Reservoir Analogue Research Articles

Analog reservoir computing via ferroelectric mixed phase boundary transistors

Analog reservoir computing (ARC) systems have attracted attention owing to their efficiency in processing temporal information. However, the distinct functionalities of the system components pose challenges for hardware implementation. Herein, we report a fully integrated ARC system that leverages material versatility of the ferroelectric-to-mixed phase boundary (MPB) hafnium zirconium oxides integrated onto indium–gallium–zinc oxide thin-film transistors (TFTs). MPB-based TFTs (MPBTFTs) with nonlinear short-term memory characteristics are utilized for physical reservoirs and artificial neuron, while nonvolatile ferroelectric TFTs mimic synaptic behavior for readout networks. Furthermore, double-gate configuration of MPBTFTs enhances reservoir state differentiation and state expansion for physical reservoir and processes both excitatory and inhibitory pulses for neuronal functionality with minimal hardware burden. The seamless integration of ARC components on a single wafer executes complex real-world time-series predictions with a low normalized root mean squared error of 0.28. The material-device co-optimization proposed in this study paves the way for the development of area- and energy-efficient ARC systems.

Depositional and diagenetic controls on the reservoir quality of marginal marine sandstones: An example from the Early Devonian subbat member, jauf formation, northwest Saudi Arabia

The reservoir quality of marginal marine sandstones can vary significantly across different depositional lithofacies. This variation is primarily due to differences in depositional processes and subsequent diagenetic alterations occurring during various stages of burial. To address this issue, this study focuses on the Early Devonian Subbat sandstones of the Jauf Formation, which serve as an important analogue for subsurface gas reservoirs and have potential for CO2 sequestration. An integrated approach was employed, including field observations, petrography, geochemical analyses, and petrophysical analyses, to investigate the impact of depositional and diagenetic processes on reservoir quality. The findings indicate that the sandstones range from poorly to well sorted, very fine to medium-grained arkosic and quartz arenites that were deposited in a range of environments including shoreface-to-offshore transition zones, wave-dominated deltas, fluvial and tidal estuarine channels. The sandstones experienced both shallow and deep burial diagenesis, while key diagenetic events affecting reservoir quality include compaction, carbonate cementation, the formation of authigenic clays (kaolinite, illite, and chlorite), quartz overgrowth, and the dissolution of unstable feldspar and mica grains. Authigenic pore-filling cements and grain-coating clays significantly influence reservoir quality. The effect of quartz cementation was minimal where illite and/or chlorite coatings are well-developed. Mechanical compaction is more pronounced in the shoreface-to-offshore transition compared to the estuarine channels likely due to the higher detrital matrix content (21.7–35%, avg. 26.7%). The well-sorted fluvial to estuarine channel sandstones exhibit the best reservoir quality, with porosity ranging from 15.9% to 25.5% (average 20.4%) and permeability between 433.8 mD and 1261.2 mD (average 720 mD). This high reservoir quality is attributed to the low detrital matrix content (0–1%, average 0.2%) and limited pore-filling cements. In comparison, the moderately sorted, wave-dominated delta sandstones have lower porosity (5.3–11.2%, average 8.2%) and permeability (17.8–80 mD, average 42.8 mD), despite a relatively higher detrital matrix content (0–11.5%, average 2.8%). The poorly sorted shoreface-to-offshore transition sandstones exhibit the lowest reservoir quality, with porosity ranging from 1% to 2% (average 1.5%) and permeability between 0.3 and 1.1 mD (average 0.7 mD). These variations in reservoir quality among different depositional facies are primarily linked to depositional factors (sorting and detrital clay matrix) and shallow to deep burial diagenetic processes (compaction and cementation). A comprehensive understanding of these processes can enhance reservoir quality prediction in the Jauf Formation and similar reservoirs elsewhere.

Methanogenic activity in water-saturated reservoir analogues for underground hydrogen storage: The role of surface area

The activity of methanogenic Archaea in porous formations is influenced by various pore characteristics, including porosity, surface area, and the gas-liquid interfacial area. This study explores the impact of surface area on methanogenic activity using techniques such as MICP, NMR, SEM, and μCT. The cells of Methanothermococcus thermolithotrophicus, ranging from 1 to 2 μm, indicate that pores smaller than this threshold are not accessible for microbial traversal and colonization. Upon normalization of microbial activities based on pore volume and interfacial area, the findings exhibit strong correlations with specific surface areas of accessible pores in the examined rocks, as determined by MICP, NMR, and SEM. These areas ranged from 0.001 to 0.017 m2/g, 0.003–0.024 m2/g, and 0.012–0.02 m2/g, respectively. The normalized activities increase from 0.19 to 0.44 mM/(h·cm3·cm2) with an increase in the specific surface area, varying by method. Furthermore, an empirical model has been established to quantitatively evaluate hydrogen loss during underground hydrogen storage or the efficiency of bio-methanation, incorporating pore volume, specific surface area, and interfacial area.

Effects of overconsolidation on seismic rock physics — A comparative study between unconsolidated sands and weakly cemented sandstone

In seismic rock physics, models typically assume rocks are normally consolidated, often neglecting the effects of overconsolidation. Recent studies reveal that overconsolidated sands, resulting from stress release, show different physical property variations than normally consolidated sands. However, similar research is lacking for weakly cemented sandstones, a common reservoir analog. This study aims to systematically compare the effects of overconsolidation and stress direction on unconsolidated sandstones and weakly cemented sandstones. It also assesses the impact of overconsolidation on seismic interpretation, monitoring, and rock physics modeling applied to the two types of rocks. Experimental measurements of porosity, P-wave, and S-wave velocities were collected under different stress paths between loading and unloading. For weakly cemented sandstone, well-log data from the Norwegian Sea and Barents Sea were compared with experimental data. Analyses focused on the velocity-porosity relationship, VP/VS ratio vs. AI, and VP/VS ratio vs. effective stress.

Volcanic weathered crust reservoir analog: Insights from fault-controlled fracture permeability in the trachytic rocks of the Pernambuco Basin, NE Brazil

Naturally fractured volcanic rocks represent a globally significant potential hydrocarbon reservoirs and can also be used for CO2 storage; however, the study of volcanic reservoirs in Brazil is limited. Although numerous volcanic reservoir types have been classified, relatively few studies are dedicated to the weathering of crust-like reservoirs, i.e., volcanic rocks undergoing subaerially alteration by weathering prior to deep burial. This study aims to characterize a volcanic weathered crust reservoir analog located in the coastal zone of the Pernambuco Basin, NE Brazil. We applied a multiscale approach motivated by the expressive potential of volcanic rocks as reservoirs in this marginal basin and considered their implications for CO2 geological storage projects. The deformational aspects observed in this analog have also been observed in other volcanic rocks that crop out in the coastal zone, thus, the data provided here can guide future characterization of both onshore and offshore reservoirs. We focused on an 80 m wide outcrop and employed geometric and topological analysis of two-dimensional fracture networks to investigate the influence of regional fault zone control on the fracture permeability tensors. The parameters of fracture systems were studied using terrestrial gravimetric data, orthophoto mosaic obtained by an unmanned aerial vehicle (UAV), petrography, and outcrop-based structural data. The investigated outcrop includes porphyritic trachytes with euhedral sanidine crystals and minor quartz phenocrysts, sourced from the Ipojuca Magmatic Suite. The residual Bouguer map indicates the influence of at least two regional rift fault zones, i.e., NW-SE (strike-slip) and NE-SW (normal) trending systems, in the studied rocks. These trachytic rocks exhibited a marked dissolution of sanidine phenocrysts and matrix, columnar disjunctions, and natural fractures, causing the porosity and permeability of the reservoir analog to increase. Geometric and topological analyses showed that the south-central sector of the outcrop exhibits heightened connectivity within the fracture network. Furthermore, the principal fracture permeability is controlled by the primary families of the fracture network and regional fault zones. Our results demonstrate that the fracture network observed in the volcanic reservoir analog was influenced by the post-rift tectonic reactivation of Cretaceous structures within the Pernambuco Basin. The secondary porosity resulting from weathering and subsequent dissolution of the primary constituents and fractures of the rocks studied demonstrates the potential for the exploration of these reservoirs as models for known occurrences of volcanic rocks in the onshore and offshore domains of the Pernambuco Basin.

Heterolytic tide-dominated sedimentary facies and depositional environment: An Example from the Boka Bil formation, Sitapahar anticline, Bangladesh

The Baraichari Shale Formation, which is equivalent to the Boka Bil Formation, is well exposed within the Neogene sequence of the Sitapahar Anticline in the Chittagong-Tripura Fold Belt, Bengal Basin, Bangladesh. Regardless of its importance in hydrocarbon accumulation, a comprehensive facies analysis is essential to understand and explain the heterogeneity within different depositional architectural elements. The purpose of this work is to delineate the lithofacies characteristics, depositional environment heterogeneities and propose a generic depositional model for the Middle to Late Miocene shallow marine sediments of the formation. The sedimentary facies were investigated at three outcrops along the Kaptai–Chandraghona road cut sections of the Sitapahar anticline. The formation is composed of dark to bluish-gray shale, silty shale, yellowish brown siltstone, and gray to yellowish brown fine-to medium-grained sandstone. Eight distinct sedimentary facies have been identified and were categorized into three facies associations: subtidal or estuarine, mixed flats with tidal creeks, and tidal mud flats. The subtidal facies, predominant in the middle member, consists of fine to medium-grained ripple cross-stratified sandstone-siltstone, herringbone cross-stratified sandstone, and trough cross-stratified sandstone, indicating sub-tidal channel deposition. Mixed flats with tidal creeks exhibit heterolithic facies, suggesting energy level changes in intertidal to sub-tidal zones influenced by tidal currents. Tidal mud flats are predominantly laminated shale/mudstone and lenticular laminated sandstone-siltstone, reflecting deposition during tide transitions in the intertidal zone. Fining upward cycles within the formation indicate progressive progradation or changes in inner tidal flats conditions during regressive periods. These depositional settings serve as analogs for equivalent subsurface reservoirs and contribute to the construction of reservoir models with greater accuracy.

Using U–Pb carbonate dating to constrain the timing of extension and fault reactivation within the Bristol Channel Basin, SW England

The Bristol Channel Basin is a Mesozoic continental rift basin. The basin is an important analogue for offshore reservoirs. Relative cross-cutting relationships and correlation with adjacent sedimentary basins have previously been used to constrain the timing of basin development. In situ U–Pb carbonate geochronology has been used to date calcite slickenfibre development in the cores of normal, thrust and strike-slip faults in the East Quantoxhead and Kilve region of Somerset for the first time. Protracted north–south extension from c. 150 to 120 Ma formed normal faults. Subsequent north–south shortening from c. 50 to 20 Ma was accommodated by (1) mutually cross-cutting strike-slip faults, (2) minor east–west-striking thrust faults and (3) the reactivation of pre-existing normal faults. Throughout Cenozoic contraction, σ 2 and σ 3 remained similar in magnitude and periodically flipped to become vertical; this was probably controlled by local stress permutations and changes in fluid pressure. The timing of inversion is contemporaneous with dominant Pyrenean and later Alpine orogenic events, as well as the opening of the Mid-Atlantic Rift. Early inversion of the Bristol Channel Basin was probably driven by far-field Pyrenean deformation, with later contraction caused by Alpine forces. Ridge push from the Mid-Atlantic Rift exacerbated the reactivation of the basin.

Three-dimensional geological modeling applied to multiscale heterogeneity of a reservoir analog: Paleocoastal deposits from the Rio Bonito formation, Paraná Basin

Coastal sandstones have high permoporosity and contain significant hydrocarbon reserves, although they present variable flow heterogeneities. The goal of this paper is to understand the distribution of potential reservoir-flow units in the Rio Bonito Formation (early Permian, Paraná Basin) and to investigate heterogeneities on multiscale. We use stratigraphic, sedimentological, 3D model, and petrological data to evaluate reservoir heterogeneities. System tracts were modeled by sectioning the entire succession into five zones. Eleven facies associations were modeled separately within each zone, using geostatistical analysis and different algorithms. The 3D model was validated by jackknife procedure, and the distribution of facies associations adequately represented both depositional and stratigraphic frameworks. The results are adequate in a curve of accommodation changes similar to previous proposal for the study area. Tidal sand bar facies association presents as elongated (parallel to depositional dip) to sheetlike geobodies according to amalgamation grade, while upper and middle shoreface one is mostly elongated (parallel to depositional strike) to sheetlike. Besides, fluvial channel facies association occurs mainly elongated parallel to depositional dip, forming multilateral and multistory geobodies. Modeled depositional geometries were distinguished along the succession, showing similarities to Rio Bonito Formation outcrops, recent environments, and other deposits around the world, such as estuarine strata from Oriente Basin and shoreface ones from Gulf of Mexico Basin. Using a detailed petrological analysis, eleven reservoir petrofacies were defined and classified into good-, medium-, and low-quality reservoirs or non-reservoirs. Tidal sand bar, upper-middle shoreface, and fluvial channel deposits were categorized as the main reservoir-flow units. This study provides predictive scenarios for heterogeneities in reservoirs and may be applied in petroleum fields.

Highly-integrable analogue reservoir circuits based on a simple cycle architecture

Physical reservoir computing is a promising solution for accelerating artificial intelligence (AI) computations. Various physical systems that exhibit nonlinear and fading-memory properties have been proposed as physical reservoirs. Highly-integrable physical reservoirs, particularly for edge AI computing, has a strong demand. However, realizing a practical physical reservoir with high performance and integrability remains challenging. Herein, we present an analogue circuit reservoir with a simple cycle architecture suitable for complementary metal-oxide-semiconductor (CMOS) chip integration. In several benchmarks and demonstrations using synthetic and real-world data, our developed hardware prototype and its simulator exhibit a high prediction performance and sufficient memory capacity for practical applications, showing promise for future applications in highly integrated AI accelerators.

Transparent gelatin as a reservoir analogue: Dimensional scaling for hydraulic fracturing laboratory experiments

Gelatin is frequently used as a reservoir analogue for modeling hydraulic fracture (HF) growth in brittle, organic-rich rocks; its transparency enabling direct, visual observation of the HF growth. However, not many works have assessed the scalability of laboratory experiments on gelatin blocks with-respect-to “real-world” HF stimulation treatments. In this work, lab-scale parameters are compared against typical slickwater and crosslinked-gel stimulation treatment parameters from the Barnett Shale in northeastern Texas, for comprehensive (geometric, kinematic, and dynamic) dimensional-scaling evaluations.Dimensionless groups relating lab-scale physical models that display HF growth to the field-scale parameters are used to quantify the representation of elastic deformation, crack formation energy, treatment time-duration, and stress confinement, honoring the governing principles for fluid-driven fracture propagation in linearly-elastic media (applicable to HF growth in rocks, as well as magmatic intrusions, such as dykes or sills). The analysis demonstrates gelatin as a reservoir analogue to exhibit enhanced scaling against crosslinked gel compared to slickwater stimulation treatments, with the laboratory conditions accentuating toughness over viscous effects in comparison to field conditions, something which if neglected can lead to biased conclusions. Henceforth, a set of laboratory parameters is proposed for gelatin blocks of a practically-attainable powder concentration that yields improved scalability against the prototype parameters, minimizing the discrepancy between the lab-scale and the corresponding field-scale values for each dimensionless group, inside the limits of standard laboratory equipment.Identical dimensional-scaling evaluations are performed on lab-scale parameters from past experimental studies reported in the literature where gelatin samples were used, to the extent that the published data allows, indicating poor scaling of the physical phenomena. Results and conclusions from such inadequately-scaled experiments should be treated with suspicion.

Geologic characterization of the Lower Cretaceous upper Travis Peak and Pettet Formations in the Wright Mountain field, Smith County, East Texas basin: Potential reservoir analog for other Travis Peak and Pettet strata

The Wright Mountain field in Smith County, Texas, is a tight carbonate reservoir that produces from the Lower Cretaceous Pettet Formation. The Pettet Formation is dominantly made up of cyclic shallow-water shelfal carbonates associated with skeletal oolitic shoal complexes. These shoals are widespread hydrocarbon-reservoir targets, have poor to fair matrix reservoir quality, and are commonly sealed by transgressive argillaceous lime mudstones and wackestones. Complex regional paleotopography has significant impact on the regional distribution of these shoal bodies and overall depositional patterns. This investigation, therefore, aims to characterize the Pettet Formation and underlying fluviodeltaic Travis Peak Formation in the Wright Mountain field, located on the western flank of the Strickland High near the northeastern margin of the East Texas Basin, to assess reservoir parameters and to compare depositional patterns to existing shoal-complex studies centered on the top of the paleohigh in Rusk County. The Pettet section in Smith County consists of three fourth-order sequences (Pettet A–C), each of which shoals upwards into a shallow-water, high-energy environment near or within shoal complexes. The best reservoir lithofacies are the mixed skeletal-ooid and skeletal grainstones, as observed elsewhere in the Pettet Formation in Rusk County. However, texture and biota vary in the Wright Mountain field area as compared to the Rusk County area as there is abundant evidence of reworking and resedimentation in the Wright Mountain field area, suggesting a different depositional setting perhaps related to off-shoal deposition or greater depositional dip. Therefore, this field characterization study is important for constructing a regional depositional model and can be applied as an analog for equivalent systems with similar lithofacies and pore networks elsewhere in the northern Gulf of Mexico.

The effect of fracture networks on the vertical permeability of a tight carbonate reservoir analogue: laminites from the Crato Formation, NE Brazil

The structural characterization of fractures is crucial to understand the processes of fluid flow in tight reservoirs. This contribution focuses on the role played by vertical fractures on the permo-porosity properties of the Aptian tight carbonate sequence of the Crato Formation, Araripe Basin (NE Brazil). The study performed a structural analysis in two different scales: reservoir scale (approximately 19.000 m2) and outcrop scale (approximately 125 m2), focusing on the fracture networks in lacustrine laminates, which have been investigated as an analogue of carbonate facies observed within the pre-salt reservoir sequence of the marginal basins in Brazil. This study employed a combination of systematic outcrop-based fracture characterization involving digital outcrop models and mechanical stratigraphy analysis. To evaluate the influence of vertical fracture systems in the fracture porosity and the equivalent permeability we performed DFN (Discrete Fracture Network) models. We focused on vertical calcite-filled fractures, oriented in two principal directions: set 1 NNW-SSE and set 2 NE-SW. Each set shows different vertical linkage patterns due to the influence of the mechanical intervals. Results of the outcrop scale model show similar behaviour for both fracture porosity and equivalent permeability, indicating that storage capacity and fluid flow may not be affected by vertical linkage of fractures. The reservoir scale DFN models show that the fracture porosity was greater in models which consider through-going continuous fractures than in models that consider the segmentation (discontinuity) of vertical fractures. Considering the vertical connectivity of fractures, the equivalent horizontal permeability (Kxx and Kyy) showed similar values in both scale models. This implies that vertical segmentation of fractures does not impact fluid flow in horizontal directions. The calculated values of equivalent vertical fracture permeability (Kzz) at reservoir scale are one order of magnitude higher in the DFNs that consider continuous fractures. Our results suggested that vertically continuous fractures enhance preferential flow pathways allowing greater vertical fluid flow than segmented fracture networks in tight carbonate reservoirs.

Integrated controls of tectonics, diagenesis and sedimentation on sandstone densification in the Cretaceous paleo-uplift settings, north Tarim Basin

The densification mechanism of the Lower Cretaceous sandstone in the western Tabei Uplift is still unclear, restricting successful petroleum exploration and development. Seismic interpretation, thin sections observation, Field emission scanning electron microscope (FE-SEM) and cathodoluminescence (CL), porosity and permeability measurements, mercury injection porosimetry (MIP) are compiled in this study, to investigate the paleo-uplift and facies co-evolution, tight reservoir characteristics, and densification mechanism of the Lower Cretaceous sandstones around the paleo-uplift. Results indicate the sedimentary facies around the Xinhe and the Sandaoqiao uplifts were controlled by the decreasing geomorphic slope and rising lake level, their evolution exhibited difference. The Xinhe area developed a fan delta with a reducing distribution in region, while the sandaoqiao area transitioned from fan delta to beach bar, eventually developing a braided river delta. Reservoir physical properties are primarily influenced by intense compaction, calcite and clay cementation and weak dissolution. Severe calcite cementation, compaction and weak dissolution predominantly influence the physical properties of the beach bar. Moderate compaction, weak cementation and moderate quartz and feldspar dissolution are the key factors impacting the physical properties of braided river delta. Additionally, reservoir quality varies with sedimentary facies where the sandstones of the braided-river delta have the best petrophysical properties and pore connectivity than those of the fan delta and beach bar. Tectonic movements around the uplift affected the distribution of various sedimentary facies, which later governed the diagenesis processes pathways. Collectively, this study can serve as a valuable reference for exploration and development of clastic reservoirs in the Tabei Uplift and analogous reservoirs with a paleo-uplift context.

Hydrothermal karst cavities in a Devonian carbonate reservoir analogue (Rhenish Massif, Germany): Implications for geothermal energy potential

Deep geothermal reservoirs can provide renewable energy for electricity and heat generation [1]. In the Rhine-Ruhr area of western Germany, where Europe's largest district heating network is located, up to 1,300 m thick carbonates of Devonian age are available in ≥ 4,000 m depth [2, 3]. Near the surface, these rocks contain karst cavities, which host some of Germany´s longest caves [4, 5]. At reservoir depth, abundant karstification may significantly increase the geothermal reservoir potential [6] (Figure 1).
 In the Munich area (southern Germany) deep-seated karstified Upper Jurassic rocks are widely used for the city´s district heating network [7]. Most deep-seated geothermal systems are located at a depth of 1,000 m or more at temperatures over 60 °C [8]. Therefore, it is important to assess deep-seated karstified structures elsewhere to assess their geothermal reservoir potential. In the Rhine-Ruhr area, these could have the potential to be used as an alternative renewable energy resource.
 This study aims at the geological characterization of deep-seated (hydrothermal) karst cavities in Steltenberg Quarry (western Germany) where Middle/Upper Devonian carbonates (Massenkalk limestone) are present in the vicinity of two regional fault zones [9, 10]. We applied state of the art petrographical, geochemical, palaeothermometrical methods, and U-Pb dating. Here we present the first U-Pb age data of deep-seated hydrothermal karst precipitates in Germany, which formed at the Permian-Triassic boundary (252.4 ± 8.6 My, Table 1). The U-Pb age data of calcite cement veins (LMC 8), which were cutting the near-surface karst cavities before they got dissolved, points to an Oligocene maximum age (30.0 ± 2.81 My) of the karst cavities.

The cambrian gog quartzite and deadwood formations of alberta: lessons for subsurface carbon sequestration

Injecting carbon dioxide into reservoirs has been undertaken since the 1940s, mostly as a method to enhance oil recovery. With the recognition of the impact of climate change, interest in carbon sequestration has increased exponentially, with hundreds of projects in progress around the globe. Many of these projects focus on Cambrian quartzites, which meet the requirements for carbon dioxide injection (CCS). Several CCS projects in Alberta, Canada, currently focus on using these reservoirs, including the Basal Cambrian Sandstone and Deadwood Formations, for injection and storage.A series of spectacular outcrops of the Cambrian Gog Quartzite are available for study in the area around Lake Louise in the Canadian Rockies of Alberta. These outcrops provide compelling analogues to other clastic Cambrian formations in the province that have been utilized for CCS. As an example, the Gog Quartzite was used by Shell as a direct reservoir analogue when modeling CO2 injection into the Basal Cambrian Sandstone in the QUEST Project. The Gog Quartzite also has potential to act as a CCS reservoir in its own right and may reach 2 kilometres in thickness.Outcrops of the Gog Quartzite were studied at Sink Lake, Spiral Tunnels and in the vicinity of Lake Louise in Alberta. They include fluvial and shallow marine, high net:gross sandstone beds with stacked trough cross-bedded sandstones. These are commonly interbedded with thin mudstone beds. Sedimentary structures include planar and trough cross-beds, wave ripples and contorted horizons interpreted as seismites with associated dewatering. Some units of the Gog Quartzite are heavily bioturbated with burrows including Arenicolites and Skolithos as well as other marine traces such as trilobite related ichnofacies.The Cambrian Deadwood Formation is also a target for carbon dioxide sequestration and provides the main reservoir for the Aquistore Project in Saskatchewan. It has been targeted by exploration wells in eastern Alberta and a new core study has demonstrated its suitability as a CO2 reservoir. Facies ranging from regolith overlying igneous basement, through alluvial fan and tidal deposits, and out into shallow marine settings with well developed parasequences, are all seen in the cores.The outcrop and core studies provide new data on Cambrian reservoirs which can be applied directly to potential Cambrian CCS targets in the subsurface of Alberta. The data can also be used to identify other potential Cambrian CO2 sinks around the world.

Lithofacies Interpretation Of Sediment Rocks In The Cipamingkis River Outcrop, Jonggol Area, Bogor District, West Java

This research aims to study sedimentary structures and determine the depositional environment of the outcrop in the Cipamingkis River, Jonggol area, Bogor Regency, West Java. The method in this study includes literature studies, field surveys, data interpretation, and facies analysis. The result shows the outcrop in the Cimangkis River can be divided into four (4) sedimentation sequences unit: Claystone Unit (Sequence 1), Limestone/Calsirudit Unit (Sequence 2), Limestone/calcarenite-Calcilutite Unit (Sequence 3), Mudstone/ Calsilutite Unit (Sequence 4). Based on the depositional environment analysis, this outcrop displays characteristics of a shallow marine environment. The Interpretation of facies from outcrops can be used as a reservoir analog and can support subsurface interpretation in the Northwest Java Basin

Analysis of the Efficiency of Petroleum Systems in Fluvial Environments in the Rift Context of the South and North Atlantic: Brazil and Portugal

The present article exhibits the achieved results based on the evaluation of two petroleum systems, which compares reservoirs of fluvial environments of sedimentary basins located in the south and north Atlantic, in Brazil (Recôncavo Basin) and in Portugal (Lusitanian Basin), respectively. The main contribution of this study is the survey of the static (source, reservoir, and sealing rocks, in addition to traps) and dynamic elements (tectonic, migration, thermal, and diagenetic processes) of the two studied petroleum systems, seeking to understand the reasons for the success and failure of the analyzed reservoirs in relation to the accumulation of hydrocarbons. The following materials were used for this study: lithostratigraphic charts, event charts of petroleum systems, interpreted 2D seismic reflection lines, lithological profiles, outcrop data, geochemical analysis of source rocks, petrographic analysis, and description of diagenetic processes, which acts in the reservoir rocks. The methodology presents two phases: the first with a multiscale characterization of the elements of petroleum systems and economic aspects, and another with an integrated analysis of the reservoir potentials, based on the efficiency analysis table of the petroleum system elements and interpretative diagrams of the petroleum system elements. The occurrences of hydrocarbon accumulations indicate that the structuring of the Recôncavo Basin in horsts and grabens provides the formation of efficient migration routes, combined with an excellent source rock, reservoirs with good permo-porous characteristics, and effective seal rocks. On the other hand, in the Lusitanian Basin, the Paleozoic source rocks occur in mini-basins, with little lateral continuity, which negatively affects the generation of hydrocarbons. Besides this fact, saliferous tectonics were the main cause of hydrocarbon migration along faults or their walls towards the upper strata and to the surface. The fluvial reservoir rock shows a strong action of diagenetic processes, which affects its petrophysical properties. The main implication of this work is its contribution to the analysis of analogous reservoirs, based on the detailed investigation of the static and dynamic elements of petroleum systems.

The Method for Selecting Analogous Reservoirs Based on SEC

To support remaining economic recoverable reserves and undeveloped reserves compliant with SEC rules, different types of recovery analogous reservoir sequences need to be established. Based on the SEC reserves estimation standards and the actual development characteristics of the oilfield, a classified and optimal evaluation method of analogous reservoirs, which can select a reasonable analogous reservoir fast, has been proposed. This method mainly includes 7 steps to select analogous reservoirs. With practical application in an oilfield, this method has obtained good effects. Selection results can cover all the typical reservoir blocks, and it provides a reliable basis for analogizing the target reservoir in the future. The method herein could provide a new method to select analogous reservoirs based on SEC, and it can be widely used in other oil fields.

New approaches to the architectural analysis of deltaic outcrops: Implications for subsurface reservoir characterization and paleoenvironmental reconstruction

This study defines a new workflow to investigate the internal facies architecture of a river-dominated delta deposit using outcrops of the Cretaceous Panther Tongue of the Star Point Sandstone in central Utah, U.S.A. Photorealistic virtual outcrop models (VOM) were created from ~13 linear-km of outcrop. The VOMs, alongside field observations, were used to identify and map facies and facies associations over the ~25 m-thick stratigraphic interval. In order to investigate this system as a potential subsurface reservoir analog, a database of measurements was constructed using 60 digital sections that were measured within the VOMs at 152 m (~500 ft) spacing. This database characterizes a total of 508 sandstone beds by their thickness, length, and dip, from which the average thickness (0.78 m), bed length (330 m), and bed dip (2˚ towards the south) were calculated. Thinning rates were also calculated in both depositional strike and depositional dip directions (1.37x10-2 and 1.01x10-2 respectively). These comparable values suggest that the sandstone beds thin equally laterally and longitudinally from the sediment source, a characteristic typical of modern-day river-dominated deltas. The dataset also includes siltstone unit thickness data, recording an average thickness of 0.81 m, and a trend of increasing siltstone abundance and thickness moving from proximal areas where siltstones comprise 3% of the succession, and 77% in the most distal areas. The impact of observational scale was also investigated by querying the database at multiple physical length scales to include more typical well spacings of 305 and 610 m (500 and 1000 ft). This additional analysis emphasizes the role of variability in lithologically heterogeneous systems and underscores the utility of outcrop analogs to better understand sources of uncertainty. From these data, a series of depositional environment maps was constructed, illustrating the evolution of eight delta lobes that encompass the preserved depositional history of the study area. These maps document the compensational stacking of individual lobes and the progressive southward directed trajectory of the Panther Tongue delta system. Results of this analysis provide insight into depositional processes and scales of heterogeneity of the Panther Tongue and, by extension, analogous river-dominated delta systems. The workflow established in this study is exportable to other sedimentary outcrops and environments, thus demonstrating that VOMs can be used as a basis for quantitative database development and reservoir modeling inputs.

Are open-source aerial images useful for fracture network characterisation? Insights from a multi-scale approach in the Zagros Mts.

Multi-scale fracture characterisation in reservoir analogues is crucial for determining orientation clustering, length scaling laws, abundance, and topology of the fracture network, all of which are essential for modelling flow of geofluids. In this study, we examine the application of Bing Maps imagery for fracture network analysis in the Kuh-e-Asmari anticline (Zagros Mountains, Iran), a scarcely vegetated area which is a good outcropping analogue for fractured reservoirs. Image-derived fracture characterisation is conducted at three distinct scales (1:50,000, 1:5,000 and 1:500) using the NetworkGT plugin in QGIS and was compared with structural data collected in the field (i.e. scan lines). The results reveal a scale dependency, with the advantages and disadvantages of each scale summarised as follows. The 1:50,000 is the only spatially continuous dataset. The 1:5,000 dataset, potentially spatially continuous, enables the analysis of fracture and connectivity distribution in great detail, emphasising strongly fractured/connected elongated zones, which may represent damage zones of known, previously mapped fault strands. The 1:500 scale does not ensure the spatial continuity of the dataset; however, similar to scan lines, it can perform detailed analyses of the fracture network in potentially interesting areas. We conclude that structural field surveys can be combined with multi-scale mapping on aerial images to better define the length and abundance distribution of fractures.