Method of and composition for recovering circulation of drilling fluids in wells

Claim 1

A SEALING MATERIAL FOR ADDITION TO DRILLING FLUIDS FOR PREVENTING AND CURING LOST CIRCULATION, THE SAID MATERIAL COMPRISING HARD GRANULAR PARTICLES SELECTED FROM THE GROUP CONSISTING OF NUT SHELLS, SYNTHETIC RESINS, HARD WOOD, AND RESIN IMPREGNATED WOOD, CONTAINING PARTICLES OF MAXIMUM SIXE THAT ARE AT LEAST ABOUT 1/4 INCH IN ANY ONE DIMENSION, AND HAVING A COMPOUNDED SIZE DISTRIBUTION SUCH THAT BETWEEN 2 AND 9 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON A SCREEN OF AN OPENING THAT IS 90 PERCENT OF THE MAXIMUM PARTICLE SIZE, BETWEEN 12 AND 28 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON A SCREEN OF AN OPENING THAT IS 70 PERCENT OF THE MAXIMUM PARTICLE SIZE, BETWEEN 27G THAT AND 46 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON A SCREEN OF AN OPENING THAT IS 50 PERCENT OF THE MAXIMUM PARTICLE SIZE, BETWEEN 54 AND 75 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON A SCREEN OF AN OPENING THAT IS 20 PERCENT OF THE MAXIMUM PARTICLE SIZE, BETWEEN 67 AND 88 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON A SCREEN OF AN OPENING THAT IS 10 PERCENT OF THE MAXIMUM PARTICLE SIXE, AND BETWEEN 78 AND 94 CUMULATIVE PERCENT BY WEIGHT IS RETAINED ON AN OPENING THAT IS 5 PERCENT OF THE MAXIMUM PARTICLE SIZE, SAID SEALING MATERIAL HAVING BEEN PREPARED BY SEPARATING PARTICLES OCCORDING TO THEIR SIZE AND THEN COMBINING PARTICLES OF DIFFERENT SIZE IN PROPORTIONS TO GIVE A MIXTURE HAVING THE PARTICLE SIZE DISTRIBUTION DEFINED HEREIN.