致密砂岩储层微观孔隙结构与天然气运聚动力学机制OA

Cores of tight sandstone from the Shaximiao Formation in the Central Sichuan Basin were se-lected for high-pressure mercury porosimetry,micro-CT scanning,and NMR analysis,along with natu-ral gas accumulation physical simulation experiments and online dynamic physical simulation experi-ments.These studies aimed to clarify the pore structure of the tight sandstone samples,investigate the influence mechanism of micro-pore structure on natural gas transport and accumulation in tight sand-stone reservoirs,and establish a natural gas migration discrimination chart for tight sandstone reser-voirs.Results indicate that the Shaximiao Formation in the Central Sichuan Basin exhibits four reservoir types:Type Ⅰ and Ⅱ reservoirs exhibit intense dissolution,well-developed chlorite coatings,and fa-vorable pore-throat configurations,with average pore-throat ratios of 2.27 and 3.08,and average coor-dination numbers of 2.63 and 2.38,respectively.Type Ⅲ and Ⅳ reservoirs exhibit intense compaction and cementation with poor pore-throat configuration,yielding average pore-throat ratios of 3.32 and 4.03,respectively.The ultimate gas saturation reaches 75.35％of Type Ⅰ reservoirs and 48.50％of Type Ⅳ reservoirs.Rocks with higher connectivity exhibit greater reservoir capacity.Wider throats and improved pore-throat connectivity reduce the capillary forces overcome by gas displacing formation wa-ter,thereby enhancing gas migration and accumulation.Natural gas in tight sandstone reservoirs exhib-its non-migratory zones,non-stable migratory zones,and stable migratory zones.Based on rock physics simulation experiments,this study reveals the gas charging mechanisms in sandstones with different pore structures,providing important insights for guiding the development of tight sandstone gas reser-voirs.