Basic research and technological progress of CO₂ fracturing

Unconventional oil and gas, represented by shale oil and gas and low-permeability tight oil and gas, are important replacement resources in China. Due to their poor reservoir properties, effective exploitation is difficult. Currently, reservoir transformation is mainly carried out through horizontal well volume fracturing technology. However, there are still problems such as water resource waste, reservoir damage, and poor increasing production. Because of the the low viscosity, high density, and high diffusivity, supercritical/liquid CO₂ can quickly enter reservoir micropores and microfracture. CO₂ fracturing can effectively reduce fracture pressure, form complex fracture networks, increase formation energy, improve backflow rate, reduce reservoir damage, and achieve single well production increase. It is suitable for efficient and green exploitation of unconventional oil and gas resources. This paper introduces the basic research progress of CO₂ fracturing from the aspects of the mechanism of rock breaking and fracture making by CO₂ fracturing, the mechanism of influence of CO₂ on rock properties, the flow characteristics of CO₂ fracturing wellbore, CO₂ fracturing stimulation and geological storage, and briefly describes the development and application of several main fracturing technologies, including CO₂ foam fracturing, CO₂ dry fracturing, CO₂ acid fracturing, and CO₂ mixed fracturing. Against the background of China’s current “dual carbon” goals and increased exploration and development efforts for unconventional oil and gas resources such as shale oil and gas, CO₂ fracturing technology is one of the key core technologies for building a clean, environmentally friendly, low-carbon, and efficient energy security and development technology system, with great potential for development and promotion.