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Abstract

A method is provided for blocking high permeability regions in subterranean geological formations, using a reinforced swelling clay gel. A reinforced clay slurry is prepared by mixing swelling clay, such as bentonite, an aqueous solution containing the salt of certain cations, which inhibit clay swelling, and a reinforcing agent. The cations K.sup.+, Ca.sup.2+, Mg.sup.2+, Cs.sup.2+, Fe.sup.2+, Al.sup.3+ and NR.sub.4.sup.+, where each R can independently be H, CH.sub.3, C.sub.6 H.sub.5, or CH.sub.2 CH.sub.3, and combinations thereof, among others, are clay swelling inhibitors. The reinforcing agent is non-swelling particles, including, without limitation, particles of produced sand, silica sand, sandy or silty soil, crushed rock, minerals, mine tailings, and combinations thereof. The reinforced clay slurry is introduced into a geological formation, where it preferentially enters high permeability regions. There the slurry is contacted by NaCl brine solution present in natural or injected drive fluids, and the inhibitive cations bound to the clay particles are replaced by Na.sup.+ ions, which attract water molecules and promote clay swelling. The reinforced Na.sup.+ -clay swells, causing the slurry to acquire a gel-like consistency. The reinforced clay gel so formed is capable of controlling the flow of at least a majority of a fluid into or from a high permeability region.

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