Synergistic surfactant mixtures containing lignosulphonates



Enhanced oil recovery (EOR) schemes have been gaining importance over the past several years. Of the various methods being tested, surfactant (or micellar) flooding appears to be one of the most promising ones. It involves injecting into the well the solution of a surfactant which reduces the inter-facial tension between the displacing aqueous solution and the oil trapped in the reservoir. Depending on the concentration of the surfactant, oil displacement proceeds either by a miscible process (surfactant concentration > 10%) or by a immiscible process (surfactant concentration = 2–3%). Miscible flooding converts to the immiscible process as the system is diluted by connate (interstitial) water. Under immiscible conditions, the most significant parameter affecting recovery is the interfacial tension(1,2). Petroleum sulfonates are perhaps the most important group of surfactants capable of producing very low interfacial tensions between crude oil and the water phase. Their relatively high cost, however, renders many potential applications uneconomical.