A. Nadeeka Upamali, Karasinghe (The University of Texas at Austin) | Liyanage, Pathma Jith (The University of Texas at Austin) | Cai, Jiajia (The University of Texas at Austin) | Lu, Jun (The University of Texas at Austin) | Jang, Sung Hyun (The University of Texas at Austin) | Weerasooriya, Upali P. (The University of Texas at Austin) | Pope, Gary A. (The University of Texas at Austin)
The ability to develop high performance, low cost chemical formulations for chemical EOR involves the use of not only highly efficient surfactants tailored to specific crude oil and reservoir conditions, but also the technical know-how for combining the surfactants and other chemicals to create the best formulation as a complete package. Scientific understanding of how the molecular structures of surfactants and co-solvents affect microemulsion properties greatly speeds up the process of arriving at optimal formulations for enhanced recovery of a specific crude oil in a specific oil reservoir. With the main emphasis on reducing the chemical cost of the formulations, a new slate of novel chemicals, both surfactants and co-solvents, has been developed and shown to have superior performance. We have synthesized and tested new classes of surfactants with different hydrophobe sizes and structures varying from large-medium-short-ultrashort in order to meet the needs of a variety of crude oil requirements. We have also developed ultra-short hydrophobe surfactants (with 2-ethylhexanol hydrophobe) possessing dual surfactant / co-solvent properties. Such duality in performance helps, in some cases, to minimize or altogether offset the use of co-solvents while maintaining low microemulsion viscosities, faster equilibration, and other desirable behavior. Thus, 2-ethylhexanol-propoxy-sulfate was developed as a surfactant that also encompasses co-solvent properties. The novel Gemini surfactants have also been incorporated in formulations and core flood experiments with excellent results. The new co-solvents offer advantages such as short equilibration time for the microemulsion formation and lower microemulsion viscosity. Systematic studies using these new surfactants and co-solvents clearly show that we now have the capability of developing highly robust formulations to meet the needs of a variety of reservoirs, resulting in high oil recoveries with low surfactant retention, which is the key to lowering the chemical costs and improving the economics of chemical enhanced oil recovery.