Use of X-ray computed microtomography to understand why gels reduce relative permeability to water more than that to oil

• Published in: Journal of petroleum science & engineering Vol. 39; no. 3; pp. 217 - 230
• Main Authors: Seright, R.S., Liang, J., Lindquist, W.Brent, Dunsmuir, John H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 2003; Elsevier Science
• Subjects: Applied sciences; Characteristics of producing layers. Reservoir geology. In situ fluids; Crude oil, natural gas and petroleum products; Crude oil, natural gas, oil shales producing equipements and methods; Disproportionate permeability reduction; Energy; Exact sciences and technology; Fuels; Prospecting and production of crude oil, natural gas, oil shales and tar sands; X-ray computed microtomography; X-ray computed microtomography; Disproportionate permeability reduction; Water influx; Acrylic acid copolymer; Gelling agent; Wettability; Porous medium flow; Reservoir rock; Acrylamide copolymer; Oil field; Tomography; Relative permeability; X ray; Sandstone
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/S0920-4105(03)00064-0

X-ray computed microtomography (XMT) was used to investigate why gels reduce relative permeability to water more than that to oil in strongly water-wet Berea sandstone. XMT allows saturation differences to be monitored for individual pores during various stages of oil, water, and gelant flooding. The method also characterizes distributions of pore size, aspect ratio, and coordination number for the porous media. We studied a Cr(III) acetate–HPAM gel that reduced permeability to water (at S or) by a factor 80–90 times more than that to oil (at S wr). In Berea, the gel caused disproportionate permeability reduction by trapping substantial volumes of oil that remained immobile during water flooding (i.e., 43.5% S or before gel placement versus 78.7% S or after gel placement). With this high trapped oil saturation, water was forced to flow through narrow films, through the smallest pores, and through the gel itself. In contrast, during oil flooding, oil pathways remained relatively free from constriction by the gel.