# A Review of Recent Progress of Carbon Capture, Utilization, and Storage (CCUS) in China
## 4 Progress of CO\({}_{2}\) Utilization in China
### Development Status of CO\({}_{2}\) Geological Utilization in China
#### 4.3.3 CO\({}_{2}\)-Enhanced Coalbed Methane Recovery (CO\({}_{2}\)-ECBM) in China  
A large amount of coabled methane in coal seams is formed and stored in the process of coalification. Unlike free-state natural gas in reservoirs, coabled methane resides in the adsorbed state within coal seams. Different storage forms result in various production mechanisms and processes. In general, the production of coabled methane is more complicated than that of conventional natural gas. Due to the lower permeability of coal seams, stimulation measures such as hydraulic fracturing and CO\({}_{2}\) injection, are required during coabled methane production [150]. The kinetic process of CO\({}_{2}\) adsorption and displacement of CH\({}_{4}\) is the key mechanism of CO\({}_{2}\)-ECBM. By injecting CO\({}_{2}\) into the coal seam, the partial pressure of CH\({}_{4}\) is reduced, which speeds up the desorption of CH\({}_{4}\) adsorbed on the surface of coal particles. Meanwhile, when CO\({}_{2}\) and CH\({}_{4}\) are present in the coal seam at the same time, they compete for adsorption. Due to the higher adsorption energy of CO\({}_{2}\)[151], the injected free-state CO\({}_{2}\) can take over the initial adsorption position of CH\({}_{4}\) in the coal seam so that the adsorbed-state CH\({}_{4}\) can be converted into the free state, facilitating CH\({}_{4}\) production and achieving coabled methane enhancement by CO\({}_{2}\).  
China's CO\({}_{2}\)-ECBM project has completed the pilot phase study. Although China has abundant coabled methane resources, the development of coabled methane is constrained by the \"three low and one high\" properties of coabled methane reservoirs, namely low pressure, low saturation, low permeability, and high adsorption [152]. Therefore, a series of studies have been conducted in China to address this situation. [PERSON] et al. established a thermos-hydro-mechanical-chemical (THMC) coupled model to simulate the displacement of coabled methane by CO\({}_{2}\), providing insights into key processes controlling key factors [153]. [PERSON] et al. analyzed the impact of CO\({}_{2}\) injection on some key parameters in coal seams through experiments and summarized the changes in gas outflow rate, gas components, coal seam temperature, CH\({}_{4}\) desorption rate and other displacement parameters during this process, establishing a crucial theoretical basis for the CO\({}_{2}\) storage effect in coal seams and the enhanced development of coabled methane [154]. [PERSON] et al. investigated the microstructure changes of coal samples after the injection of supercritical CO\({}_{2}\) and confirmed that the injected supercritical CO\({}_{2}\) could enlarge the pores and fractures in coal samples by dissolving the coal minerals, thus enhancing coalbed methane recovery [155].  
[PERSON] et al. focused on the geochemical reactions that occurred after CO\({}_{2}\) injection into coal seams and put forward the insight that anthracite may be a potential geological body for CO\({}_{2}\) storage [156].  
In addition to the above studies, there are currently two CO\({}_{2}\)-ECBM projects in operation in China, both of which are under the responsibility of China United Coalbed Methane Corp., Ltd. (CUCMC). Both the Shizhuang CO\({}_{2}\)-ECBM project and the Liulin CO\({}_{2}\)-ECBM project have a CO\({}_{2}\) injection capacity of 1000 tonnes/year [50], as shown in Table 7.