Study on Fracture Morphology of CO₂ Energized Fracturing of Continental Shale Oil in Dongying Sag

In the process of CO₂ energized fracturing, the evaluation of fracturing stimulation effect and production effect is affected by fracture distribution. In order to clarify the fracture mechanism of CO₂ fracturing of continental shale oil in Dongying Sag, the changes in rock mass fracture pressure, natural fracture shear/opening stress, and in-situ stress with time under CO₂ immersion were determined by experiments. On this basis, by considering the rock stress parameters under CO₂ immersion, the Pen-Robinson equation was used to describe the change of CO₂ physical property parameters. In addition, combined with experimental and numerical methods, a simulation method for fracture propagation by CO₂ energized fracturing based on node connection method was developed, and an example analysis of an oil well in Dongying Sag was carried out. The results show that the CO₂ ratio has a great influence on the induced fracture density. When the CO₂ ratio increased from 0.1 to 0.3, the induced fracture density increased by 117%. The stress difference mainly affects the fracture length and induced fracture density. When the horizontal stress difference increased from 5 MPa to 30 MPa, the fracture network length increased by 52%, and the induced fracture density decreased by 13.85%. The simulation results of fracture morphology are in good agreement with the actual monitoring. This study can provide a theoretical reference for the formulation of continental shale oil fracturing schemes.