METHOD FOR PLUGGING LOST CIRCULATION AREAS AND LOST CIRCULATION MATERIAL TO BE USED THEREFOR

摘要

A method for plugging the areas of lost circulation occurring during the drilling of a well with the use of a drilling mud, and a lost circulation material to be used therefor. The lost circulation material comprising 1 to 90 parts by weight of a water-soluble solvent containing no active carbon atoms and at most barely miscible with mineral oils and 10 to 99 parts by weight of a hydrophilic urethane prepolymer, and the method comprises injecting through the drilling pipe the lost circulation material sandwiched between spacers of mineral oils, so as to allow the lost circulation material to penetrate into the lost circulation areas, to react with water which is present at the areas, and to plug the areas through its polymerization. PAT 13704-1