Understanding the rate of clean up for oil zones after a gel treatment

To understand the rate of oil clean up after a gel treatment, pore-scale X-ray microtomography images were obtained at a variety of oil (hexadecane) throughput values after gel placement (involving a pore-filling Cr(III)-acetate-HPAM gel). For each pore in the image volume, oil and water saturations were followed as a function of oil throughput. These studies were performed both in water-wet Berea sandstone and in hydrophobic porous polyethylene. In hydrophobic porous polyethylene, oil saturations increased and gel was destroyed quickly in the smallest pores. Oil saturations increased and gel was destroyed quickly in the largest pores. In contrast, oil saturations increased much more gradually for the most common or intermediate-sized pores. The minimum in oil saturation versus pore size might result from a balance between gel dehydration by oil film growth versus gel extrusion. In contrast with water-wet Berea sandstone, increases in oil saturation occurred evenly over all pore sizes for all oil throughput values. Gel extrusion was not significant in the Berea pores. This in an abstract of a paper presented at the 2008 SPE/DOE Improved Oil Recovery Symposium (Tulsa, OK 4/19-23/2008).