Experimental study on feasibility of the weak base ASP flooding in Chengbei Oilfield

Characteristics of Chengbei Oilfield is high oil viscosity, high permeability, and serious heterogeneity which resulted in bad water flooding effect and a large reserve volume of remaining oil. At present, the working time of producing platform has met its design lifetime, so it is necessary to develop high efficient technique to enhance oil recovery. Aiming at the reservoir geologic characteristics, fluid property and present developing situation, making use of the instrument detection and theoretical analysis, property of the polymer solution, ASP multisystem, modified ASP multisystem and its effect on profile control and oil displacement was studied. The results showed that the addition of Cr³⁺ has little influence on the viscosity and interracial tension of ASP multisystem, but there is an apparent increase in resistance factor and residual resistance factor. Under the condition of the similar cost, the "adjusting entry profile+ASP multisystem" and modified ASP multisystem have better effect on enhancing oil recovery than the conventional ASP multisystem, and recovery ratio is increased by more than 15%. Therefore, the weak base ASP multisystem is recommended to adopt in Chengbei Oilfield, its composition is as follows: "the polymer (Daqing Chaogao) (C_p=1 600~1 800 mg/L)+weak base Na₂CO₃(C_A=0.6%~1.0% )+heavy alkyl benzene mahogany sulfonate (C_s=0.10%~0.15%)+chromium (polymer: Cr³⁺=120:1 240:1)", and its slug array mode is "0.025~0.05 PVCr³⁺ polymer gel+0.12~0.15 PV ASP multi-system"