The Critical Factors in the Formation of Ultra‐Deep Carbonate Reservoirs: A Case Study of Tarim Basin and Sichuan Basin, Midwest China

ABSTRACT Deeply buried dolomite reservoirs within craton basins are important hydrocarbon reservoirs. This study employs a comprehensive statistical analysis of key craton basins, including Sichuan and Tarim Basin. The analysis identifies three main types of deeply buried dolostone: granular dolostone, microbial dolostone and crystalline dolostone. These types are characterised by distinct pore structures, specifically cavity‐type and pore‐type. The study highlights the critical importance of favourable sedimentation conditions as the foundation for pore development, while also emphasising the essential role of early dissolution processes. Additionally, early dolomite replacement facilitates the preservation of primary porosity. Moreover, reservoir properties receive enhancement from epigenetic karstification and tectonic fracturing mechanisms. Notably, this study elucidates that deep‐buried, high‐quality dolomite reservoirs, of which storage and flow properties that are useful for hydrocarbon recovery, maintain a distinct level of stratigraphic control, with inheritance outweighing modification. Vertical distribution of the dolomite reservoirs is controlled by high‐frequency cycles and the burial depth, and exhibiting periodic cycles, not entirely controlled by reservoirs burial depth, whereas plane distribution is ascribed to advantageous sedimentation instead of karstification processes. As the paper concludes, it advocates future exploration endeavours targeting the inner rift within the platform and carbonate ramp areas, thus illuminating promising directions to seek deep‐buried effective dolostone reservoirs. The underground storage space of ultra‐deep carbonate reservoirs is enormous, and it is currently the most feasible large‐scale CCUS‐EOR approach.