Recent Advances and Perspectives of CO<sub>2</sub>-Enhanced Coalbed Methane: Experimental, Modeling, and Technological Development
Chaojun Fan, Lei Yang, Hao Sun, Mingkun Luo, Lijun Zhou, Zhenhua Yang, Sheng Li
Abstract
Carbon dioxide (CO 2 )-enhanced coalbed methane recovery (CO 2 -ECBM) is a critical way to increase methane production and reduce greenhouse gas (CO 2 and CH 4 ) emissions. As captured CO 2 is continuously injected in the coal seams, a low cost of CO 2 sequestration and high efficiency of CH 4 recovery can be achieved via the flooding and replacing effects driven by the injected CO 2 flow. Scientific insights into the complex process of CO 2 -ECBM in experiments, modelings, and technological developments need to be made to propose appropriate countermeasures. This review first highlights the progress of CO 2 -ECBM under laboratory conditions, e.g., the binary gas competitive adsorption and gas displacement experiments in the macroscale and porous structure tests using technologies of nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and computed tomography (CT) in the microscale. Then, the advances of mathematical models for changing in coal permeability and porosity during CO 2 -ECBM are reviewed, accompanying with the multi-field and multi-phase coupling responses of competitive sorption, diffusion, gas–water seepage, heat transfer, and solid deformation. Furthermore, the field pilot tests of CO 2 -ECBM in various countries and regions are also covered to reveal the key technical challenges confronted with the development of CO 2 -ECBM technology. The perspectives in experiments, models, and field pilots of CO 2 -ECBM are made, which include but are not limited to the following: conducting a core CH 4 /CO 2 flooding test under in situ conditions, modeling CO 2 -ECBM with real fractures/faults and coal failure, developing a new method for gas migration and leakage monitoring in the field, and enacting relevant standards, laws, and regulations to promote CO 2 -ECBM.