Chemicals loss and effective distance of ASP flooding in second-class oil layers

Key words:  alkali/surfactant/polymer flooding  Daqing second class oil layers  outcrop cores  adsorption and retention  ultra-low interfacial tension  enhanced oil recovery

Abstract:

The interfacial tension (IFT) change and the chemicals loss of alkali/surfactant/polymer (ASP) at different migration distances in the oil layer were investigated through the simulation experiments of oil displacement using natural outcrops cores. The results show that the chemical loss of ASP in second class oil layer is serious. The loss percentage of surfactant is 80％ in the former 20％ migration distance, and the loss percentage of alkali and polymer is 23％ and 12％ respectively. After ASP flooding 100％ migration distance, the loss percentages of surfactant, alkali and polymer reach 92％, 42.8％ and 31％ respectively, which is significant. The chemicals loss occurs near the injection well in the oil layer, which is mainly useless and has limited contributions to the enhanced oil recovery. And this loss leads to gradually reduce the oil displacement efficiency of ASP flooding. Only the top 20％ of the distance of the ultra-low IFT for ASP system is effective, therefore its contributions to oil recovery enhancement is extremely limited. The displacement of residual oil after former 20％ well spacing is the potential direction of ASP flooding development.