The use of inorganic sacrificial agents in combination with surfactants in enhanced oil recovery

Current literature on optimization of surfactants in enhanced oil recovery is summarized. Effectiveness of the use of surfactants in chemical EOR processes is dependent on many factors. Uncontrollable factors such as reservoir parameters, minerology, and the nature of the crude oil influence the choice of a chemical process. Each reservoir offers a different set of problems to be solved. When the use of a surfactant is warranted, one attempts to optimize further the activity of this surfactant by modifying the chemistry of the reservoir system. Cost aside, maintenance of optimal surfactant activity is essential to minimize the oil/water interfacial tension. Also, loss of surfactant activity due to adsorption on substrate material is particularly disadvantageous because the water wet nature of the rock may be decreased. The use of alkaline, weak acid anions, such as sodium silicate, phosphate and carbonate to enhance surfactant effectiveness has been studied. These sacrificial agents can reduce the hardness (divalent cation) activity of the solution and compete with surfactant for active sites on the reservoir rock surface. Core flood results show that there is an inverse correlation between surfactant retention in the core and residual oil recovery. They also suggest that surfactants may be recovered for reinjection by the optimal use of sacrifical agents-in particular, the sodium silicates.