Pore Geometry and Its Influences on Methane Adsorption in Shale Gas Reservoirs: A Case Study of Longmaxi Shale in the Da’an Area, Chongqing, China

Understanding pore structure and methane sorption (MS) in shale gas reservoirs is critical for accurately estimating gas‐in‐place and prospective natural gas resources. The Longmaxi Shale, a leading formation for deep shale gas development in China, faces challenges in its economic production due to its strong spatial heterogeneity, complex pore structure, and poorly characterized methane adsorption volume. In this study, six core samples collected from the Da’an area, Chongqing Municipality, were analyzed to determine lithology, pore structure, and water vapor adsorption by using integrated approaches of X‐ray diffraction (XRD), total organic carbon (TOC) quantification, microscopy, μ‐X‐ray fluorescence (μ‐XRF), mercury intrusion porosimetry (MIP), N 2 physisorption (NP) and CO 2 physisorption (CP), and MS. A specialized sampling workflow was designed to mitigate spatial heterogeneity effects. The results indicate that the samples comprise argillaceous‐siliceous mudstone, clay‐rich siliceous mudstone, and mixed siliceous mudstone. Porosity ranges from 1.88% to 2.84%, specific surface area changes between 20.1 and 31.5 m 2 /g, and absolute MS capacity varies between 1.88 and 3.19 m 3 /t. TOC and pore size are the two major controlling factors of MS. These findings advance mechanistic understanding of pore structure and MS in shale, offering insights for optimizing production in shale reservoirs.