A New Technology for Enhanced Oil Recovery in Tight Oil Reservoirs: CO2/Low Interfacial Tension Viscoelastic Fluid Co-flooding

Tight reservoirs have poor physical properties, strong heterogeneity and low water flooding natural productivity. CO2 flooding can effectively improve oil recovery and reduce carbon emissions, but CO2 flooding is prone to gas channeling, which affects the enhanced oil recovery effect. Therefore, a viscoelastic fluid (GOMT) with strong adaptability to tight reservoirs, low interfacial tension and good plugging and diverting effect was constructed. GOMT/CO2 synergistic flooding can effectively prevent gas channeling in CO2 flooding, which is a new technology for enhancing oil recovery by CO2 flooding in tight reservoirs. In this paper, a viscoelastic fluid GOMT was constructed by using the self-synthesized surfactant GOM, and the GOMT performance and CO2-GOMT synergistic flooding effect were explored through rheological property, interfacial activity, wettability test and oil displacement experiment. The experiment results showed that 0.3%GOMT belongs to low interfacial tension viscoelastic fluid, which has strong adaptability to salinity water of tight reservoir (6788 mg/L– 80000 mg/L), and can emulsified crude oil, improve the wettability of reservoir, block high permeability layer and shunt start low permeability layer. CO2/0.3%GOMT alternate flooding can effectively improve water flooding recovery in tight sandstone reservoirs. Under homogeneous and heterogeneous conditions, it is better than CO2 flooding and 0.3%GOMT slug flooding. This shows a good CO2-GOMT synergistic oil displacement, which can improve the water flooding recovery of tight sandstone reservoir by 17.05%. The technology of CO2/GOMT synergistic flooding studied in this paper can effectively overcome the gas channeling of CO2 flooding, effectively improve the oil recovery of heterogeneous tight sandstone reservoirs, and reduce carbon emissions. It enriches technology and theory of EOR for heterogeneous tight reservoirs, and has broad application prospects in the EOR of unconventional reservoirs.