Core flood evaluation of hydrocarbon solvent foams

The possibility of using foams to reduce solvent mobility in hydrocarbon miscible flooding is investigated. The performance of nitrogen foams in oil-free Berea Sandstone cores is compared to the performance of foams generated with four light hydrocarbons (methane, ethane, propane and n-butane), using two surfactants of different sensitivity to oil. Both surfactants were effective in reducing the mobility of nitrogen as well as the four light hydrocarbon solvents, regardless of whether the solvents were gases, liquids or supercritical fluids, implying that foam sensitivity to oil does not translate directly into foam sensitivity to light hydrocarbon solvent. Some dependence of foam performance on solvent type and system pressure was observed. With gaseous and supercritical solvents, the mobility reduction factor decreased with decreasing system pressure, and increased, decreased or remained the same with solvent carbon number. With liquid solvents, mobility reduction was evident, but no obvious trends were observed. With hydrocarbons in the liquid phase at 23 °C, one of the surfactants caused core permeability to be reduced to near-zero by a mechanism that is not fully understood, possibly by hydrate formation.