Experimental and numerical simulation study on the CO₂ pre-injection fracturing optimization parameters in continental shale oil.

This article focuses on the mechanisms and optimization of CO₂ pre-injection fracturing technology for enhancing shale oil recovery in lacustrine shale reservoirs. It presents experimental findings showing that CO₂ mitigates the negative effects of water-based fracturing fluids (slickwater) on shale’s tensile strength and fracture toughness, partially restoring rock brittleness and promoting complex fracture networks. A multi-fracture propagation model coupling rock deformation and fluid flow was developed and validated, revealing that reducing slickwater viscosity and increasing CO₂ injection volume improve fracture extension and stimulated reservoir volume (SRV), while increasing stage spacing enhances SRV but reduces fracture complexity. The study also highlights how the angle between natural fractures and maximum horizontal principal stress influences fracture complexity and reservoir stimulation, providing guidance for optimizing CO₂ pre-injection fracturing parameters in field applications.