Study on the Enhancement of Recovery Rates in Heterogeneous Dense Reservoirs Using Foam Drives Stabilized by Low-Surface-Tension Nanoparticles

Aiming at the problems of low permeability, strong heterogeneity, high salinity, poor injectivity of the target reservoir, and the inability of traditional water flooding to effectively improve the oil recovery rate, a low interfacial tension and salt-resistant nano-scale particle-stabilized foam flooding system (LITF-NSF) was developed to improve the recovery rate of low-permeability oil reservoirs. Through core dynamic plugging and injectivity experiments, single/dual-tube core displacement experiments, and static imbibition oil displacement experiments, the injectivity, plugging effect, imbibition effect, oil displacement mechanism, and optimal injection parameters of the LITF-NSF foam flooding system were studied from three aspects: injection pressure, slug volume, and gas–liquid ratio. The LITF-NSF foam flooding system has good injectivity in the target reservoir, with a resistance coefficient ranging from 1.086 to 15.468; the optimal injection parameters are a constant pressure difference of 5 MPa, a gas–liquid slug volume of 0.3 PV, and a gas–liquid ratio of 2:1. Under these optimal injection parameters, the subsequent water flooding recovery rate can be increased by 29.77%; it can produce a good plugging effect on the high-permeability reservoirs of the target reservoir with a permeability difference of less than 50, and can increase the comprehensive recovery rate of heterogeneous oil reservoirs by more than 10%; the static imbibition recovery rate is 4.38% higher than that of pure water without surfactant, and has a certain permeability-enhancing oil displacement effect. The LITF-NSF foam flooding system has good adaptability to the target reservoir environment and stable foam performance, which can effectively improve the subsequent water flooding recovery rate and has a good application prospect in chemical flooding for improving the recovery rate of low-permeability oil reservoirs.