Controls on hydrocarbon accumulation in ultra-deep carbonate reservoirs of the Ordovician Yingshan Formation, Catake Uplift, Tarim Basin

Ultra-deep carbonate hydrocarbon reservoirs represent a key target for hydrocarbon exploration in the Tarim Basin. Characterized by great burial depth and strong reservoir heterogeneity, they pose significant challenges to reservoir prediction and the understanding of hydrocarbon accumulation mechanisms. Taking the Ordovician Yingshan Formation in the Catake depression of the Tarim Basin as a case study, this paper systematically analyzes the main controlling factors and hydrocarbon accumulation models of such reservoirs based on seismic, logging, and core data. The results indicate that the Yingshan Formation reservoirs generally exhibit low porosity and low permeability, and their reservoir effectiveness is mainly controlled by multi-stage tectonic-karstification processes. The reservoir types are dominated by dissolution pores, vugs, and structural fractures. The NE-trending strike-slip faults in the study area serve as critical migration pathways, connecting deep Cambrian source rocks and governing the hydrocarbon accumulation process featuring “multi-stage charging and late-stage accumulation”. Through a systematic comparative analysis of existing drilling data, it is concluded that three core conditions are essential for encountering high-quality hydrocarbon reservoirs: an effective oil-source fault migration system, well-developed high-quality fracture-vug reservoir bodies, and favorable structural conditions, all of which are considered essential. Subsequent drilling results support this interpretation. This study provides useful insights and practical value for the precise exploration of similar ultradeep and complex carbonate hydrocarbon reservoirs.