Assessment of in-situ CO2 Sequestration Potential and Enhanced Coalbed Methane (ECBM) Production of Continental Coal-bearing Basins in China

Abstract

The utilization of CO₂-Enhanced Coal Bed Methane (CO₂-ECBM) technology is pivotal in realizing the environmentally responsible and efficient exploitation of Coalbed Methane (CBM) energy resources. The optimization of carbon capture, utilization, and storage (CCUS) for carbon reduction mandates a nuanced understanding of the diverse geological attributes present in CBM reserves globally. Traditional estimations of CO₂-ECBM's carbon sequestration potential have predominantly relied on rudimentary empirical models, notably those proposed by the United States Department of Energy (DOE), which overlook the intrinsic geological conditions and the physicochemical properties of subsurface fluids. Addressing these limitations, our study implements the advanced DR/Henry mixed adsorption model in tandem with the Peng-Robinson equation of state (PR-EOS). This approach meticulously identifies the critical parameters governing the mass exchange ratios between CO₂ and CH₄, pertinent to in-situ geological environments. Subsequently, we have formulated a comprehensive carbon sequestration potential assessment framework. This innovative model adheres to the mass conservation principles for individual CO₂ and CH₄ components, taking into account the specific surface and stratigraphic conditions prevalent. Employing this refined methodology, we evaluated the CO₂-ECBM carbon sequestration potential of the 40 evaluation units of extensional, compressive, and cratonic continental coal bearing basins in China's three major temperature-pressure systems across different depth domains and coal ranks within 2000 m. Our findings reveal that the theoretical carbon sequestration capacity of China's continental coal-bearing basins is approximately 59.893 billion tons. Concurrently, the potential ECBM output stands at an estimated 4.92 trillion cubic meters, underscoring the substantial environmental and energy benefits inherent in harnessing CO₂-ECBM technology effectively. The regional analysis revealed that North and Northwest China hold the highest sequestration and recovery potential, followed by the Northeast and Southern regions, respectively. Specific areas, including the eastern edge of the Ordos Basin and southern Junggar Basin, Qinshui, Huoxi, Xishan, and other areas in Shanxi, present promising future prospects for geological carbon storage in unrecoverable coal seams.