Associated Copolymer and Preparation Method Thereof, and Drilling Fluid

摘要

Disclosed are an associated copolymer, a method for preparation of a polymer and a polymer prepared with the method, a use of the associated copolymer and/or the polymer in drilling fluids, and a drilling fluid containing the associated copolymer and/or the polymer. The associated copolymer comprises acrylamide structural units, zwitter-ionic structural units, and cationic polyamine structural units at a specific proportion, and the cationic polyamine structural units have specific kinematic viscosity and cationic degree; thus, when the associated copolymer is used as a viscosity improver for drilling fluids, the obtained drilling fluid not only has favorable apparent viscosity after it is aged at a high temperature, but also has high dynamic shear force, and is resistant to high temperature up to 200° C. or above, resistant to NaCl up to saturated concentration, and resistant to CaCl2 up to 20 wt % concentration.

主权项

1. An associated copolymer, comprising a structural unit A, a structural unit B and a structural unit C, wherein the structural unit A is represented by formula (I): wherein, R1, R2, and R3 independently are H, substituted or unsubstituted C1-C5 alkyl; wherein the structural unit B is a Zwitter-ionic structural unit; and the cation in the Zwitter-ionic structural unit is N+, and the anion in the Zwitter-ionic structural unit is SO3−; wherein the structural unit C is an ionic associate of the structural unit B and a cationic polyamine; wherein, based on a total weight of the associated copolymer, a weight percentage of the structural units A is 10-75 wt %; a weight percentage of the structural unit Bis 15-65 wt %; and a weight percentage of the cationic polyamine is 1-50 wt %; wherein the structural unit C is at least one of structures represented by formulae (III-1), (III-2), and (III-3): wherein, the dotted line represents ionic association; X− is an inorganic anion; R, R9, R9′, R10 and R10′ independently are structures represented by formula (IV): wherein, R11 is H, substituted or unsubstituted C1-C5 alkyl, t is an integer within the range of 1-5, and z is an integer within the range of 0-5; n and p independently are an integer within the range of 1-5; x is an integer within the range of 0-10; y is an integer within the range of 1-10; values of I, I′ and I″ are such that a kinematic viscosity of the cationic polyamine is 100-500 mm2/s and a cationic degree of the cationic polyamine is 0.5-2 mmol/g.