Preparation of water self‐dispersible nano‐ <scp> CaCO ₃ </scp> and its enhancement of P( <scp>AM</scp> ‐ <scp>SA</scp> ‐ <scp>MO8</scp> ) gel for profile control

Abstract In this paper, a novel water self‐dispersible nano‐CaCO 3 was obtained by surface modification method using the betaine surfactant as the modifier and its potential to enhance the performance of polymer gels for enhancing oil recovery was investigated. The synthesis conditions of nano‐CaCO 3 and the formulation of polymer gel profile control system were optimized. Based on the experimental results, the recommended synthesis conditions for nano‐CaCO 3 are as follows: calcium oxide slurry concentration of 5%, laurylamine propyl betaine (LAB) dosage of 0.6 wt.% to calcium oxide, carbonation temperature of 10°C, using a 0.5 μm aeration head and a gas flow rate of 0.1 L/min. The product is referred to as LAB‐CaCO 3 . The optimal formulation of polymer gel profile control system is 1500 mg/L LAB‐CaCO 3 , 5000 mg/L polymer, and 3500 mg/L crosslinker. This system can achieve a blocking efficiency of 98.51% and an enhanced oil recovery rate of 35.4%, demonstrating long‐term stability and excellent profile control performance. The findings of this study provide valuable insights for the development of polymer gel profile control in oilfield.