Rheological Investigation of High Performance Polymer-Surfactant Systems for EOR Applications in Carbonate Reservoirs

The demand of oil has increased in last few decades and it will remain a major source of energy in next few decades. To meet the increasing demand of oil, it is important to increase the current production level by either exploring new fields or maximizing the production from existing fields. To maximize the production from a field, various enhanced oil recovery (EOR) techniques are employed which includes thermal EOR, gas EOR and chemical EOR.

In chemical EOR, different chemicals such as surfactants, polymers and/or alkalis are used to recover the residual oil from the reservoir. Surfactants are added to lower the interfacial tension between water and oil. Alkalis can reduce the adsorption of surfactants and adjust the pH. Water-soluble polymers are used to increase the viscosity of displacing fluid (water). Partially hydrolyzed polyacrylamide is most widely used polymer for EOR application due to low cost, high viscosity and availability. However, it is not suitable for high-temperature and high-salinity reservoir due to thermal degradation that leads to huge reduction in the viscosity In this work, novel acrylamide-based terpolymers and amidosulfobetaine surfactant systems were evaluated using rheology for application in carbonate reservoir. Rheology is an important tool for screening different polymers. One of the polymer was terpolymer of acrylamide, acrylamido tertiary butyl sulfonate, and acrylic acid while other polymer was terpolymer of acrylamide, N-vinylpyrrolidone and acrylamido tertiary butyl sulfonate. The acrylic acid-based terpolymer showed higher viscosity compared to N-vinylpyrrolidone-based terpolymer. In-house synthesized surfactants were compatible with all three polymers. The added surfactant has negligible effect on the rheological properties of the polymers. Detailed results will be presented and discussed.

The investigated polymer-surfactant systems showed good potential due to good thermal stability, rheological properties and compatibility at reservoir conditions.