# The Influencing Factors of CO2 Utilization and Storage Efficiency in Gas Reservoir
## 5 Discussions  
Due to cost constraints and extraction efficiency, CCUS research in the past has mainly focused on oil reservoirs. With the further strengthening of CCUS subsidy policies and the urgent demand for CO2 emission reduction, CCUS research on gas reservoirs will gradually return to hot spots. Currently, there are not many studies on CCUS related to gas reservoirs. This study mainly focuses on the effects of factors on recovery and storage efficiency during CO2 injection in gas reservoirs, which could provide theoretical supports for CCUS technology research and references for CCUS field application. Based on the results and the literature review, the main points are as follows.  
This paper adopted a research method combining long core experiments and numerical simulations, which ensured the accuracy of simulation results by refining the simulation grid and fitting with the experiments results. Additionally, the inclusion of numerical simulations simplifies the experimental process and expands the types of sensitive factors.  
The effects of fluid property differences, temperature, pressure, permeability, heterogeneity and CO2 purity on recovery and storage efficiency were investigated, and the influence rules of parameters could be mutually confirmed with previous scholars' research.  
As for residual water and injection velocity, there are still different conclusions: some scholars believe that residual water occupies the flow space of pore throats and intensifies CO2 channeling; some studies also believe that residual water will dissolve CO2, thereby inhibiting the breakthrough. Some scholars believe that the greater the CO2 injection rate, the smaller the proportion of CO2 diffusion, and the better the recovery and storage effects; some studies also believe that with the increase in CO2 injection rate, both convection and diffusion effects will be strengthened, and the recovery and storage effects become worse. The above differences may be caused by heterogeneity and differences in experimental conditions, which should be further researched systematically in the future.  
Meanwhile, the effects of different dip angles on the recovery and storage effect were considered emphatically, and the importance of gravity differentiation in inhibiting CO2 breakthrough and diffusion was highlighted. It was believed that the larger the dip  
Figure 23: The variation curves of storage analysis. (**a**) Relation curves between CO2 storage amount and injection volume under different storage mechanisms; (**b**) relation curves between CO2 storage amount and development time under different storage mechanisms; (**c**) the variation curves of ions contents in irreducible water; (**d**) the variation curve of average reservoir pressure.  
angle, the better the recovery and storage effects. The above conclusions are significant for implementing CCUS measures in tilted gas reservoirs.  
Based on the complete process of depletion, gas injection and storage, the study analyzed and quantified the influence of different factors on the recovery and storage effects, which is of guiding significance for the actual implementation of CCUS measures to balance the benefits and storage capacity.