Advanced Applications of Polymers for Enhanced Oil Recovery
Hirasaki, George J
Doctor of Philosophy
With the increasing global demand for crude oil, it is essential to increase the oil production in economic ways. This requires a significant increase in application of advanced technologies in this area. Enhanced Oil Recovery (EOR) processes are known as series of different advanced technologies, which can be used to increase the oil production from a given oil reservoir. The traditional use of polymers in EOR is almost limited to increasing viscosity of the aqueous fluids injected into the reservoir. By increasing the viscosity of the injected fluids, more areas of the reservoir can be swept, and therefore more oil is expected to be recovered. In this thesis proposal, a number of advanced polymer applications for EOR are investigated. Polymers are known as a very promising class of materials with wide range of properties, especially combined with other advanced materials, such as nanoparticles. Therefore, there is a huge potential for developing new application of polymers in EOR processes. The first application introduced in this thesis is to use polymers as sacrificial adsorption agents for anionic surfactants. In a subclass of EOR, known as chemical EOR, surfactants are injected to lower the interfacial tension of oil and brine, resulting in recovery of more oil. However, one of the challenges facing these processes is the adsorption of surfactants onto the reservoir rock, which requires excessive injection of surfactant to compensate for the adsorption. This significantly increases the cost of the chemical EOR to values much more than what is actually needed for oil recovery. In second chapter of this thesis, sodium polyacrylate is introduced as a sacrificial adsorption agent, a chemical that is injected to decrease the adsorption of anionic surfactant. The results show that the material cost of chemical EOR can be reduced by up to 80% in case of using polyacrylate as a sacrificial agent for anionic surfactants. In addition, application of polyacrylate as a sacrificial agent for zwitterionic surfactants was investigated. In spite the significant reduction seen in the adsorption of anionic surfactants once polyacrylate is used, adsorption of zwitterionic surfactants is only slightly reduced after adding polyacrylate. In order to understand the reasons behind this dismal reduction, the effect of pH on adsorption of lauryl betaine (as the zwitterionic surfactant in this study) is studied. Based on the experimental data, a hypothetic mechanism is introduced to explain the adsorption properties of betaine. This hypothetic mechanism also explains why polyacrylate shows a very slight reduction in adsorption of zwitterionic surfactants while it significantly reduces adsorption of anionic surfactants. Finally, the effect of polymer coating on interfacial properties of nanoparticles in the absence or presence of surfactants is studied. Interfacial properties of polymer-coated nanoparticles in EOR have been traditionally limited to only emulsions (Pickering Emulsions). In this thesis, we have provided experimental evidence that polymer-coated nanoparticles can migrate to micro-emulsion phases even in the absence of emulsions. Some of these polymer-coated nanoparticles are dispersed in aqueous solutions, but they will precipitate in the micro-emulsion phase once mixed with the oil. This observation by itself can be used in EOR applications through understanding the fact that aqueous stability of nanoparticles is not the sufficient condition for nanoparticles to remain stable when injected into oil reservoirs. Many previous researchers have only focused on stability of nanoparticles in aqueous solutions as the only requirement for stability of nanoparticles even after injection into oil reservoir. This assumption is challenged based on our work in this thesis.