Hydraulic Fracturing Technology for Deep Marine Shale Gas in Ordos Basin

The marine shale gas reservoir of Wulalike Formation in the western Ordos Basin covers a favorable gas enrichment area of approximately 9,000 km². However, the reservoir is deep buried, has a low formation pressure coefficient, and exhibits low indicators in terms of total organic carbon content (TOC) and gas-bearing properties, making hydraulic fracturing for production more challenging. This work conducted a comparison and analysis of geological characteristics and fracturing difficulties of Wulalike shale gas, and the problem of fracture propagation and sand-adding of deep marine shale gas has been solved by optimizing more stages and fewer clusters fractures and upgrading the wellhead pressure level to 140 MPa. In response to the requirement of continuous drainage after fracturing with large liquid volume under low formation pressure conditions, by liquid nitrogen injection or pre-loading liquid CO₂ to enhance formation energy, the post-fracturing pressure-controlled drainage production system was optimized through laboratory simulation and field data fitting. On site tests of high-pressure hybrid fracturing of vertical wells and multi-cluster energized volume fracturing technology of horizontal wells were conducted, the key parameters such as operation liquid capacity, sand amount, and discharge rate of energized fracturing of horizontal wells have reached the level of shale gas in Sichuan. The length and width of fracture zone is 579 m and 266 m according to the microseismic monitoring results, respectively. The absolute open flow has exceeded 10×10⁴ m³ for vertical wells and 20×10⁴ m³ for horizontal wells, suggesting that the production has been improved with large scale volume stimulation. The hydraulic fracturing technology for deep marine shale in Ordos Basin has provided technical support for the exploration and development of shale in Ordos Basin.