Electrically assisted liquid hydrocarbon transport in porous media

Electrically assisted mass transport of hydrocarbon compounds in natural porous media can be used to recover residual oil from clay rich rock formations, for which other means of recovery is infeasible. Momentum transfer from electrosmotic flow of water achieved on the water wet pore surfaces, and increased permeability due to enlargement of capillaries by colloidal dislodging are thought to be some of the direct mechanisms responsible for oil transport under an applied electric field. In this paper, the efficacy of electrically assisted hydrocarbon recovery in laboratory and field cores of hydrocarbon bearing formations is investigated. In all the laboratory experiments, the mass transport was induced under a constant applied potential gradient, without supplemental water flooding under pressure. It was found that oil recovery was maximized for surrogate cores containing 10–15% clay by mass. At higher clay contents the recovery was limited by low charge efficiency, while at lower clay contents the recovery appeared to be influenced by colloidal transport. The electroosmotic pumping effect was investigated and found to potentially contribute to the oil transport to the cathode reservoir. Low permeability sandstone cores showed increased permeability under applied electric field. Larger oil recovery was observed in the cathode reservoir than in the anode reservoir.