Self-thickening mechanism of an amphiphilic polymer during acid rock reaction and performance testing

Using acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, and 2-acrylamido-2-methylpropanesulfonic acid as raw materials, an amphoteric ionic self-thickening acid ADAM was prepared. The viscosity changes of ADAM during the acid-rock reaction process were studied, demonstrating that the self-thickening behavior of ADAM depends on the concentration of Ca²⁺ in the solution. Specifically, the ADAM acid solution demonstrated a post-reaction viscosity increase of 110 mPa s, representing a rise of 183%. Temperature and shear resistance of the residual acid solutions were examined using the HAKKE MARS IV. After 1 hour of shear, ADAM retained viscosities of 123, 83, and 28 mPa s at 90, 120, and 150 °C, respectively. These values exceed those of the ADC system by 162%, 295%, and 211% under identical conditions. The ADAM formulation exhibits effective self-thickening capability, and its robust temperature and shear stability support its potential for large-scale application in high-temperature carbonate reservoirs.