Carbon circular utilization and sequestration in depleted hydrocarbon reservoirs: Towards a carbon-neutral China

The technology of carbon dioxide (CO₂) enhanced hydrocarbon recovery is favored over other Carbon Capture, Utilization, and Sequestration (CCUS) methods for achieving the “double carbon” goal in China due to its ability to sequester CO₂ geologically while enhancing the recovery rates of oil and gas resources. However, current technologies face significant challenges, such as limited recovery enhancement capacity, as well as high costs and low efficiency in carbon utilization and sequestration. To address these issues, an innovative carbon-negative technology termed Carbon Capture, Circular Utilization, and Sequestration (CCCUS) is proposed. This technology integrates CO₂-microbial enhanced hydrocarbon recovery, CO₂ underground bio-methanation, and CO₂ sequestration in depleted hydrocarbon reservoirs. Compared to conventional CCUS technologies, CCCUS stands out through both its modes of carbon utilization and the forms in which carbon exists, by cyclically biochemically converting endogenous and exogenous CO₂ into renewable natural gas (RNG). A preliminary assessment indicates that CCCUS holds significant developmental potential in China, with 661 million tonnes of CO₂ utilized per cycle and 3.47 billion tonnes ultimately sequestered. However, there is a significant lack of research on the core technology of CCCUS, specifically CO₂ underground bio-methanation, in China. To bridge this gap and mitigate potential challenges during the development of CCCUS, targeted proposals have been formulated. This paper provides new insights into advancing the development of a circular carbon economy and accelerating the achievement of carbon neutrality in China.