Practice and Development Suggestions for Volumetric Fracturing Technology for Shale Oil in the Ordos Basin

The use of volumetric fracturing technology can greatly increase the output of single well of shale oil in the Ordos Basin, but it is difficult to achieve economic and effective development under the condition of low oil prices due to the fact that the technical idea, technical mode and parameter system of fracturing are not reasonable enough. For this reason, based on field practice and laboratory test results of volumetric fracturing of shale oil at the Chang 7 Member of the Yanchang Formation in the Ordos Basin, the technical idea for volumetic fracturing was changed, thereby forming the technical mode of “large well clusters, long horizontal wells, subdivision cutting, cluster perforation, soluble ball seats, and variable-viscosity slickwater”. Then, the parameter system for volumetric fracturing was optimized. The mechanism and key technology for fracturing stimulation were systematically analyzed with the geological characteristics of the shale oil formation in the basin. The research results showed that the understanding of the seepage mechanism of shale oil in the reservoirs has gradually evolved from a single effective displacement mechanism for conventional reservoirs to a compound mechanism of effective displacement and oil-water imbibition displacement. The technical mode of volumetric fracturing proposed for the Ordos Basin was researched and developed independently, and its utilization obtained good field application results. In order to deepen and improve the volumetric fracturing technology and obtain higher productivity, some suggestions for the development of shale oil in the basin were put forward, including the further study of mechanism for fracturing stimulation, optimization of key technical parameters, and development of visualized volumetric fracturing technology. The research results can provide a basis for the optimal design of volumetric fracturing of horizontal shale oil wells, and can be used as a reference for the fracturing stimulation of similar reservoirs.