Stepan Company
Enhanced oil recovery methods

Abstract:

Methods for enhanced oil recovery. In one method, an oil-bearing sandstone formation having a clay content of at least 5 wt. % is injected with a surfactant mixture, a solution comprising 0.5 to 3 wt. % aqueous alkali, and an aqueous solution comprising a polyether. In another method, a sandstone formation having a salinity within the range of 20,000 to 100,000 ppm total dissolved solids and a divalent ion content within the range of 1,000 to 10,000 ppm is injected with a surfactant mixture and an aqueous solution comprising a polyether. In both methods, the polyether solution is injected as a sacrificial agent prior to injection of the surfactant mixture or is injected as a mitigation agent concurrently with the surfactant mixture. Surprisingly, adsorption of the surfactant mixture onto the formation can be reduced by 20-70% or more compared with similar methods performed without the aqueous alkali solution, the polyether solution, or both.