Tannic acid-enhanced double network tough, heat-resistant hydrogel for water plugging in high-temperature oilfield

Preformed particle gels (PPGs) have extensive application potential for reducing excess water content in reservoirs due to their adaptability, stability, and deformability. However, the mechanical properties of conventional PPGs are poor, and the swollen particles are susceptible to damage when passing through formation fractures. In this paper, a novel methacrylated crosslinking agent (ChMA) was prepared and cross-linked with functional monomers to form the first hydrogel network, and then the ChMA crosslinking based double network structure hydrogels (CBDCH) were prepared by stepwise modification via tannic acid (TA). TA forms hydrogen bonds with amino, carboxyl, or sulfonic groups in the hydrogel through its phenolic hydroxyl groups, thereby promoting the formation of a physical crosslinked network. The CBDCH with double network structure exhibited excellent rheological and mechanical properties, including excellent elastic modulus (12,041 Pa), high strength (0.124 MPa) and high toughness (1.63 MJ m −3 ). In addition, the thermal stability of CBCH and CBDCH hydrogels were tested at different temperatures and salinities. The results showed that the CBDCH hydrogel has excellent thermal stability and better swelling properties at high temperature and high salt (10.29 at 120 °C). A core drive test was conducted on naturally fractured cores, and the results indicated that at a water injection flow rate of 0.5 mL/min, the breakthrough pressure of CBDCH was 180 psi/ft, demonstrating a significant blocking effect that meets the fundamental standards for water plugging in oilfields. This study highlights the potential of incorporating a dual network structure into PPGs to develop tough, temperature-resistant, and salt-resistant water-plugging materials.