Properties of high‐temperature‐resistant drilling fluids incorporating acrylamide/(acrylic acid)/(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) terpolymer and aluminum citrate as filtration control agents

A terpolymer of acrylamide (AM), acrylic acid (AA), and 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) was synthesized by a free‐radical solution polymerization technique, characterized by FTIR methods, and applied together with aluminum citrate in oilfield drilling as a high‐temperature‐resistant filtration control agent. Before and after thermal aging for 16 h at 180°C, the combined effect of the terpolymer and aluminum citrate on the Bingham‐type rheological and fluid‐loss properties of the corresponding fresh‐water and salt‐water muds was further investigated. The results showed that before the thermal aging, there was a similar changing trend in the rheological and fluid‐loss properties of the muds with terpolymer concentration, regardless of the presence of aluminum citrate. After the thermal aging, some hydrophilic polycomplexes of AM‐AA‐AMPS terpolymer with aluminum citrate may have been formed and consequently inhibited viscosity loss of the muds, thereby improving the fluid‐loss properties. A possible mechanism is proposed to explain the improvement. J. VINYL ADDIT. TECHNOL, 2010.