Fracturing Stimulation Technology for Ultra-Deep Shale Gas in Qiongzhusi Formation in Ziyang Area

Shale gas reservoirs of the Cambrian Qiongzhusi Formation in the Sichuan Basin are characterized by ultra-deep burial, high stress, overpressure, high porosity, high total organic carbon (TOC) content, and high gas content. Therefore, fracturing operations encounter challenges including difficult fracture initiation and propagation, simple fracture morphology, and ambiguous stimulation mechanisms. To this end, numerical simulation of fracture initiation characteristics in micro-scale and physical simulation tests of macro-meter-scale fracturing were analyzed. The fracture mechanism of multi-dominant minerals dominated by felsic minerals and the law of fracture propagation under overpressure environments were elucidated, and the stimulation mechanism of complex fractures caused by lamina fracturing was clarified. Based on the seepage model of “three fractures and three zones”, the ultra-deep fracture network volume fracturing technology of “fine sweet spot optimization+ultra-high-pressure and large-rate lamina activation+large-scale full fracture domain support” was developed. The laminae opened to form micro-fractures and complex fracture networks. Field applications showed that the average open-flow rate after fracturing for 15 well treatments exceeded 200×10⁴ m³/d, realizing sufficient productivity release. The research results could provide theoretical support and technical paths for the large-scale development of shale gas in the Qiongzhusi Formation.