Shallow Marine Sandstones Research Articles

Experimental study on frequency‐dependent elastic properties of weakly consolidated marine sandstone: effects of partial saturation

ABSTRACTInvestigating seismic dispersion and attenuation characteristics of loosely compacted marine sandstone is essential in reconciling different geophysical measurements (surface seismic, well logging and ultrasonic) for better characterization of a shallow marine sandstone reservoir. We have experimented with a typical high‐porosity and high‐permeability sandstone sample, extracted from the Paleogene marine depositional setting in the Gulf of Mexico, at the low‐frequency band (2–500 Hz) as well as ultrasonic point (106 Hz), to investigate the effects of varying saturation levels on a rock's elasticity. The results suggest that the Young's modulus of the measured sample with adsorbed moisture at laboratory conditions (room temperature, 60%–90% humidity) exhibits dispersive behaviours. The extensional attenuation can be as high as 0.038, and the peak frequency occurs around 60 Hz. The extensional attenuation due to moisture adsorption can be dramatically mitigated with the increase of confining pressure. For partial saturation status, extensional attenuation increases as increasing water saturation by 79% with respect to the measured frequencies. Additionally, the results show that extensional attenuation at the fully water‐saturated situation is even smaller than that at adsorbed moisture conditions. The Gassmann–Wood model can overall capture the P‐wave velocity‐saturation trend of measured data at seismic frequencies, demonstrating that the partially saturated unconsolidated sandstone at the measured seismic frequency range is prone to be in the relaxed status. Nevertheless, the ultrasonic velocities are significantly higher than the Gassmann–Wood predictions, suggesting that the rocks are in the unrelaxed status at the ultrasonic frequency range. The poroelastic modelling results based on the patchy saturation model also indicate that the characteristic frequency of the partially saturated sample is likely beyond the measured seismic frequency range.

The Svalbard Eocene‐Oligocene (?) Central Basin succession: Sedimentation patterns and controls

AbstractA synthesis has been undertaken based on regionally compiled data from the post early Eocene foreland basin succession of Svalbard. The aim has been to generate an updated depositional model and link this to controlling factors. The more than kilometer thick progradational succession includes the offshore shales of the Gilsonryggen Member of the Frysjaodden Formation, the shallow marine sandstones of the Battfjellet Formation and the predominantly heterolithic Aspelintoppen Formation, together recording the progressive eastwards infill of the foredeep flanking the West Spitsbergen fold‐and‐thrust belt. Here we present a summary of the paleo‐environmental depositional systems across the basin, their facies and regional distribution and link these together in an updated depositional model. The basin‐margin system prograded with an ascending shelf‐edge trajectory in the order of 1°. The basin fill was bipartite, with offset stacked shelf and shelf‐edge deltas, slope clinothems and basin floor fans in the western and deepest part and a simpler architecture of stacked shelf‐deltas in the shallower eastern part. We suggest a foredeep setting governed by flexural loading, likely influenced by buckling, and potentially developing into a wedge top basin in the mature stage of basin filling. High‐subsidence rates probably counteracted eustatic falls with the result that relative sea‐level falls were uncommon. Distance to the source terrain was small and sedimentation rates was temporarily high. Time‐equivalent deposits can be found outbound of Stappen High in the Vestbakken Volcanic Province and the Sørvestsnaget Basin 300 km further south on the Barents Shelf margin. We cannot see any direct evidence of coupling between these more southerly systems and the studied one; southerly diversion of the sediment‐routing, if any, may have taken place beyond the limit of the preserved deposits.

Petroleum exploration potential of the Mid-Norway Continental Margin

The deepwater basins in the Mid-Norway Continental Margin of North Atlantic continental shelf is one of the hot spots of global petroleum exploration in deepwater area,and its exploration potential is very large. On the basis of synthesizing regional geologic information and the earlier researches of the Mid-Norway Continental Margin, guided by leading edging theories of Reservoir Sedimentology, Petroleum Geology, we found that main source rocks occur in the Upper Jurassic marine shale of Spekk Formation. The main reservoir is shallow marine sandstone of Fangst group of the Middle Jurassic rift stage. Petroleum migration through two ways: petroleum migrate a little distance by means of the cracks, grooming, faults a short distance, and pass through unconformity surfaces or connected sand bodies migrate a long distance,and and eventually into the reservoir. The Mid-Norway Continental Margin is rich in hydrocarbon,its reserve reaches about 73.2 billion barrels of oil equivalent and the undiscovered fields may be up to 36.

Cretaceous lithostratigraphy of North-East Greenland

An updated and revised lithostratigraphic scheme is presented for the Cretaceous of North-East Greenland from Traill Ø in the south to Store Koldewey in the north. The Ryazanian to lower Maastrichtian succession is up to several kilometres thick and comprises four groups, 12 formations and 18 members. The groups record the tectonic evolution of the East Greenland depocentre on the western flank of the evolving proto-Atlantic seaway. The Wollaston Forland Group encompasses the uppermost Jurassic – lowermost Cretaceous rift-climax succession and contains the Lindemans Bugt and Palnatokes Bjerg Formations; two new members of the latter formation are erected from Store Koldewey. Post-rift Cretaceous strata are referred to the new Brorson Halvø Group and the Home Forland Group. The Brorson Halvø Group (uppermost Hauterivian – middle Albian) is dominated by slope and basinal mudstones of the new Stratumbjerg Formation but also includes fluvio-deltaic and shallow marine sandstones of the revised Steensby Bjerg Formation on northern Hold with Hope and submarine slope apron breccias and conglomerates of the revised Rold Bjerge Formation on Traill Ø. The Home Forland Group covers the middle Albian – Coniacian succession. The basal unconformity records an important mid-Albian tectonic event involving intrabasinal uplift, tilting and erosion, as exemplified by the middle Albian conglomerates of the new Kontaktravine Formation on Clavering Ø. The Home Forland Group is dominated regionally by mud-dominated slope to basinal deposits of the elevated and revised Fosdalen Formation; it also includes lowstand basin-floor fan sandstones of the new upper Albian Langsiden Member. The new Jackson Ø Group (upper Turonian – lower Maastrichtian), records a phase of basin reorganisation marked by a significant fall in sedimentation rate in North-East Greenland, probably linked to rift events in, and bypass to, the central proto-Atlantic rift system. The base of the group is an erosional unconformity on Traill Ø and Geographical Society Ø overlain by submarine slope-apron conglomerates of the Turonian Månedal Formation. The base is conformable on Hold with Hope but is defined by a condensed interval (the Coniacian Nanok Member) that is succeeded conformably by slope and basin-floor turbidite sandstones of the Coniacian–Santonian Østersletten Formation and slope to basinal mudstones of the Campanian – lower Maastrichtian Knudshoved Formation. The new Leitch Bjerg Formation of Campanian slope-apron conglomerates and sandstones in eastern Geographical Society Ø erosionally overlies the Knudshoved Formation.

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.

Geostatistical Earth modeling of cyclic depositional facies and diagenesis

In siliciclastic and carbonate reservoirs, depositional facies are often described as being organized in cyclic successions that are overprinted by diagenesis. Most reservoir modelling workflows are not able to reproduce stochastically such patterns. Herein, a novel geostatistical method is developed to model depositional facies architectures that are rhythmic and cyclic, together with superimposed diagenetic facies. The method uses truncated Pluri-Gaussian random functions constrained by transiograms. Cyclicity is defined as an asymmetric ordering between facies, and its direction is given by a three-dimensional vector, called shift. This method is illustrated on two case studies. Outcrop data of the Triassic Latemar carbonate platform, northern Italy, are used to model shallowing-upward facies cycles in the vertical direction. A satellite image of the modern Bermuda platform interior is used to model facies cycles in the windward-to-leeward lateral direction. As depositional facies architectures are modelled using two Gaussian random functions, a third Gaussian random function is added to model diagenesis. Thereby, depositional and diagenetic facies can exhibit spatial asymmetric relations. The method is applied in two regions of the Latemar carbonate platform that experience two different types of diagenetic transformation: syn-depositional dolomite formation, and post-depositional fracture-related diagenesis. The method can also incorporate proportion curves to model non-stationary facies proportions. This is illustrated in Cretaceous shallow-marine sandstones and mudstones, Book Cliffs, Utah, for which cyclic facies and diagenetic patterns are constrained by embedded transition probabilities.

Application of Induced Polarization and Vertical Electrical Sounding to Locate Coal and Aquifers in Ojoma Akpa, Benue State

The study area Ojoma is located in Akpa district of Otukpo Local Government Area of Benue State, Nigeria. The area is underlain by Awgu Shale Formation that comprises shallow marine dark Shales, carbonaceous mudstones, limestones, siltstones and sandstones. The survey applied integrated geophysical techniques such as Induced Polarization and Vertical Electrical Sounding in order to locate a speculative coal deposit and prolific aquifers. ABEM Resistivity meter (Tetrameter SAS 1000) was used for the survey and Interpred 1D Software was used for processing, interpretation of field data and modeling of the subsurface. Four survey profiles (VES 1-4) were established with traverse lines between 1000 – 1300m each. No coal deposit was discovered. However, two aquiferous zones were located at depths of 9 – 12m and 25 – 50m respectively. It is recommended that drilling of boreholes may be carried out to tap water from the second hydrogeologic zone between the depths of 25-50m. The survey result also explained the major features revealed by the survey in terms of the types of likely geological bodies and structures which gave rise to the resistivity curves and models, thereby extending geological knowledge of the area. The underlying structures which gave rise to the geological models are the existence of folded and faulted sedimentary beds in the area.

Sedimentological characterization, petrophysical properties and reservoir quality assessment of the onshore Sandakan Formation, Borneo

Sedimentological parameterization of rock heterogeneity and prediction of shallow-marine siliciclastic reservoir quality remains a challenge globally to date, especially in regions with complex depositional histories, in that, variations in petrographic and petrophysical properties can occur within the same sedimentary sequence of similar age and rock type. Because exploratory drilling strategies and reservoir models can significantly be augmented through direct observation of outcrops that are representative of equivalent reservoir stratigraphic intervals in the offshore zone, outcrop sedimentological characterization can help improve the understanding of subsurface reservoirs of similar strata in surrounding petroliferous basins. To this end, we analyzed well-exposed successions of the mid Mio–Pliocene shallow-marine sandstone deposits of the Sandakan Formation, Borneo, through conventional field investigation, petrographic and petrophysical studies of different sandstone facies types to predict reservoir quality and heterogeneity within different depositional settings. On the basis of these evaluations, the studied sandstone was grouped into three qualitative reservoir rock classes: Class I (Ø = 18.10–43.60%; K = 1265.20–5986.25 mD), Class II (Ø = 17.60–37%; K = 21.36–568 mD) and Class III (Ø = 3.4–15.7%; K = 3.21–201.30 mD). The petrographic and petrophysical results reveals a consistent rise in both gamma ray and permeability values due to a change in depositional environment from proximal lower shoreface to upper shoreface of some successions within the sequence. The change in depositional setting for each sandstone type establishes certain variation in classes within the same facies type. For instance, the permeability may indicate low values due to the presence of bioturbation and increased mud content owing to the burrows with bimodal grain classification, regardless of change in gamma ray readings. This phenomenon signifies that there exists no strict correlation between gamma ray and permeability profile despite containing good quality reservoir rocks and appropriate classification. Our study is of paramount significance to the development of initial exploration strategies in regions where similar siliciclastic strata can be potential reservoirs because it serves as analogs to offshore hydrocarbon bearing packages.

Petrophysical interpretation and fluid substitution modelling of the upper shallow marine sandstone reservoirs in the Bredasdorp Basin, offshore South Africa

The fluid substitution method is used for predicting elastic properties of reservoir rocks and their dependence on pore fluid and porosity. This method makes it possible to predict changes in elastic response of a rock saturation with different fluids. This study focused on the Upper Shallow Marine sandstone reservoirs of five selected wells (MM1, MM2, MM3, MM4, and MM5) in the Bredasdorp Basin, offshore South Africa. The integration of petrophysics and rock physics (Gassmann fluid substitution) was applied to the upper shallow marine sandstone reservoirs for reservoir characterisation. The objective of the study was to calculate the volume of clay, porosity, water saturation, permeability, and hydrocarbon saturation, and the application of the Gassmann fluid substitution modelling to determine the effect of different pore fluids (brine, oil, and gas) on acoustic properties (compressional velocity, shear velocity, and density) using rock frame properties. The results showed average effective porosity ranging from 8.7% to 16.6%, indicating a fair to good reservoir quality. The average volume of clay, water saturation, and permeability values ranged from 8.6% to 22.3%, 18.9% to 41.6%, and 0.096–151.8 mD, respectively. The distribution of the petrophysical properties across the field was clearly defined with MM2 and MM3 revealing good porosity and MM1, MM4, and MM5 revealing fair porosity. Well MM4 revealed poor permeability, while MM3 revealed good permeability. The fluid substitution affected rock property significantly. The primary velocity, Vp, slightly decreased when brine was substituted with gas in wells MM1, MM2, MM3, and MM4. The shear velocity, Vs, remained unaffected in all the wells. This study demonstrated how integration of petrophysics and fluid substitution can help to understand the behaviour of rock properties in response to fluid saturation changes in the Bredasdorp Basin. The integration of these two disciplines increases the obtained results’ quality and reliability.

Sediment‐supply‐dominated stratal architectures in a regressively stacked succession of shoreline sand bodies, Campanian Desert Member to Lower Castlegate Sandstone interval, Book Cliffs, Utah–Colorado, USA

AbstractStrongly progradational regressive stacks of shallow marine sandstones are ubiquitous in modern and ancient coastal depositional systems. Many ancient examples form prolific hydrocarbon and freshwater reservoirs in the subsurface. One of the best areas in the world to study progradational shallow marine successions is the Campanian Book Cliffs of Utah and Colorado, where the Desert Member to Lower Castlegate Sandstone interval served as a foundational data set for early sequence stratigraphic models. A strongly progradational stack of 17 parasequences comprises the Desert–Castlegate interval. Parasequences are 6·5 to 20·7 m thick. Normally regressive coarsening‐upward successions are abundant, as are flat‐topped, rooted foreshore sandstones. Conformable facies contacts mark the transition between the laterally adjoining nearshore terrestrial and shallow marine deposits which are genetically, temporally and spatially linked. The width of the shoreface to inner shelf facies belts varies from 4·8 to 19·9 km per parasequence, with a mean of 12·6 km. Solitary tongue shoreline trajectories are all very low to low angle ascending regressive, varying from +0·0004° to +0·171°. Stacked shoreline system trajectories are also dominantly low angle ascending regressive, with only two descending regressive trajectories, one of which intersects the depositional slope. The predominance of ascending regressive shoreline trajectories and normal regression, rarity of high frequency sequence boundaries, regressive surfaces of marine erosion and descending regressive shoreline trajectories, and absence of third‐order sequence boundaries, incised valley fill deposits and no prolonged and regionally extensive sediment bypass, all point towards increasing sediment supply as the dominant driver of the Desert–Castlegate stratal architectures, while reduced accommodation (i.e. decreasing tectonic subsidence) played a secondary role.

U–Pb detrital zircon ages used to infer provenance and tectonic setting of Late Triassic–Miocene sandstones related to the Tethyan development of Cyprus

Zircons from Late Triassic deep-water sandstone turbidites of the Mamonia Complex (west Cyprus) have prominent Ediacaran–Cryogenian and Tonian–Stenian age populations, with smaller populations at c. 2.0 and 2.7–2.5 Ga, but only minor concordant Paleozoic zircons. Late Jurassic–Early Cretaceous deep-water gravity-deposited sandstone, also from the Mamonia Complex, has a greater proportion of Ediacaran–Cryogenian and Tonian–Stenian zircons, but less abundant Paleoproterozoic, Archean and Paleozoic zircons. Similar zircon populations characterize an Early Cretaceous shallow-marine sandstone block in the Moni Melange (southern Cyprus). The dominant Ediacaran–Cryogenian and Tonian–Stenian zircon populations originated in the NE Africa/Arabian–Nubian Shield (north Gondwana). However, they were probably recycled from Paleozoic sandstones within Anatolia following South Neotethyan rifting, which also gave rise to sparse Permian–Triassic zircons. Paleozoic zircons reflect Variscan magmatism within Anatolia. Both Late Cretaceous and overlying Eocene sandstone turbidites in the Kyrenia Range (north Cyprus) contain prominent Ediacaran–Cryogenian populations, together with small Archean, Tonian, Carboniferous and Late Cretaceous populations, with additional Triassic zircons in the Eocene sample. Late Cretaceous zircons dominate an overlying Late Miocene sandstone turbidite, together with minor Ediacaran–Cryogenian, Eocene and Miocene populations. The Late Cretaceous zircons record continental margin arc and/or ophiolite-related magmatism, whereas the Eocene and Miocene zircons represent collision-related magmatism, both located in southern Turkey. Supplementary materials : Detailed zircon U–Pb geochronological data and supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.4483736

Laurel Gas Play, Canning Basin - Recent Stratigraphic Learnings

Well, core and seismic data from the Lennard Shelf and Fitzroy Trough were integrated to produce a predictive sequence stratigraphic framework of the Laurel Formation consisting of Lower, Middle and Upper depositional sequences. Significant encouragement for potentially commercial flow rates was achieved by the hydraulic stimulation of the Middle Laurel in the Eastern Gas Province (Valhalla North 1 and Asgard 1 wells) in late 2015 and in the Western Gas Province (Yulleroo) in 2010. The Laurel tight gas play extends over a 20,000km2 area developed within a 2000m thick succession of marine clastics and carbonates. Condensate rich wet gas associated with overpressure is encountered regionally within low porosity and permeability sands at depths below 2000m. This was correlated across the basin from Yulleroo to the Meda Embayment and Northern Gas Province where a number of prospective plays were identified. Upper Laurel shallow marine sandstones commonly possess good oil and gas shows and have potential for tight gas where overpressured. A prominent Middle Laurel lowstand prograding shelf slope wedge supported by the presence of conglomerates in updip wells suggest better clastic sediment supply and the potential for the development of conventional lowstand topset sandstone reservoirs in the Northern Province. The Middle Laurel interval in the Northern Gas Province likely consists of a similar and potentially better tight gas reservoir than the interval stimulated in the Eastern Gas Province. Further drilling is required to confirm this and also to prove the viability of the tight gas play in the Northern Gas Province

Northwest Africa’s Ediacaran to early Cambrian fossil record, its oldest metazoans and age constraints for the basal Taroudant Group (Morocco)

The Anti-Atlas area in southern Morocco preserves one of the most complete latest Ediacaran to Cambrian shallow-marine carbonate records in the world and serves as a standard for global chemostratigraphic δ13Ccarb curves. Contrary to the excellent chemostratigraphic coverage, neither metazoan fossils (only stromatolites and calcified algae) nor radiometric age constraints were hitherto available for the basal part of this carbonate record, the Tifnout Member of the Adoudou Formation of the Taroudant Group. We report an Ediacara-type fauna from shallow-marine sandstones from the basal Tabia Member and microfossils from dolostones from both the Tabia and the Tifnout members of the Adoudou Formation. The former are discoidal fossils and share many characteristics with the form genus Aspidella and exhibit a peculiar style of preservation, pointing towards an early diagenetic two-stage (carbonate followed by silica) cementation history, leading to good preservation of these supposedly once soft-bodied organisms. The dolostone-hosted microfossils are preserved as sparite-filled molds enclosed by a thin opaque envelope. Despite their small size, they resemble late Ediacaran calcifying metazoans such as Namacalathus and tubular small shelly fossils. Together, these fossils constitute the oldest known direct evidence for presumably metazoan life from Northwest Africa. We also report new time constraints for the Adoudou Formation and fossils enclosed therein based on combined LA-ICP-MS and high-precision CA-ID-TIMS U-Pb zircon geochronology of detrital and volcanic zircons. Together with new chemostratigraphic (δ13Ccarb) and literature data, these new age constraints suggest a late Ediacaran age (time span between ca. 561 and 542 Ma) for the discoidal Ediacara-type fossils from the basal Tabia Member, and a latest Ediacaran to earliest Cambrian (time span between ca. 544 and 540 Ma) and an early Cambrian age (time span between ca. 528 and 523 Ma) for the two microfossil faunas from the Tifnout Member.

Probabilistic evaluation of multi-fluid-phase carbon dioxide storage capacities of saline formations in the Pohang Basin, Korea using three-dimensional geologic modeling and grid-based Monte Carlo simulation

A series of probabilistic evaluation is performed sequentially using three-dimensional geologic modeling and grid-based Monte Carlo simulation as a linked methodology to estimate multi-fluid-phase (i.e., individual gas-, liquid-, supercritical-, and whole fluid-phase) carbon dioxide (CO2) storage capacities of the target clastic saline formations in the Pohang Basin, Korea. The Pohang Basin is subdivided into the six geologic formations including the two clastic saline formations, which are the sandstone-dominant Fluvial Conglomerate and Sandstone (FCSS) and Shallow Marine Sandstone (SMSS) in ascending order. The results of the three-dimensional geologic modeling show that the six geologic formations are distributed very complicatedly both onshore and offshore with irregular depths and thicknesses, and they are partly dissected and offset by the eight major faults. The two clastic saline formations FCSS and SMSS are deep and thick at the three prospective areas such as Areas 1, 2, and 3 in the modeling domain. The results of the grid-based Monte Carlo simulation show the following three main contents. First, in the two clastic saline formations SMSS and FCSS, CO2 exists as gas, liquid, and supercritical phases with the corresponding distinctive density ranges depending on the pressure and temperature with depth. Second, the theoretical multi-fluid-phase CO2 storage capacities of the SMSS and FCSS all show asymmetric normal distributions. On the other hand, the effective multi-fluid-phase CO2 storage capacities of the saline formations all show log-normal distributions, and their values are much lower than the values of the theoretical multi-fluid-phase CO2 storage capacities. The mean theoretical fluid-phase CO2 storage capacities of the SMSS and FCSS are equal to 2,511.60 Mton and 1,370.91 Mton, respectively. The mean effective fluid-phase CO2 storage capacities of the SMSS and FCSS are equal to 64.19 Mton and 35.32 Mton, respectively. Third, in the SMSS, the grid-wise (elemental) median theoretical and effective multi-fluid-phase CO2 storage capacities are probabilistically higher at Area 1 (mainly as supercritical and liquid phases), intermediate at Area 2 (mainly as liquid and gas phases), and lower at Area 3 (mainly as a gas phase). However, in the FCSS, the grid-wise median theoretical and effective multi-fluid-phase CO2 storage capacities are probabilistically higher at Area 2 (mainly as supercritical and liquid phases), intermediate at Area 1 (mainly as a supercritical phase), and lower at Area 3 (mainly as a gas phase). Finally, four key criteria (parameters) for selecting or ranking the optimal CO2 storage locations are decided by summarizing and analyzing the results of the three-dimensional geologic modeling and grid-based Monte Carlo simulation. On the basis of the four key criteria (parameters), the overall suitability ranks of Areas 1, 2, and 3 for geologic CO2 storage are determined to be the first, second, and third, respectively.

Pore pressure and reservoir quality evolution in the deep Taranaki Basin, New Zealand

The Palaeocene fluvial to shallow marine sandstones of the Farewell Formation are an important proven hydrocarbon reservoir in the Taranaki Basin, New Zealand. The Kapuni Deep-1 well was drilled to target Farewell Formation sandstones in the deeper overpressured (>5000 m, >3000 psi/21 MPa) sections of the onshore Manaia Graben of the Taranaki Basin. However, the Farewell Formation sandstones display anomalously low measured helium porosities (1–4.5%) and intergranular volumes (6–11%) even for their present-day, close to maximum, burial depth (c.5000 m). One dimensional burial history modelling demonstrates initial rapid burial leading to significant porosity reduction via mechanical compaction, enhanced by poor sorting, angular grain morphology and the presence of ductile grains, which allowed efficient packing and plastic deformation. Low intergranular volume (IGV), anhedral nature of quartz overgrowths, a general lack of fluid inclusions, and poor crystalline clay mineral content indicate that early burial compactional processes significantly influenced reservoir quality. The lack of mudstone to siltstone grade lithologies within the overlying Eocene section inhibited the early or shallow onset of overpressure in the Farewell Formation. One dimensional basin modelling has shown that rapid Pliocene subsidence related to exceptionally high sedimentation rates generated overpressure through disequilibrium compaction in the overlying Oligocene to early Miocene section during the past 6 Ma. However, the late and deep (>3000 m) onset of overpressure had no effect on arresting porosity loss in the Farewell Formation. Continued compaction of Farewell Formation sandstones after dissolution of early carbonate cements of CO2 rich fluids creates zones of extremely low permeability, which have the potential to act with interbedded shales to form pressure seals as seen in the Kapuni Field.

Facies Distribution and Petrophysical Properties of Shoreface-Offshore Transition Environment in Sandakan Formation, NE Sabah Basin

Newly exposed outcrop of Miocene shallow marine sandstone in Sandakan Formation, allows characterization of the facies distribution and petrophysical properties of shoreface to offshore transition environment. Six facies are defined: (1) Poorly bioturbated Hummocky Cross Stratified (HCS) sandstone (F1), (2) Moderately bioturbated HCS sandstone (F2), (3) Well bioturbated HCS sandstone (F3), (4) Poorly bioturbated Swaley Cross Stratified (SCS) sandstone (F4), (5) Interbedded HCS sandstone with sand-silt mudstone, (6) Heterolithic mudstone. The sedimentary successions were deposited in upper to lower shoreface, and offshore transition environment. Facies F3, F4 and F5 shows good reservoir quality with good porosity and fair permeability values from 20% to 21% and 14 mD to 33 mD respectively. While Facies F1 exhibits poor reservoir quality with low permeability values 3.13 mD.

Stratigraphy of the marine Lower Triassic succession at Kap Stosch, Hold with Hope, North-East Greenland

The classical marine uppermost Permian – Lower Triassic succession exposed on the north-east coast of Hold with Hope in East Greenland, south-east of Kap Stosch, is placed in the Wordie Creek Group. A new lithostratigraphic subdivision of the group is proposed here. The group comprises the revised Kap Stosch Formation overlain by the new Godthåb Golf Formation. The Kap Stosch Formation is dominated by alternating fine- and coarse-grained, cliff-forming units that constitute the basis for the erection of eight new members. They are (from below): 1. The Nebalopok Member, uppermost Permian, Hypophiceras triviale ammonoid zone, and lowermost Triassic, lower Griesbachian, Hypophiceras triviale – H. martini ammonoid zones, composed of basinal and base-of-slope siltstones and turbiditic sandstones. 2. The conglomeratic Immaqa Member (H. martini ammonoid zone), consisting of a thick clinoform-bedded unit commonly overlain by horizontally bedded deposits, representing the foreset and topset, respectively, of a Gilbert-type delta. 3. The fine-grained Fiskeplateau Member (H. martini ammonoid zone), composed of siltstones and fine-grained sandstones, representing basinal and delta front deposits. 4. The conglomerate-dominated Knolden Member (H. martini ammonoid zone), comprising a clinoform-bedded unit overlain by horizontally-bedded deposits, representing foreset and topset, respectively, of a Gilbert-type delta. 5. The fine-grained Pyramiden Member, (lower–upper Griesbachian Metophiceras subdemissum, Ophiceras commune and Wordieoceras decipiens ammonoid zones), composed of variegated siltstones and sandstones deposited in proximal basin and slope environments. 6. The Naasut Member (top Griesbachian, probably Wordieoceras decipiens ammonoid zone), dominated by thick structureless coarse-grained sandstones commonly showing clinoform bedding, deposited in slope, base-of-slope and proximal basin environments. 7. The Falkeryg Member (lowermost Dienerian, Bukkenites rosenkrantzi ammonoid zone), comprising thick, commonly pebbly sandstones deposited in shelf, slope and base-of-slope environments. 8. The Vestplateau Member (lower Dienerian, Bukkenites rosenkrantzi ammonoid zone) composed of siltstones and fine-grained sandstones deposited in basinal environments. The overlying Godthåb Golf Formation (Dienerian, Anodontophora breviformis – A. fassaensis bivalve zones) is dominated by shallow marine sandstones with several coarser grained levels. The rich ammonoid faunas of the Wordie Creek Group allow a biostratigraphic zonation which can be correlated with schemes from other parts of the Arctic region. This zonation is complemented with information on palyno, conodont, fish and isotope stratigraphy.

Greater South China extended to the Khanka block: Detrital zircon geochronology of middle-upper Paleozoic sandstones in Primorye, Far East Russia

In order to examine paleogeographic link between Primorye and Japan with respect to other continental blocks in East Asia, middle-upper Paleozoic shallow marine sandstones of the Khanka block and Sergeevka belt were analyzed by LA-ICPMS U-Pb dating of detrital zircons. The age spectra of detrital zircons of the Devonian Lyutorgian Formation, Lower Carboniferous Shevelevka Formation, and Permian Lyudyanza Formation in the Vladivostok-Nakhodka area share more or less the same age range; the majority of detrital zircons are dated 500–400Ma (Cambrian to Silurian). These ages are common in previously dated granitoids with arc signature in Primorye and also in Japan, thus suggest a probable derivation from a single subduction-related Paleozoic batholith belt along the Pacific rim. The zircon age spectra of the Devonian and Carboniferous sandstones show similarities to those of coeval sandstones in NE and SW Japan. The middle-late Paleozoic sedimentary basins in Primorye and Japan commonly had a provenance featuring early Paleozoic arc rocks. In addition, all of these Paleozoic terrigenous clastics in Primorye and Japan consistently contain Proterozoic zircons. Occurrence of Meso- to Neoproterozoic (ca. 1500 and 600Ma) grains positively suggests a link to the South China block, as other blocks in East Asia lack crusts of this age of pan-African affinity. The common age spectra of detrital zircons of the Paleozoic sandstones in southern Primorye and NE-SW Japan support the concept of “Greater South China” that is comprised of conterminous South China to extend to Japan/Primorye, which is consistent with the mutual similarities recognized in Paleozoic marine fauna. Paleozoic South China was much larger than previously imagined, and this greater size, almost double the present conterminous South China, requires much larger area in the paleogeographical reconstruction of Rodinia.

Generic hierarchy of sandstone facies quality and static connectivity: an example from the Middle-Late Miocene Miri Formation, Sarawak Basin, Borneo

A significant percentage of the world’s hydrocarbon reserves are found in shallow marine sandstone rocks. Understanding reservoir connectivity and quality of shallow-marine sandstones from outcrop analysis and facies characteristics is a challenging task. Here, we analyze well-exposed outcrops of the Miri Formation, Sarawak Basin, Borneo, to characterize reservoir properties (grain-size, petrography, pore-perm, and static connectivity) of different sandstone facies and to construct a 2D intermediate-scale model of sandstone distribution and connectivity. The outcrops, with lateral extent of ∼200–500 m, consist of mostly sandstone with mud-rich deposits including some isolated sand bodies. Field description in terms of facies distribution and dimensions of sand bodies and rock sampling for grain-size (Folk and Ward methods), petrographic (point count method for porosity, sorting, grain-size, and sand-mud %), and poro-perm (for porosity and permeability) analyses were performed to quantify and examine seven different types of sandstones facies, i.e., (i) hummocky cross-stratified sandstones (HCSS, ∼0.5–4 m thick), (ii) herringbone cross-bedded (HBCBS, ∼0.5–3 m thick), (iii) trough cross-bedded sandstones (TCBS, ∼0.5–2 m thick), (iv) wavy- to flaser-bedded (W-FBS, ∼1–3 m thick), (v) cross-bedded sandstone (CS), ∼0.5–3 m thick), (vi) bioturbated sandstone (BS, ∼1–5 m thick), and (vii) massive sandstone (MS, ∼0.5–2 m thick). Our results show that compared to other sandstone facies, sandstones of HCSS and HBCBS are better sorted, have minimal mud content, and display increasing vertical and lateral connectivity due to depositional patterns even in bioturbated rich sand. Sandstones of BS and CB are of poor quality in terms of grain sorting and poro-perm, while TCB and MS sandstone facies are of less lateral and vertical extent. On the basis of these results, a 2-D outcrop-based model is constructed that provide additional insights into the significance of small-scale heterogeneity and static connectivity of shallow marine sandstone deposits which can be an analogue for subsurface reservoir quality analysis.

Shallow-marine Sandstone Reservoirs, Depositional Environments, Stratigraphic Characteristics and Facies Model: A Review

Shallow-marine Sandstone Reservoirs, Depositional Environments, Stratigraphic Characteristics and Facies Model: A Review