This study investigates the microscopic structural changes and the evolution of physical properties in typical shale samples from three wells in southwestern China during water–rock interactions. Using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and other techniques, we analyzed the changes in pore structure, mineral dissolution behavior, and fracture propagation in shale samples of different types (organic-rich, mixed, and inorganic) during water immersion. The results show that water–rock interaction significantly affects the porosity, fracture width, and physical properties of shale. As the reaction time increases, the pore volume and number of pores generally increase in all shale types, with significant fracture propagation. Furthermore, fracture width changes exhibit varying trends depending on the reaction depth. NMR T2 spectrum analysis indicates that water–rock interaction not only influences the expansion of microfractures but also shows different responses in organic and inorganic pores. SEM images further reveal the impact of water–rock interaction on mineral dissolution, particularly during the early stages, where the dissolution of minerals significantly alters the pore structure. Overall, water–rock interaction plays a crucial role in the development of shale gas reservoirs, providing valuable data and theoretical support for future shale gas extraction.

Low permeability oil reservoirs hold an important position in the global oil resource reserves. They boast abundant reserves and serve as one of the crucial sources for crude oil reserve replacement in China and even the world. The mechanisms for improving the oil recovery rate in high-oil-bearing reservoirs include improving fluid properties, enhancing displacement efficiency, etc. However, their development is quite challenging, requiring continuous exploration and innovation in development technologies. This study addresses the unclear distribution patterns of microbial communities and the incomplete understanding of microbial enhanced oil recovery (MEOR) mechanisms in low permeability reservoirs. Utilizing high-throughput genomics and functional gene analysis techniques, combined with laboratory and field data, the study investigates the distribution and growth patterns of microbial communities in a low permeability reservoir, exemplified by the S169 block. Additionally, the potential of MEOR to enhance oil recovery and its underlying mechanisms are explored. The results indicate that microbial communities in low permeability reservoirs exhibit strong heterogeneity, with their distribution closely correlated to geological factors such as reservoir permeability and porosity. The diversity of microbial communities is positively correlated with oil recovery efficiency, and highly active microbial populations promote the production of metabolites that enhance oil recovery. The metabolic products of microorganisms help reduce the interfacial tension between oil and water, improve the fluidity of oil, and enhance the recovery rate. In addition, the structural changes in microbial communities are closely related to factors such as the permeability and porosity of reservoirs. This study provides a theoretical basis for the optimization of microbial enhanced oil recovery (MEOR) technology.

Clay content is a critical geological parameter influencing the pore structure, compaction sensitivity, and flow capacity of sandstone reservoirs. In this study, representative Tertiary sandstones from a major sedimentary basin in western China were selected, covering natural and synthetic core samples with clay contents ranging from 20% to 70%. Utilizing a self-developed apparatus capable of both static and dynamic compaction experiments, we systematically performed staged static loading and gas–water two-phase displacement tests. This enabled us to obtain comprehensive datasets on porosity, permeability, pressure response, and two-phase flow characteristics under various clay content, confining pressure, and gas drive rate conditions. Results demonstrate that high clay content leads to pronounced pore structure compaction and substantially greater permeability reductions compared to low-clay reservoirs, indicating heightened stress sensitivity. The synergy between gas drive rate and confining pressure regulates intralayer water production efficiency: initially, increased gas drive enhances mobile water production, but efficiency drops sharply at late stages due to pore contraction and increased bound water. As confining pressure increases, the mixed-flow region for two-phase flow shrinks, with water permeability decreasing sharply and gas permeability increasing, revealing the dynamic fluid transport and productivity decline mechanisms controlled by effective stress. The research deepens understanding of compaction–flow mechanisms in clay-rich sandstones, offering bases for evaluating reservoir stress sensitivity and supporting efficient, sustainable gas reservoir development, which increasingly helps offset global energy shortages.

Shale gas, as an important component of unconventional natural gas, plays a crucial role in resource development. This paper proposes a comprehensive analytical method that combines field analysis and well logging interpretation to evaluate gas content in shale reservoirs. Core analysis experiments are conducted to obtain microscopic gas content data, and well logging parameters are calibrated and extended to reveal vertical and lateral distribution characteristics of the reservoir. In the analysis of typical wells in the study area, it is found that gas content in shale gas reservoirs is significantly influenced by total organic carbon (TOC) content, mineral composition, and pore characteristics. Micro‐pores and meso‐pores mainly store adsorbed gas, while macro‐pores and micro‐fractures are the primary storage space for free gas. The content of clay minerals significantly suppresses the total gas content and free gas volume, while quartz and TOC content enhance the gas storage capacity of the reservoir. The comprehensive analytical method proposed in this paper overcomes the limitations of single methods and establishes a framework for evaluating gas content in shale gas reservoirs from microscopic to macroscopic scales, providing a scientific basis for resource potential assessment and development planning.

Formation clogging in carbonate gas reservoirs is a significant challenge in natural gas extraction, particularly due to the complex mineral composition and physicochemical characteristics of carbonate rocks, which make clogging phenomena even more complex. This study aims to delve into the formation mechanisms of formation plugs in carbonate gas reservoirs by analyzing the chemical composition, mineral characteristics, and organic components of the clogging materials. Formation clogging usually results from multiple factors acting together, including the migration of rock particles, scaling of formation water, deposition of organic matter, and corrosion of downhole equipment. These clogging materials not only hinder gas flow but may also accelerate the corrosion of pipelines and other facilities, increasing maintenance costs, and in severe cases, leading to gas well failure. Although numerous studies have focused on formation clogging in carbonate gas reservoirs, a comprehensive understanding of their complex mechanisms of action is still lacking. This paper employs advanced analytical techniques such as X‐ray diffraction (XRD), gas chromatography‐mass spectrometry (GC‐MS), and X‐ray photoelectron spectroscopy (XPS) to analyze clogging materials from the Pengtan‐1, which is part of the Ancient Carbonate Reservoirs, in the Sichuan Basin. The results indicate that the clogging materials are complex, consisting of a mixture of inorganic and organic substances, and multiple factors synergistically contribute to the formation of clogging. The study provides new insights into the formation mechanisms of clogging materials and offers a theoretical basis for developing more effective prevention and control strategies. This research provides significant support for improving the development efficiency, stability, and economic viability of carbonate gas reservoirs.