Preparation of Ultratemperature-Resistant Cleaning Thickener and Research on the Mechanism of Acid Resistance

Acidizing systems are widely employed in the exploitation of carbonate reservoirs. However, the reaction kinetics of conventional hydrochloric acid are excessively rapid, and the penetration distance is limited. To address these issues, a purely cationic thickening polymer, ADDD, was designed and synthesized for ultrahigh-temperature reservoirs based on supramolecular interaction principles. The electrostatic repulsion between cationic groups alleviates the compression of the polymer’s electric double layer by H +, while the hydrophobic association structure imparts rigidity and thermal resistance to the polymer. The substitution of dimethyl diallyl ammonium chloride (DMDAAC) for the commonly used AMPS monomer further reinforces the polymer backbone, significantly enhancing its heat resistance, acid resistance, and compatibility with carbonate reservoirs. At 180 °C and a shear rate of 170 s –1, the viscosities of 15 and 20 wt % ADDD gelled acids stabilized at 40 mPa·s and 35 mPa·s, respectively, after 120 min of shear treatment. The gelled acid retained 45.83% of its viscosity after aging at 180 °C for 4 h. Its corrosion rate on P110SS was only 9.38 g/(m 2 ·h), corresponding to 9.73% and 15.27% of the rates observed for hydrochloric acid and AE gelled acid at the same concentration, respectively. Under conditions of 180 °C and 300 rpm, the acid–rock reaction rate of ADDD gelled acid was reduced to merely 12.5% and 50.68% of those of hydrochloric acid and AE gelled acid, respectively. The residual acid exhibited a viscosity as low as 1 mPa·s, and no obvious precipitation was observed. After breaking with 0.05 wt % ammonium persulfate at 180 °C, the viscosity of the ADDD gelled acid dropped to 1.5 mPa·s. The conformational differences between ADDD and AE in acidic media were collaboratively elucidated through zeta potential measurements and dynamic light scattering (DLS) analysis. Molecular dynamics simulations combined with analyses of H + diffusion coefficients, binding energies, and radial distribution functions revealed that hydrophobic association and cationic electrostatic effects synergistically enhance acid resistance and suppress acid–rock reaction rates. Meanwhile, electrostatic repulsion effectively prevented the incompatibility issues of the corrosion inhibitor that arise from amide thermal degradation under high-temperature conditions. The acid- and temperature-resistant thickener synthesized in this study provides technical and theoretical support for the development of ultrahigh-temperature carbonate reservoirs.