Heat-Resistant Hydrogel for Temporary Plugging in High-Temperature and High-Pressure Fractured Reservoirs
Dalong Sun, Yang Yang, Wenjing Ma, Shuangxiang Ye, Hao Zhang, Jiang Zhang, Bin Yang
Abstract
Polymer hydrogels have shown considerable potential as materials for lost circulation control. Nevertheless, implementation in high-temperature and high-pressure (HTHP) formations has been challenging due to their poor thermal stability and strength. To overcome this limitation, a heat-resistant hydrogel (HT-Gel) composed of a terpolymer (PAAA) and chromium (III) acetate was developed in this study. PAAA was produced from acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and N-acryloyl morpholine (ACMO). The sulfonated groups of AMPS and the ring structure of ACMO endowed HT-Gel with favorable temperature resistance and pressure-bearing performance. HT-Gel gelled at 150 °C could effectively plug fractures of 0.1–5.0 mm, and the breakthrough pressure exceeded 4.0 MPa. After aging at 150 °C for 7 days, the elastic modulus only decreased by 14.29%. The gel strength and gelation time of HT-Gel could be adjusted by terpolymer concentration, cross-linker concentration, temperature, and salinity, which was beneficial for HT-Gel to enter and plug fractures smoothly. Additionally, HT-Gel exhibited exceptional resistance to shear and contamination. The viscosity of the gelants decreased by less than 16 mPa·s at high shear rates, and the elastic modulus of HT-Gel changed by less than 13% when combined with various drilling materials. Extensive laboratory experiments indicated that HT-Gel had outstanding thermal stability and pressure-bearing performance, making it a promising candidate for lost circulation control in high-temperature and high-pressure formations.