Research progress on formation mechanism and hydrocarbon accumulation of strike-slip fault-karst reservoir

[Significance] Fault-karst systems are widely developed in many basins in China and have become a new hot topic in geoscience due to the huge petroleum resources. However, the reservoirs of fault-karst systems are typically deeply buried and challenging to explore, resulting in an urgent need for a consensus understanding of trap classification, formation mechanisms, and controlling factors. [Progress and Conclusions] Based on a comprehensive literature review, this paper deeply discusses the formation mechanism of fault-karst reservoirs, which are fracture-vuggy carbonate systems formed by karstification influenced by multi-stage tectonic activities. First, the basic concept of the fault-karst reservoir is reviewed. The fault-karst reservoirs are characterized by deep burial, strong heterogeneity, and significant variations in fluid properties. Then, the critical role of strike-slip faults in hydrocarbon accumulation and migration is emphasized. Based on the analysis of geological data in the Shunbei area and other regions of the Tarim Basin, this paper reveals the trap types, formation mechanisms, and reservoir-controlling factors of the fault-karst reservoir. The analysis concludes that the segmentation of strike-slip faults, the activity of solvent fluid, and the timely emplacement of hydrocarbons are crucial to the development of fault-karst reservoir. Furthermore, the roles of atmospheric freshwater, hydrothermal fluids, and hydrocarbon fluids in reservoir reconstruction are discussed, illustrating how they jointly affect the formation and distribution of fault-karst reservoir. Finally, the paper summarizes the reservoir-forming models of the fault-karst reservoir. [Prospects] The discovery and ongoing research into fault-karst reservoirs have unveiled a new and promising frontier for petroleum exploration.