Study of Continental Shale Hydrocarbon Accumulation in a Synclinal Structure using BPSM - the Lianggaoshan Shale of the Wanxian Syncline in the Fuling Area: A Case Study in the Southeastern Sichuan Basin

ABSTRACT The evaluation of unconventional hydrocarbon accumulation in a synclinal belt presents challenges, particularly in continental shale formation. The Middle Jurassic Lianggaoshan shales within the Wanxian syncline in the Fuling area are currently a focal point in the research on continental shale oil. To gain insights into the hydrocarbon generation and migration processes of continental shale in the high-steep synclines of the southeastern Sichuan Basin, we built a numerical model of a typical syncline and the invasion percolation method was used to reconstruct the history of shale oil generation, evolution, and migration through basin and petroleum system modelling (BPSM). The source rock thermal history suggests that the Lianggaoshan shale developed to low maturity in the Early Cretaceous, leading to the generation of significant natural gas and limited oil. The Lianggaoshan shale had reached high maturity and was predominantly generating oil by the later part of the Early Cretaceous. A 2-D simulation highlighted the preferential accumulation of liquid hydrocarbons in silty shales, identifying them as sweet spots in tight shale reservoirs. The simulation results show that the fault has little effect on shale oil and gas migration, but there are adjustments to the hydrocarbon near the fault. The stable structure of the synclinal nucleus, continuous strata, and excellent preservation of liquid hydrocarbons make it an ideal location for shale oil accumulation, with the synclinal slope holding more gas. BPSM analysis offers a quantitative framework for studying unconventional oil and gas accumulation in high and steep synclinal zones, potentially enhancing the efficacy of resource evaluation in this context.