Further investigations of why gels reduce k<inf>w</inf> more than k<inf>o</inf>

The ability of polymers and gels to reduce the permeability to water much more than to oil is critical to the success of water-shutoff treatments in production wells if hydrocarbon-productive zones cannot be protected during placement. In this paper we first briefly review previous findings and the validity of several possible explanations for this disproportionate permeability reduction. Second, we describe experiments that test the validity of a promising mechanism - the segregated pathway theory. This theory speculates that on a microscopic scale, aqueous gelants follow water pathways more than oil pathways. Our experimental results in Berea cores support this mechanism for oil-based gels, but not for water-based gels. Third, we explore another interesting mechanism that was suggested after viewing a videotape of micromodel experiments that were performed by Dawe and Zhang. This mechanism involves a balance between capillary and elastic forces. Results from our experiments support this mechanism for flow in tubes and micromodels, but not in porous rock. Finally, we examine yet another mechanism that assumes that during brine injection, polymer leaches from the gel and significantly decreases the brine mobility. Our experimental results do not support this mechanism.

Further investigations of why gels reduce kw more than ko Conference Paper