Method of sealing formations in completed wells

Claim 1

IN THE PRODUCTION OF OIL AND GAS WELLS WHEREIN A WELL TRAVERSES A HYDROCARBON-PRODUCING FORMATION AS WELL AS A LOWER AND MORE PERMEABLE SECOND FORMATION TO BE SEALED OFF, THE METHOD OF SEALING OFF SAID SECOND FORMATION IN A WELL CONTAINING A CASING STRING WHICH HAS BEEN PROVIDED WITH PERFORATIONS AT LEAST AT A LEVEL ADJACENT SAID HYDROCARBON-PRODUCING FORMATION AND THE FORMATION TO BE SEALED, SAID METHOD COMPRISING INSERTING THROUGH SAID CASING STRING A PIPE STRING HAVING PACKER MEANS CARRIED AT THE LOWER END THEREOF, POSITIONING SAID PACKER MEANS AGAINST SAID CASING WALL IN A FLUIDTIGHT MANNER TO ISOLATE A PORTION OF THE CASING STRING AT A LEVEL OPPOSITE THE FORMATION TO BE SEALED, PUMPING DOWN THROUGH SAID PIPE STRING A FLUID CONTAINING A QUANTITY OF PARTICULATE SOLID MATERIAL SUFFICIENT IN VOLUME TO FILL THE ELONGATED ANNULAR SPACE OUTSIDE THE WELL CASING ADJACENT THE FORMATION TO BE SEALED, THE PARTICLES OF SAID SOLID MATERIAL BEING MADE OF A PLASTIC POLYMER CAPABLE OF EXPANSION UPON