# The Influencing Factors of CO2 Utilization and Storage Efficiency in Gas Reservoir
## 1 Introduction
The effects of anisotropy were studied through displacing different directionally cored sandstones with CO\({}_{2}\). The storage capacity enhanced when the normal vector of the dense layer became closer to the gas flow direction [24]. The contributions of different storage mechanisms were quantified through detail 3D reactive transport modeling study on a carbonate-depleted carbonate field. An amount of 79% of CO\({}_{2}\) was trapped by structure storage; 19% was trapped by residual storage; 3% was trapped by solubility storage and no mineral storage after 1000-year storage [25]. The effects of impurity (N\({}_{2}\) and H\({}_{2}\)S) were studied by numerical simulation of gas injection in brine formation. As the ratio of impurity increased, the gas migration became wider due to the lower viscosity and solubility of N\({}_{2}\) under reservoir condition [26]. However, there are fewer studies addressing the mechanism and influencing factors of CCUS in gas reservoir. The effects of physical property differences between CO\({}_{2}\) and CH\({}_{4}\) under reservoir condition were studied by core flooding experiments, which could inhibit the fluid mixing and diffusion and achieve more piston-like displacement [27]. The effects of temperature, injection rate and impurities were studied by numerical simulation and long core experiment [28]. As the temperature decreased from 114 \({}^{\circ}\)C to 75 \({}^{\circ}\)C, the CO\({}_{2}\) storage capacity became higher. The higher the injection rate, the less the enhanced recovery efficiency, but with better economics due to shorter production cycles [29]. As the impurity content increases (N\({}_{2}\)), the CO\({}_{2}\) diffusion effect is enhanced, and the difference in physical properties between fluids becomes smaller, potentially causing more natural gas pollution and poorer enhanced recovery efficiency [30]. In the presence of residual water, CO\({}_{2}\) dissolves in water first, thus delaying CO\({}_{2}\) breakthrough, and secondly making the displacing front more stable, thus inhibiting fingering [31]. The stronger the heterogeneity, the more pronounced the CO\({}_{2}\) fingering, and the earlier the breakthrough [32]. There are stronger inhibition effects on CO\({}_{2}\) breakthrough when CO\({}_{2}\) is injected in larger dip angle formation and in lower spot, because of the gravity segregation caused by density differences [33; 34]. So far, there are few field tests and laboratory mechanism studies on CO\({}_{2}\) injection for enhanced recovery and storage in gas reservoirs, especially research focusing on enhanced CH\({}_{4}\) recovery and CO\({}_{2}\) storage at the same time. Based on previous studies, this paper comprehensively analyzed the influence of different parameters on CO\({}_{2}\) displacement and storage process. The long core experiments were conducted for parameters sensitive analysis of injection rate, dip angle, permeability and irreducible water. Then, the simulations were carried out for supplement, which analyzed the effects of temperature, pressure, CO\({}_{2}\) purity and heterogeneity. Finally, the proportion of different storage mechanisms in gas reservoirs were quantified, and the transformation laws between different mechanisms were obtained.