Preparation and Evaluation of a Novel Branched Polymer as Thickener for Calcium Chloride-Based Drilling and Completion Fluids.

Calcium halide-based fluids are often used in drilling and completion operations due to their high density, clay inhibition and low solid content. However, there is a lack of thickeners to promote gel strength, which improves the fluid's capacity to carry and suspend cuttings. To solve this problem, the branched polymer (hereafter abbreviated as PAD-B) was prepared by the copolymerization of N,N-dimethylacrylamide (DMAM) and 2-acrylamide-2-methylpropane sulfonic acid (AMPS), using polyethylenimine as a branching agent and cerium ammonium nitrate as the initiator.