Asphalt plug emplacement process

Claim 1

An oil-in-water emulsion for penetrating into and plugging the pores within the first few inches of a portion of a subterranean earth formation that is encountered by a fluid injected into a well, which emulsion consists essentially of: an emulsified mixture of an asphalt-containing oil-phase liquid, an aqueous liquid, and a cationic emulsifier, having compositions and concentrations such that (a) the particles dispersed within the aqueous liquid are capable of flowing through the pores of said earth formation, (b) the emulsion has a relatively neutral pH of from about 4 to 8, and (c) the emulsion breaks when its pH is increased by a significant amount; and dissolved in said aqueous liquid, a pH-increasing reactant having a composition and concentration such that the pH of the emulsion is increased to one at which the emulsion breaks when it is subjected to a time-temperature exposure of from about 5-60 minutes at from about 80°-140° E equivalent to that to which a fluid is exposed when it is injected into said earth formation, said pH-increasing reactant being a member of the group consisting of: mixtures of water-soluble epoxides and water-soluble chlorides, mixtures of water-soluble nitrite salts and water-soluble amides of carbonic acid, and water-soluble cyanate salts.