Patent ID: 8697610
Filing Date: 2014-04-15
Classification: C09K

Abstract:
1. A method of treating a subterranean formation penetrated by a well bore, the method comprising: mixing into an aqueous mixture a crosslinkable, hydratable polymer and a delayed crosslinking agent, in amounts effective to obtain an aqueous mixture that can form a persistent gel at a crosslinking condition comprising an onset temperature of from 40° C. to 60° C., the aqueous mixture being formed at a pH where a pH sensitivity slope of 5° C. per pH unit to 25° C. per pH unit can be observed for at least one pH unit range within a pH range from 8.5 to 12.5, wherein where pH 1 and pH 2 are and higher pH values, respectively, and T XL1 and T XL2 are the corresponding crosslinking temperatures for the respective pH value, and the crosslinking agent comprises a complex comprising injecting the aqueous mixture into the well bore; and gelling the aqueous mixture at the persistent crosslinking condition.