Abstract:Objective In order to solve the problem of high water injection pressure in low permeability reservoir, taking advantage of the small size and large specific surface area of carbon quantum dots, the compound carbon quantum dots were studied. Methods Polysulfonic acid surfactant APS and amphiphilic carbon quantum dots ACQDs were used to construct a compound injection system. The interfacial tension measurement, capillary imbibition height measurement, contact Angle measurement, static oil washing and core displacement experiments are used to evaluate the pressure reduction and injection system. Results The results show that the APS/ACQDs composite pressure reducing injection system with a mass concentration of 1000 mg/L can reduce the interfacial tension of oil and water to 3.861×10-2 mN/m, the capillary imbibition height can reach 24 mm, the core contact Angle can be reduced to 52°, and the static oil washing efficiency is 77.89%. Conclusion The core displacement experiment shows that after 1PV injection of the composite system, the maximum pressure reduction rate is 23.81%, which is significantly higher than that of the single system, achieving the purpose of reducing the water injection pressure, and providing a new reference for the development of low permeability reservoir pressure reduction and injection technology.