Shale Reservoir Characteristics and Development Control Factors of Lower Cambrian Qiongzhusi Formation in Sichuan Basin

Abstract

Recently, breakthroughs have been made in the down warping region SZY1 well, the “intracratonic sag” type Z201 well and the JS103 well in central Sichuan and southwest Sichuan, showing that the Lower Cambrian Qiongzhusi Formation in the Sichuan Basin has good exploration potential, but the differences and main controlling factors of different types of shale reservoirs are still unclear, and it is urgent to carry out comparative research on reservoir characteristics. Based on the data of three wells, this paper systematically compares and analyzes the petrology, geochemistry, re-servoir prosperities and crushability of different types of shale reservoirs in the Lower Cambrian Qiongzhusi Formation in the Sichuan Basin. The results show that the content of TOC and clay minerals in Cambrian shale of continent down warping region in northern Sichuan is higher, mainly organic matter pores and flaky clay mineral pores, the specific surface area and pore size are larger, and the pore development is mainly controlled by organic matter abundance and diagenesi. The black shale in the deep-water shelf facies of the intracratonic sag in central Sichuan basin had high TOC and gas content, mainly organic matter pores, and there was a good positive correlation be-tween porosity and organic matter abundance. The intracratonic sag shallow shelf facies sandy shale in southwest Sichuan has low TOC and low gas content, ntergranular pores, tiny crackand flaky clay minerals pores are the main pore types. The pore development is mainly controlled by diagenesis. The organic-rich shale of the Qiongzhusi Formation deposited in the deep-water shelf facies of the northern Sichuan basin and central Sichuan basin has certain similarities, with high TOC and high-quality shale sections dominated by organic pores. The intracratonic sag shallow shelf facies sandy shale in southwest Sichuan has low TOC, mainly inorganic pores, higher porosity and good crushability, and has certain exploration potential