Abstract
Surfactant related chemical flooding has great potential for improving oil recovery in carbonate reservoirs, as surfactants are able to effectively lower the oil/water interfacial tension (IFT) and alter wettability toward water-wet. The loss of surfactant during the propagation process in the reservoir is one of the major concerns in determining the feasibility of a chemical flooding project. Many efforts have been made to reduce the surfactant adsorption in various scenarios to make the project economically successful. The addition of polymer in the chemical formulation is commonly used in the applications, which can not only be used to control the water/oil mobility ratio but also affect the surfactant adsorption in different ways.
This paper presents the results of a laboratory study on the effect of polymer on reducing the surfactant adsorption onto carbonate reservoir cores. An amphoteric surfactant and a sulfonated polyacrylamide were used in three series of dynamic adsorption tests conducted at reservoir conditions, including surfactant only, polymer followed by surfactant, and mixture of surfactant and polymer (SP). The experimental results showed that when surfactant alone was injected, the surfactant adsorption on the carbonate reservoir cores ranged from 0.125 to 0.203 mg/g-rock, with an average value of 0.163 mg/g-rock. When the surfactant was injected following the injection of a pre polymer slug, the surfactant adsorption reduced to 0.0739 to 0.0848 mg/g-rock, with an average reduction of 51.3%. If SP mixture was injected, the surfactant adsorption ranged from 0.0794 to 0.0872 mg/g-rock, with an average reduction of 48.9%. It indicates that the adsorptions of surfactant and polymer take place competitively on the sites of the rock surfaces. This laboratory study helps understand the synergetic effect of surfactant and polymer in SP formulations and design the injection schemes of chemical flooding processes.
