Parallel-laminated Sandstone Research Articles

Sequence stratigraphic controls on the gas-reservoirs distribution and characterization along the Messinian Abu Madi incision, Nile Delta Basin

The Abu Madi sandstones represent the largest gas-bearing reservoirs in Nile Delta Basin of Egypt. This paper aims to perform a sequence stratigraphic analysis besides petrophysical appraisal for the Abu Madi Formation along the Messinian incised valley. Eight facies types (F1–F8) are identified in the Abu Madi Formation, ranging in lithology from sandstone, siltstone, shale and mudstone with different sedimentary structures trough/planar cross-bedding, ripple laminated/laminated and massive. The sequence stratigraphic analysis for thirteen wells extends in both offshore and onshore parts of this incision revealed that the Abu Madi Formation is divided into two depositional sequences: LMDSQ-1 (lower Abu Madi) and LMDSQ-2 (upper Abu Madi). The findings of the petrophysical assessment exhibit that the favorable gas intervals in each depositional sequence correspond the sandstones of the lowstand systems tract (shale content: 4–22%; effective porosity: 12–27%; water saturation: 20–63%) rather than the highstand systems tract or the transgressive systems tract (shale content: 5–30%; effective porosity: 7–20%; water saturation: 30 and 53%). The entire sandstones of the LSTs comprise four reservoir rock types: trough/planar cross-bedded sandstones (Type-1, F1), parallel-laminated sandstones (Type-2, F2), massive sandstones (Type-3, F5) and ripple cross laminated sandstone/siltstones (Type-4, F3). The massive sandstone (Type-3) is the best reservoir type since it contains interparticle pores with porosity up to 26% and horizontal permeability varies between 460 mD and 1439.37 mD. However, the ripple cross laminated sandstone/siltstones (Type-4) have the worst reservoir type, with an average porosity of 12% and a permeability of 0.6 mD.

Cretaceous Forearc Sedimentation and Contemporary Basin Tectonics in Northwestern Borneo: New Sedimentological Insights from Pedawan Formation, Kuching Zone, East Malaysia

Sedimentary successions developed at the destructive plate margin settings are extremely important as they bear valuable record of contemporary basin tectonics and consequent sedimentation. Intense deformation and metamorphism often obliterate the primary sedimentary texture and structures of the sedimentary successions formed at destructive plate margins. However, sedimentological analysis of young unmetamorphosed forearc successions provides rare opportunity to infer the interplay between tectonics and sedimentation. Therefore, a process-based sedimentological facies analysis and provenance studies of the Cretaceous Pedawan Formation in the Kuching Zone, Borneo, have been undertaken for the first time. The sandstones are compositionally and texturally immature. They are normally graded with sole marks and have erosional lower contacts with mudstones and generally have gradational upper contacts. The massive sandstones, parallel-laminated sandstones, and the combination of rippled sandstones with thin mudstones are interpreted as turbidites. The lack of wave-generated structures, including hummocky cross stratification, indicates that deposition took place below storm wave base, possibly in a shelf setting. The lower part of the Pedawan Formation is mudstone dominated, and the upper part progressively becomes sandstone dominated. The Pedawan Formation bears several penecontemporaneously deformed horizons sandwiched between laterally persistent undeformed beds. Deformation structures include folds with reclined to recumbent geometry and layer-confined normal and reverse faults. We have interpreted these deformed horizons as seismites. Modal analyses of the sandstones indicate recycled orogenic as well as arc provenance and thus indicate mixing of recycled orogenic sediments with arc-derived volcanic material. The sedimentary facies characteristics of the Pedawan Formation in combination with numerous penecontemporaneous deformation features at selected stratigraphic levels indicate that the turbidites formed in a seismically active deepwater depositional setting as part of a long-lived subduction complex in eastern Sundaland during which several crustal fragments were accreted to Borneo.

TB or not TB: banding in turbidite sandstones

ABSTRACT Recognition and interpretation of sedimentary structures is fundamental to understanding sedimentary processes. Banded sandstones are an enigmatic sedimentary facies comprising alternating mud-rich (as matrix and/or mud clasts) and cleaner sand layers. The juxtaposition of hydrodynamically different grain sizes contradicts established models of cleaner-sand bedform development. Here, outcrop, subsurface core, and petrographic data from three deep-water systems, with well-constrained paleogeographic contexts, are used to describe the range of sedimentary textures, bedform morphologies, and facies associations, and to quantify the mud content of banding. Banding can occur in any part of a bed (base, middle, or top), but it typically overlies a structureless basal sandstone or mud-clast conglomerate lag, and is overlain by clean parallel-laminated sandstone and/or ripple cross-lamination. Banding morphology ranges from sub-parallel to bedforms that comprise low-angle laminae with discontinuous lenses of mudstone, or asymmetric bedforms comprising steeply dipping foresets that transition downstream into low-amplitude bedwaves, or steeply dipping ripple-like bedforms with heterolithic foresets. This style of banding is interpreted as a range of bedforms that form progressively in the upper-stage plane-bed flow regime via tractional reworking beneath mud-laden transitional plug flows. The balance of cohesive and turbulent forces, and the rate of flow deceleration (aggradation rate), govern the style of deposit. Banded sandstones and linked debrites are rarely found juxtaposed together in the same bed because they are distributed preferentially in proximal and distal settings, respectively. Understanding the origins of banding in turbidite sandstones, the conditions under which it forms, and its distribution across deep-water systems and relationship to linked debrites, is important for it to be used effectively as a tool to interpret the geological record.

Characteristics of a Campanian delta deposit controlled by alternating river floods and tides: the Loyd Sandstone, Rangely Anticline, Colorado, U.S.A.

ABSTRACTThe Campanian Loyd Sandstone Member of the Mancos Shale (Loyd) along the Rangely Anticline, Piceance Basin, Colorado, contains a series of multi-meter-thick, heterolithic, coarsening-upward successions (CUSs) with internal clinoforms comprising low-angle-dipping (< 5°), parallel-laminated sandstone beds interbedded with bioturbated flaser-wavy-lenticular bedded sandstone and siltstone. Loyd clinoforms are delta foresets composed of prodelta and delta-front deposits, including mouthbars. Many CUSs exhibit scours filled with bioturbated sandstone, or interbedded bioturbated sandstone and siltstone or mudstone representing aggradational fill of subaqueous terminal distributary channels or the migration of mouthbars into channel scours. Mud drapes on sedimentary structures and mud rip-up clasts are extremely common. A high-abundance, high-diversity, trace-fossil assemblage includes vertical, 1–4-m-deep Ophiomorpha that may penetrate multiple bedsets of parallel-laminated sandstones and highly bioturbated finer-grained interbeds. Bioturbation increases sandstone content in finer-grained interbeds, and provides sandy conduits that increase connectivity between beds.Although parallel-laminated sandstones volumetrically dominate Loyd delta clinoforms, they likely represent relatively short-term freshwater and sediment input during river flooding that produced delta-front turbidity currents. Interbedded finer-grained beds, mud-draped sedimentary structures, and the high-abundance, high-diversity trace-fossil assemblages record longer amounts of time during reduced fluvial discharge, tidal reworking of sediments, and intense bioturbation under marine salinities. Controls on the internal characteristics of the Loyd delta deposits include: 1) a high sediment influx into a relatively shallow marine basin protected from wave action during normal regression; 2) relatively short-duration, episodic freshwater and sediment discharge from distributaries that reduced salinities, deposited sand as turbidity currents, and promoted delta-front channelization; and 3) longer-duration periods of reduced discharge with deposition of finer-grained sediment, tidal reworking, and bioturbation of sediments under higher salinities. These controls combined to produce the heterolithic, highly bioturbated, river-flood delivered, and tidally modified clinoforms of the Loyd that differ from deposits typically considered to be classic examples of fluvial-flood-dominated or extensively tidally modified deltas.

Rapid subsidence and preservation of fluvial signals in an otherwise wave-reworked delta front succession: Early-mid Pliocene Orinoco continental-margin growth, SE Trinidad

Outcrops of the early-mid Pliocene Orinoco Delta succession on the Atlantic-facing Trinidad continental margin demonstrate facies and stratigraphic architecture of a shelf margin developed in a setting of high sediment supply (Orinoco River) and unusually rapid, sediment accumulation/subsidence (averaging >1 km/My). The studied Moruga clastic wedge of the Orinoco margin consists of a series of topset to deepwater clinoforms with channelized sandstones, river- and mixed-process delta front, wave-dominated delta front, shoreface, prodelta-offshore transition-shelf, upper-slope turbidite channels and mass-transport deposits. The succession is sand-prone and generally consists of coarsening- and thickening-upward delta-front lobes with hummocky/swaley and wave-ripple stratified sandstones indicating dominant storm wave reworking of the delta, particularly when the delta lobes had reached outer shelf sites after long shelf transits. The lower parts of distributary channels are well preserved and characterized by cross-bedded to parallel-laminated sandstones with mud clast lags. The upper parts of channel fills were wave reworked during transgressions, creating hummocky/swaley cross-stratified strata. River-dominated and mixed-process (wave and tide) delta-front deposits occur commonly within stacked, coarsening-upward units. The river-dominated delta front deposits exhibit parallel-laminated to current ripple-laminated intervals with normally graded thin beds changing upward to parallel and low-angle cross lamination, but mixed-process delta front deposits also contain wave and bidirectional current ripples as well as discrete intervals of hummocky/swaley cross-stratification. The preservation of the channel-base as well as river- and mixed-process delta-front deposits in the otherwise storm wave-dominated Atlantic-facing setting suggests some sheltering of the coastal morphology, and possibly low-frequency of large storms, but it is more likely that the unusually rapid subsidence (at rates competing well with Icehouse rates of eustatic sea-level change) and burial of deposits may have prevented the fluvial and tidal signals from being completely reworked by the storm waves in the studied outcrop area. This study demonstrates an example of how the interactions of river-, tide- and wave-generated facies impacted stratigraphic architecture of a rapid subsiding shelf margin built by shelf-edge deltas with high sediment supply.

A new world-class deep-water play-type, deposited by the syndepositional interaction of turbidity flows and bottom currents: The giant Eocene Coral Field in northern Mozambique

Abstract The discovery of the super-giant Coral and Mamba gas fields in the offshore of Northern Mozambique provides a unique insight into the architecture of a new deep-water play-type. High-quality seismic and extensive well data from both fields shows that very clean (clay matrix-poor) sandstone reservoirs, with thickness >100 m and extended over tens of km can be formed by the syndepositional interaction of down-slope high-density turbulent gravity flows and across-slope bottom currents. This is recorded by: i) the marked asymmetry of submarine channels and lateral stacking in which top-of-fan seismic reflectors show a lateral transition from high to low amplitude response from axis to off-axis locations; ii) the occurrence of laterally-deviated lobe deposits, sediment waves and channel-associated drifts in the inferred bottom current direction; iii) the presence of very clean sandstones forming the bulk of the fan units and the consistent lack of interbedded fine-grained facies; iv) the occurrence of fine-grained and thin-bedded facies adjacent to the main fan axes, which are characterized by repeated transitions between ripples and parallel-laminated sandstones, mud-drapes, shale clasts and bi-directional cross-laminae in the same bed, indicating intense traction and velocity pulsations. This association forms a mixed depositional system, in which only the basal and coarse-grained part of the turbidity current load is deposited and preserved in the axial part of the system, whilst all the finer-grained sediments are pirated from the turbulent cloud by laterally flowing bottom currents and deposited in the adjacent sediment drifts. The inferred process results in exceptionally high quality reservoirs whose architectural and facies models were confirmed by the appraisal campaign and production well tests and incorporated into the reservoir model. The results of this study indicate a significant exploration potential in similar geological settings and the definition of a potential new play type, that could lead to the reinterpretation of existing deep-water datasets.

Sedimentary facies analysis and seismic interpretation of deep-water reservoirs, “PAC” field, offshore depobelt, Niger Delta basin

A high-resolution study involving the integration of cores, wireline logs and reflection seismic dataset was used to unravel the facies assemblages, reservoir quality and hydrocarbon potential of E1 and H9 reservoirs in the “PAC” field, Offshore Niger Delta. Facies analysis of the cored PAC-14 well shows six lithofacies: massive mudstone, parallel-laminated mudstones with sideritic bands, fine-grained parallel-laminated sandstone, medium-grained parallel-laminated sandstone, fine-grained ripple laminated sandstone, and coarse massive sandstone. These lithofacies were grouped into five facies associations: channel story axis (CSA), channel story margin (CSM), inter-channel thin beds (ICTB), mud-rich thin beds (MRTB) and injectites (INJ). These facies associations are typical of a confined channel and basin floor fan deposit of a deep-water turbidite depositional environment. Reservoir unit E1 was dominated by the facies association CSA while the H9 reservoir consists mainly of the facies associations MRTB and INJ. The observed sand injectites are suggested to have formed due to overloading of compacted sands leading to upward remobilization of sand into the overlying shale. Seismic horizons and faults were mapped to understand the structures, trend and reflections within the study area. Results from petrophysical volumetrics estimated the net hydrocarbon pore volume for the E1 and H9 reservoirs as 456 MMBBL and 378 MMBBL, respectively. Exploration for deep-water reservoir mainly targets high amplitude and bright seismic reflectors and ignores the low amplitude reflectors (dim loops) which are typically interpreted as non-reservoir units. However, this study shows a low-amplitude reflector containing medium-grained sand injectite unit, which has high porosity (31.7%) and permeability (4472 mD) values, and contains recoverable hydrocarbon.

An enhanced approach to predict permeability in reservoir sandstones using artificial neural networks (ANN)

A key challenge in the oil and gas industry is the ability to predict key petrophysical properties such as porosity and permeability. The predictability of such properties is often complicated by the complex nature of geologic materials. This study is aimed at developing models that can estimate permeability in different reservoir sandstone facies types. This has been achieved by integrating geological characterization, regression models and artificial neural network models with porosity as the input data and permeability as the output. The models have been developed, validated and tested using samples from three wells and their predictive accuracy tested by using them to predict the permeability in a fourth well which was excluded from the model development. The results indicate that developing the models on a facies basis provides a better predictive capability and simpler models compared to developing a single model for all the facies combined. The model for the combined facies predicted permeability with a correlation coefficient of 0.41 which is significantly lower than the correlation coefficient of 0.97, 0.93, 0.99, 0.96, 0.96 and 0.85 for the massive coarse-grained sandstones, massive fine-grained sandstones-moderately sorted, massive fine-grained sandstones-poorly sorted, massive very fine-grained sandstones, parallel-laminated sandstones and bioturbated sandstones, respectively. The models proposed in this paper can predict permeability at up to 99% accuracy. The lower correlation coefficient of the bioturbated sandstone facies compared to other facies is attributed to the complex and variable nature of bioturbation activities which controls the petrophysical properties of highly bioturbated rocks.

Permeability heterogeneity in bioturbated sediments and implications for waterflooding of tight-oil reservoirs, Cardium Formation, Pembina Field, Alberta, Canada

Bioturbated sediments recording distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1–10 mD), pressure decay profile permeametry (micropermeability) data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel-laminated sandstone beds in the central, northeast and northwest parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.Micropermeability values enable correlation of bulk permeability from plugs and full-diameter samples to the heterogeneous permeability distributions in intensely bioturbated strata. Bulk and micropermeability data are graphically compared, and permeability distributions are mapped across the field. Using isopach thickness of bioturbated facies, production data, and permeability data, “sweet spots” are identified for placement of effective waterfloods.Production information for recently drilled horizontal wells in the Pembina Field demonstrate that bioturbated muddy sandstones and sandy mudstones in paralic environments can be economically exploited when sand-filled burrows provide connectivity between sand beds. However, well performance within these poorly understood unconventional tight oil plays can better be predicted with an in-depth characterization of their facies and complex permeability heterogeneities. Based on our results, it is clear that micropermeability analysis can be effectively employed to differentiate between economic and sub-economic plays, identify areas with high effective permeability, and high-grade areas for enhanced oil recovery schemes.

Lithofacies and environments of deposition within the Middle–Upper Cretaceous successions of Southeastern Nigeria

This paper presents findings from detailed geologic mapping of the Cenomanian–Campanian sediment package of southern Benue Trough, outcropping in Afikpo area of Southeastern Nigeria. The aim was to integrate outcrop and sedimentological log data with lithofacies analyses to better understand prevalent depositional processes and environments of deposition, across the Amaseri–Ngodo outcrop sections. Ten lithofacies with their associated subordinate lithofacies were identified and grouped into five facies associations (FA 1–5) to aid depositional environment interpretation. FA 1 consists of silty-shale and shales of the mudstone (MS) lithofacies deposited within an oxygenated offshore/open shelf setting, probably below fair-weather and storm wave base. FA 2 comprises medium–coarse-grained sandstone (MCS), hummocky cross-bedded sandstone (sub-lithofacies 4 of CBS), bioturbated sandstone (BSs) facies, bioturbated siltstone (BSt) and planar parallel-laminated sandstone (PPLS) lithofacies, interpreted to be storm wave-dominated shelf deposits. FA 3 consists of tabular/planar and trough cross-bedded sandstones (sub-lithofacies 1 and 2 of CBS) and wave ripple-laminated sandstones (RLS) lithofacies interpreted as shorefaces deposits above fair-weather wave base. Herringbone cross-bedded sandstones (sub-lithofacies 3 of CBS) and bioclastic limestone (BcL) lithofacies constitute FA 4, interpreted as tidal inlet/lagoonal deposits. FA 5 is characterized by conglomeritic sandstone (CS) lithofacies, as well as CBS, PPLS, RLS lithofacies, deposited within fluvial channels. Furthermore, vertical stacking patterns reveal the occurrence of two facies successions: the fining-upwards/thinning-upwards (FU/TnU) succession (typical of deepening or shallow to proximal offshore marine environments), dominating the northern and central part of the study area; and coarsening-upwards/thickening-upwards (CU/TkU) succession (typical of shoaling or proximal offshore to shallow marine environment), dominating the southern part of the study area. Overall, these lithofacies represents deposits within the littoral (marginal marine) and sub-littoral (shallow marine) environments.

Lithofacies and depositional environment of the Amasiri Sandstone, southern Benue Trough, Nigeria

Eight lithofacies typical of tidally-influenced shelf, mass flow and turbidity current processes characterize the Amasiri Sandstone (Cenomanian – Turonian) in the southern Benue Trough, Nigeria. The cross bedded sandstone lithofacies (Sxm) in Afikpo area were deposited in tidally influenced, shallow sandy shoreline environment while similar lithofacies associated with the conglomeratic lithofacies (Sfc) in Akpoha are proximal canyon–fill deposits. The conglomeratic lithofacies with rip-up clasts together with the massive, horizontal-bedded lithofacies (Smm) and parallel-laminated sandstone lithofacies (Sfl) in Akpoha were deposited in confined channels in proximal submarine canyon setting. The wavy/ripple-laminated sandstone lithofacies (Sfw) and very fine grained bioturbated sandstones lithofacies (Sfb) represent weakly confined distributary splay and unconfined associations in proximal to distal submarine canyon settings. The bioturbated mudstone lithofacies (Msb) and parallel-laminated mudstones lithofacies (Msl) comprise the bypass/levees association in the inner to outer shelf and in the distal canyon settings. Overall, these lithofacies indicate deposition in shelf to deep water depositional environments.

Depositional facies of the subsurface Neogene Surma Group in the Sylhet Trough of the Bengal Basin, Bangladesh: record of tidal sedimentation

The Bengal Basin, in the north-eastern part of the Indian subcontinent, contains a thick (± 22 km) early Cretaceous-Holocene sedimentary succession. The Neogene succession in the Sylhet Trough of the basin reaches a thickness of more than 6 km of which the Surma Group contains important sandstone reservoirs. Lithologically, the group consists of a succession of alternating shales, siltstones, sandy shales and sandstones, with minor conglomerates. This research work is a sedimentological analysis of the subsurface Neogene succession encountered in the petroleum exploration wells in the Sylhet Trough of the Bengal Basin. Detailed lithologic logs of the cores, based on considering texture and sedimentary structure, permit a subdivision into eight lithofacies, e.g., a shale-dominated facies, interbedded fine sandstones and mudstones, ripple-laminated sandstones, parallel-laminated sandstones, massive sandstones, cross-bedded sandstones, cross-bedded sandstones with pebble/granule lag and conglomerates. Characteristic sedimentary structures of the Surma Group, such as flaser-, wavy- and lenticular-bedding, bipolarity of ripple cross-stratification, evenly laminated sand/silt-streaked shales, reactivation surfaces within cross-bedded sandstone sets, mud-drapes on foreset laminae and herringbone cross-stratification as well as small-scale vertical sequences (several fining-upward cycles) are diagnostic for tidal influence. On the basis of the lithofacies associations and prograding character of the deposits revealed from the electrofacies associations, the Surma Group sediments have been interpreted as representing deposits of tide-dominated deltaic depositional setting.

Rapid and major coastal subsidence during the late Miocene in south-central Chile

Sedimentological and paleontological studies, including foraminifera, ostracodes, gastropods, and trace fossils, were carried out on Neogene sedimentary successions and offshore boreholes of south-central Chile (∼33°–45°S). Sedimentology shows the occurrence of a thin, shallow marine, basal conglomerate overlain by a succession that includes the following facies: massive sandstones, conglomerates, interbedded siltstones and sandstones showing Bouma cycles, parallel-laminated sandstones, synsedimentary breccias, slides, slumps, diamictites, and massive siltstones. These facies were deposited by gravity flows, with turbidity currents and sandy debris flows as the main modes of deposition. Paleontology indicates the occurrence of trace fossils assigned to the Zoophycos ichnofacies and deep-water (∼2000 m) benthic foraminifers, ostracodes, and gastropods. Sedimentology and paleontology indicate that deposition took place on a slope apron during a period of rapid and major forearc subsidence. Planktic foraminifers indicate ages ranging from the late Miocene to the early Pliocene (zones N16–N19) for these successions. We attribute this episode of major Neogene subsidence to an important event of subduction erosion that would have removed the underside of the upper continental plate and caused its thinning.

Detailed internal architecture of a fluvial channel sandstone determined from outcrop, cores, and 3-D ground-penetrating radar: Example from the middle Cretaceous Ferron Sandstone, east-central Utah

Ideally, characterization of hydrocarbon reservoirs requires information about heterogeneity at a submeter scale in three dimensions. Detailed geologic information and permeability data from surface and cliff face outcrops and boreholes in the alluvial part of the Ferron Sandstone are integrated here with three-dimensional (3-D) ground-penetrating radar (GPR) data for analysis of a near-surface sandstone reservoir analog in fluvial channel deposits. The GPR survey covers a volume with a surface area of 40 x 16.5 m and a depth of 12 m. Five architectural elements are identified and described in outcrop and well cores, using a sixfold hierarchy of bounding surfaces. Internally, the lower four units consist of fine-grained, parallel-laminated sandstone, and the upper unit consists of medium-grained, trough cross-bedded sandstone. The same sedimentary architectural elements and associated bounding surfaces are distinguished in the GPR data by making use of principles developed in seismic stratigraphic analysis. To facilitate comparison of geologic features in the depth domain and radar reflectors in the time domain, the radar data are depth migrated. The GPR interpretation is carried out mainly on migrated 100 MHz data with a vertical resolution of about 0.5 m. Measures of the spatial continuity and variation of the first- and second-order bounding surfaces are obtained by computing 3-D experimental variograms for each architectural element (each radar (Begin page 1584) facies). The maximum correlation length of the dominant internal features ranges between 4 and 6 m, and the anisotropy factor ranges between 0.6 and 0.95.

96/04870 Recovery and utilization of coal seam gas. Impetus by the German hard coal mining industry

Bioturbated sediments recording distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1–10 mD), pressure decay profile permeametry (micropermeability) data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel-laminated sandstone beds in the central, northeast and northwest parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.Micropermeability values enable correlation of bulk permeability from plugs and full-diameter samples to the heterogeneous permeability distributions in intensely bioturbated strata. Bulk and micropermeability data are graphically compared, and permeability distributions are mapped across the field. Using isopach thickness of bioturbated facies, production data, and permeability data, “sweet spots” are identified for placement of effective waterfloods.Production information for recently drilled horizontal wells in the Pembina Field demonstrate that bioturbated muddy sandstones and sandy mudstones in paralic environments can be economically exploited when sand-filled burrows provide connectivity between sand beds. However, well performance within these poorly understood unconventional tight oil plays can better be predicted with an in-depth characterization of their facies and complex permeability heterogeneities. Based on our results, it is clear that micropermeability analysis can be effectively employed to differentiate between economic and sub-economic plays, identify areas with high effective permeability, and high-grade areas for enhanced oil recovery schemes.

96/04860 Hydrogen production methods

Bioturbated sediments recording distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1–10 mD), pressure decay profile permeametry (micropermeability) data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel-laminated sandstone beds in the central, northeast and northwest parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.Micropermeability values enable correlation of bulk permeability from plugs and full-diameter samples to the heterogeneous permeability distributions in intensely bioturbated strata. Bulk and micropermeability data are graphically compared, and permeability distributions are mapped across the field. Using isopach thickness of bioturbated facies, production data, and permeability data, “sweet spots” are identified for placement of effective waterfloods.Production information for recently drilled horizontal wells in the Pembina Field demonstrate that bioturbated muddy sandstones and sandy mudstones in paralic environments can be economically exploited when sand-filled burrows provide connectivity between sand beds. However, well performance within these poorly understood unconventional tight oil plays can better be predicted with an in-depth characterization of their facies and complex permeability heterogeneities. Based on our results, it is clear that micropermeability analysis can be effectively employed to differentiate between economic and sub-economic plays, identify areas with high effective permeability, and high-grade areas for enhanced oil recovery schemes.

96/04863 Low temperature liquefaction of coal with simulated coke oven gas

Bioturbated sediments recording distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1–10 mD), pressure decay profile permeametry (micropermeability) data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel-laminated sandstone beds in the central, northeast and northwest parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.Micropermeability values enable correlation of bulk permeability from plugs and full-diameter samples to the heterogeneous permeability distributions in intensely bioturbated strata. Bulk and micropermeability data are graphically compared, and permeability distributions are mapped across the field. Using isopach thickness of bioturbated facies, production data, and permeability data, “sweet spots” are identified for placement of effective waterfloods.Production information for recently drilled horizontal wells in the Pembina Field demonstrate that bioturbated muddy sandstones and sandy mudstones in paralic environments can be economically exploited when sand-filled burrows provide connectivity between sand beds. However, well performance within these poorly understood unconventional tight oil plays can better be predicted with an in-depth characterization of their facies and complex permeability heterogeneities. Based on our results, it is clear that micropermeability analysis can be effectively employed to differentiate between economic and sub-economic plays, identify areas with high effective permeability, and high-grade areas for enhanced oil recovery schemes.

High Resolution Sequence Stratigraphy of Miocene Deep-Water Clastic Outcrops, Taranaki Coast, New Zealand: ABSTRACT

Approximately 700m of deep water clastic deposits of Mt. Messenger Formation are superbly exposed along the Taranaki coast of North Island, New Zealand. Biostratigraphy indicates the interval was deposited during the time span 10.5-9.2m.y. in water depths grading upward from lower bathyal to middle-upper bathyal. This interval is considered part of a 3rd order depositional sequence deposited under conditions of fluctuating relative sea-level, concomitant with high sedimentation rates. Several 4th order depositional sequences, reflecting successive sea-level falls, are recognized within the interval. Sequence boundaries display a range of erosive morphologies from metre-wide canyons to scours several hundred metres across. All components of a generic lowstand systems tract--basin floor fan, channel-levee complex and progading complex--are present in logical and temporal order. They are repetitive through the interval, with the relatively shallower-water components becoming more prevalent upward. Basin floor fan lithologies are mainly m-thick, massive and convolute-bedded sandstones that alternate with cm- and dm-thick massive, horizontally-stratified and ripple-laminated sandstones and bioturbated mudstones. Channel-levee deposits consist of interleaving packages of thin-bedded, climbing-rippled and parallel-laminated sandstones and millstones; infrequent channels are filled with sandstones and mudstones, and sometimes lined with conglomerate. Thin beds of parallel to convoluted mudstone comprise prograding complex deposits. Similar lowstandmore » systems tracts can be recognized and correlated on subsurface seismic reflection profiles and wireline logs. Such correlation has been aided by a continuous outcrop gamma-ray fog obtained over most of the measured interval. In the adjacent Taranaki peninsula, basin floor fan and channel-levee deposits comprise hydrocarbon reservoir intervals. Outcrop and subsurface reservior sandstones exhibit similar permeabilities.« less

Incision and Filling of a Lowstand Valley: Late Albian Viking Formation at Crystal, Alberta, Canada

ABSTRACT Crystal field in the Albian Viking Formation represents the fill of a lowstand incised valley at least 55 km long, 7-12 km wide, and up to 32 m deep. The valley trends south-north, with a smaller arm trending east-west; the open sea lay to the north and east. The valley cuts into five regionally extensive sandier-upward successions of open marine bioturbated mudstones and sandstones. There were two separate episodes of valley filling. The first consists of (1) dominantly parallel-laminated sandstones in the south that grade northward into (2) bioturbated mudstones in the central part of the valley. These grade in turn into (3) bioturbated sandstones at the northern (seaward) end of the valley. The valley morphology, restricted trace fauna, and tripartite facies distribution suggest an estuarine environment. The sandstones in the south are interpreted as deposits of a bay-head delta, and the central basin mudstones represent the turbidity maximum. The bioturbated sandstones in the north were emplaced into the estuary from the marine end. There is little evidence of tidal deposits, and the estuary appears to have been wave-dominated. The second valley at Crystal is narrower and cuts into the first till. The second fill consists of (1) interbedded fluvial sandstones and conglomerates in the south that grade northward through (2) sandstones into (3) bioturbated sandstones. There are no central basin mudstones, and the filling appears to have been fluvially dominated. The base of Valley 1 represents an original fluvially formed sequence boundary completely modified by marine transgression, whereas the base of Valley 2 is a fluvially cut sequence boundary in the south and a marine-modified sequence boundary in the north. The valley-fill deposits are truncated by a transgressive surface of erosion. The valley morphology suggests a drop of relative sea level of at least 30 m to incise Valley 1, and an equivalent rise to fill the valley. There was then a second 30 m relative fall and a second 30 m rise to fill Valley 2. The sandbodies within the valley are poorly connected as reservoirs. Their distribution is related to the two separate phases of valley cutting and filling, and to the different points of coarse sediment input; the bayhead delta, and the marine ends of the main valley and the east arm.

Estuarine Deposits of the Albian Paddy Member (Peace River Formation) and Lowermost Shaftesbury Formation, Alberta, Canada

ABSTRACT Outcrop exposures of the Peace River Formation in northwestern Alberta contain evidence of significant relative sea-level fluctuations that occurred during the middle to late Albian. These include Paddy Member channels that incised into the Cadotte Member shoreline deposits and the subsequent estuarine-frill. The upper Cadotte Member contact is irregular and siderite-cemented; it has been scoured into and infilled by sandstone of the Paddy Member. The lower sandstone of the Paddy Member is crossbedded, with abundant comminuted, carbonaceous debris. Channels cut into the Cadotte Member are up to 5 m deep and are locally overlain by in situ coal and roots. The channels are infilled with alternating couplets of moderately to intensely bioturbated sand and mud which form inclined h terolithic stratification: mud plugs are also present. Internally these sands are ripple and parallel cross-laminated. This part of the Paddy Member is interpreted as estuarine fill that resulted from a relative sea-level rise. The channel fill is overlain by intensely bioturbated, locally rooted, finely interbedded sandstone, siltstone and shale, with minor reworked bentonites, interpreted as tidal flat deposits. Tidal flat sediments are overlain by 2 to 3 m of scoured, parallel-laminated sandstone and capped by 1.5 m of planar-tabular crossbedded sandstone interpreted as shoreface and transgressive, estuary-mouth deposits, respectively. Evidence for tides throughout the Paddy Member includes inclined heterolithic stratification, mud couplets, reactivation surfaces, reversing paleoflows and compound crossbeds. The incised channels and related fill are correlative with a sequence of paleosols 300 km southwest in the Boulder Creek Formation. A brackish influence is indicated by the presence of a few species of peridinioid dinoflagellates occurring in abundance at certain levels and the trace fossil assemblage. The Paddy Member is overlain by marine mudstone of the Shaftesbury Formation. A 20 to 30 cm thick, wave-rippled layer of fish teeth, fish bones and pebbles, near the base of the Shaftesbury Formation, can be traced along the Peace River for at least 75 km. The layer of fish remains is interpreted as transgressive lag.