Temperature-Controlled Dual-Gradient Drilling for Arctic Deep Water: Process Design and Thermal Analysis

Summary Deepwater drilling in Arctic environments faces a narrow operating window due to temperature-sensitive permafrost and hydrate formations. While conventional dual-gradient drilling (DGD) manages pressure, it lacks active thermal control. To address this, we propose a temperature-controlled DGD (TC-DGD) technology that strategically relocates the injection point of low-temperature dilution fluid below the sensitive zone. A comprehensive hydrothermal coupling model was developed to simulate transient heat transfer, incorporating a power-law fluid rheology model to accurately characterize flow regimes. The model was rigorously validated against WOA23 oceanographic data, Yaha#501 field records, and laboratory freeze/thaw experiments. Numerical simulations indicate that TC-DGD establishes a continuous “thermal barrier,” effectively isolating permafrost from high-temperature returns, unlike conventional DGD, which causes annular temperature rises of 10–20°C. Parametric analysis identifies a critical injection flow rate of approximately 27.8 L/s for the modeled conditions; exceeding this threshold significantly expands the cooling zone. It should be noted that such quantitative operational thresholds are site-specific and must be calibrated according to local geological and wellbore parameters. In addition, an injection temperature of ≤ –5°C is recommended to ensure formation stability. The system exhibits a characteristic “cooling-then-warming” transient response, reaching thermal equilibrium after approximately 32 hours. This work defines critical operational windows and offers a robust theoretical framework for enhancing the safety of Arctic deepwater drilling.