Effect of Surfactants on Water Imbibition into Heterogeneous Carbonate Rocks at an Elevated Temperature

摘要

Spontaneous imbibition of water into water-wet reservoirs has a positive effect on oil displacement and recovery. For carbonate reservoirs which are generally neutral to preferential oil-wet, surfactants may be used to alter wettability towards water-wet that assists water imbibition and consequently oil recovery. Depending on the surfactants selected, oil recovery can be significantly improved for carbonate reservoirs. This paper presents the results from a laboratory study on improved spontaneous imbibition of water into oil saturated carbonate rocks using surfactants. Three kinds of surfactants and one surfactant/polymer formulation were selected and evaluated in terms of compatibility with field brines, critical micelle concentration, interfacial tension, contact angle, and viscosity. The imbibition experiments were performed at 75°C to investigate oil recovery potential and the impact of interfacial tension, wettability, and viscosity. The results show that the addition of the surfactants can significantly oil recovery in the secondary oil recovery mode, compared to the imbibition process of water alone. Similar oil recoveries were observed when surfactant was used alone or mixed with a polymer. In tertiary oil recovery mode, low interfacial tension fluid showed a greater incremental oil recovery. This paper provides insights on selection and utilization of chemicals in increasing oil recovery from carbonate reservoirs, based on imbibition experiments.