Composition and method of controlling lost circulation from wellbores

Abstract

A method and composition for controlling the lost circulation of drilling mud in a wellbore during a drilling operation comprising the introduction of a pelletized composition, comprising a water-insoluble, water-absorbent polymer and bentonite, in a weight ratio of water-absorbent polymer to bentonite in the range of from about 9:1 to about 1:9, and preferably in the range of from about 3:1 to about 1:3, into the wellbore to reduce or eliminate drilling mud loss by sealing porous subterranean formations. The pellets essentially maintain their original size as the pellets pass through the wellbore to the site of lost circulation. At the site of lost circulation, the pellets accumulate, absorb water and swell to form an essentially fluid-tight plug. The porous subterranean formation is thereby sealed and further loss of drilling mud is prevented.

Dependencies are inferred from the claim text.