Characterizing Disproportionate Permeability Reduction Using Synchrotron X-Ray Computed Microtomography

R.S. Seright; J. Liang; W. Brent Lindquist; John H. Dunsmuir – 2002

Abstract

Synchrotron X-ray computed microtomography (XMT) was used to investigate why Cr(III)-acetate-HPAM gels reduce water permeability 80–90 times more than oil permeability in both strongly water-wet Berea sandstone and oil-wet porous polyethylene. Despite different porosities (22% vs. 40%), pore size and aspect ratio distributions were similar between the two media. The gel caused comparable DPR ratios in both. Water and oil saturation distributions versus pore size were substantially different before, during, and after gel placement, providing pore-level insight into the mechanism. This first application of synchrotron XMT to DPR characterization opened the door to direct pore-scale observation of the gel-fluid interactions that cause the asymmetric permeability reduction.

Key Takeaways

  • Synchrotron XMT was first applied to DPR characterization, enabling direct pore-scale observation of fluid and gel distributions during water, oil, and gelant flooding — resolving the pore-scale ambiguity that earlier macroscale experiments could not address.
  • A Cr(III)-acetate-HPAM gel reduced water permeability 80–90 times more than oil permeability in both strongly water-wet Berea sandstone and oil-wet porous polyethylene — confirming that DPR is robust across wettability conditions.
  • Water and oil saturation distributions versus pore size were substantially different before, during, and after gel placement — these pore-level saturation changes are the physical record of how gel preferentially obstructs water pathways vs. oil pathways.
  • The comparable DPR ratios in water-wet and oil-wet porous media despite very different wettabilities suggests that wettability alone does not determine DPR magnitude — pore geometry and the gel-oil interaction mechanism both play important roles.
  • This paper established the XMT experimental platform and protocols for pore-scale DPR investigation, enabling the subsequent series of studies that identified oil trapping and gel dehydration as the mechanistic drivers.
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