CO₂ Regional Enhanced Volumetric Fracturing Technology for Shale Oil Horizontal Wells in Ordos Basin

In response to the problems of low pressure, high fluid flow resistance, low energy enhancement efficiency of slick water fracturing, and low complexity of fracture networks in shale oil reservoirs in Ordos Basin, a physical simulation experiment of slick water and CO₂ fracturing was conducted in the Qingcheng shale oil block of Ordos Basin. The expansion law of CO₂ fracturing fractures was monitored using high-energy computerized tomography (CT) scanning, and the feasibility of CO₂ fracturing to form complex fractures was analyzed. By using reservoir numerical simulation methods, the key parameters of CO₂ injection were optimized, forming a CO₂ regional energy enhancement and volumetric fracturing technology suitable for the Qingcheng shale oil block. Research showed that pre-CO₂ fracturing could increase the complexity of fractures in Chang 7 shale oil, with fractures spreading along weak bedding planes and forming a fracture network through the layers vertically. The concept of energy enhancement should be achieved by injecting energy into the platform as a whole instead of alternating energy enhancement between single well sections and injecting energy into the platform as a whole, achieving a transformation of integrated energy enhancement between wells and sections. The single well that adopted the full well section injection energy enhancement mode could achieve full coverage of the fracture control area. Based on a platform in the Qingcheng shale oil block, a shale oil CO₂ regional energy enhancement and volumetric fracturing test was conducted. Compared with conventional volumetric fracturing adjacent wells, the average pressure retention of the three test horizontal wells increased by 1.5 times, and the average initial oil production of a single well increased by 28.6%. Research and on-site experiments showed that CO₂ regional energy enhancement and volumetric fracturing could increase the complexity of fractures, enhance regional formation energy, and improve single well productivity, providing technical support for shale oil development in Ordos Basin.