Role of Rock Surface Charge in the Carbonated Water Flooding Process

Carbonated Water Flooding (CWF) is an alternative EOR method where an oil reservoir is flooded with carbonated (CO2-enriched) water. It is a promising solution for improving oil recovery that benefits from oil viscosity reduction, an increase in oil relative permeability and enhancement of oil mobility. At the same time CWF is a possible mitigation option for the increasing carbon dioxide concentration in the atmosphere and a chance for safe disposal of CO2 underground. We present Bentheimer sandstone surface charge behavior, mainly as a function of the CO2 concentration, in an aqueous solution. To investigate the electrokinetic properties of Bentheimer surface, the coupling coefficient and zeta potential are measured in a streaming potential experiment. The results show that the zeta potential can vary over at least one order of magnitude with different salinities and different CO2 concentrations. It strongly depend on both pore fluid concentration and pH, as well as a set of mineral and temperature specific electrochemical parameters. The results are base case results for the determination of surface behavior of Bentheimer sandstone with presence of oil. The results of the conducted experiment have an application in planning CWF processes, monitoring CO2 sequestration and streaming potential measurements in reservoirs.