Enhaced oil recovery : from control of the interfaces to nanofluidic flows – ENCORE

Optimizing the efficiency of oil-recovery from existing fields will remain of upmost importance for the next 20-30 years, during the transition towards energies not based on fossil ressources. The aim of this project is to produce a profound advance in the understanding of the molecular mechanisms governing the flow behavior of polymer solutions when forced in narrow channels or in porous media where interfacial friction plays a major role, and to use this new knowledge to optimize enhanced oil recovery (EOR) processes. To reach the goals set by ENCORE, three world-class academic teams with expertise in surface modification with polymers, characterization of friction mechanism at solid-polymer interfaces, and flow behavior of complex fluids down to nanometric confinements have joined forces with a French major international Oil & Gas Company. For oil recovery applications, water solutions of high molecular weight polyacrylamides (HMWPAM) are injected to push out the oil trapped in the reservoir; they represent the best trade-off between viscosifying power, cost, and industrial availability. A large number of phenomena involving solution-surfaces interaction can take place during the transport of the polymer solution inside the porous medium: adsorption of the polymer on the pore walls, modification of the adsorbed conformation because of the flow field, size exclusion chromatography effect, apparent slip at the wall of the polymer solution, chain degradation if the elongational component of the flow is too high… A joint scientific program based on a complementary approach will be used. We will tackle this program, first by specific experiments exploring the relevance of results obtained on model systems for situations closer to the application, and second by macroscopic flow experiments such as those commonly developed by the industrial partner. To be more specific, the consortium proposes a three steps program based on complementary skills of the academic partners, each step leading to the identification of interfacial mechanisms whose relevance for EOR will be checked. What are the mechanisms of formation of an adsorbed layer on a surface under flow? What are the molecular mechanisms of interaction between a surface anchored polymer layer and a flowing polymer solution Finally, what happens in the case of confined solutions? Another particularity of this project will be to deal with extra long charged polymer chains where means of characterization and more rigorous physics are needed.
Finally, a better knowledge of polymer flow, adsorption and its interaction with the rock should enable to optimize polymer injection strategies and improve the design of the macromolecules. By combining both model and commercial macromolecules, the results from the experiments planned in ENCORE project should directly applicable to the oil industry.