Experimental and simulation study on the mechanism of associated gas near-miscible flooding in Weizhou 12-1 oil fieldLEI

Near miscible flooding may make the same displacement effects of low interfacial tension as that of miscible displacement besides reduces injection pressure.Based on the PVT experimental data of multi-contact process and miscibility expansion test by injecting gas from Wei Southwest oilfield group into formation oil in Weizhou 12-1 oilfield,combining the analog computation of PVT properties and phase behavior,the displacement characteristics of muti-contact immiscible and near miscible analyzes and expansion characteristic of accompanying gas injection in Weizhou12-1 oilfield are analyzed.It shows that under present formation pressure(20.47~20.77 MPa),the theoretical miscible pressure of formation oil in Weizhou12-1 oilfield corresponding to is above 39.45 MPa when mole proportion of injecting gas reaches about 0.68 and system reaches a theoretical contacting mixed phase status.Displacement mechanism formed by injecting external transmitting gas into Weizhou12-1 oilfield is multi-contact dynamic non-miscible flooding and weak near miscible flooding.If achieving obvious near miscible flooding and miscible flooding,the injecting pressure should be increased to 40 MPa above.