Experimental investigation of asphaltene adsorption in porous media due to solvent injection and effects on relative permeability. (February 2018) - Hematfar, Vahid
Highlights: Effects of asphaltene adsorption on relative permeability and displacement performance of waterflooding has been investigated by designed experiments. Dynamic asphaltene adsorption in sand-packs is commenced by co-injection of asphaltene solution (asphaltene ++ toluene ++ C7 ) and heptane (C6 ). The effects of water phase salinity, kaolinite clay and composition change on asphaltene adsorption are determined. This work takes advantage of water film salinity to interpret the change in performance of waterflooding (relative permeability) due to asphaltene adsorption. The main focus of the work: not only the level of permeability reduction, but the change in relative permeability and recovery factor should be used to indicate the net effect of asphaltene on fluid flow in porous medium. Abstract: While reduction in rock permeability due to deposition of asphaltene fraction of crude oil imposes negative effects on oil production rate from producing formation, there is no clear understanding about adsorption of asphaltene and the resulting effects on rock-fluid properties such as relative permeability. This work reports the results obtained from a series of experimental investigations to address the adsorption of asphaltene in porous media and the consequent impacts on relative permeability and recovery of waterflooding. Experiments are implemented by means of a designed experimental rig for specific set of water salinity, asphaltene concentration, clay content and composition of injected fluids. Waterflooding is performed in sand-pack prior and after the dynamic adsorption step to measure relative permeability and evaluate the change in recovery factor of waterflooding. Adsorption level is measured from spectrophotometry analysis of injected asphaltene solution and collected samples using the developed material balance calculations for asphaltene. In addition, the extracted sand at the end of experiment is analyzed to clarify the distribution of adsorbed asphaltene along the sand-pack. Obtained results show that the salinity of water phase acts as a resistive force to adsorption. However, waterflooding experiments and the corresponding relative permeability curves show the possible improvement in displacement performance and recovery factor of waterflooding under effect of asphaltene adsorption at certain conditions. Longer breakthrough time, more favorable transient flow and reduced residual saturation during waterflooding indicate the positive effects of asphaltene on recovery factor.