Commonalities and differences of hydrocarbon accumulation in channel sandstones of Jurassic Lianggaoshan Formation, Sichuan Basin

To address the key issues in the efficient exploration and development of tight sandstones in the Jurassic Lianggaoshan Formation across different blocks of the Sichuan Basin, and to clarify the hydrocarbon accumulation models and main controlling factors for guiding subsequent exploration deployment, this study took the channel sandstones of the Lianggaoshan Formation in Bazhong (northern Sichuan) and Fuxing (eastern Sichuan) areas as the research objects. Multi-type and multi-scale data, including drilling cores, well logging, seismic data, and production performance, were comprehensively utilized to conduct systematic benchmarking analysis of petroleum geological conditions and detailed examination of hydrocarbon accumulation processes. The study revealed that the hydrocarbon-rich zones of the Lianggaoshan Formation were mostly located at the spatial overlapping areas of high-quality shale hydrocarbon-generating centers and facies-controlled porous reservoirs, generally developing volatile oil reservoir-condensate gas reservoir with co-production of oil and gas. Based on this, two types of hydrocarbon accumulation models, namely "near-source charging and sandbody migration" and "mixed-source charging and fault-sand migration", were established. It was clarified that the hydrocarbon enrichment of channel sandstones in the study area was controlled by the coupling of multiple factors such as structural evolution, source-reservoir configuration, and thermal evolution degree of source rocks. Comparative analysis indicated that significant regional differences were observed between the Bazhong area in northern Sichuan and the Fuxing area in eastern Sichuan in terms of pressure systems, condensate oil content, hydrocarbon-rich horizons, and enrichment intensity. The core commonalities and key regional differences in the hydrocarbon accumulation of the Lianggaoshan Formation across different areas were systematically refined. The study clarified that the north-south structural differentiation primarily controlled the natural gas accumulation and enrichment model, the hydrocarbon source and thermal evolution degree of source rocks constrained gas reservoir characteristics and fluid geochemical properties, and the source-reservoir matching relationship affected the hydrocarbon-rich horizons and enrichment degree. The research findings can provide targeted theoretical support and reference for the efficient exploration and development of Jurassic channel sandstone hydrocarbons in similar geological settings.