mehrten and Nomlaki Tuff deposition. Cenozoic fluvial aggradation was interrupted by three periods of valley cutting, which occurred 1) during the Oligocene, between deposition of the lone and Mehrten Formations; 2) during the late Pliocene, between deposition of the Nomlaki Tuff and Laguna Formation; and 3) during the middle Pleistocene, after most Laguna deposition was completed. The Oligocene and late Pliocene paleovalleys, 24 to 61 m deep, are filled with vertically and laterally interconnected channel pebble-cobble gravel of the Mehrten and Laguna sequences. The principal aquifer zones in the study area are >30-m-thick units of hydraulically continuous channel gravel and sand of the Laguna, Mehrten, and lone Formations. These aquifer zones are continuous across Oligocene and late Pliocene paleovalley margins through channel-fill gravel and sand of the various formations. Floodplain clay and volcaniclastic debris-flow units act as aquitards, which locally limit the interaction between permeable zones. A dissolved pentachlorophenol plume in local ground water originates at the Superfund site (a wood treatment plant) in the northern end of the study area, where it initially moves within the Laguna Formation. The plume has migrated into hydraulically continuous Mehrten and lone gravels that are in contact -425 m south of the plant site. The plume has also passed into juxtaposed Mehrten and Laguna gravels 1,400 m south of the plant site. Pumping-test data demonstrate that no marked changes in hydraulic conductivity occur across the paleo v alley- fu11 boundaries. Local changes in the hydraulic-gradient vector are caused by changes in the permeability of the aquifer material or in the thickness of the aquifer zones, both of which are associated with lateral changes in formations and facies.

Abstract Fluid-flow units and fluid-flow barriers are distinguished through mapping distributions of facies and bounding surfaces of coalesced channel belts within the Lower Cretaceous J Sandstone in the Peoria field, Colorado. Measured rock properties (porosity, permeability, relative permeability, and capillary pressure) were calibrated to facies, which were distinguished by common associations of grain sizes, clay content, and sedimentary structures. The three-dimensional distribution of rock properties in the J sandstone reservoir was obtained through facies mapping. Within a meander belt, trough cross-stratified and clean, ripple-laminated point-bar sandstones act as flow units, and clay-rich abandonment fills act as flow barriers. Hydraulic communication between vertically stacked channel belts depends on the thickness and continuity of muddy sandstones having abundant clay inclusions that commonly overlie basal scour surfaces. The effect of smaller scale sedimentary bounding surfaces on fluid flow was not measurable at the scale of the well spacing and engineering data available. Compartmentalization of the reservoir is indicated by two elevations of oil-water contacts along the downdip, west flank of the field. This is explained by a concentration of abandonment-fill facies and a lack of hydraulic communication between coalesced channel belts in the center of the field. Pre- and post-injection production patterns are explained by the geologic model.

Abstract Gas production (7.2 Bcf) from low-permeability sandstones in the Early Cretaceous Travis Peak Formation, North Appleby field, Nacogdoches County, Texas, is enhanced through hydraulic fracturing of stacked, blocky to upward-fining sandstones encased in impermeable mudstone interbeds. Pervasive quartz cement in the sandstones decreases porosity and permeability and contributes to formation of the reservoir seal. Subsurface data indicate that much of this 615-m-thick section represents aggradation of alluvial-valley deposits. Multiple channel belts form a network of overlapping, broad, tabular sandstones having thickness-to-width ratios of 1:850 (2.4 to 13.2 m thick; widths exceed 6.4 to 8 km). Six to eight channel belts, each containing 80 to 90% medium- to fine-grained sandstone, locally occupy a 61 -m-thick interval. In a vertical sequence through one channelbelt sandstone, basal planar cross-bedding grades upward into thinly interbedded sets of planar cross-beds and ripple cross-lamination. Clay-clast conglomerates line scoured channel bases. Adjacent to the channels, fine-grained sediments accumulated in well-drained swamps and lakes. Poorly sorted sandstones represent overbank deposition. During Travis Peak deposition, alluvial styles evolved from dominantly bed-load deposition near the base of the formation to more mud-rich, mixed-load systems at the top. Sandstone geometry, continuity, and internal heterogeneity influence reservoir performance and well-to-well communication. Small-scale bedforms, biogenic structures, and scour surfaces create fluid-flow barriers and segment reservoirs. Within the channel belts, best-quality reservoir sandstone (high porosity and low-water saturation) exists in narrow bands that are oriented subparallel to depositional dip. Reservoir quality decreases at channelbelt margins (levees) and tops (abandoned channel) and in fine-grained interchannel areas (shadow zones behind longitudinal bars).

Abstract The Dunvegan Formation (mid-Cenomanian) comprises a thick clastic wedge deposited in the West Alberta foreland basin. This wedge consists of a complex series of interbedded shales, siltstones, and sandstones and has been subdivided into seven allomembers (A-G), each separated by widespread flooding surfaces. Allomember E consists of four offlapping, shingled, heterolithic sedimentary units that progressively built seaward to the southeast. Isolith maps of the sandstones within these shingles reveal deltaic morphologies consisting of well-developed sandy depositional lobes fed by sandy distributary channels separated by mudstone-dominated interchannel and interlobe areas. The plan-view morphologies and facies successions in the lobes are typical of prograding river-dominated delta fronts. Superposition of sandbodies within each shingle reveals the autocyclic fashion in which the sedimentary basin was filled. The arcai pattern and scale of overlapping depositional delta lobes are similar to those of the Mississippi delta during the last 5 ka.

Abstract Large-scale Gilbert-type delta deposits occur on the southern side of the Gulf of Corinth in Greece. They accumulated adjacent to the very steep margins of listric-fault blocks. The deltaic complexes consist of very thick (up to 700 m) foreset packages that pass into bottomset strata, which, in turn. pass into thin-bedded turbidites. Topset deposits are well preserved and are the keys to interpreting the fan-delta bodies in architectural terms. The geometric pattern is discussed in terms of accommodation, that is the vertical space made available for the sedimentation. Where there is no accommodation, the topset environment is bypassed and, geometrically, toplap boundaries occur. With increasing accommodation, fluvial topset strata are formed: they pass downdip into the foreset beds. At higher accommodation values, transgressive deposits occur. If accommodation is too high, the transgressive sediments are drowned and foreset beds form on top.