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- 摘要：Numerous oil and gas fields have been discovered in the Paleozoic strata of the Ordos Basin， demonstrating significant exploration and development potential. Faults developed within the basin play an important role in controlling hydrocarbon migration， accumulation， and differential enrichment. The planar and sectional characteristics， structural styles， activity stages， and genetic evolution of faults in this area were systematically analyzed based on detailed structural interpretation of 3D seismic data from the Yangquan area， Fuxian County， combined with the regional tectonic setting consideration. As indicated by the research results， （1） two sets of large-scale conjugate strike-slip faults， trending nearly W-E and NE-NW， are developed in the Yangquan area， Fuxian County， Ordos Basin. These faults are distributed primarily in the central and eastern parts of the study area and exhibit distinct segmentation. The nearly W-E-trending faults display transtensional deformation west of the NE-trending faults and transpressional deformation to the east. Six common structural styles are recognized： horsts， grabens， roof-ridge， inverted roof-ridge， positive flower， and negative flower structures. （2） Integrated with the regional tectonic evolution， fault activity was divided into three major stages： the Caledonian sinistral strike-slip （with inherited development during the Hercynian）， Indosinian sinistral strike-slip， and the Yanshanian-Himalayan dextral strike-slip. A fault evolution sequence controlled by the superposition of multiple tectonic stress fields was established. （3） Significant differences exist in the development patterns of faults with different strikes during the same tectonic period. The W-E-trending faults were highly active during the Caledonian， Indosinian， and Yanshanian periods， with a strong genetic relationship between the early- and late-stage faults， indicating inherited development. In contrast， the NE- and NW-trending faults were strongly active during the Caledonian and Hercynian periods with decreasing activity and diminishing fault inheritance in later stages. （4） The temporal match of fault development timing with burial and hydrocarbon generation histories indicates that the Yanshanian fault activity was essentially synchronous with the peak hydrocarbon generation stage， providing effective pathways for the vertical migration of natural gas. Faults formed during the Indosinian and earlier periods predated the hydrocarbon generation peak and therefore contributed little to hydrocarbon accumulation. Faults active during the Himalayan period postdated the hydrocarbon generation peak and primarily modified pre-existing gas accumulations. （5） The fault systems surrounding high-yield wells provide favorable conditions for hydrocarbon migration and preservation： deep-seated faults effectively connect source rocks with reservoirs， strike-slip faults within the reservoirs improve reservoir space， and shallow faults do not breach the caprock.关键词：fault activity stages;fault-controlled reservoir development;strike-slip fault;structural characteristics;Paleozoic;Yangquan area in Fuxian County;Ordos Basin3|0|0更新时间：2026-10-15
- 摘要：The characteristics and development model of the paleo-provenance system of the Paleogene Wenchang Formation in the Kaiping Sag， Pearl River Mouth Basin， remain poorly understood， resulting in uncertainties regarding the genesis and distribution of favorable sand bodies and hindering the identification of favorable exploration targets. Using data from lithic fragment identification， heavy mineral analysis， detrital zircon U-Pb dating， and seismic surveys， this study systematically analyzed parent rock types， sediment source area characteristics， and provenance directions， investigated the evolution and development model of the provenance system， seeking to provide a scientific basis for predicting favorable sand bodies. As indicated by the research results， the provenance of the Wenchang Formation in the Kaiping Sag was derived predominantly from rejuvenated orogenic belts and volcanic arcs， with the majority being composed of felsic components from the upper crust. Zircon U-Pb dating and heavy mineral analysis reveal potential sediment source areas in the south， northwest， southwest， and northeast parts of the study area. Synsedimentary volcanic activity also contributed abundant tuffaceous material， giving rise to a multi-directional， multi-source， and non-steady provenance system. Stratigraphic comparison indicates that the lower member of the Wenchang Formation was jointly influenced by sediment supply from the Shenhu Uplift to the north， the Shunhe Uplift to the south， the Yunkai Low Uplift to the northeast， and contemporaneous intra-basin volcanic sources. In the upper member， the contribution from the Shenhu Uplift progressively increased， whereas that from contemporaneous intra-basin sources diminished. Tectonic evolution and paleogeomorphology controlled the development model of the provenance system and the types of sedimentary systems within the Wenchang Formation. A transitional fault slope-fault nose provenance system developed in the north dominated fan-delta development in the lower member of the Wenchang Formation and is characterized by a proximal， small-scale fan system. A proximal， gentle-slope fault-trough provenance system developed in the southwest governed the development of braided-river delta along the gentle-slope zone of the western sub-sag. A distal， gentle-slope paleo-valley provenance system developed in the south controlled braided-river delta development in the gentle-slope zone of the southern main sub-sag and is characterized by a distal， large-scale fan system.关键词：zircon U-Pb dating;heavy mineral assemblage;provenance analysis;source-to-sink system;Wenchang Formation;Kaiping Sag;Pearl River Mouth Basin2|0|0更新时间：2026-10-15
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Pore-scale simulation of dynamic CO₂-brine-rock dissolution in carbonate gas reservoirs with water AI导读
摘要：CO2 injection into carbonate reservoirs is a key technology for enhancing natural gas recovery and achieving carbon sequestration. After injection， CO2 reacts with formation water to form acidic fluids， which dissolve certain minerals and consequently alter the porosity and permeability of porous media. A Lattice Boltzmann Method （LBM） coupled with a reactive transport model was developed and validated against high-temperature and high-pressure micro-computed tomography （micro-CT） displacement experiments to reveal pore-scale dissolution mechanisms after CO2 injection into carbonate reservoirs. Dissolution reaction simulations under different displacement pressure differentials （0.5 ~ 2.0 MPa）， back pressures （10.0 ~ 50.0 MPa）， and temperatures （40 ~ 140 ℃） were conducted to determine the corresponding reaction kinetic characteristics and pore evolution patterns. As indicated by the research results， （1） increasing the displacement pressure differential expands the fluid swept area and elevates hydrogen ion concentrations in pores， thereby improving dissolution efficiency. The carbonate dissolution amount increases from 10.6% to 17.9%. （2） Elevating back pressure enhances CO2 solubility， thereby increasing hydrogen ion concentrations and solution acidity and promoting dissolution reactions. Carbonate dissolution increases from 10.6% to 19.0%. （3） Under high-temperature conditions， although reduced CO2 solubility decreases hydrogen ion concentrations and partially inhibits dissolution reactions， the effect of increased reaction rates dominates， resulting in continuous enhancement of carbonate dissolution from 10.6% to 42.7%. Pronounced heterogeneous dissolution characteristics were observed under all working conditions， confirming that pore structures control the morphological evolution of mineral dissolution.关键词：Lattice Boltzmann Method （LBM）;reaction kinetics;mineral dissolution;pore-scale simulation;CO2-brine-rock system;carbon capture2|0|0更新时间：2026-10-15 - 摘要：Deepwater oilfields have become one of the principal strategic frontiers for global reserve replacement and production growth. Deepwater turbidite sandstone oilfields， such as those in Block 18， Angola， have generally entered a stage of high water cut and high recovery， while substantial marginal reserves remain distributed around the developed fields. However， the development of these reserves has long been constrained by great water depths， small reserve size， high single-well investment， and significant development risks. An integrated technical system for efficient development of marginal reserves was developed based on the principle of “minimum wells with high and stable production，” to address three key challenges in marginal reserve development—rapid assessment of economic feasibility， mismatch between well-pattern configurations and reservoir architecture， and the conflict between high-rate oil production and stable production. As indicated by the research results， （1） an economic recoverable reserve threshold model coupling oil price， tieback distance， and geological risk was established to define the minimum economic recoverable reserves required for tieback development. Under an oil price of USD 60/bbl， a tieback distance of 20 km， and moderate geological risk， the minimum threshold ranges from 8.4 × 106 t to 10.1 × 106 t， enabling rapid screening of marginal targets and identification of candidates suitable for detailed development planning. （2） Differentiated injection-production well patterns constrained by reservoir architecture and reserve abundance were developed. Massive reservoirs within confined composite turbidite channels adopted a regular well pattern characterized by dense crestal wells， sparse flank wells， and peripheral water injection， whereas layered reservoirs within unconfined turbidite channels adopted an irregular well pattern with crestal producers and peripheral water injection， thereby improving the compatibility between well-pattern design and reservoir architecture. （3） A multi-parameter optimization method for injection-production dynamic balance was developed to achieve coordinated high-rate oil production and stable production while defining the optimal production-rate range for different well-pattern configurations. The proposed technical system has been successfully applied to deepwater marginal oilfields in Angola. In the PT oilfield （in confined turbidite channel facies）， a relatively regular “two-injector + two-producer” well pattern maintained stable production for three years and achieved cumulative oil production of 420 × 104 t， extending the life of the mature field by six years. In the CS oilfield （in unconfined turbidite channel facies）， an irregular “two-injector + two-producer” well pattern is predicted to achieve a recovery factor of 35.6%. These results provide a replicable technical framework and decision support for the efficient development of similar deepwater marginal reserves worldwide.关键词：turbidite channel;well pattern adaptability;minimum economic threshold of recoverable reserves;marginal reserves;development model;deep‑water oilfield;Angola2|0|0更新时间：2026-10-15
- 摘要：Deep to ultra-deep reservoirs are becoming increasingly important for hydrocarbon reserve growth and production increase. However， these reservoirs are characterized by great burial depths， complex diagenesis， and variable pore-fracture networks and in-situ stress conditions， resulting in significant inter-well productivity differences. It is therefore urgent to identify the key geological factors controlling these productivity variations. Focusing on the Cretaceous Bashijiqike and Baxigai formations in the Bozi-Dabei area of the Kuqa Depression， this study systematically analyzed the main geological controls on single-well productivity differences based on integrated core and cast thin-section observation， conventional and image logging， as well as production performance data. The analysis was built on reservoir characterization. As indicated by the research results， the reservoirs in the study area are typical deep to ultra-deep fractured clastic reservoirs featuring low porosity and low permeability. The reservoir space is dominated by primary intergranular pores， supplemented by intergranular dissolution pores， intragranular dissolution pores， and microfractures. Natural fractures are widely developed， primarily as moderate- to high-angle tectonic fractures， while microfractures include transgranular， grain-boundary， and intragranular fractures. Productivity differences are jointly controlled by sedimentary microfacies， diagenesis， present-day in-situ stress， fluid overpressure， and fracture development and effectiveness， with fracture development and effectiveness being the key controls. Fracture seepage capacity is the most important factor for high productivity. Based on these findings， a fracture effectiveness evaluation index （FRA） was constructed， which integrates fracture permeability， fracture length， the present-day horizontal differential stress， and the friction coefficient of fracture surfaces. This index serves to effectively characterize fracture conductivity and its control on productivity. Combined with the FRA-permeability and FRA- productivity relationships， we classified the fractures into Type Ⅰ （FRA > 0.43）， Type Ⅱ （0.25 ≤ FRA ≤ 0.43）， and Type Ⅲ （FRA < 0.25）， which can directly reflect productivity variations under different fracture effectiveness conditions. Deposition and diagenesis jointly determine the matrix reservoir properties. Medium- to fine-grained sandstones of subaqueous distributary channels and mouth bars are favorable facies for high-quality reservoir development. Carbonate cementation reduces the effectiveness of both pores and fractures， whereas late-stage dissolution can locally improve reservoir space and seepage capacity. Formation overpressure facilitates primary pore preservation and fracture opening by reducing effective stress and mitigating mechanical compaction. Present-day in-situ stress conditions exert a significant control on fracture opening and reservoir effectiveness， with a smaller differential horizontal stress more conducive to keeping fractures open and forming effective seepage pathways. In summary， productivity differences in deep to ultra-deep clastic reservoirs in the study area are jointly controlled by pore-fracture-pressure-stress conditions. High-quality sand bodies， constructive diagenetic modification， effective fracture development， overpressure， and a weakly compressive stress regime are the keys to the formation of high-productivity wells. The research results can provide a geological basis for selecting deep to ultra-deep natural gas exploration and development targets， and offer theoretical reference for energy development at depths exceeding 10 000 m.关键词：productivity characteristics;main geological controlling factors;fracture effectiveness;natural fracture;reservoir characteristics;deep to ultra-deep formation;Kuqa Depression;Tarim Basin4|0|0更新时间：2026-10-15
- 摘要：Shoreline trajectory analysis is an effective method for finely characterizing sequence-stratigraphic architecture and predicting the distribution of deltaic and gravity-flow sand bodies. Taking the middle and upper intervals of the Triassic Yanchang Formation in the Huanxian area， Ordos Basin， as an example， this study systematically investigated the dynamic evolution and sand-controlling mechanisms of clinothems in a Mesozoic continental depression basin by integrating high-resolution 3D seismic interpretation， well-log spectral analysis， and quantitative characterization of shoreline trajectory parameters. As indicated by the research results， （1） under the base-level control of the falling half-cycle of a second-order sequence， which was characterized by the alternation of long-term lake regression and short-term lake transgression， the clinothems in the study area were classified into three types according to seismic reflection configurations and quantitative shoreline trajectory parameters： wedge-mound type， corresponding to low-aggradation flat trajectories； lenticular type， corresponding to high-aggradation rising trajectories； and tabular type， corresponding to negative-aggradation falling trajectories. （2） Under the coupled control of basin-floor morphology， autocyclicity， sediment supply， and base-level fluctuations， the clinothems successively underwent three evolutionary stages： wedge-mound reworking on a gentle basal topography， continuous lenticular aggradation accompanied by slope instability， and tabular infilling that rapidly prograded across the slope break into the lake basin. （3） These differentiated evolutionary stages produced specific sand-enrichment patterns： the sand bodies in wedge-mound clinothem were mainly enriched in late-stage topset beds， corresponding to the delta front； the sand enrichment in lenticular clinothem occurred in two belts， namely the topset beds corresponding to the delta front and the late-stage bottomset beds corresponding to gravity flows； and the sand enrichment in tabular clinothem was dominated by large-scale lobes below the slope break in the bottomset beds. This study not only provides a theoretical supplement to the evolutionary model of clinothems in continental depression basins， but also identifies favorable zones for sand-body development in oil and gas exploration in the Ordos Basin.关键词：shoreline migration trajectory;type and evolution of clinothem;sand-body genetic model;favorable sand body;sequence stratigraphy;Triassic Yanchang Formation;Huanxian area;Ordos Basin0|0|0更新时间：2026-10-15
- 摘要：Tight sandstone reservoirs are important targets for unconventional oil and gas exploration， and brittleness evaluation is of great significance for predicting reservoir fracability and achieving efficient development. However， these reservoirs are generally characterized by thin beds， frequent interbedding， and strong lateral heterogeneity， making it difficult for conventional methods to systematically evaluate the spatial distribution of brittleness. Based on an integrated analysis of rock-physics experimental data， well-log data， and prestack seismic data， we calculated and compared the brittleness index by integrating five mineral-composition methods and three elastic-parameter methods. The initially preferred methods were then locally optimized using data specific to the study area. An optimal brittleness characterization approach for the area was selected and cross-validated， thereby achieving the systematic integration and local optimization of multiple brittleness evaluation methods. The tight sandstones of the Paleogene Enping Formation in the Kaiping Sag， Pearl River Mouth Basin， were selected as a case study. As indicated by the research results， （1） quartz and feldspar are the principal brittle minerals， followed by calcite and dolomite， and the mineral-composition-based brittleness formula derived from the Liu Zhishui method is applicable to the study area. （2） Among the elastic parameters， Poisson’s ratio exhibits greater lithologic discrimination capability than Young’s modulus， the Lamé coefficient， and shear modulus， and the locally modified Rickman formula is the optimal elastic-parameter-based brittleness characterization method. （3） Calibration using core samples shows that the brittleness indices calculated using the Liu Zhishui method and the modified Rickman formula have a correlation of 81%， confirming the consistency between the two methods. （4） A three-dimensional brittleness volume can be predicted by combining prestack elastic-parameter inversion with the elastic-parameter-based method. （5） The brittleness index in the study area ranges from 60% to 85% and generally exhibits an NE-SW-trending banded distribution. Finally， an integrated suite of brittleness-index prediction methods applicable to tight sandstone reservoirs was established， providing an important basis for the exploration evaluation and fracturing and development design of tight sandstone reservoirs in the study area.关键词：brittleness index;elastic parameters;mineral composition;tight sandstone;Enping Formation;Kaiping Sag;Pearl River Mouth Basin2|0|0更新时间：2026-10-15
- 摘要：Kerogen type is a key factor controlling the nature of hydrocarbon generation products. The Benxi Formation in the Ordos Basin contains coal seams with Type Ⅲ and Type Ⅱ₂ kerogens， representing an important target for deep coalbed methane exploration in ChinaThe chemical structure basis underlying the significant differences in hydrocarbon generation potential between these two kerogen types， however， remains poorly constrained. This knowledge gap hinders a deeper understanding of the hydrocarbon generation mechanisms and resource potential. This study systematically characterized the chemical structural differences between Type Ⅱ₂ and Type Ⅲ kerogens in low-maturity coal rocks from the No. 8 coal seam of the Benxi Formation using integrated analytical techniques， including total organic carbon （TOC） analysis， Rock-Eval pyrolysis， organic elemental analysis， organic petrology， solid-state ¹³C nuclear magnetic resonance （¹³CNMR）， Fourier transform infrared spectroscopy （FTIR）， and X-ray photoelectron spectroscopy （XPS）. The research results revealed that although both kerogen types are dominated by aromatic carbon skeletons， they differ markedly in structural composition. The Type Ⅱ₂ kerogen features a higher hydrogen-to-carbon （H/C） atomic ratio， abundant aliphatic structures， and long-chain methylene groups （-CH2-）， indicating strong potential for liquid hydrocarbon generation. In contrast， the Type Ⅲ kerogen is characterized by a high proportion of aromatic carbon， abundant aromatic clusters， oxygen-containing functional groups （C-O）， and methyl structures （-CH3）， suggesting a tendency for gaseous hydrocarbon generation. On this basis， two-dimensional visualized molecular structural models （Type Ⅱ₂： C₁₈₆H₂₁₇O₃₀N₃S； Type Ⅲ： C₁₇₈H₁₅₇O₂₉N₃S₂） were constructed， followed by the establishment of structurally reliable three-dimensional aggregated models for the kerogens， providing a structural basis for understanding the fundamental chemical structural differences between the two kerogen types.关键词：molecular model;chemical structure;kerogen;coal rock;Benxi Formation;Carboniferous;Ordos Basin3|0|0更新时间：2026-10-15
- 摘要：The Middle Permian Qixia and Maokou Formations in the Sichuan Basin represent current hotspots for marine carbonate hydrocarbon exploration and constitute critical domains for future natural gas reserve and production growth. As indicated by the research results， the Middle Permian exhibits three unique geological features： （1） it developes in a micro-weakly extensional tectonic settings， where the NW-trending Nanjiang-Tongjiang and Guangyuan-Changshou sags formed under the combined influences of the Emeishan mantle plume and the Mianlüe Ocean subduction； （2） it represents a cool-water deposition environment characterized by lime mud matrix surpportting and proliferation of heterotrophic organisms， an absence of non-skeletal grain deposits， and weak early cementation； （3） it is a sepiolite-containing succession， in which sepiolite-talc clay minerals are widely developed， significantly improving the quality of both source rocks and reservoir rocks. Based on these unique attributes， hydrocarbon exploration in the Middle Permian is confronted with three key geological issues. The first concern is the identification of main source rocks and effective hydrocarbon migration systems： under conditions of multi-source hydrocarbon supply， tracing highly mature marine hydrocarbon sources remains challenging， and the effectiveness of strike-slip fault-controlled migration systems has yet to be clarified， restricting the understanding of hydrocarbon accumulation patterns associated with long-distance migration. The second concern is the types， genesis， and distribution of high-quality reservoirs： under cool-water depositional conditions， the sources and stages of dolomitization fluids remain unclear， and the preservation mechanisms of matrix porosity in limestones and the main factors controlling pore-fracture development in unconventional reservoirs require further investigation. The third concern is gas accumulation types， characteristics， and accumulation processes： in structural-lithologic composite traps， the temporal-spatial matching relationships among reservoirs， faults， and seals are highly complicated， and significant differences exist in the dynamic accumulation processes and enrichment patterns of various gas pools. Further investigation of these issues will provide an important geological basis for advancing hydrocarbon exploration in the Middle Permian.关键词：source rock;reservoir genesis;fault conduit system;hydrocarbon accumulation process;hydrocarbon exploration;Middle Permian;Sichuan Basin4|0|0更新时间：2026-10-15
- 摘要：Fault-fractured oil reservoirs in the Fuman Oilfield， Tarim Basin， represent a new reservoir type and a key domain for increasing oil production from ultra-deep carbonate rocks in the Tarim oilfield. Insufficient understanding of the internal architecture and seepage characteristics of such reservoirs has constrained the optimization of injection-production relationships. Based on an integrated analysis of data including field outcrops， cores， drilling and well logging， seismic surveys， and production performance， this study systematically clarifies the constituent elements and structural characteristics of carbonate fault zones， and elucidates their permeability variation patterns using fault-zone permeability data. The fault-fractured oil reservoirs in the Fuman oilfield， Tarim Basin， is taken as a typical case for the study. As indicated by the research results， （1） the internal architecture of ultra-deep fault-fractured oil reservoirs in the Fuman oilfield has a “dual-element， three-level， multi-cluster” structural system. （2） The fault zones are characterized by seepage characteristics of fault-core connectivity， fault-zone conduction， and sealing by barriers and interlayers. （3） Three types of seepage connectivity modes were constructed： strongly-connected mode， in which the well penetrates the reservoir in the fault core and achieve overall connectivity； weakly-connected mode， in which the well penetrates the fault damage zone with no initial connectivity but subsequent connectivity over time； and disconnected mode， in which the well penetrates the fault-fracture zone and remains relatively isolated. Understanding the internal architecture， seepage characteristics， and connectivity modes of fault-controlled fractured reservoirs serves to provide technical support for optimizing injection-production relationships and constructing three-dimensional well patterns. This understanding plays an important role in the major development pilot test for enhanced oil recovery in the Fuman oilfield， Tarim Basin. The research findings can also provide a transferable technical model and development strategy for reservoirs with similar geological conditions， thereby supporting their efficient development and breakthroughs in production capacity.关键词：internal architecture;seepage characteristics;connectivity mode;fault-fractured reservoir;carbonate reservoir;Fuman oilfield;Tarim Basin3|0|0更新时间：2026-10-15
- 摘要：Carbonate oil and gas reservoirs constitute a core component of global hydrocarbon resources. For a long time， the exploration of deep to ultra-deep carbonate rocks at burial depth greater than 4 500 m has generally followed the “dolomite priority” paradigm. It was conventionally believed that limestones are prone to densification due to compaction and pressure solution， and high-quality porous limestone reservoirs only occur in the medium-to-shallow strata. However， recent domestic and international drilling has successively discovered multiple suites of high-quality porous limestone reservoirs in the deep to ultra-deep domains， which has broken the traditional cognition and pushed the research on deep carbonate reservoirs into a new stage of “equal attention to multiple lithologies.” By investigating the development characteristics of global deep to ultra-deep porous limestone reservoirs， this paper systematically analyzed their distribution pattern， petrological and physical properties， discussed the main factors controlling reservoir development and the pore preservation mechanisms， and forecasted their exploration targets and potential in combination with exploration practices. The research results show that high-energy reef-shoal facies sedimentation serves as the material foundation for the development of such reservoirs； key factors for effective pore preservation include early hydrocarbon charging， overpressure associated with closed systems， and gypsum-salt rock sealing； key exploration domains therein are sub-salt carbonates， proximal-to-source-rock carbonates sandwiched between top and bottom seals， and structurally reworked carbonates. These findings can provide important technical support and reference for hydrocarbon exploration， resource evaluation and theoretical research of porous limestone reservoirs in deep to ultra-deep carbonates both at home and abroad.关键词：pore preservation mechanism;porous limestone reservoir;deep to ultra-deep formation;carbonate rock3|0|0更新时间：2026-10-15
- 摘要：To elucidate the mechanism by which differences in mineral composition influence product generation pathways during in-situ upgrading of oil shale in supercritical water （SCW）， two representative oil shale samples， one from the Changqing oilfield in the Ordos Basin （sample CQ， pyrite-rich） and the other from the Longkou area in the Huangxian Basin （sample LK， calcite-rich）， were selected and subjected to high-temperature and high-pressure thermal simulation experiments under SCW conditions at 400 ℃ and 25 MPa. A combination of X-ray diffraction （XRD）， gas chromatography （GC）， Fourier transform infrared spectroscopy （FT-IR）， and gas chromatography-mass spectrometry （GC-MS） was employed to investigate the evolution behavior and compositional characteristics of gaseous， liquid， and solid products. As indicated by the research results， differences in mineral matrix significantly influence the reaction pathways of oil shale upgrading in SCW. The abundant calcite （53.0%） in the sample LK underwent extensive dissolution and decomposition under SCW conditions， releasing large amounts of CO₂ （accounting for 55.94% of the total gas yield）. This process inhibited the water-gas shift reaction， resulting in a low H2 yield （only 10.01%）. Consequently， the liquid products exhibited characteristics of high asphaltene content （42.18%） and low aromatic content （18.89%）. In contrast， the pyrite-rich sample CQ contained abundant pyrite （25.5%）， which was transformed into reactive phases， including pyrrhotite， magnetite， and elemental sulfur through in-situ redox reactions under SCW conditions. These reactive phases not only released acidic components that promoted organic matter cracking， but also enhanced methanation and hydrogenation reactions. As a result， the yields of CH₄ and H₂ increased substantially， reaching 32.52% and 18.88%， respectively. The resulting liquid product exhibited pronounced lightening characteristics， with the asphaltene content decreasing to 35.32% while the contents of aromatic fractions （23.83%） and low-carbon-number hydrocarbons （carbon number ≤ 16） increasing significantly. This study delves into the synergistic co-evolution mechanism among minerals， fluids， and organic matter， and demonstrates that the “dissolution-CO2 inhibition” effect of calcite and the “acidification-hydrogenation” effect of pyrite are the two key factors controlling the upgrading pathways of oil shale in SCW. These findings provide important theoretical support for developing differentiated in-situ recovery strategies for oil shales with different mineralogical compositions.关键词：light hydrocarbon enhancement;oil composition;gas differentiation;mineral-fluid interaction;supercritical water upgrading;oil shale2|0|0更新时间：2026-10-15
- 摘要：Sedimentological interpretation of stratigraphic slices of seismic clinothems has long been a research focus in integrated geology-geophysics study. Focusing on the middle Yanchang Formation in the Huanxian area， Ordos Basin， this study systematically investigated representative clinothems using sequence-stratigraphic and seismic-sedimentological methods， while integrating newly acquired three-dimensional （3D） seismic data， well logs， and extensive core data. Integrated prediction error filter analysis （INPEFA） curves and maximum entropy spectral analysis （MESA） were used to establish a high-resolution chronostratigraphic framework （SQ1-SQ3）， revealing base-level changes characterized by alternating slow lacustrine regression and rapid lacustrine transgression. Key techniques， including 90°-phase shift， stratigraphic slicing， and seismic waveform indication inversion， were applied to finely depict the spatiotemporal evolution of three major depositional systems： braided-river delta， shore-shallow-lacustrine， and deep-water gravity-flow systems. As indicated by the research results， during the early stage （SQ1）， lake level fell slowly， forming flat-bottomed， convex-topped clinothems. Accommodation exceeded sediment supply （A/S > 1）， and sand-body distribution was controlled by sediment supply （S）， with sand bodies thicker in the west and thinner in the east. During the middle stage （SQ2）， lake level fell rapidly， and lenticular clinothems and a complete gravity-flow succession developed. Sediment supply remained dominant， resulting in a pattern of sand enrichment at both ends and mud enrichment in the middle. During the late stage （SQ3）， the lacustrine basin contracted， forming flat-topped， convex-bottomed clinothems. Accommodation was insufficient relative to sediment supply （A/S < 1）， and accommodation （A） became the main controlling factor， reversing the sand-body distribution pattern， with thicker sand bodies in the east and thinner ones in the west. This evolutionary model not only provides a new depositional model for the Yanchang Formation in the Ordos Basin but also provides a methodological reference for investigating the genetic mechanisms of clinothems and predicting lithologic traps in similar lacustrine basins.关键词：progradational reflection;lithofacies analysis;seismic waveform indication inversion;seismic sedimentology;Triassic Yanchang Formation;Huanxian area;Ordos Basin3|0|0更新时间：2026-10-15
- 摘要：The Ledong 8-1 diapir in the Yinggehai Basin is a multi-phase collapsed diapir controlled by strike-slip faulting， which is closely related to hydrocarbon accumulation. Newly acquired ocean bottom node （OBN） seismic data in the Ledong 8-1 diapir zone have resolved long-standing imaging challenges in the diapir core， where previous datasets often yielded poor or no resolution. Based on the interpretation results of the OBN seismic data， the fault deformation characteristics and activity in the Ledong 8-1 diapir zone were systematically analyzed， and the fault formation mechanism was discussed in combination with regional tectonic stress regimes and the causes of diapir collapse. As indicated by the research results， （1） seven types of faults are identified in the Ledong 8-1 diapir zone， exhibiting a distinctive pattern of “plan-view classification， vertical stratification， and multi-phase evolution.” Sub-vertical ridge-like strike-slip faults are developed in the deep section of the diapir zone， whereas master strike-slip faults and their derived R-shears， R'-shears， P-shears， and T-shears， as well as ring faults formed under collapse effects， are developed in the shallow section. （2） Intense fault activity primarily occurred during three major phases： the late Middle Miocene to early Late Miocene （early stage）， the middle Pleistocene to early Holocene （middle stage）， and the late Holocene （late stage）. Kinematic indicators show that the early-stage faults are sinistral strike-slip， while the middle- and late-stage faults are dextral strike-slip. （3） Faults in the Ledong 8-1 diapir zone are controlled by the regional stress field generated by the activity of the No. 1 Fault at the basin margin. During the early phase， the diapir zone was controlled by the sinistral strike-slip of the No. 1 Fault， developing NNE-trending sinistral strike-slip faults and forming structural ridges， whereas at the middle and late stages， the continuous dextral strike-slip of the No. 1 Fault led to the development of extensional fracturing and deep-seated fault reactivation.关键词：collapsed type;formation mechanism;strike-slip fault;Ledong 8-1 diapir;Yinggehai Basin29|37|0更新时间：2026-08-13
- 摘要：The conventional “Golden Zone” theory restricts the stable preservation of liquid hydrocarbons to shallow-to-moderate burial depths and a limited temperature range. However， major discoveries of ultra-deep ancient carbonate oil reservoirs in recent years have challenged this classical understanding. The preservation mechanisms over ultralong timescales have become a critical scientific issue constraining the evaluation of deep petroleum exploration potential. The intrinsic controls on the ultralong-term preservation of ancient oil reservoirs in the northern Tarim Basin were revealed by systematically analyzing their petroleum geological characteristics， hydrocarbon accumulation stages， and post-accumulation alteration mechanisms. As indicated by the research results， （1） the favorable configuration of static geological elements provides the material foundation for preservation. High-quality source rocks of the Lower Cambrian Yuertusi Formation supplied a sustained oil charge； multi-stage karstification coupled with faulting created large-scale fracture-cavity reservoirs； and extremely thick Upper Ordovician mudstones formed a multi-level regional sealing system with high breakthrough pressure. The perfect spatiotemporal matching of these three elements laid the inherent foundation for the formation of giant oil reservoirs. （2） The coupling of a “cold basin” thermal regime with “late-stage rapid deep burial” is the dynamic key to preservation. The basin in this area has maintained a low geothermal gradient over a long geological period and is characterized by a burial history of sustained shallow burial in the early stage followed by rapid deep burial in the late stage. Although the reservoirs were ultimately buried to a depth of more than 7 000 m after the main accumulation period at approximately 250 Ma， they were exposed to high-temperature conditions （>160 ℃） for an extremely short duration （< 5 Ma）， resulting in a markedly insufficient time-temperature compensation effect and fundamentally suppressing the thermal cracking of crude oil. In addition， the coupled effect of high-pressure and overpressure conditions further reduced the risk of crude oil cracking. （3） Weak post-accumulation secondary alteration is the key guarantee for maintaining the liquid hydrocarbon phase state and geochemical stability of the reservoirs. The reservoirs experienced only weak late-stage alteration， including thermochemical sulfate reduction （TSR）， biodegradation， and gas washing. As a result， the geochemical properties of the crude oil remained stable， showing the typical characteristics of “early accumulation and late-stage deep-burial preservation.” In summary， this study establishes a preservation model for ultra-deep ancient oil reservoirs over ultralong timescales and reveals the core mechanism of time-temperature-pressure coupled inhibition. These findings break through the limitations of the traditional “Golden Zone” theory and provide new theoretical guidance for evaluating the exploration potential of ultra-deep liquid hydrocarbons in ancient cratonic basins and selecting favorable zones.关键词：time-temperature compensation effect;reservoir preservation mechanism;ancient carbonate oil reservoir;ultra-deep reservoir;Tarim Basin35|40|0更新时间：2026-07-29
- 摘要：The Ordovician sub-salt mound-shoal dolomite reservoirs in the central-eastern Ordos Basin are important targets for natural gas exploration. However， systematic research on such reservoirs is limited， and unclear understanding of their development characteristics and distribution patterns have constrained exploration progress. To address these issues， a systematic investigation was conducted based on integrated core， thin-section， well log， petrophysical， and geochemical data. As indicated by the research results， （1） the reservoir lithology is mainly of the algal-laminated dolomite， intraclastic grainstone （very fine-crystalline） dolomite， oolitic dolomite， and recrystallized granular dolomite types. The reservoir spaces include dissolution vugs， intercrystalline （dissolution） pores， intergranular （dissolution） pores， intragranular dissolution pores， and microfractures， with an average porosity of 5.79%. （2） The development of mound-shoal dolomite reservoirs is jointly controlled by sedimentary microfacies， dissolution， and bioturbation. Microbial mounds and grain-shoal deposits serve as the material basis for reservoir development. Dissolution acts as the key process responsible for the formation of dissolution vugs， and burrows formed by bioturbation further improve their physical properties. （3） The reservoir distribution exhibits distinct stratigraphic and geographic controls. Vertically， the reservoirs are layered within the middle-to-upper part of high-frequency shallowing-upward cycles in transgressive hemicycles of third-order sequences， exhibiting a layered distribution. Laterally， they are predominantly distributed in paleohigh crests， paleohigh flanks， and on depression margins. The conclusion is that the Shenmu-Wuqi area is characterized by relatively high paleotopography and strong hydrodynamic conditions during deposition of the 2nd and 4th member， as well as the 9th and 7th sub-members of the 5th member of the Ordovician Majiagou Formation. Microbial mounds and grain shoals are distributed in belts and prone to penecontemporaneous dissolution， providing favorable geological conditions for the large-scale development of multi-layer mound-shoal dolomite reservoirs. Therefore， this area represents a favorable zone for reservoir development.关键词：dissolution;bioturbation;sedimentary microfacies;mound-shoal dolomite reservoir;Ordovician;Ordos Basin40|50|0更新时间：2026-07-17
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