Experimental Analysis of Gas Injection Feasibility and Evaluation of Enhanced Recovery Potential in Mahu Tight...

A series of development technologies of "horizontal well plus volume fracturing" have been established to achieve an annual output of one million tons of crude oil in 7 the Mahu tight conglomerate reservoir. However, such oil fields generally face problems such as rapid pressure drop, rapid production decline, difficulty in water injection, and gas channeling, seriously affecting the beneficial development of tight conglomerate reservoirs. To solve these problems, in this study, we carried out the feasibility experiment of different gas injection developments and the potential evaluation of enhanced oil recovery based on the combination of laboratory experiments and numerical simulation. The results show that CO₂, rich gas, and dry gas can be miscible with crude oil in X oilfield under the original formation conditions. Both CO₂ and hydrocarbon gas have expansion and viscosity reduction abilities. Under the same mole fraction of injected gas, the volume expansion ability and viscosity reduction ability of CO₂ to crude oil are 2.14 and 2.25 times that of hydrocarbon gas, respectively. Numerical simulation results show that the well pattern suitable for gas injection and energy supplement is a vertical well injection and horizontal well production, and the angle between the horizontal well direction and the horizontal maximum principal stress direction is between 0° and 30°. Both laboratory experiments and numerical simulations show that the CO₂ injection medium has the best recovery effect, which can increase the recovery rate by 13.8% compared with the depletion development. This research provides insights into the effective development of tight conglomerate reservoirs.