Study on Enhanced Oil Recovery by Associated Gas Flooding in Light Oil Reservoir of Changing Oilfield

Based on the analysis of the geological features and fluid properties of the Triassic reservoir in Gao 52,the feasibility of associated gas miscible flooding was evaluated by the flooding experiment and the calculation of minimum miscibility pressure.The minimum miscibility pressure calculated was of 15.11 MPa,which was greater than the initial formation pressure(13.05 MPa).Therefore,the reservoir could be developed by the associated gas immiscible oil displacement rather than by the miscibility of associated gas.The oil displacement effects of different associated gas slug and the single-well gas injection volume in different injection-production ratio were studied.The experiment results showed that oil displacement efficiency of water flooding was of 42.5% and that of associated gas flooding was of 53.3%,increasing by 10.8%.The gas injection volume and the wellhead pressure of injection well calculated were of 8784 m3/d and 8.89 MPa,respectively,which could satisfy the field application in the injection-production ratio of 1.2.