Experimental Study on Improving Tight Oil Recovery by Injecting Natural Gas

In order to solve the problem of rapid decrease in oil production rate in the late stage of depletion development of tight reservoirs in the Mahu area, as well as issues such as shortage of CO2 gas source, high cost, and corrosiveness, a method of natural gas displacement is proposed to develop tight reservoirs. The mechanism, development characteristics, and influencing factors of natural gas displacement to improve tight oil recovery are discussed from the aspects of micro development mechanism and macro development effect through the experimental study of feldspar core displacement. The important operating parameters such as gas injection speed and gas injection timing are optimized. The experimental results show that the gas injection rate has a great influence on the recovery factor, and there is a gas injection rate (0.10 cm3/min). That is optimized for development efficiency. The determination of the minimum miscibility pressure of crude oil and natural gas of 44.61 MPa provides a theoretical basis for the development of a tight oil reservoir by natural gas injection. Through displacement experiments conducted under current formation pressures of 37 MPa, depleted to 31 MPa, and depleted 25 MPa, it was found that the best time for natural gas injection is under the current reservoir pressure. The results optimize the key injection parameters that can guide the field application and confirm the feasibility and potential of natural gas to enhance tight oil recovery. To provide a strong basis for field development.