Mobility control in carbon dioxide-enhanced oil recovery process using nanoparticle-stabilized foam for carbonate reservoirs

Recent developments in the subject of using silica-nanoparticles (SiNPs) for stabilizing carbon dioxide (CO2)foam have led to a renewed interest in the enhanced oil recovery (EOR) in oilfields. This study investigates the mobility control in the process of CO2 EOR through unfractured and fractured limestone cores. Toward this aim, laboratory tests were performed by co-injection of CO2 and 12 nm methyl-coated SiNPs solution to generate stable CO2 foam in the cores. In addition, sodium chloride (NaCl) and decane were used to examine the sensitivity of foam generation to salinity and to signify hydrocarbon (HC) phase in the experiments, respectively. The results revealed that SiNPs were able to generate stabilized CO2 foam in both unfractured and fractured limestone cores. A critical shear rate was established in the generation of foam with different conditions in the core-flood experiments. The cores with lower matrix permeability had a lower value of critical shear rate for foam generation. Moreover, the magnitude of apparent viscosity was found to be a crucial factor for mobility control and to obtain an optimum quality of foam. The results indicated that increasing NaCl concentration to 3 wt.% causes a decrease in the value of critical shear rate at applied temperatures. Furthermore, the findings revealed that a real mobility control in CO2 EOR process can only be reached when the generated foam still interacts with HC in the reservoir.