The heterogeneity of shale pore systems, which is controlled by thermal maturation, fundamentally governs hydrocarbon storage and migration. Artificial sequence maturity samples of Xiamaling shale were obtained through a temperature–pressure simulation experiment (350–680 °C, 15–41 MPa). In combination with low-pressure CO₂/N₂ adsorption experiments, mercury intrusion porosimetry experiments and fractal theory, the heterogeneity of the pore size distribution of micropores, mesopores and macropores in shale of different maturities was quantitatively characterized. The results reveal that the total porosity follows a four-stage evolution with thermal maturity (R_o = 0.62–3.62%), peaking at 600 °C (R_o = 3.12%). Multifractal parameters indicate that areas with a low probability density are dominant in terms of pore size heterogeneity, while monofractal parameters reflect enhanced uniform development in ultra-over maturity (R_o > 3.2%). A novel Fractal Quality Index (FQI) was proposed to integrate porosity, heterogeneity, and connectivity, effectively classifying reservoirs into low-quality, medium-quality, and high-quality sweet-spot types. The findings contribute to the mechanistic understanding of pore evolution and offer a fractal-based framework for shale gas reservoir evaluation, with significant implications for hydrocarbon exploration in unconventional resources.

The research on deepwater oil and gas exploration areas is relatively limited, and sample collection is difficult. A drilled coal sample from Yanan Depression was used to investigate the hydrocarbon generation process, and the potential, by a gold tube thermal simulation experiment. The results show that the total gas yield was much higher than the oil yield. According to an analysis of the gas pyrolysis data, as represented by ln(C₁/C₂) and ln(C₂/C₃), the gas generation process consisted of two forms, namely, primary gas with ~1.33% Ro and secondary gas that occurred at levels greater than 1.33% Ro. The primary gas from kerogen was generated at ~1.33% Ro, which coincided with the %Ro value of the maximum oil yield. The activation energy distribution of the C₁–C₅ generation processes ranged from 54 to 72 kcal/mol, with a frequency factor of 6.686 × 10¹⁴ s⁻¹ for the coal sample. We constructed the history of gas generation on the basis of the process and kinetic parameters, combined with data on the sedimentary burial and thermal history. The extrapolation of the gas history revealed that the gas has been generated from 5 Ma to the present, with a maximum yield of 178.5 mg/gTOC. This history suggests that the coal has good primary gas generation potential and provides favorable gas source conditions for the formation of gas fields. This study provides a favorable basis for expanding the effective source rock areas.

Frequent coal mine gas disasters pose significant threats to the safety of miners and the continuity of coal mining operations. Understanding and mastering the patterns of gas occurrence is the foundation for controlling gas outbursts. This study, drawing on previous theories, research, and practical coal mine production data, analyzes the structural characteristics of the Kaiping syncline, with particular emphasis on the structural differentiation at its northeastern uplifted end. The study examines how gas generation and storage are influenced by progressively layered structures and their effect on coal mine gas management. The results indicate that the Kaiping syncline has a NE-SW axial orientation, which gradually shifts to an asymmetric syncline with a nearly EW trend, rising towards the northeastern end. At the turning end, the strata on the northwest limb are steep—locally vertical or overturned—gradually transitioning into the gentler southeast limb with dips of 10° to 30°, further complicated by a series of sub-parallel secondary folds. The gas formation process in coal seams has undergone multiple stages, regulated by structural burial and thermal evolution. The current gas storage characteristics result from the combined effects of these structural factors. The Kaiping syncline can be divided into two gas zones: a high-gas zone in the northwest limb and a shallow low-gas zone paired with a deep high-gas zone in the southeast limb. At the turning end, structural differentiation results in significant variations and gradations in the gas storage conditions of the coal seam. This differentiation directly causes a transition from coal and gas outburst mines in the northwest limb to low-gas mines in the southeast limb, highlighting the significant influence of structural factors on gas generation, preservation, and mine gas emissions. This study integrates theoretical analysis with measured data to enhance the understanding of structural evolution and its influence on gas storage. It offers guidance for preventing coal seam gas disasters and ensuring the safe production of coal mines in the Kaiping coalfield.

The dynamic changes in shale pore structure due to tectonic uplift are crucial for understanding the processes of shale gas enrichment and accumulation, particularly in complex tectonic regions. To explore the heterogeneous changes in pore structure and their influencing factors during the last tectonic uplift of Longmaxi shale, triaxial creep experiments were performed under varying confining pressure conditions. In addition, FE-SEM, MIP, LN2GA, and LCO2GA experiments were employed to both qualitatively and quantitatively characterize the pore structure of three distinct groups of Longmaxi shale samples. To further investigate pore heterogeneity, the multifractal dimension was applied to examine the evolution of the shale pore structure under the influence of the last tectonic uplift. The results revealed that the primary pore types in Longmaxi shale include organic matter pores, microfractures, intergranular pores, and intragranular pores. The shale’s mechanical properties and mineral content have a significant impact on the heterogeneity of these pores. Notably, the shale pores exhibit distinct multifractal characteristics, highlighting the complex nature of pore heterogeneity. The singular index (α₀) and ten other multifractal dimension parameters provide valuable insights into the heterogeneity characteristics of shale pores from various perspectives. Additionally, dynamic changes in pore heterogeneity are primarily controlled by the mineral composition. Under identical creep pressure variation conditions, significant differences are observed in the pore rebound behavior of Longmaxi shale with different mineral compositions. Under high-pressure conditions, the content of TOC and quartz plays a dominant role in controlling pore heterogeneity, with their influence initially decreasing and then increasing as pressure decreases. The reduction in creep pressure emphasizes the controlling effect of TOC, quartz, and feldspar content on pore connectivity. This study introduces high-pressure triaxial creep experiments to simulate the stress response behavior of pore structures during tectonic uplift, offering a more comprehensive reflection of pore evolution in organic-rich shale under realistic geological conditions.

The pore structure of shale defines the space available for gas generation and storage, with the evolution of these pores being closely linked to shale gas accumulation and migration. Investigating the evolution of shale pores under basin-orogenic tectonic settings is crucial for under-standing the variations in resource potential across different blocks of the Anchang Syncline. This study focuses on the Longmaxi Formation shale within the Anchang Syncline, systematically examining the differences in the lateral pore structure evolution across three distinct blocks during basin-mountain tectonic development. By integrating reservoir property characterization with burial-hydrocarbon generation modeling, and employing experimental techniques including X-ray diffraction (XRD), low-pressure nitrogen adsorption (LN₂GA), and low-pressure carbon dioxide adsorption (CO₂GA), this research reveals the pore evolution mechanisms in contemporaneous shale strata during tectonic uplift from the perspectives of multifractal theory and controlling factor correlation analysis. The results indicate that (1) Pore characteristics differ significantly among the three blocks. Samples from block A (e.g., MAY2) are predominantly microporous, while samples from block C (e.g., MAD4) exhibit a higher proportion of mesopores (2–50 nm). Samples from block B (e.g., MAD3) show an intermediate pore structure. (2) Despite similar thermal maturity evolution levels and TOC contents across the blocks, as well as comparable burial and hydrocarbon generation histories, the primary factors controlling the pore differences are the magnitude of latestage tectonic uplift, the duration of thermal maturity evolution, and preservation conditions. (3) Analysis of fractal dimensions suggests that mineral composition promotes the complexity of microporous structures while inhibiting the complexity of mesoporous structures. (4) Based on the interblock variations, two distinct evolutionary models are established: model 1 (“rapid evolutionsustained overpressureweak uplift modification”) features a shorter maturity evolution duration, longer overpressure preservation, and minor late-stage uplift; model 2 (“slow evolutiontransient overpressurestrong uplift modification”) is characterized by a longer maturity evolution duration, shorter overpressure preservation, and significant latestage uplift.