Research on the Adsorption Law of HFAD Agents on the Surface of Porous Media during Hydraulic Fracturing-Assisted Oil Displacement in Low-Permeability Reservoirs

Adsorption loss of surfactants in porous media is one of the key factors affecting their application in low-permeability reservoirs. The hydraulic fracturing-assisted oil displacement (HFAD) technology can effectively reduce the adsorption loss of surfactants in porous media. However, the adsorption laws of HFAD agents (surfactants) during the HFAD process are still unclear. It was studied based on physical simulation experiments in this paper. The results showed that 0.3% SY-D as the HAFD agent achieved the best effect, which could reduce the oil-water interfacial tension to 0.0239 mN/m and increase the wettability index to 0.7492. In the high-pressure injection process of HFAD technology, the injection pressure and core permeability are positively correlated with the dynamic saturation adsorption capacity of the HFAD agent on the surface of porous media and the ambient temperature is negatively correlated with it. The higher the injection pressure and the larger the core permeability, the lower the dynamic saturation adsorption capacity of the HFAD agent on the porous media surface. In addition, since adsorption is an exothermic process, increasing the temperature has an inhibitory effect on adsorption. The higher the temperature, the slower the adsorption process of the HFAD agent on porous media. Among the three influencing factors, permeability has the greatest influence on the dynamic saturation adsorption capacity of the HFAD agent on the surface of core porous media, followed by injection pressure, and temperature has the least influence on it. Therefore, when implementing HFAD technology for the reservoir with low permeability, it can be considered to increase the injection pressure of HFAD technology to reduce the dynamic saturation adsorption capacity so as to increase the effective concentration of the agent. The research results have certain guiding significance for the application of HFAD technology in the field.