Comparative Effectiveness of Alkaline Flooding and Alkaline-Surfactant Flooding for Improved Heavy-Oil Recovery

摘要

Chemical flooding is a promising technique for enhanced heavy-oil recovery, especially for reservoirs where thermal methods are not feasible. This paper discusses results of a laboratory investigation, including sandpack flooding experiments and micromodel flooding studies, for assessing the suitability and effectiveness of alkaline flooding ana alkaline-surfactant (AS) flooding for heavy-oil recovery. The sandpack flood results show that the tertiary oil recovery ot AS flooding is lower than those of alkaline-only flooding, although the interfacial tension between the heavy oU and AS system can be reduced to be ultralow. The micromodel tests indicate that the mechanisms for enhanced oil recovery by alkaline flooding are the penetration of the alkaline solution into the crude oil and the subsequent formation of water-in-oil (W/O) droplet flow that tend to reduce the mobility of the water phase and damp viscous fingering, leading to the improvement of sweep efficiency. However, the formation of W/O droplet flow is inhibited with the addition of surfactant, and the viscous oil is easily emulsified into the water phase to form oil-in-water emulsions and then entrains along with the flowing aqueous phase. As a result, viscous fingering phenomena occur during the AS flooding, resulting in a relatively lower sweep efficiency.