Gas-In-Place Content of Deep Shales and Its Main Controlling Factors: A Case Study on the Wufeng-Longmaxi Shales in the Middle Luzhou Block of the Southern Sichuan Basin, China

Deep shale gas (>3500 m) is a promising fossil energyresourcein the context of global efforts to achieve carbon neutrality. However,the accumulation, enrichment, and distribution of deep shale gas arecomplicated, which makes the gas-in-place (GIP) content and its maincontrolling factors of deep shales unclear. In this study, a groupof deep shale samples with burial depths of 4200-4350 m werecollected from the Wufeng-Longmaxi (WF-LMX) formations from the middleLuzhou block, southern Sichuan Basin, and the TOC contents, mineralogicalcompositions, porosities, pore water contents, water saturations,and GIP contents of the shales were systematically investigated. Theresults indicate that the TOC and brittle mineral contents, water-bearingcharacteristics, and effective porosities are the main factors controllingthe GIP contents of deep shales. The deep WF-LMX shales in the middleLuzhou block have high TOC and brittle mineral contents, low porewater content (C (PW)), and water saturation(S (W)), and great effective porosity, whichbenefits the generation, storage, and development of shale gas. TheGIP contents of the deep WF-LMX shales are in the range of 1.36-7.17cm(3)/g and are higher for the shales located in the lowersublayer of the first member of the Longmaxi formation (LMX1(1-3)). In general, the deep WF-LMX shales in the middle Luzhou blockhave advantageous reservoir properties and GIP contents, which indicategreat shale gas potential, and the LMX1(1-3) shalesare the most promising exploration and development targets.