Hydraulic cement composition containing a mixture of polymeric additaments and method of cementing a well therewith

Claim 1

AN AQUEOUS HYDRAULIC CEMENT SLURRY FOR USE IN CEMENTING A WELL PENETRATING A SUBTERRANEAN FORMATION, HAVING INCREASED THICKENING AND SETTING TIMES AND DECREASED FLUID LOSS WHEN IN CONTACT WITH THE FORMATION, COMPRISING WATER, HYDRAULIC CEMENT, AND BETWEEN 0.2 AND 5.0 PERCENT, BASED ON THE DRY HYDRAULIC CEMENT EMPLOYED, OF (1) A COPOLYMER PREPARED BY COPOLYMERIZING MALEIC ANHYDRIDE AND AN N-VINYL NITROGEN-CONTAINING RING COMPOUND SELECTED FROM THE CLASS CONSISTING OF N-VINYL MORPHOLINONE, N-VINYL-PYRROLIDONE, N-VINYL-2-OXAZINIDINONE, N-VINYL-2OXAZOLIDINONE AND RING-SUBSTITUTED ALKYL DERIVATIVES THEREOF WHEREIN THE ALKYL GROUP CONSISTS OF C1 AND C2 GROUPS, AND (2) A POLYMER PREPARED BY POLYMERIZING AN ARYL-VINYLBENZYL MONOMER, SELECTED FROM THE CLASS CONSISTING OF POLY(AR-VINYLBENZYL) ALKYL- AND HYDROXYALKYLSUBSTITUTED QUATERNARY AMMONIUM BASES AND SALTS, AND POLY(AR-VINYLBENZYL) SULFONIUM ALKYL- AND HYDROXYALKYLSUBSTITUTED BASES AND SALTS WHEREIN SAID ALKYL OR HYDROXYALKYL SUBSTITUENT CONTAINS NOT MORE THAN 4 CARBON ATOMS, THE TOTAL NUMBER OF CARBON ATOMS IN THE ALKYL AND HYDROXYLALKYL GROUPS IS NOT GREATHER THAN 8, AND NO MORE THAN 1 HYDROXYALKYL GROUP IS PRESENT PER RECURRING OR REPEATING UNIT OF THE POLYMER, IN A RATIO OF SAID COPOLYMER OF MALEIC ANHYDRIDE AND THE N-VINYL RING COMPOUND TO SAID POLYMER OF THE ARNYL-VINYLBENZYL PREPARED FROM SAID ARYL-VINYLBENZYL MONOMER OF BETWEEN 32 AND 3 OF THE COPOLYMER OF MALEIC ANHYDRIDE AND N-VINYL RING COMPOUND TO 1 OF THE ARYL-VINYLBENZYL POLYMER.