Rheology, Stability, and Adsorption of an Amphoteric Foaming Agent for CO2 Mobility Control Applications under Reservoir Conditions

Abstract

Summary Foam injection is one of the most promising techniques to overcome gas mobility challenges during gas injection processes. Foam reduces gas mobility by increasing the gas apparent viscosity and reducing its relative permeability and, consequently, improving the gas sweep efficiency. The stabilization of foam at reservoir conditions, together with reducing surfactant adsorption on the rock minerals are the major challenges facing this technique. The objective of this study is to extensively evaluate the effectiveness of a potential surfactant on generating stable foams using sc-CO2 at high temperature and salinity conditions. In this study, bulk and dynamic foam tests were conducted to evaluate the effectiveness of an amphoteric surfactant, Amphosol LB, on stabilizing foams at harsh reservoir conditions (more than 2000 psi, 100 oC and 57,000 ppm of brine salinity). For bulk foam tests, the stability of surfactant solutions as well as the foam rheological properties using foam rheometer apparatus were analyzed and quantified. For dynamic foam tests, the CO2 mobility reduction factor as a result of foam generation using the surfactant was measured using two different systems: microfluidic device (chip with physical rock network) and coreflooding apparatus (actual rock samples). Also, the adsorption of the surfactant on carbonate rock minerals was quantified using the coreflooding apparatus. The experimental results demonstrated that the surfactant solution is chemically stable and able to generate foams at different reservoir conditions. The Amphosol LB surfactant solution produced foam with relatively high apparent viscosity when compared to those used for foam applications. The results also demonstrated that the foam viscosity increased as the foam quality decreased. For retention test, the results revealed that 86.56% of the injected surfactant solution was recovered. The amount of surfactant adsorbed by rock is about 0.257 mg/g rock. In the microfluidic chip and actual rock sample, the results also demonstrated that Amphosol LB surfactant solution showed higher resistance to gas flow and, accordingly, higher mobility reduction factor of sc-CO2 at 70% foam quality when compared to the other tested foam qualities. High apparent viscosity, small adsorption to the rock, and an acceptable CO2 mobility reduction factor are indicative of strong and more stable foam for reservoir applications.