Influence of Temperature-Controlled Dual-Gradient Drilling Technology on Wellbore Stability in Polar Cold Marine Environments

During drilling operations in polar cold marine regions, heat exchange between the drilling fluid and the wellbore can induce melting of the permafrost near the wellbore, potentially leading to wellbore instability. Ensuring operational safety in such environments is therefore of utmost importance. In response, this study proposes an innovative “temperature-controlled dual-gradient drilling” technology. To highlight the effectiveness of this technique in improving the thermal and stress conditions within permafrost zones, the research comprehensively considers the coupled effects of temperature, hydraulic potential, and pressure on the migration and phase transitions of the soil skeleton, pore ice, and pore water. The stress distribution model of wellbore-adjacent permafrost is optimized and its stability evaluated accordingly. Based on this framework, the model is validated against experimental data from the literature, achieving simulation errors within 15%. Comparative analyses of a case well demonstrate that, relative to conventional dual-gradient drilling, the temperature-controlled dual-gradient technique significantly enhances the temperature and stress state in the permafrost region. The findings of this research provide an effective approach for assessing wellbore stability under drilling fluid–wellbore heat exchange in polar cold marine environments and offer valuable reference for the safe drilling of temperature-sensitive formations.