The Synthesis of ATP Loaded Heterocyclic Amphoteric Copolymer and Its Performance and Mechanisms of Reducing Filtration Rate under Ultra-High Temperatures

The AMPS copolymer filter loss reducers have obvious thinning effect which is detrimental to the ultra-high temperature settling stability cement slurries. To solve this problem, an ultra-high temperature cement slurry filter loss reducer ATP-FLA is developed for use at elevated temperatures to weaken the high temperature dispersion side-effect of pure copolymers. ATP-FLA is synthesized as an attapulgite (ATP) loaded heterocyclic amphoteric copolymer. Comparison of the copolymer with and without ATP loading shows that in a temperature range of 150-240 ℃, a cement slurry treated with 4.0%-6.0% ATP-FLA and 2.0%-4.0% suspending agent has API filtration rate of less than 40 mL and density difference from settlement of the cement slurry of not greater than 0.03 g/cm³. After aging at 240 ℃ and 120 MPa, the cement slurry has flow index of 0.897,6 as well as high thickness and shear resistance at high temperatures. To evaluate the compatibility of the filter loss reducer ATP-FLA, ultra-high temperature cement slurry samples were taken from several wellsites. The evaluation test results show that the ATP-FLA can control the filtration rate without affecting the other properties of the cement slurries. Study on the working mechanisms of ATP-FLA using molecular dynamics shows that ATP-FLA has advantages over conventional ionic copolymers in that the disturbances to the molecular chains of ATP-FLA from the “dehydration” effect of metal ions in the environment are weakened, and the ATP-FLA molecules are therefore resistant to the attack of the metal ions, and this is why, on the basis of mechanisms, the ATP-FLA filter loss reducer is more adaptable to the metal ion environment prevailing in cement slurries.