Transgressive Sandstone Research Articles

Anatomy and provenance of a typical transgressive sandstone: the Lower Cretaceous Martin House Formation, Northern Canada

Abstract The Martin House Formation is a transgressive sandstone interval representing the first stage of foreland basin deposition in northwestern Canada during the Cretaceous and offers a template for recognition of transgressive sandstones in other regions. Results from outcrop sections, wire-line logs, drill core, palynology, petrographic analyses, and detrital zircon dating were integrated to better constrain the paleogeographic setting for the northern part of the Western Interior Basin during the Albian. Twelve facies and four facies associations were defined across the study area. Earliest Albian floodplain deposits (FA1) were overlain by estuarine (FA2), shallow marine (FA3) and offshore strata (FA4) deposited during a major Albian transgression. During the Lower Cretaceous, the Mackenzie Corridor was on the eastern side of a foreland basin and the Keele Arch formed a north-south trending highland. Facies maps show that the basin paleotopography imparted significant control on the distribution and lateral continuity of stratigraphic units. The results of this study help elucidate controls on sediment routing in northwestern Canada during the Albian and provide insight into processes that affected the development of stratigraphic architecture in the Western Interior Basin. The most likely basin reconstruction involving non-marine Albian strata in the study area is to infer a marine trough forming the Cordilleran foredeep to the west of the study area. Résumé La Formation de Martin House est un intervalle de grès transgressif du Crétacé représentant le premier étage d’un dépôt d’avant-pays dans le Nord-Ouest du Canada et elle fournit un modèle nous permettant de reconnaître les grès transgressifs d’autres régions. Les résultats de sections d’affleurement, de diagraphies de puits, de carottes de forage, de palynologie, d’analyses pétrographiques et de datation de zircon détritique ont été intégrés pour mieux restreindre le contexte paléogéographique de la partie nord du bassin intérieur occidental pendant l’Albien. Nous avons trouvé douze faciès et quatre associations de faciès dans le secteur étudié. Les dépôts les plus précoces parmi les plaines d’inondation de l’Albien (FA1) étaient recouverts de strates de dépôts estuariens (FA2), de strates de mer peu profonde (FA3) et extracôtières (FA4) déposées durant une transgression majeure de l’Albien. Au cours du Crétacé inférieur, le corridor de Mackenzie se situait du côté est d’un bassin d’avant-pays, tandis que l’arche de Keele formaient un haut-pays d’orientation nord-sud. Les cartes de faciès montrent que la paléotopographie du bassin régissait de manière significative la répartition et la continuité latérale des unités stratigraphiques. Les résultats de cette étude permettent d’expliquer ce qui régissait le cheminement des sédiments dans le Nord-Ouest du Canada pendant l’Albien, en plus de nous donner un aperçu des processus qui influent sur l’évolution de l’architecture stratigraphique du bassin intérieur occidental. La reconstruction la plus probable du bassin dans le secteur étudié comprenant des strates non marines de l’Albien supposerait une dépression marine qui aurait formé l’avant-fosse cordillériennne à l’ouest du secteur étudié. Michel Ory

Hydrocarbon potential and reservoir characteristics of incised-valley transgressive sandstones: A case study of the Messinian gas reservoirs (Nile Delta Basin, Egypt)

The incised-valley sandstones have been identified as a significant contributor to global hydrocarbon resources. This study aims to assess the Messinian Abu Madi (AM) sandstone's reservoir properties in the incised valleys of the Baltim, Nidoco, and Abu Madi gas fields in the Nile Delta Basin, Egypt. The hydrocarbon potential of these sandstones is assessed through the analysis of seismic, well logs, and core data. The seismic interpretation reveals that extensional faults played a significant role in controlling the deposition of the Abu Madi Formation in the study area, formed during the tectonic rifting of the Messinian age. The northernmost portion of the study area in the Abu Madi field exhibits the most promising location for gas exploitation, suggesting the need for further exploration and evaluation. The sandstones exhibit a fining upward trend with a relatively clean composition, moderate to well sorting and mild calcareous tendencies. The presence of sedimentary structures, such as cross-bedding and ripples, suggests a dynamic depositional environment. The rock composition, dominated by quartz with variable sorting and cementation, influences the porosity and permeability of the sandstones. Petrophysical investigations indicate favourable reservoir conditions with significant porosity and permeability, enhancing hydrocarbon storage and extraction potential. The analysis of petrophysical parameters in the AM sandstones reveals favourable properties for gas production, including low shale content (4%–12%), high porosity (18%–22%), and low water saturation (20%–54%) levels. The findings of this study indicate that the gas-pay zones within the Abu Madi sandstones are primarily associated with the transgressive sandstones of the estuarine facies (TST) rather than the lower sandstones of the fluvial facies (LST). The complex sandstone channels within the TST exhibit diverse geometries and contribute to reservoir heterogeneity. The presence of well-connected channels enhances reservoir productivity by facilitating fluid flow. The understanding of the distribution and characteristics of these channels is essential for reservoir characterisation and optimisation of hydrocarbon recovery.

Initial development and sedimentary provenance of a middle Paleozoic foreland basin: Clam Bank Formation, western Newfoundland

The upper Silurian(?) to Lower Devonian (Lochkovian) Clam Bank Formation is the most northerly exposed middle Paleozoic foreland-basin succession in the Appalachian orogen. Understanding of its sedimentary history is poor, and there are contradictory interpretations of placement of its lower structural boundary. Our study redefines the lithostratigraphy and subdivides the ∼600 m thick formation into three paleoenvironmental successions: a lower coastal plain setting with fluvial channels giving way upsection to coastal flats with carbonate, colluvium with reworked paleosol material, and aeolian (silt) deposits; a middle coastal zone succession following marine transgression and deposition of shoreface sandstone; and an upper alluvial succession host to pedogenic and groundwater calcretes. A basal disconformity, though not exposed, is inferred from lithic and geochemical evidence for sediment mixing with underlying Upper Ordovician sources in the lowermost part of the formation. This supports previous interpretations of Silurian uplift along the Laurentian margin in response to the Salinian orogeny. Sedimentary provenance indicates quartzo-feldspathic sources throughout the formation, and sediment-transport indicators identify a northeast–southwest-oriented basin with northwest-directed fluvial input. U–Pb detrital zircon distributions associated with the paleocolluvium and younger transgressive sandstone document upsection loss of prominent age peaks of late Grenville (∼0.98 Ga) and pre-Grenville (1.5, 1.65, and 1.75 Ga) sources. The coastal plain succession and related detrital-zircon signature imply a mixture of distal and proximal sediment sources, the latter related to erosion of a weathered upland and exhumed Precambrian inliers in western Newfoundland. A more regional provenance signature with marine transgression suggests sediment transport in response to Acadian orogenesis.

Seismic sequence stratigraphy and depositional evolution of the Cretaceous-Paleogene sedimentary successions in the offshore Taranaki Basin, New Zealand: implications for hydrocarbon exploration

The seismic stratigraphy and sedimentary facies of the Cretaceous and Paleogene sedimentary successions in north-eastern offshore part of Taranaki Basin, New Zealand have been investigated in order to unravel their depositional evolution and identify the potential hydrocarbon plays. Interpretation of regional seismic lines covering the entire shelf-slope and deepwater regions as well as integrating seismic and sedimentary facies allows the identification of several seismic-stratigraphic sequences within the studied successions. Early Cretaceous syn-rift successions (C1 sequence) were deposited in the structural lows near the present-day slope as swamp and marsh facies changing basinwards into turbidites and marine shales. The post-rift Cretaceous sequences (C2, C3 sequences) started with the progradation of the Taranaki delta (C2A-C2D units) followed by sedimentation of the transgressive C3A-E facies accumulated in response to thermal subsidence and high-rates of clastic supply. Extensive shelf conditions prevailed during the deposition of C2 and C3 Cretaceous sequences continued during the Paleogene with deposition of uniform marine shales throughout the basin. Rates of sediment supply substantially decreased during Oligocene prompting the deposition of marine micrite-rich carbonate. Variation in fossil content confirms the occurrence of several cycles of sea level fluctuations and episodic variations in terrigenous input. Organic-rich facies could be associated with the prograding clinoforms of the C2B unit and probably contain, basinward, large amount of gas and oil prone kerogen. The transgressive facies of C2D unit may also contain organic-rich shales basinward and coal near the present day Taranaki shelf. Potential reservoirs are hosted on the C3 transgressive estuarine sandstones. Paleogene mudstones are excellent regional seals for the hydrocarbons generated and trapped in the underlying Late Cretaceous facies.

Sedimentological analysis and reservoir quality of the early Cenomanian transgressive sandstones, northern Western desert, Egypt

Depicting depositional models of transgressive sandstone reservoirs is challenging due to their internal complexity and limited case studies. This study presents an example for transgressive sandstone reservoirs from the Bahariya Formation at Hayat-Yasser oil field, Shushan Basin (northern Western Desert, Egypt). The upper part of the Bahariya Formation accumulated in an estuarine setting as a consequence of a successive sea level rise. Detailed reservoir characterization, employing sequence stratigraphic and sedimentological approaches, revealed that the studied reservoir consists of a mixed siliciclastic-carbonate transgressive estuarine-shelf succession. Four conventional core samples of this succession at Khalda ridge (Shushan Basin), permit the analysis of their sedimentology and internal architecture (mesoscopic heterogeneities) along correlation lines parallel or slightly oblique to depositional dip. The succession consists of six backstepping parasequence sets that record the overall shift from tidal-dominated to wave-dominated estuaries/bays. The transgressive component of the parasequences sets includes bay mudstones, flood-tidal deltas, and shoreface/barrier deposits; while the regressive component includes estuarine point bars, bay head deltas, and tidal deltas. The reservoir properties show significant variation according to the facies assemblages. The tidally-dominated estuarine channels show low net-to-gross, as it is characterized by lenticular sandstone bodies with several lateral and vertical baffles and barriers. On the other hand, the shoreface/barrier and tidal delta sandstones show high net-to-gross and consist of amalgamated sandstone bodies with little mud barriers or baffles. Petrographically, the upper Bahariya reservoir includes intergranular and secondary porosities. The microscopic heterogeneities are mainly due to the fine grain nature, poor sorting, presence of matrix, and continuous mud barriers or baffles. Destruction of porosity, affecting the reservoir quality, occurred by silica overgrowths, ferroan calcite, grain coating chlorite, and kaolinite cementation, as well as compaction. Feldspar dissolution is the main diagenetic process responsible for the formation of secondary porosity, enhancing the reservoir quality.

Diagenesis and reservoir quality in high-resolution sandstone sequences: An example from the Middle Jurassic Ravenscar sandstones, Yorkshire CoastUK

A section of the Middle Jurassic Ravenscar sandstones exposed between Cloughton Wyke and Burniston Bay was studied to understand fine-scale variation in reservoir quality that can affect flow properties at the reservoir scale. The study has identified two 3rd-order depositional sequences consisting of twelve 4th-order high-resolution sandstone sequences deposited mostly in a lower delta plain. Although these sandstones exhibit a narrow range in porosity values, however, a sharp disparity exists in their permeability which can have implications at the scale of reservoir development. Diagenetic studies have revealed that mechanical compaction produced the same effect for most of these sandstones. However, dissolution and cementation vary, hence, are mostly responsible for the sharp contrast in their reservoir quality. The distributary channel sandstones developed during normal regression of the area in the FS9 sequence are considered the best reservoir sand bodies. However, these LST sandstones are compartmentalised by authigenic illite, quartz and kaolin into two reservoir segments. The upper portion lacks illite with resultant higher permeability values above 1100 mD (ave. 2217 mD) and classified as reservoir group 4. In contrast, the lower part contains illite with relatively lower permeability values in the range of 300–1100 mD (ave. 879 mD) and classified as reservoir group 3 together with the transgressive crevasse channel sandstones in the FS11 sequence. The presence of illite cement in these sandstones is linked to the occurrence of k-feldspar, hence, facilitated illitization of kaolin in contrast to group 4, which lacks this mineral. The other transgressive sandstones deposited in interdistributary bay, crevasse delta, back-barrier lagoon, lagoon, and estuarine environments which form reservoir groups 1 and 2 have permeability values in the range of 0–50 mD (ave. 6 mD) and 50–300 mD (ave. 184 mD) respectively. These sandstones have complex styles of diagenetic cement with variable higher volumes of total authigenic cement consisting of quartz, kaolin, illite, chlorite and calcite than reservoir groups 3 and 4, hence, have significantly reduced their reservoir potential. Therefore, for effective reservoir development of these sandstone reservoirs in the North Sea and elsewhere in the world with a similar geological setting, detailed reservoir characterisation involving linking lithofacies, sequence stratigraphy and diagenesis at high-resolution are essential for understanding the distribution of reservoir flow properties.

Characteristics and context of high-energy, tidally modulated, barred shoreface deposits: Kimmeridgian–Tithonian sandstones, Weald Basin, southern U.K. and northern France

ABSTRACTThe influence of tides on the sedimentology of wave-dominated shorefaces has been emphasized in recent studies of modern shorelines and related facies models, but few ancient examples have been reported to date. Herein, we use a case study from the stratigraphic record to develop a revised facies model and predictive spatio-temporal framework for high-energy, tidally modulated, wave-dominated, barred shorefaces.Kimmeridgian–Tithonian shallow-marine sandstones in the Weald Basin (southern England and northern France) occur as a series of laterally extensive tongues that are 5–24 m thick. Each tongue coarsens upward in its lower part and fines upward in its upper part. The lower part of each upward-coarsening succession consists of variably stacked, hummocky cross-stratified, very fine- to fine-grained sandstone beds and mudstone interbeds that are moderately to intensely bioturbated by a mixed Skolithos and Cruziana Ichnofacies. This lower part of the succession is interpreted to record deposition on the subtidal lower shoreface, between effective storm wave base and fairweather wave base. The upper part of each upward-coarsening succession comprises cross-bedded, medium- to coarse-grained sandstones that are pervasively intercalated with mudstone-draped, wave-rippled surfaces (including interference ripples) which mantle the erosional bases of trough cross-sets. Bioturbation is patchy, and constitutes a low-diversity Skolithos Ichnofacies. Cross-bedded sandstones are arranged into cosets superimposed on steeply dipping (up to 10°) clinoforms that dip offshore and alongshore, and extend through the succession. These deposits are interpreted to record shallow subtidal and intertidal bars on the upper shoreface, which likely contained laterally migrating rip channels or formed part of a spit. The lower, upward-coarsening part of each sandstone tongue represents an upward-shallowing, regressive shoreface succession in which the internal bedding of upper-shoreface sandstones was modulated by tidal changes in water depth. The upper, upward-fining part of each sandstone tongue typically comprises an erosionally based bioclastic lag overlain by subtidal lower-shoreface deposits, and constitutes an upward-deepening succession developed during transgression.Regressive–transgressive sandstone tongues fringe the northeastern margin of the basin, which was exposed to an energetic wave climate driven by westerly and southwesterly winds with a fetch of 200–600 km. The high tidal range interpreted from the shoreface sandstone tongues is attributed to resonant amplification in a broad (150–200 km), shallow (18–33 m) embayment as the tidal wave propagated from the Tethys Ocean into the adjacent intracratonic Laurasian Seaway, of which the Weald Basin was a part.

Provenance Signatures Recorded In Transgressive Sandstones of the Upper Cretaceous Iberian Seaway

Abstract: Maximum Mesozoic transgressions flooded many continental areas worldwide, forming a wide and shallow seaway on the Iberian Microplate during the Late Cretaceous. Several siliciclastic and mixed siliciclastic–carbonate units developed along the Iberian Massif (cratonic area) while, at the same time, epeiric carbonate platforms spanned Iberia. These siliciclastic deposits unconformably cover the Variscan basement, as well as the Permian and Triassic deposits. This study focuses on sandstone provenance in central Spain, in a transgressive, relatively quiet tectonic setting with a wide rock variety in the potential source areas. Results shown in this paper can be applied in analogue systems; transgressive sandstones often form important hydrocarbon reservoirs due to their high primary porosity. The Cretaceous siliciclastic deposits are included in four formations ranging in age from the Cenomanian to the early Coniacian. The deposits were initially of fluvial origin, followed by a coastal-tidal setting. Quantitative petrographic analysis of sandstones from these formations reveals compositional variations related to provenance and weathering degree. The oldest formation (Utrillas Fm.) was deposited on a paleorelief surface. Sandstone composition changes from arkosic sandstones in the depressed area (Petrofacies P1a) to younger quartzarenites when sediments were deposited on top of the paleotopographic high (Petrofacies P1b). Quartz grains in both sub-petrofacies are angular to subangular, and the framework is poorly sorted. Intense weathering conditions are deduced for Petrofacies P1b, manifested by grain infiltration, clay coatings, and the absence of plagioclase grains and alteration features on K-feldspars. All these observations have been related to wetter conditions during P1b deposition. Main source areas of the Utrillas Fm were Ordovician metasediments and orthogneisses, Permian volcanic rocks, and Triassic Buntsandstein facies. Petrofacies 2 encompasses the three coastal-tidal formations, constituted mainly by subarkoses generally showing a subangular and poorly sorted framework. The deduced source areas are mainly associated with Variscan granitoids, pre-Ordovician schists and paragneisses, and Ordovician metasediments. Glauconite and carbonate grains support intrabasinal inputs. The low degree of sorting of this petrofacies related to a low-energy sedimentary environment produced lower values of original porosity compared to transgressive sandstone hydrocarbon reservoirs. Also, intrabasinal inputs promoted carbonate cementation and contribute to almost occlude the porosity.

Transgressive successions of the Mahakam Delta Province, Indonesia

Abstract Sedimentological and stratigraphic analysis of outcrops and subsurface data in the Mahakam Delta province, combined with concepts of transgressive sedimentary processes derived from a study of the modern Mahakam Delta, indicate that a significant portion of the palaeo-Mahakam Delta succession was deposited during transgressive phases. Some of the transgressive successions resulted from major transgressions and are regionally extensive, but many reflect small, short-lived transgressions within dominantly progradational phases. Two sandstone facies with significant reservoir potential are common within the transgressive successions. Backfilled distributary sandstones occur in outcrop as 10–20 m thick, fining-upward channel sands that become more marine upward and in the subsurface as elongate, coastline-perpendicular sand bodies with a back-stepping stratigraphic architecture and highly variable thickness. Transgressive shoreline sandstones also fine upward, but they are shoreline-parallel, their lateral extent is controlled by the pre-transgression delta morphology and their thickness depends on the rate of relative sea-level rise. Both types of transgressive sandstone can be difficult to distinguish from specific progradational sandstones with wireline log data, especially when they occur within predominantly progradational successions. However, their sand body geometries, volumetrics and connectivity are much different from the stratigraphically adjacent sandstones deposited during progradational phases of deltaic deposition.

PASSIVE TRANSGRESSION: REMARKABLE PRESERVATION AND SPATIAL DISTRIBUTION OF UPPERMOST DEVONIAN (FAMENNIAN) MARGINAL AND NEARSHORE MARINE FACIES AND FAUNA OF WESTERN LAURENTIA

Abstract The stratigraphic record of shallow-water shoreline paleoenvironments is characterized by significant facies heterogeneity and laterally discontinuous stratal geometries. In contrast, we investigate a uniquely extensive and microstratigraphically spatially uniform interval of upper Famennian (Upper Devonian) marginal marine strata in the Rocky Mountains. This transgressive deposit (< 5 m thick) rests on a depositional sequence boundary, and is composed of a thin, discontinuous basal transgressive sandstone bed, two thin fossiliferous shale beds, and several meters of oncolite-bearing carbonate wackestone. The lower shale is a consistently thin (~ 0.1 m) bed with a fossil fauna of spinicaudatans (clam shrimp or conchostracans), which are extant, bivalved, chitinous, benthic crustaceans that live in fresh to brackish water, in ephemeral ponds, estuaries, and other shoreline settings. Isotopic data for the oncolitic unit record deposition in an epicontinental seaway with restricted circulation and l...

Sedimentology and Ichnology of Late Oligocene Delta Front Reservoir Sandstone Deposit, Greater Ughelli Depobelt, Niger Delta

Sedimentological and ichnological study of cored reservoir sands correlated with wireline logs between two wells, 0.8 km distance apart along dip direction, enabled vertical and cross sectional facies variability assessment aimed at determining intra sand-body continuity in longitudinal or down-dip direction; and sub-environments of deposition and factors that controlled depositional processes. Ten lithofacies described 62 meters cores of the reservoir sands and seals. Sub-environments of deposition identified with lithofacies associations include proximal delta front-mouth bar, distal delta-front, prodelta-offshore, transgressive marine sandstone and tidal flat. High mica content, poor sorting, very coarse quartz grains, high angle bedding contact, micro-slump folds and absent to sparse bioturbation at the base of an upward-coarsening sequence indicated mouth bar deposition and direct link to a distributary channel. The study of vertical and lateral intra-reservoir depositional trends indicated that sediment structural and textural (grain sizes and biogenic features) heterogeneities in the deltaic deposit were controlled by variations in physical energy and mixed interactions of seal level changes, tide, wave, fluvial influx, storm, food supply and oxygen levels. Consequently, there is down-dip lithofacies heterogeneity, pinch out of lithofacies or gradation from coarse grains to finer grains and better sorting. Though ichnodiversity is fairly uniform between the two wells, ichno-abundance and burrow sizes decrease down-dip especially at the proximal delta front-mouth bar deposit. The results of this study improve our knowledge of the characteristics of a mouth bar deposit in a mixed-processes deltaic environment and it can be applied in the characterization of delta front deposit elsewhere with similar depositional processes and tectonic setting.

Stratigraphy and vertebrate paleoecology of Upper Cretaceous–?lowest Paleogene strata on Vega Island, Antarctica

The Upper Cretaceous (Maastrichtian) Sandwich Bluff Member of the López de Bertodano Formation is well exposed on Vega Island in the James Ross Basin off the northeastern coast of the Antarctic Peninsula. Although this unit is one of the richest sources of end-Cretaceous vertebrate fossils in Antarctica, it is also one of the least sedimentologically and stratigraphically characterized units in the basin. New facies and stratigraphic analyses of the Sandwich Bluff Member and the underlying Cape Lamb Member of the Snow Hill Island Formation were performed in tandem with intensive prospecting for fossil vertebrates and stratigraphic assessment of historic paleontological localities on Vega Island. This effort has led to a revised stratigraphy for the Sandwich Bluff Member and the precise stratigraphic placement of important terrestrial and marine vertebrate fossil localities.Facies analysis reveals a fining and shallowing upward trend through the section that culminates in a newly recognized sequence boundary near the top of the Sandwich Bluff Member, followed by the deposition of a previously unrecognized, 6m-thick, matrix-supported pebble–cobble conglomerate of probable alluvial origin. Immediately overlying this unit, well-developed Thalassinoides burrow networks in fine-grained transgressive sandstones and siltstones indicate a rapid return to marine conditions. A similar stratigraphic pattern is well documented at the top of the López de Bertodano Formation and the base of the overlying (Paleocene) Sobral Formation on Seymour Island in the southern part of the basin. Although no fossils were recovered to constrain the age of the upper 10–15m of the succession on Vega Island that preserves the newly recognized upper sequence boundary, strata below this level can be confidently placed within the Manumiella bertodano interval zone, which extends to a short distance below the K–Pg boundary on Seymour Island. Hence, based on sequence stratigraphic and lithostratigraphic evidence, the uppermost 10–15m of the succession on Vega Island may encompass the Cretaceous–Paleogene boundary together with a few meters of the Paleocene Sobral Formation.

A quantitative method for characterizing transport capability of compound hydrocarbon carrier system

The occurrence of hydrocarbon migration in petroliferous basins depends on the balance of driving force and resistance of carriers, which restricts mostly the quantity and positions of hydrocarbon accumulation. The driving forces of hydrocarbon migration have been quantitatively studied, whereas the migration pathways and carriers were only qualitatively discussed up to now. Establishing a compound hydrocarbon carrier system and quantitatively characterizing its transport capability are significant for understanding the dynamic process of hydrocarbon migration and revealing the hydrocarbon accumulation characteristics. It has become an innovatory trend and also a difficult topic in study of hydrocarbon migration. In this article, a method is described for using displacement pressure to quantitatively characterize the transport capability of the compound carrier system, which composed of sandstone carriers, unconformities and faults. When the weathered and leached zone rarely developed, the basal conglomerate or transgressive sandstone of unconformities can be treated as part of sandstone carriers. An empirical relationship among core porosity, air permeability, and the pore aperture radius corresponding to a mercury saturation of 10% (r 10) can be obtained by multiple regression. Using porosity and permeability inversed by seismic data, the displacement pressure of sandstone carriers can be calculated by the empirical relationship and Washburn Equation. Displacement pressure of fault plane can be estimated by the regression formula between fault opening index (FOI) and hydrocarbon column height it can support. This method is applied in the eastern part of south slope in Dongying (东营) depression, Bohai (渤海) Bay Basin, China, to quantitatively characterize the transport capability of the compound carrier system of Shahejie (沙河街) Formation. The results have good agreement with data from drilling wells. This method may be a step further in study of compound hydrocarbon carrier system in petroliferous basins. It may provide the basis of coupling expulsion quantity, migration driving force and hydrocarbon carrier system to simulate hydrocarbon migration and accumulation. Therefore this will help predict hydrocarbon migration pathways and the locations of hydrocarbon accumulation.

The Werra cyclotheme (Upper Permian, Fore-Sudetic Monocline, Poland): Insights into fluctuations of the sedimentary environment from organic geochemical studies

A study of the extracts of samples recording a transgressive–regressive succession of the Werra cyclothem, Zechstein (Upper Permian), from the southern margin of the European Permian Basin (the Fore-Sudetic Monocline, Poland) provides an insight into major sources of organic matter and diagenetic processes. The studied cross-section comprises all lithologies representative for the European basin, including transgressive sandstones (Weissliegend) and organic-rich shales (Kupferschiefer) followed by carbonates as well as regressive anhydrites with intercalations of rock salt. Due to the variable influence of overlapping diagenetic processes that affected the organic matter, i.e. maturation and late diagenetic oxidation related to base metal mineralisation, a reliable comparison of the biomarker results is only possible for the major upper part of the section (ca. 38m, including carbonates and evaporites) but not for the oxidised first 2–3m from the base of the Kupferschiefer.The transition from carbonate to evaporate sedimentation is associated with a shift to predominant even C-numbered n-alkanes, increased abundance of carotanes and high homohopane index reflecting enhanced reducing conditions. The presence of the C25 regular isoprenoid, squalane, biphytane and the rapid decrease in the pristane/phytane ratio in the evaporites are mainly controlled by the important contribution from both halophilic and methanogenic archaea. The occurrence of gammacerane in the anhydrites suggests development of water column stratification at some stages of the sea regression. This is associated with appearance of specific aryl isoprenoids with a lycopane carbon skeleton most likely related to Botrycoccus braunii race L algae. Lycopane derivative occurrence suggests that such an algal race could have occurred since Permian (currently known Recent-Eocene). The presence of the abundant freshwater/brackish algal biomarkers in evaporititic deposits can be envisaged in the costal part of the Zechstein basin with temporary salt wedge estuary water stratification. The algae bloomed in the top fertile fresh/brackish water layer fed by rivers, and the algal biomass was deposited on the sea floor covered with evaporitic brine. The stratification periodically broke down during precipitation of the rock salt, presumably due to a decrease in riverine water input, as revealed by characteristic disappearance of gammacerane and hopane distributions similar to those observed for the carbonate rocks.The methylphenanthrenes/phenanthrene ratio was used together with methyldibenzothiophenes/ dibenzothiophene ratio to assess maturity. These maturity estimations indicate that the peak of oil window has been reached, which is confirmed by other biomarker maturity parameters based on sterane and hopane distributions. The maturity stage of oil generation and expulsion was further confirmed by the presence of solid bitumen as cements in the sandstone underlying Kupferschiefer and bitumen veins and lenses in the carbonates.

Sequence Stratigraphy of Miocene Tide-Influenced Sandstones In the Minas Field, Sumatra, Indonesia

Abstract The Miocene Sihapas Group in the Minas field, Indonesia, is composed of a succession of tens-of-meters-thick, erosionally based, tide-influenced sandstone intervals interbedded with marine shale-dominated intervals. Despite more than 1600 wells drilled into this 12-km-wide by 30-km-long mature super-giant field, complex internal tidal facies architecture within these sandstone intervals makes predicting local connectivity within the reservoirs challenging. Past interpretations of Minas field suggested that reservoir sandstone intervals are incised-valley deposits, based on assumptions that abrupt coarsening at the base of reservoirs reflects river incision into the shelf and tidal reservoir facies formed in coastal embayments during transgression. In this paper a new interpretation is proposed that suggests that shorelines remained strongly tide-influenced throughout regressive–transgressive depositional episodes. Pronounced discontinuity surfaces in these deposits are interpreted to have formed by a variety of mechanisms: (1) tidal erosion of the sea floor in front of regressing shorelines; (2) lowstand fluvial valley incision; and (3) the reworking of deposits during transgression of the shelf. Consideration of a wider variety of regressive and transgressive tidal depositional settings and erosional processes allowed revision of Minas field stratigraphy to better explain the observed complex facies variations that control reservoir production behavior. Minas field is divided into five major reservoir intervals that overlie low-grade metamorphic basement. The older deposits, comprising the S and D reservoir intervals, contain multiple upward-coarsening tide-influenced regressive shoreline successions, locally cut out by tide-influenced channel sandstone bodies, and capped by thin beds of marine shelf transgressive sandstone and overlying marine shale. Seismic images indicate that these deposits filled erosional basement topography during a period of long-term relative sea level rise. The upper three reservoir intervals (B, A2, and A1) are each interpreted to be fourth-order regressive shoreline deposits that were variably reworked by tidal currents during transgression. Successive intervals record progressively lower average rate of accommodation development, more rapid falling-stage regression, deeper lowstand incision, and greater reworking during intervening transgressions. Together, these three intervals comprise a third-order, flooding-surface-defined, forward-stepping sequence set deposited on a low-gradient continental shelf. Paradoxically, because intervals deposited during more rapid progradation tend to be thinner, in most wells more regressive sandstone intervals contain proportionally more open marine shelf deposits. This reflects that valley incision is localized, and regressive deposits that formed in lower long-term accommodation growth rate settings tend to be more completely reworked by tidal currents during subsequent transgression.

Sharp‐based marine sandstone bodies in the Mulichinco Formation (Lower Cretaceous), Neuquén Basin, Argentina: remnants of transgressive offshore sand ridges

AbstractThe interpretation of sharp‐based shallow‐marine sandstone bodies encased in offshore mudstones, particularly transgressive units, has been a subject of recent debate. This contribution provides a multiple‐dataset approach and new identification criteria which could help in the recognition of transgressive offshore sandstone bodies worldwide. This study integrates sedimentology, ichnology, taphonomy and palaeoecology of Mulichinco Formation strata in the central Neuquén Basin (Argentina) in order to describe and interpret sharp‐based sandstone bodies developed in ramp‐type marine settings. These bodies are sandwiched between finer‐grained siliciclastics beneath and thin carbonates above. The underlying sediments comprise progradational successions from offshore mudstones to offshore transition muddy sandstones, grading occasionally into lower shoreface sandstones. The surfaces capping the regressive siliciclastics are flat and regionally extensive, and are demarcated by skeletal concentrations and a Glossifungites suite; they are also marked by sandstone rip‐up clasts, with encrustations and borings on all sides. These surfaces are interpreted as composite discontinuities, cut during a relative sea‐level fall and remodelled during the initial transgression. The overlying transgressive sandstone bodies are 3 to 7 m thick, &gt;4 km long and about three times longer than wide; they are composed of fine‐grained sandstones with little lateral change in grain size. Cross‐stratification and/or cross‐lamination are common, typically with smaller‐scale structures and finer grain size towards the top. Large‐scale, low‐angle (5° to 8°) inclined stratification is also common, dipping at ca 30° with respect to body elongation and dominant currents. These sandstone bodies are interpreted as offshore sand ridges, probably developed under the influence of tidal currents. Intense burrowing is typical at the top of each unit, suggesting an abandonment stage. Final deactivation favoured colonization by epibenthic‐dominated communities and the formation of skeletal‐rich limestones during the latest transgressive conditions. As partial reworking of pre‐existing ridges occurred during this stage, the Mulichinco sandstone bodies are considered the remnants of transgressive offshore sand units.

Sedimentological–ichnological model for tide‐dominated shelf sandbodies: Lower Cambrian Gog Group of western Canada

AbstractDunes and bars are common elements in tide‐dominated shelf settings. However, there is no consensus on a unifying terminology or a systematic classification for thick sets of cross‐stratified sandstones. In addition, their ichnological attributes have hardly been explored. To address these issues, the properties, architecture and ichnology of compound cross‐stratified sandstone bodies contained in the Lower Cambrian Gog Group of the southern Canadian Rocky Mountains are described here. In these transgressive sandstones, five types of compound cross‐stratified sandstone are distinguished based on foreset geometry, sedimentary structures and internal heterogeneity. These represent four broad categories of subtidal sandbodies: (i) compound‐dune fields; (ii) sand sheets; (iii) sand ridges; and (iv) isolated dune patches; tidal bars comprise a fifth category but are not present in the Gog Group. Compound‐dune fields are characterized by sigmoidal and planar cross‐stratified sandstone in coarsening‐upward and thickening‐upward packages (Type 1); these are mostly unburrowed, or locally contain representatives of the Skolithos ichnofacies, but are intercalated with intensely bioturbated sandstone containing the archetypal Cruziana ichnofacies. Sand‐sheet complexes, also composed of compound dunes, cover more extensive subtidal areas, and comprise three adjacent subenvironments: core, front and margin. The core is characterized by thick‐bedded sets of cross‐stratified sandstone (Type 2). A decrease of bedform size at the front is recorded by wedges of thinner‐bedded, low‐angle and planar cross‐stratified sandstone (Type 3) exhibiting dense Skolithos pipe‐rock ichnofabric. The margin is characterized by interbedded sandstone and mudstone, and hummocky cross‐stratified sandstone. Sand‐sheet deposits exhibit clear trends in trace‐fossil distribution along the sediment transport path, from non‐bioturbated beds in the core to Skolithos ichnofacies at the front, and a depauperate Cruziana ichnofacies at the margin. Tidal sand ridges are large elongate sandbodies characterized by large sigmoid‐shaped reactivation surfaces (Type 4). Sand ridges display clear ichnological trends perpendicular to the axis of the ridge, with no bioturbation or a poorly developed Skolithos ichnofacies in the core, a depauperate Cruziana ichnofacies in lee‐side deposits, and Cruziana ichnofacies at the margin. While both tidal ridges and tidal bars migrate by means of lateral accretion, the latter occur in association with channels while the former do not. Because tidal bars tend to occur in brackish‐water marginal‐marine settings, their ichnofauna are typically of low diversity, representing a depauperate Cruziana ichnofacies. Isolated dune patches developed on sand‐starved areas of the shelf, and are represented by lenticular sandbodies with sigmoidal reactivation surfaces (Type 5); they typically lack trace fossils, but the interfingering muddy deposits are intensely bioturbated by a high‐diversity fauna recording the Cruziana ichnofacies. The variety of sandbody types in the Gog Group reflects varying sediment supply and location on the inner continental shelf. These, in turn, governed substrate mobility, grain size, turbidity, water‐column productivity and sediment organic matter which controlled trace fossil distribution.

Utilising borehole image logs to interpret delta to estuarine system: A case study of the subsurface Lower Jurassic Cook Formation in the Norwegian northern North Sea

The Lower Jurassic Cook Formation forms a regressive and transgressive sandstone wedge of shallow marine reservoir sandstones. It is distributed mainly in the Norwegian sector of the northern North Sea and the formation has proven to be hydrocarbon bearing. A case study of this formation from the Tampen Spur area presents a methodology for reconstructing depositional environments in areas of scarce data coverage and poor seismic quality using limited core-coverage, wire-line logs and borehole image logs. The core material and image logs are from different wells. The latter offer interesting opportunities for sedimentological descriptions and interpretations both in cored and uncored sections, particularly as the resolution of the tool (mm-scale under optimal conditions) enables identification of sedimentary structures. In order to avoid over-interpretation, a system of descriptive, simple and robust image facies was established for this study. These include: horizontal lamination, low-angle lamination, cross-stratification, as well as mottled and deformed strata. The Cook Formation is interpreted here as a regressive tidal-fluvial delta to transgressive wave-dominated estuary couplet with offshore shale above and below. The tidal-fluvial delta of the regressive part seems to be at odds with the regional context as the regressive part of the Cook Formation in the Tampen Spur area is interpreted as a wave-dominated delta system. Internally, the regressive part of the Cook Formation thickens westwards with 68% which is unusual for the otherwise tabular regressive Cook Formation in the Tampen Spur area. Both the thickness and depositional environment difference of the regressive part of the Cook Formation can be explained with temporary fault movement of a blind fault located basinward during basin infill. This could have created a fault-induced monocline that led to wave sheltering of the tidal-fluvial delta system. A spit-barrier system was probably associated with the monocline sourced by longshore drift from the otherwise wave-dominated coast of the regressive Cook Formation. After basin infill and removal of basin relief, the subsequent transgression resulted in the formation of a wave-dominated estuary.

Stratigraphy and sedimentary environments of the Lower Cambrian Gog Group in the southern Rocky Mountains of Western Canada: Transgressive sandstones on a broad continental margin

Research Article| December 01, 2010 Stratigraphy and sedimentary environments of the Lower Cambrian Gog Group in the southern Rocky Mountains of Western Canada: Transgressive sandstones on a broad continental margin Patricio R. Desjardins; Patricio R. Desjardins University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK S7N 5E2, patricio.desjardins@gmail.com 1Shell International Exploration and Production, 200 N Dairy Ashford Street, Houston, TX, 77079-1101, USA Search for other works by this author on: GSW Google Scholar Luis A. Buatois; Luis A. Buatois University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK S7N5E2, luis.buatois@usask.ca Search for other works by this author on: GSW Google Scholar Brian R. Pratt; Brian R. Pratt University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK S7N5E2, brian.pratt@usask.ca Search for other works by this author on: GSW Google Scholar M. Gabriela Mángano M. Gabriela Mángano University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK S7N 5E2, gabriela.mangano@usask.ca Search for other works by this author on: GSW Google Scholar Bulletin of Canadian Petroleum Geology (2010) 58 (4): 403–439. https://doi.org/10.2113/gscpgbull.58.4.403 Article history received: 15 Apr 2010 accepted: 22 Dec 2010 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Patricio R. Desjardins, Luis A. Buatois, Brian R. Pratt, M. Gabriela Mángano; Stratigraphy and sedimentary environments of the Lower Cambrian Gog Group in the southern Rocky Mountains of Western Canada: Transgressive sandstones on a broad continental margin. Bulletin of Canadian Petroleum Geology 2010;; 58 (4): 403–439. doi: https://doi.org/10.2113/gscpgbull.58.4.403 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of Canadian Petroleum Geology Search Advanced Search Abstract The architecture, distribution and facies of sandstone bodies in the Gog Group of the southern Rocky Mountains of Western Canada record the dynamics of sand movement on the broad continental shelf of West Laurentia during the Early Cambrian phase of worldwide transgression. These sandstones represent early deposits of a passive margin under high rates of sediment supply; accommodation was sustained by high rates of thermal subsidence plus sea-level rise. This study focuses on the stratigraphy and sedimentology in the Bow Valley region, specifically the sector from Mount Assiniboine northwest to the North Saskatchewan River. The objectives are to: 1) revise the existing stratigraphic nomenclature; 2) provide a general facies description and paleoenvironmental analysis of the constituent units; and 3) place the depositional setting in the context of the evolution of the Western Canada Sedimentary Basin.The Gog Group in this area has historically comprised four units: the Fort Mountain Lake Louise, St. Piran and Peyto formations. North of Bow Pass, an additional unit, the Jasper Formation, occurs below the Fort Mountain Formation and is related to accommodation created by active rift-faulting during the latest Neoproterozoic. In the Lake Louise and Lake O’Hara area, four new formal subdivisions within the St. Piran Formation are proposed: Lake O’Hara, Lake Oesa, Lake Moraine and Wiwaxy Peaks members.A wide range of subenvironments is recognized. The Fort Mountain Formation and the uppermost part the Lake O’Hara and Moraine Lake members record shallow-subtidal sedimentation. The correlative interval at Mount Assiniboine appears to have been deposited closer to the source area, and paleocurrents reveal sediment transport towards the north, parallel to the shoreline. The Lake Louise Formation was deposited in a protected low-energy, inner-shelf setting, while most of the Lake O’Hara Member records inner-shelf compound dunes and sand sheets. The Lake Oesa Member, which erosively overlies the Lake O’Hara Member, represents deposition in a tidal-flat environment. It is capped by a transgressive shoreface consisting of the lowermost deposits of the Moraine Lake Member. A record of sedimentation in inner-shelf conditions dominates the middle part of this unit, but with facies indicative of deposition in shallow-subtidal conditions in the upper part. The Wiwaxy Peaks Member represents an inner-shelf sand-ridge complex, followed by development of a shoreface environment. The overlying limestone-dominated Peyto Formation records deposition on a carbonate ramp related to a decrease in siliciclastic sediment supply. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Delineation of a sandstone-filled incised valley in the Lower Cretaceous Dina-Cummings interval: implications for development of the Winter Pool, west-central Saskatchewan

Abstract Major heavy oil deposits are present in Lower Cretaceous strata of west-central Saskatchewan. The Winter Heavy Oil Pool (approximately 566 044 mmbl) consists of bitumen-rich sands from the Aptian–Albian Dina and Cummings members of the Mannville Group. This succession unconformably overlies Paleozoic carbonates and is conformably overlain by the Lloydminster Member. Lower Cretaceous deposition in the Winter area was influenced by topography on the regional sub-Cretaceous unconformity, including the Unity uplands south of the study area and major paleovalleys opening to the northwest. The overall depositional framework consists of a lowstand and transgressive fluvial sandstone deposit (Dina Member) that evolved into a brackish embayment system (Cummings Member). Upon sea level fall, a valley was incised into the mudstone-dominated marginal marine deposits, which filled with sandstone during a subsequent sea-level rise (Cummings Member). Exploitable heavy oil reservoirs are contained within these incised valley sandstone beds. Further transgression led to a rising water table with widespread deposition of an organic-rich shale and coal followed by marine shale of the Lloydminster Member. The new depositional model for the area should lead to more optimal placement of horizontal wells in the reservoir, which is vital to continued bitumen extraction from the Winter Pool.