# 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
#### 4.3.2 CO\({}_{2}\)-Enhanced Natural/Shale Gas Recovery (CO\({}_{2}\)-EGR) in China  
Natural gas mainly exists in a free state under natural conditions, and it is stored in underground porous formations, primarily in oil and natural gas fields. Natural gas is easy to produce in large amounts due to its free state. Although shale gas has the same composition as natural gas, it is trapped within the microcracks of shale rock. The characteristics of shale, such as the low pore pressure, porosity, and permeability, make shale gas production much more difficult. Therefore, shale gas is considered as unconventional natural gas. The utilization of CO\({}_{2}\) has a considerable positive impact on the production of both natural gas and shale gas. The primary premise of CO\({}_{2}\)-enhanced natural gas recovery is to leverage the physical differences between the supercritical-state CO\({}_{2}\) and the free-state natural gas to accomplish natural gas displacement by CO\({}_{2}\) in natural gas reservoirs [140], while the CO\({}_{2}\)-enhanced shale gas recovery process mainly relies on distinctions in the adsorption characteristics of shale for CO\({}_{2}\) and CH\({}_{4}\). Because shale preferentially absorbs CO\({}_{2}\) over CH\({}_{4}\), shale gas recovery can be enhanced by replacing CH\({}_{4}\) in the shale formation with CO\({}_{2}\) injection [141]. The proven reserves of gas in China have rebounded since 2018 [142]. In 2019, new proven natural gas reserves of over 100 billion m\({}^{3}\) were discovered in three gas fields, including two gas fields in the Ordos Basin and one in the Sichuan Basin [138]; the Sichuan Basin added 124.7 billion m\({}^{3}\) of proven shale gas fields [143], and Guizhou added 642.4 billion m\({}^{3}\) of predicted shale gas geological reserves [144]. Theoretically, China's CO\({}_{2}\)-EGR has approximately 9 billion tonnes of CO\({}_{2}\) storage potential, while China's CO\({}_{2}\)-EGR technologies currently are still in the basic research stage [50]. Both natural gas and shale gas in China show great development potential [145]. The geological conditions of some gas reservoirs limit their development efficiency, especially shale gas reservoirs. China's continental shale gas enrichment areas have typical characteristics of low porosity, low permeability, high adsorption, high clay content, and high depth. These characteristics lead to huge water consumption and clay hydration swelling by hydraulic fracturing during the shale gas production process, further causing fracture blockage and low gas recovery [146]. Given the above-mentioned characteristics of shale gas reservoirs and the difficulties in exploitation, Chinese experts and scholars have launched a series of research on CO\({}_{2}\) utilization to enhance shale gas recovery, covering the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Project**} & **Capture** & **Operation** & \multirow{2}{*}{**Transport**} & **CO\({}_{2}\) Injection** & **Oil Production** \\  & **Technology** & **Start Year** & & **Capacity** & **Capacity** \\  & & & & **(Tonnes/Year)** & **(Tonnes/Year)** \\ \hline Jilin Oilfield & & & & & \\ CO\({}_{2}\)-EOR project & Pre-combustion & 2008 & Pipeline & 600,000 & 100,000 \\ Daqing Oilfield & & & & & \\ CO\({}_{2}\)-EOR project & Pre-combustion & 2003 & \
\begin{tabular}{c} Tanker truck \\ and pipeline \\ \end{tabular} & 300,000 & 100,000 \\ Zhongyuan Oilfield & & & & & \\ CO\({}_{2}\)-EOR project & & & & \\ East China OilkGas CCUS & & & & \\ full-process & & 2005 &
\begin{tabular}{c} Tanker truck \\ and ship \\ \end{tabular} & 100,000 & N/A \\ demonstration project & & & & \\ Xinjiang Oilfield & & & & \\ CO\({}_{2}\)-EOR project & & & & \\ Changqing Oilfield & & & & \\ CO\({}_{2}\)-EOR project & & & & \\ Shaanox Yanchang & & & & \\ Petroleum CO\({}_{2}\)-EOR project & & & & \\ Shengli Oilfield & & & & \\ CO\({}_{2}\)-EOR project & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: CO\({}_{2}\)-EOR projects in China [50; 83].