四川盆地自贡地区龙一1亚段富有机质页岩储层特征和主控因素OA

The Lower Silurian Longmaxi Formation in the Southwestern Sichuan Basin represents a high-quality marine hydrocarbon source rock with significant exploration value.Focusing on organic-rich shale from the Long 11 Sub-member in the Zigong Area of the Sichuan Basin,this study employed tech-niques including total organic carbon mass fraction analysis,whole-rock X-ray diffraction,scanning elec-tron microscopy,and CO2 and N2 adsorption to characterize reservoir properties,pore structure fea-tures,and their governing factors.Results indicate that the shale mineral composition in the study area is primarily clay minerals and quartz.Pore types in the organic-rich shale of the Long 11 Sub-member in-clude organic pores,inorganic pores,and microfractures.Organic pores constitute the dominant pore type,accounting for 42.31％-93.04％of total porosity with an average of 66.88％.The total organic carbon(TOC)content in the organic-rich shale of the Long 11 Sub-member ranged from 0.16％to 5.05％,averaging 1.63％.The shale organic matter predominantly belonged to type Ⅰ,with an average vitrinite reflectance of 2.30％.The shale's total porosity ranged from 0.018 0 to 0.031 0 cm3/g,with a total specific surface area ranging from 23.15 to 45.26 m2/g.The Long 11 Sub-member shale reservoirs predominantly developed mesopores,followed by micropores,which together accounted for approxi-mately 95％of the total pore volume,while macropores constituted the smallest proportion.Organic matter abundance and maturity are the primary factors controlling organic pore development.Hydrocar-bon generation promotes the formation of nanoscale pores,while high thermal maturity causes kerogen shrinkage and partial closure of organic pores.Clay mineral interconversion and compaction negatively impact pore development.Brittle minerals like quartz and calcite provide structural support for pore spaces during diagenesis,preserving intergranular pores and increasing porosity.These findings provide a basis for predicting sweet spots in deep marine shale gas exploration within the Sichuan Basin.