The Role of Polymer on Surfactant-Foam Stability During Carbon Dioxide Mobility Control Process

Abstract

The in-situ generation of foam is one of the most promising techniques to solve gas mobility challenges in petroleum reservoirs and subsequently improve the volumetric sweep efficiency. The stabilization of foam at reservoir conditions is a major challenge. The harsh reservoir conditions, such as high temperature, high brine salinity, together with surfactant adsorption on the rock may result in unstable foam and, consequently, poor sweep efficiency. Foam additives, such as polymers, might help strengthen the physical properties of foam film and improve foam stability. This work evaluates the effectiveness of a polymer on enhancing CO2-foam stabilization at harsh reservoir conditions. Static and dynamic foam tests were conducted to evaluate the role of polymer on foam stability. Three foaming surfactants were used to assess the ability of the polymer on enhancing foam stabilization. The static foam tests were conducted at conditions similar to reservoir conditions using test tubes. Foam column, and foam life were measured to evaluate the role of the polymer on foam stabilization. Foam viscosity in absence and presence of the polymer was measured using foam rheometer apparatus. The dynamic foam tests were conducted to assess the ability of tested materials to generate viscous foams and also measure the CO2 mobility in porous media using a coreflooding system. The mobility reduction factor (MRF) was measured at high pressure and high temperature (HPHT) conditions, 3200 psi and 100°C. The static foam tests and foam rheology measurements indicated that the addition of the polymer enhanced foam stability as a result of increasing the bulk viscosity of the aqueous solutions. The results found that the foam life increased with the polymer concentration. However, the increase of polymer concentration makes the solution very viscous, hence, the foam generation becomes challenging. The dynamic foam tests showed that the foam generated in absence of the polymer was able to reduce the CO2 mobility 13 fold. However, the addition of the polymer resulted in higher pressure drops during CO2 floods, more resistance to gas flow and, therefore, lower gas mobility compared to that obtained with surfactant alone. The addition of the polymer reduced the CO2 mobility 50 fold. This higher reduction in the CO2 mobility as a result of adding the polymer can be attributed to the effectiveness of the polymer in improving the foam stabilization and prolong the life of generated foam.