Novel Chemical Flooding System Based on Dispersed Particle Gel Coupling In-Depth Profile Control and High Efficient Oil Displacement

In order to achieve both in-depth profile control and high efficient oil displacement, a novel heterogeneous combination flooding system (HCFS) composed of dispersed particle gel (DPG) and dodecyl dimethyl sulfo-propyl betaine (DDSB) was proposed and prepared. According to the in-depth profile control property and interfacial tension reduction capacity, the compositions of the HCFS were optimized as 20–30 wt % DPG and 0.4–0.5 wt % DDSB. The prepared HCFS exhibited good wettability alteration ability and emulsifying capacity. Results of double-layer heterogeneous core flooding tests showed that the enhanced oil recovery (EOR) result was great in the HCFS flooding stage and the subsequent water flooding stage, which was up to 31%. Moreover, on account of synergistic action of the soft granular profile control agent (DPG) and high efficient oil displacing surfactant (DDSB), the EOR result of HCFS flooding (31.04%) was much better than that of single DPG flooding (21.14%) or DDSB flooding (8.49%). Furthermore, the synergistic EOR mechanism by HCFS treatment was proposed based on the microscopic visualization experiment. In the HCFS flooding stage, DPG particles migrate to the depth and block the dominate channels by accumulating in pore throats; meanwhile, the HCFS efficiently strips the residual oil in high permeability channels. During the subsequent water flooding process, the injected water is diverted to low permeability zones with high oil saturation because of the in-depth profile control effect of DPG. What's more, the surfactant diffuses to the high oil saturation zones with subsequently injected water, which significantly improved the oil displacement efficiency of subsequent water flooding. Therefore, the HCFS can greatly improve oil recovery by the synergism of increasing swept volume and enhanced oil displacement efficiency.