Controls of Depositional and Diagenetic Attributes on the Reservoir Quality of the Fluvial‐Delta Tight Sandstones of the Southeastern Sichuan Basin

ABSTRACT

The quality of tight sandstone reservoirs is primarily controlled by deposition and diagenesis, which are crucial for hydrocarbon exploration and reservoir modeling. This study focuses on the lithic arenite of the Lianggaoshan and Xiashaximiao formations in the southeastern Sichuan Basin. We analysed sandstone samples and identified four lithologic assemblages: massive sandstone, lenticular sandstone, sheet sandstone, and sandstone‐mudstone interbeds. Massive sandstones in fluvial facies exhibit poor sorting and rounding, displaying larger primary intergranular porosity. However, compaction and clay coatings reduce permeability. The sandstone‐mudstone interbeds, lenticular sandstones and sheet sandstones in delta facies have moderate sorting and rounding resulting in less and smaller intergranular porosity, with low porosity and permeability paramount due to authigenic clay mineral infillings. In particular, chlorite significantly impacts reservoir quality by reducing permeability in massive sandstones and infilling pores of sandstones in delta facies. Dissolution had minimal effect on improving reservoir quality but contributed to the formation of authigenic clay minerals. This study proposes a continuous fluvial‐delta depositional model and a hydrocarbon migration model, offering insights for diagenetic modeling and hydrocarbon exploration in similar systems worldwide.