Time setting clay cement and method of correcting lost circulation

Claim 1

A METHOD OF CORRECTING LOST RETURNS OF DRILLING FLUID IN THE DRILLING OF A WELL INTO THE EARTH COMPRISING PLACING IN SAID WELL AT A LOCATION WHERE DRILLING FLUID IS BEING LOST FROM SAID WELL INTO AN EARTH FORMATION A SLURRY OF CLAY CEMENT COMPRISING A CLAY HAVING GEL STRENGTH PROPERTIES, A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACTIVATED SILICA, ACTIVATED ALUMINA, AND SILICA-ALUMINA IN AN AMOUNT NOT GREATER THAN ABOUT 10 PERCENT BY WEIGHT OF SAID CLAY CEMENT, SAID SILICA-ALUMINA HAVING THE FORMULA MA(SIO2)B(A12O3)C(H2O)D, WHERE M IS SELECTED FROM THE GROUP CONSISTING OF THE ALKALI AND ALKALINE EARTH METALS AND A=0-0.08, B=0.7-1.56, C=0.02-0.4, AND D=0.25-1.0, AND WATER IN AN AMOUNT NOT GREATER THAN ABOUT 65 PERCENT BY WEIGHT OF SAID SLURRY.