The Middle Eocene Epoch was a pivotal period marked by pronounced climatic instability during the transition from a greenhouse to icehouse climate. The Jiyang Depression, located in the Bohai Bay Basin of East Asia, experienced the deposition of marginal-marine black shales under episodic marine influence, preserving a continuous and highly detailed record of past environmental changes. This study analyzes approximately 400 m of core samples from the Shahejie Formation in the Jiyang Depression to investigate carbon and nitrogen cycling processes and assess the environmental impacts of both volcanic activity and the Middle Eocene Climatic Optimum (MECO) during the deposition of Eocene marginal-marine shales formed under episodic marine influence. Geochemical analyses reveal nitrogen isotope anomalies in the middle part of the lower third member of the Shahejie Formation (Es3l), coinciding with the MECO and accompanied by significant fluctuations in nitrogen cycling during this transitional period, indicating climatic instability. A second episode of nitrogen disruption is observed in the lower part of the upper fourth member of the Shahejie Formation (Es4u), where fluctuations in nitrogen isotopes likely reflect the combined effects of episodic marine incursions and localized volcanic activity. The identification of two distinct nitrogen isotope anomalies provides new insights into the mechanisms controlling organic carbon enrichment in black shales.

Abstract Widespread organic‐rich shales are associated with perturbations in productivity or preservation conditions; however, the major controlling factors, especially the phosphorus (P) and iron (Fe) interactions and their impacts on organic carbon burial in the paleolake ecosystem remain poorly understood. Here, we report iron and phosphorus speciation data from the Chang 7 Member of Ordos Basin to elucidate iron–phosphorus–carbon cycling (Fe–P–C) in the freshwater lacustrine system during the Middle Triassic. Our results show that the redox conditions and phosphorus cycling exhibit strong spatiotemporal heterogeneity. During Interval I (0–140 kyr), oxic–ferruginous conditions were dominant in the water column, and abundant Fe (oxyhydr)oxides promoted sedimentary P retention and sustained oligotrophic conditions. During Interval II (140–405 kyr), the widespread development of euxinic water bodies expanded from the basin floor to the slope belt of the lake basin, leading to extensive P recycling back to the photic zone, thereby increasing primary productivity and organic matter production. This transition is probably attributed to enhanced volcanic activity and a significant shift in redox conditions, which play an important role in regulating the concentration of bioavailable P in the water column. This study sheds new light on Fe–P–C cycling in an ancient freshwater lake under volcanic perturbations, providing guidance on the link between biogeochemical feedback and carbon burial.

Accurate prediction of wellbore heat transfer is crucial for improving thermal recovery efficiency via superheated steam injection in coalbed methane (CBM) reservoirs. Conventional models treat annular convective (hc) and radiative (hr) heat-transfer coefficients as constants, neglecting their dynamic nature and potentially misrepresenting the dominant heat-transfer mechanism along the wellbore. To overcome this limitation, this study establishes a dynamically coupled model that links hc and hr with local wellbore conditions, solved using a finitedifference method with an iterative algorithm. Model validation against field data yields maximum relative deviations of 1.08% for temperature and 0.68% for pressure, demonstrating high accuracy. Quantitative analysis reveals three novel findings. First, hc increases by 219% (3.7 -> 11.8 W/(m2 & sdot;K)) with depth, whereas hr decreases exponentially by 71% (36.0 -> 10.3 W/(m2 & sdot;K)). Second, these opposing trends lead to a critical transition depth of approximately 430 m, where the dominant annular heat-transfer mechanism shifts from radiation-dominated to convection-dominated-a phenomenon not previously reported. Third, injection parameters dynamically regulate this transition: raising injection pressure (2.5 -> 4.5 MPa) shifts the transition depth downward (330 -> 430 m), while increasing injection rate (100 -> 300 t/d) shifts it upward (490 -> 350 m). Annular gas properties also play distinct roles: thermal conductivity governs convection, whereas wall temperature controls radiation. These findings revise the conventional view of annular heat transfer as a static process and provide a robust framework for wellbore thermal management in CBM recovery, with broad applicability to heavy-oil, geothermal, and oil-shale thermal extraction.

The rapid lateral facies variations, complex reservoir characteristics, and strong heterogeneity of the continental shale sequences have led to an inadequate understanding of the main controlling factors on shale oil enrichment and high productivity, making “sweet spot” identification challenging and hindering cost-effective exploitation. Current evaluations of shale oil enrichment and high productivity largely rely on region-specific empirical parameters, lacking universally applicable evaluation methods and quantitative models, which impedes consistent comparative evaluation across different regions and shale oil types. Guided by the concept that shale oil enrichment and productivity are jointly governed by the coupling of “medium-hydrocarbon-energy”, this study proposed a quantitative evaluation methodology for “sweet spot” identification in continental shale oil across different regions and types. Here, “medium” refers to the properties of the storage medium, which serves as the carrier for shale oil accumulation and controls reservoir capacity, permeability, and fracturability. “Hydrocarbon” refers to hydrocarbon fluids, which collectively reflect the type of organic matter and its maturity, largely determining the flowability of shale oil. “Energy” denotes formation energy, which is the potential energy contained in fluids within the shale formation, and it plays an important role in the accumulation and production of shale oil. The spatiotemporal coupling of these three elements jointly controls the degree of shale oil enrichment and recoverability. A shale oil “sweet spot” evaluation parameter system including porosity, brittle mineral content, free hydrocarbon content, and pressure coefficient was initially established. Furthermore, an integrated evaluation model based on the “medium index-hydrocarbon index-energy index” coupling was developed, forming a technical workflow from parameter acquisition and index calculation to “sweet spot” delineation. The method was validated using the shale of the Shahejie Formation in the Bonan Sag of the Bohai Bay Basin as an example. This demonstrated that it could effectively identify “sweet spots”, thereby providing methodological guidance for shale oil exploration and development deployment.

The Dina-2 gas reservoir is a large edge-water tight sandstone gas reservoir in the Tarim Basin, with strong reservoir heterogeneity. Natural fractures are key factors influencing its high production and water invasion. Investigating fractures is crucial for understanding the water invasion patterns and formulating water control strategies for the gas reservoir. Based on geological data including core samples, thin sections, and imaging logs, this study analyzed the static geological characteristics of natural fractures. By combining production dynamic characteristics including water production, gas production, and pressure, this study analyzed the influence of different factors on water invasion. The analytic hierarchy process was used to identify the controlling factors, and the influence of structural fractures with different morphologies on water invasion characteristics was studied, and water invasion patterns for the gas reservoir were established. The results showed that structural fractures in the study area were classified into shear fractures and tensile fractures, with filled fractures being dominant. The fillings were mainly calcite, followed by quartz and clay minerals, but the fracture apertures were relatively large. Based on production dynamic characteristics, the production wells were categorized into four types: early-stage violent water-flooded wells, late-stage violent water-flooded wells, water-producing wells, and water-free wells, each with significantly different production characteristics. Based on the production and geological characteristics, the main controlling factors for water invasion in the gas reservoir were analyzed considering five factors: structural position, faults, interlayers, formation coefficient, and fractures. Fractures were identified as the primary controlling factor, with faults, interlayers, and formation coefficient as secondary factors, and structural position as irrelevant. A comprehensive water invasion evaluation index was established using the analytic hierarchy process. By considering fracture morphology differences and production characteristics, this study clarified the influence of complex fractures on high gas production and water production in gas wells. Accordingly, three water invasion patterns were established: dominant fracture-controlled type, fault-fracture compartment-controlled type, and dominant fracture-fault-sandbody composite type, summarizing the water invasion patterns of the gas reservoir. These findings provide strategic guidance for the development of similar gas reservoirs and offer valuable insights for studying water invasion patterns and development evaluation in similar water-bearing gas reservoirs.

Evaluating wettability in hydrocarbon-bearing shales poses significant challenges due to their fine-grained structure, heterogeneous mineralogy, and intricate pore-fracture networks. This paper reviews the wettability testing methods, influencing factors, and wettability characteristics of hydrocarbon-bearing shales from different sedimentary facies. The main results include: (1) Although analytical methods such as contact angle, spontaneous imbibition, nuclear magnetic resonance, calorimetry, electron microscope, etc. have been employed, a universally accepted standard remains elusive. The oft-cited neutral wettability, indicating both hydrophilic and hydrophobic characteristics, is highly variable and influenced by the intrinsic shale properties and experimental uncertainties. (2) Shale wettability is governed by the matrix composition, surface functional groups, and microstructural features, as well as by the physical and thermodynamic properties of interacting fluids, including formation water and hydrocarbons. Geological factors, such as tectonic burial, diagenetic evolution, thermal maturation, and hydrocarbon generation, further complicate wettability characteristics. Shales from different sedimentary facies display marked differences: marine shales are predominantly affected by organic pore development and mineral composition; transitional shales by inorganic pore-fractures and organic matter type; and lacustrine shales by inorganic pore-fracture systems and mineralogy characteristics. (3) The complex fluid–solid interactions within multi-scale pore networks dictate heterogeneous wettability, which in turn influences hydrocarbon distribution, retention, and migration. Future studies should focus on in-situ wettability characterization under reservoir conditions (T&P conditions, fluid property, etc.), dynamic wettability near wellbores, and the effects of external fluid intrusion to enhance predictive models and optimize hydrocarbon extraction strategies.

Although the productivity of modern volcanic soils is well established, the fertilization effects of ancient volcanic ash on aqueous ecosystems remains contentious. Here we demonstrate volcanic fertilization effects on a Late Triassic lacustrine ecosystem based on micropaleontological and geochemical records from the Yanchang Formation of North China. Frequent eruptions of a regional volcanic arc system increased cyanobacterial populations and organic carbon sinking fluxes, as recorded by extreme total organic carbon content (>30 wt.%) and positive organic carbon and negative nitrogen isotopic excursions. In turn, high levels of primary productivity induced intense water-column anoxia, facilitating preservation of organic matter. These findings underscore the potential influences of volcanism on ecological conditions, primary productivity, and carbon sequestration throughout geological history.

Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1; their increased presence contributes to a more favorable pore throat structure. Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.

Fine-grained sedimentary rocks are ideal carriers for astronomical cycle analysis as they can record and preserve significant astronomical cycle signals. Spectral analysis using the Multi-taper Method (MTM) and Evolutionary Harmonic Analysis (EHA) using the Fast Fourier Transform (FFT) were conducted on natural gamma data from key wells in the Es3l sub-member in the Bonan Sag, Bohai Bay Basin, China. Gaussian bandpass filtering was applied using a short eccentricity cycle of 100 ka, and a “floating” astronomical time scale for the Es3l sub-member (Lower 3rd sub-member of Shahejie Formation in Eocene) was established using magnetic stratigraphic ages as boundaries. Stratigraphic divisions were made for single wells in the Es3l of the Bonan Sag, and a stratigraphic framework was established based on correlations between key wells. The research results indicate the following: Firstly, the Es3l of the Bonan Sag records significant astronomical cycle signals, with an optimal sedimentation rate of 8.39 cm/ka identified. Secondly, the cyclical thicknesses corresponding to long eccentricity, short eccentricity, obliquity, and precession cycles are 38.9 m, 9.7 m, 4.6–3.4 m, and 1.96–1.66 m, respectively. Thirdly, the Es3l sub-member stably records 6 long eccentricity cycles and 26 short eccentricity cycles, and the short eccentricity curve is used as a basis for stratigraphic division for high-precision stratigraphic correlations. Fourthly, the quality of sandstone-interbedded mudrock is jointly controlled by the short eccentricity and precession. Eccentricity maximum values result in thicker sandstone interlayers, while minimum precession values promote the thickness of sandstone interlayers. Through astronomical cycle analysis, the depositional evolution mechanism of sandstone-interbedded mudrock is revealed. Combined with the results of high-precision stratigraphic division, this can provide a basis for fine evaluation and “sweet spot” prediction of lacustrine shale oil reservoirs.

To clarify the evolution law of sandstone pore structure under water pressure and reveal its dynamic change mechanism,an experimental study was conducted using nuclear magnetic resonance(NMR)technology.First,sandstone specimens with a size of 50 mm×25 mm were prepared and grouped;after pretreatment such as cleaning and drying,different water saturation pressures(5,10,20 MPa)and water saturation times(2,4,6,8,48 h)were set.Then,the NMR system was used to test parameters such as T2 spectrum,porosity,and water content of sandstone under different condi-tions,and the variation characteristics of pore structure were analyzed.Finally,the variation law of T2 spectrum was discussed from the perspective of physical mechanism,and its engineering application di-rections were sorted out.The results show that the amplitude of NMR T2 spectrum signals varies under different water pressures;as the water saturation pressure increases,the T2 spectrum curve shifts to the right with a decreasing shift amplitude,and the T2 spectrum area is positively correlated with porosity and water saturation pressure but with a decreasing growth rate;the water content and pore volume of sandstone increase rapidly within t=0～4 h,and the pore structure tends to be stable after t≥6 h;un-der the same water saturation time,the increase in water pressure causes damage inside the rock,and after the pressure reaches 10 MPa,the pore structure becomes stable and the rock is completely dam-aged;the higher the water content of sandstone,the better the pore connectivity and the lower the strength.

Quartz is one of the most common minerals in the Earth's crust, and its deposition and cycling are ubiquitous and crucial in energy and environmental sciences. Due to the existence of multiple types of quartz and diverse mechanisms that result in their formation, this variation is expected to significantly impact shale deposition, diagenesis, and reservoir properties. Moreover, it plays a crucial role in the enrichment, development, and production of shale oil and gas plays. Considering their importance, this study systematically summarizes observation and various research methods, such as optical and scanning electron microscopy (SEM), cathodoluminescence (CL), energy dispersive spectrometry (EDS), X-ray fluorescence (XRF), quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), fluid inclusion, which supports our understanding of the mineral diagenesis and generation of both detrital and authigenic origins. Parent rock type, transport distance, and depositional environment are known factors that control the grain size, sorting, roundness and types of detrital quartz. The authigenic quartz contains biogenic, hydrothermal origins and clay mineral transformation while fluid source, diagenetic mechanisms, and growth space control the formation time and crystal size of them. In addition, quartz controls the total organic carbon content, reservoir quality, fracturing ability, organic matter preservation and reservoir enrichment, etc. Notably, the microquartz cement derived from biosiliceous allochems (namely biogenic quartz) has a noticeable positive correlation with total organic carbon content and is formed during the early diagenetic stages which together with the detrital quartz form a rigid framework favorable to primary pores, ultimately forming high-quality marine shale reservoirs. Furthermore, the diagenesis of biogenic quartz also enhances the mechanical properties and fracturing potential of shale reservoirs. The biogenic quartz content and the thickness of shale intervals determine the potential and development of marine shale oil/gas reservoirs. However, in transitional and lacustrine shales, quartz is predominantly detrital in origin and negatively correlated with organic carbon content. In these two types of shales, detrital quartz and quartz formed during the transformation of clay minerals are known to play a positive role in the formation of shale reservoirs and hydrocarbon enrichment. Considering all of these factors, this study investigates different types and contents of quartz in typical shale oil and gas reservoirs worldwide and explains how they have influenced shale oil and gas enrichment and reservoir productivity.

The Devonian Liuling Group(DLLG) and its surrounding strata provide massive information about the Paleozoic subduction—suture—extension process of the North China Block(NCB) and South China Block(SCB). Systematic field-based sedimentology, sandstone modal composition, whole-rock elemental composition, and detrital zircon U—Pb dating were employed. The sedimentary sequence of DLLG shows that the water depth deepened and then shallowed, which is characteristic of an extensional basin. Analysis of the tectonic setting and geochronology revealed that the fore-arc sedimentary system(FAS) and DLLG were sourced from the North Qinling Belt(NQB) and NCB. An age population with a single peak at 420 Ma from the FAS suggests that the island arc existed at 420 Ma, indicating that the subduction of the Shangdan Ocean did not finish until the late Silurian. The DLLG deposits were mainly from basement material of the NQB, indicating that the Shangdan Ocean closed before the Middle Devonian, which implies that the NQB and South Qinling Belt(SQB)were spliced during the Early Devonian. This rapid transition from subduction to extension and the absence of molasse hint that no full orogeny occurred during the suture process and that the DLLG formed in a post-suture extensional rift basin.

With the increasing global demand for energy, the development of unconventional resources has become a focal point of research. Among these, shale gas has drawn considerable attention due to its abundant reserves. However, its low permeability and complex fracture networks present substantial challenges. This study investigates the composite fracturing technology combining supercritical CO2 and slickwater for shale gas extraction, elucidating the mechanisms by which it influences shale fracture roughness and conductivity through an integrated approach of theory, experiments, and numerical modeling. Experimental results demonstrate that the surface roughness of shale fractures increases markedly after supercritical CO2–slickwater treatment. Moreover, the dynamic evolution of permeability and porosity is governed by roughness strain, adsorption expansion, and corrosion compression strain. Based on fluid–solid coupling theory, a mathematical model was developed and validated via numerical simulations. Sensitivity analysis reveals that fracture density and permeability have a pronounced impact on shale gas field productivity, whereas fracture dip angle exerts a comparatively minor effect. The findings provide a theoretical basis for optimizing composite fracturing technology, thereby enhancing shale gas extraction efficiency and promoting effective resource utilization.

Lacustrine rift basins in China are characterized by pronounced structural segmentation, strong sedimentary heterogeneity, extensive fault-fracture development, and significant variability in thermal maturity and mobility of shale oil. This study reviews the current status of exploration and development of shale oil in such basins and examines theoretical frameworks such as "binary enrichment" and source-reservoir configuration, with a focus on five key subjects: (1) sedimentation-diagenesis coupling mechanisms of fine-grained shale reservoir formation; (2) dynamic diagenetic evolution and hydrocarbon occurrence mechanisms of organic-rich shale; (3) dominant controls and evaluation methods for shale oil enrichment; (4) fracturing mechanisms of organic-rich shale and simulation of artificial fracture networks; and (5) flow mechanisms and effective development strategies for shale oil. Integrated analysis suggests that two major scientific challenges must be addressed: the coupled evolution of fine-grained sedimentation, differential diagenesis, and hydrocarbon generation under tectonic influence and its control on shale oil occurrence and enrichment; and multi-scale, multiphase flow mechanisms and three-dimensional development strategies for lacustrine shale oil in complex fault blocks. In response to current exploration and development bottlenecks, future research will be conducted primarily to: (1) deeply understand organic-inorganic interactions and reservoir formation mechanisms in organic-rich shales, and clarify the influence of high-frequency sequence evolution and diagenetic fluids on reservoir space; (2) elucidate the dynamic processes of hydrocarbon generation, expulsion, and retention across different lithofacies, and quantify their relationship with thermal maturity, including the conditions for the formation of self-sealing systems; (3) develop a geologically adaptive, data- and intelligence-driven shale oil classification and grading evaluation system of shale oil; (4) reveal artificial fracture propagation pattern and optimize physical field coupled fracturing technologies for complex lithofacies assemblages; and (5) overcome challenges in multi-scale geological modeling and multiphase flow characterization, and establish advanced numerical simulation methodologies.

Shale oil exploration and development have made significant breakthroughs in Paleozoic marine shales and Mesozoic-Cenozoic lacustrine shales. However, the shale oil potential of older Precambrian sediments remains poorly constrained. Our two newly drilled boreholes reveal shale oil shows in the Mesoproterozoic Hongshuizhuang and Xiamaling shales in the Yanshan Basin, China. In order to further evaluate the shale oil potential, multiple experimental methods were employed, including TOC and thermal maturity analyses, routine and step-by-step Rock-Eval pyrolyses, X-ray diffraction, field emission scanning electron microscopy, low-temperature nitrogen adsorption, and hydrocarbon vapor adsorption. The results show that Hongshuizhuang shale, which is characterized by type II kerogen and low-medium maturity of R-0 = 0.65-0.92%, is a set of good source rocks, while the source rock quality of Xiamaling shale is highly variable. Moreover, the hydrocarbon generation potential of prokaryote-dominated Mesoproterozoic source rocks is comparable to that of eukaryote-dominated Phanerozoic source rocks, implying a favorable factor for shale oil accumulation in Precambrian formations. The main storage space for shale oil in both formations is provided by inorganic pores, in which the adsorbed oil is predominantly retained in micropores to fine mesopores (<15 nm) and free oil mainly stored in mesopores to macropores. Adsorbed oil exists as a multilayer oil film, with its average thickness increasing as a Langmuir adsorption curve with pore size. The evaporative hydrocarbon content of the Hongshuizhuang Formation ranges from 2.53 to 12.53 mg/g and is dominated by adsorbed hydrocarbons (mean 6.01 +/- 2.10 mg/g), while the evaporative hydrocarbon content of Xiamaling Formation is much lower, with an average value of 2.4 +/- 2.4 mg/g. TOC content, mineral composition, thermal maturity, pore volume and surface area are important factors affecting the degree of shale oil enrichment. The compilation and comparison show that the Hongshuizhuang Formation is a promising target for the oldest shale oil exploration. Furthermore, the results suggest that the combination of step-by-step pyrolysis and hydrocarbon vapor adsorption is a practical method for estimating both free and adsorbed hydrocarbon contents and revealing their storage space within shale nanopores.

The Late Triassic Carnian Pluvial Episode (CPE) witnessed enormous climate change closely associated with volcanic activity. However, the coupling relationship between volcanic activity and climate change, which may be linked to chemical weathering, has not yet been fully uncovered. We used lithium contents and isotopes of volcanic ash (VA)–bearing lacustrine shale to constrain their deposition pathways and response to climate changes, i.e., weathering intensity, during the Late Triassic era. Elevated δ 7 Li (i.e., >2.5‰) and low Li contents (i.e., <65 microgram per gram) in shale likely document the direct depositing of volcanic lithium from airborne VA, which mainly inherited Earth’s interior δ 7 Li signal. By contrast, shale yields markedly high lithium contents (i.e., >135 microgram per gram), alongside relatively low δ 7 Li (i.e., <0‰), likely implying waterborne VA dominated by intensified weathering under a super humidity climate. Hence, this study provides evidence for the differential VA-rich shale deposition model related to chemical weathering states synchronous with climate changes during the CPE period.

Taking a tight sandstone gas reservoir in Sulige area as an example, Arps analysis met hod is used to calculate production decline, and three production decline modes of exponential, hyperbolic and harmonic are explained in detail. The study shows that the decline law of different types of gas we

In light of significant advancements in shale oil exploration within China's principal oil and gas bearing basins, small to medium-sized basins such as the Subei Basin have also demonstrated considerable potential. However, the complex geological conditions within the Subei Basin present substantial challenges for the identification of favorable strata, thereby hindering large-scale shale oil development. This study utilizes practical exploration data from wells H1 and H3 within the Gaoyou Sag of the Subei Basin, integrating core observations with a suite of sophisticated analytical techniques, including X-ray diffraction, organic geochemistry analysis, argon ion polishing-scanning electron microscopy, nitrogen adsorption-mercury injection capillary pressure, and laser confocal analysis. The primary objective is to elucidate the geological characteristics and controlling factors influencing shale oil enrichment in the second member of the Funing Formation (E1f2) shale. The E1f2 member shale in the Gaoyou Sag exhibits an average total organic carbon content of 1.24% and a mean hydrocarbon generation potential of 5.38 mg/g, with a strong positive correlation observed between these parameters. The mineral composition is markedly heterogeneous, predominantly comprising mixed shale, followed by felsic shale and calcareous/dolomitic shale. The identified pore types include intergranular pores in clay minerals, carbonate intragranular dissolution pores, and a minor proportion of organic matter pores. The shale demonstrates significant vertical variability in oil enrichment, characterized by three source-reservoir couplings: "self-generating and self-reserving", "mud generating and felsic reserving", and "mud generating and carbonate reserving". Formations enriched in carbonates and felsic materials exhibit superior reservoir properties, identified as "sweet spots" due to their enhanced hydrocarbon saturation and mobility. Despite the segmentation resulting from tectonic activities, the impact on preservation conditions remains limited, primarily influencing areas adjacent to sag-controlling faults. Effective preservation conditions are critical for shale oil accumulation and retention. Consequently, the deep sag regions of major depressions in the Subei Basin emerge as prime targets for shale oil exploration, which is pivotal for the efficient development of the E1f2 member shale. This study provides valuable insights into the exploration and development of shale oil within lacustrine faulted basins.