Аннотация
Summary Conventional polymer gels for lost circulation control often suffer from poor thermal stability in high-temperature (≥150℃) fractured formations, limiting their application in deep well drilling. This study successfully prepared a polymer gel (CHYG) suitable for deep well and complex formation drilling through molecular design and multiple crosslinking. Based on the terpolymer DAN-1, the synergistic crosslinking with hexamethylenetetramine (HMTA), catechol, and resin curing agent under high-temperature conditions results in the formation of the CHYG gel with a multiple physicochemical crosslinked network. The chemical structure and thermal stability of CHYG were confirmed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). Rheological tests revealed that the gel solution exhibited a viscosity reduction of approximately 22% within the shear rate range of 0.1–100 second⁻¹, with significant hysteresis during shear rate cycling, indicating good shear resistance and thixotropic behavior. At 150°C, the gel exhibits controllable gelation (~5 hours) and excellent long-term stability. After aging for 12 days, the viscosity retention relative to the initial unaged value was approximately 86.1%. The gel resists formation water contamination (~81% viscosity retention after 3:1 mixing) and can be weighted to 1.5 g·cm⁻³. Controllable breaking (>96% efficiency within 48 hours) minimizes reservoir damage. In fracture models, the gel achieves a pressure resistance of 8.46 MPa in a 1-mm fracture. This work provides a promising polymer gel system that combines thermal stability, contamination resistance, and strong plugging performance for lost circulation control in deep, high-temperature, fractured formations.