INVESTIGATION AND APPLICATION ON GAS-DRIVE DEVELOPMENT IN ULTRA-LOW PERMEABILITY RESERVOIRS

To select a proper displacement medium with the purpose of developing ultra-low permeability reservoirs both effectively and economically, three kinds of gases, including CO(2), NG and N(2), are studied through physical modeling and numerical simulation under the specified reservoir conditions. The results indicate that the oil recovery through water injection is relatively low in ultra-low permeability reservoirs, where the water breaks through early and the water cut rises rapidly. Gas injection can enhance the production, of which the gas-drive efficiency depends on the injection pressure and the gas itself. CO(2) is proved to be the best one after comprehensive consideration of (lie recovery speed, the overall recovery efficiency and the time needed for gas to break through. The pressure of CO(2) injection in the field experiments is lower, compared with that of water-drive. The injectivity index of CO(2) is 7.2 times as high as that of water, and the oil production of the test well group increases by about 4 t/d.