Synthesis and Application of an Ultra-High Temperature Low Viscosity Filter Loss Reducer

Traditional polymer filter loss reducers have high apparent viscosity, causing high density cement slurries to have excessive initial consistency and hence affecting negatively operation safety. To deal with this problem, a low viscosity quaternary copolymer filter loss reducer SCFL-W was developed with four monomers: 2-acrylamide-2-methylpropanesulfonic acid, vinyl aromatic carboxylic acid, N, N-dimethylacrylamide and acrylic acid. The optimum reaction condition is: reaction temperature = 75℃, pH = 7, monomers’ concentration = 19%, and reaction time = 150 min. The molecular structure of SCFL-W is determined with FT-IR and TGA used to measure the thermal decomposition temperature to be greater than 380℃, meaning that SCFL-W has good thermal stability. Mechanism study proves that in the molecular structure of SCFL-W there are rigid side chains such as olefinic bonds and aromatic rings, among them entangling branches are difficult to form, thereby reducing the viscosity of the polymer. The excellent filtration rate control performance comes from the synergistic effect between the dense mud cakes formed under the action of the low-viscosity polymer and the static adsorption of the aromatic ring carboxyl groups. Evaluation of the performance of cement slurries treated with the filter loss reducer shows that SCFL-W retains most of its viscosity at elevated temperatures and has good compatibility with many additives. SCFL-W has good salt resistance. At 240℃, it reduces the API filtration rate of a saturated salt cement slurry to 45 mL. SCFL-W can be used in cement slurries with densities ranging in 1.88-2.4 g/cm³. Three well-times of field application of SCFL-W show that the quality of well cementing jobs is excellent. The successful use of this filter loss reducer has provided a new clue to the formulation of ultra-high temperature high density cement slurries.