Viscosifier agent for oilfield fluids in hard conditions

摘要

The invention relates to aviscosifier useful for oilfield fluids, especially high TDS fluids and heavy brines, comprising:at least a zwitterionic polymer, prepared by inverse emulsion polymerization of: monomers A comprising a betaine group;nonionic monomers Bmonomers C including a metal ion crosslinkable group with a molar ratio of the monomers A to the monomers B between 4/96 and 40/60; andat least a metal ion compound leading to the crosslinking of the groups carried by monomers C.