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. © 2009 Society of Plastics Engineers