Assessment of CO₂ fracturing in China's shale oil reservoir: Fracturing effectiveness and carbon storage potential

Shale oil resources are abundant in China, and their large-scale development plays a critical role in the national energy strategy. Hydraulic fracturing is widely employed for shale oil extraction, but the large-scale water consumption in this process poses serious environmental concerns. In recent years, CO₂ fracturing has been proposed as an alternative method to improve fracturing effectiveness, reduce water consumption, and simultaneously store CO₂ underground. This is the first field-testing study in China to systematically analyze the CO₂ fracturing technology and quantitatively evaluate its recovery efficiency and CO₂ storage capacity in the shale oil wells in Jianghan Basin. We designed and conducted a comparative investigation of hydraulic fracturing, CO₂-water fracturing, and CO₂ methanol-based fracturing techniques in terms of the effectiveness of fracturing, water saving, and CO₂ storage. The results showed that CO₂ methanol-based fracturing was most effective in eliminating the need for freshwater consumption on site and storing CO₂, with an effective CO₂ storage rate as high as 82.5%, suggesting a promising direction for carbon offset in the oil and gas industry. CO₂-water fracturing reduced freshwater consumption and also effectively stored CO₂ at an effective storage rate of up to 79.5%, making it more efficient than hydraulic fracturing but less so than CO₂ methanol-based fracturing. The research provides a valuable reference for the development and practice of waterless fracturing for shale resources, and also sheds light on the potential of carbon storage in the oil and gas industry to achieve the carbon neutrality goal of China.