Characterization of Carboxylate Surfactant Retention in High Temperature,Hard Brine Sandstone Reservoirs

摘要

Large hydrophobe Carboxylate surfactants(MW above 1000)are a relatively new class of surfactantsdeveloped for surfactant flooding during chemical enhanced oil recovery(EOR)processes.The presenceof carboxylate groups and alkoxylate groups in the molecules provides stability and salinity toleranceat high temperature and in high salinity environments.Many high temperature reservoirs have injectionand reservoir brine containing high concentrations of divalent ions making them prime targets for usingcarboxylate surfactants.Much of the earlier literature showed successful carboxylate applications at highpH during alkali-enhanced flooding,as the high pH stabilizes the carboxylate groups.Such processes arenot feasible in the presence of hardness at high temperatures.We present an approach where we use an alkalibuffer wherein the pH is adjusted from highly basic to near neutral.Under such conditions we demonstratedlow retention and high performance in terms of phase behavior and coreflood oil recovery.