Aqueous hydrochloric acid (HCl) systems suffer from high corrosivity and limited effective penetration depth, posing major challenges for acid fracturing in deep carbonate reservoirs. A novel autogenous solid acid, SA-G, was developed through anhydride-amine nucleophilic substitution to overcome these limitations. SA-G was systematically analyzed through high-temperature dissolution experiments, rotating disk corrosion tests, and fracture conductivity evaluations. SA-G exhibits a solubility of 70.3 g/100 mL at 25 °C. A 25 wt % SA-G solution generates acid continuously for 2.5 h at 180 °C, equivalent to a 14.36 wt % HCl concentration, with an etching efficiency of 91.14% at 95 °C. The dynamic corrosion rate at 180 °C is 61.97 g/(m2 h), and the acid-rock reaction kinetic rate is as low as −3.75 × 10–4 mol/(s cm2), demonstrating ultraslow-release characteristics at ultrahigh temperatures. Alternating injection of SA-G and gelled acid at 10 mL/min effectively etched rock plates, achieving a fracture conductivity of 17.67 D cm under 30 MPa closure stress. In field applications, SA-G was continuously delivered via a fracturing blender truck at a pumping rate of 9–10 m3/min, enabling acid fracturing in a 140 °C reservoir with reduced fracturing pressure and enhanced communication with natural fractures. SA-G overcomes the limitations of conventional liquid acids in equipment corrosion and penetration depth through its in situ slow-release acid-generation mechanism, providing a safe and deeply penetrating technical solution for efficient stimulation of ultrahigh-temperature carbonate reservoirs.
Zhang et al. (Tue,) studied this question.