Experimental study on sacrificial agent performance to reduce the adsorption capacity of surfactants

Compared with medium to high permeability reservoirs, low-permeability reservoirs have a more complex pore structure and a larger specific surface area. Therefore, it is more important to pay attention to the impact of the adsorption loss of the oil displacement system in the formation, as well as the methods for exploring the adsorption capacity of the system. Given the complexity of the reservoir environment, a single surfactant is difficult to cope with. Although some surfactants can reduce interfacial tension, they have strong adsorption properties in the formation. In this case, their adsorption performance can be optimized by compounding, and good oil displacement performance can be retained. The paper conducted experimental evaluation on the combination of sacrificial agents and surfactants, and screened three sacrificial agents by testing the interfacial tension and adsorption capacity of surfactants. The experimental results showed that the compatibility of polyethylene glycol, sodium tetraborate, and pressure reducing injection system was good, which reduced the interfacial tension of surfactants, while the compatibility of sodium hexametaphosphate with surfactants was poor. After compounding three sacrificial agents with surfactants, the adsorption capacity of surfactants showed a significant downward trend. The use of sodium hexametaphosphate as a sacrificial agent has the best effect, followed by polyethylene glycol and sodium tetraborate. The performance evaluation of sacrificial agents that reduce the adsorption capacity of surfactants can help optimize surfactants and improve the recovery rate of low-permeability oil reservoirs.