Accurate real-time estimation of pore pressure (Pp) is essential in high-temperature and high-pressure (HTHP) wells to prevent blowouts and lost circulation, given the complexity of their pressure regimes. However, conventional methods are inadequate: seismic-based and logging-based models are hindered by geological uncertainties, the dc-index principle is incompatible with PDC bits, and reliable while-drilling acoustic measurements remain prohibitively expensive. To overcome existing limitations, a surface-based and real-time Pp estimation framework is proposed, in which a direct Pp equation is derived by integrating an approximation using friction-corrected mechanical specific energy as the confined compressive strength (CCS) into the Mohr-Coulomb failure criterion. To ensure high-fidelity inputs for this equation, ridge regression is employed to invert rock strength parameters from drilling data, while a transient thermo-hydraulic model accurately calculates dynamic downhole pressure instead of relying on the static assumption. Validation on five HTHP wells in the Ying-Qiong Basin demonstrates that after accounting for thermo-pressure coupling, the method reduces the mean absolute error (MAE) in Pp equivalent density by 0.085 g/cm³ compared to the hydrostatic assumption. Furthermore, the proposed method achieves an MAE of 4.12%, outperforming the dc-index method, which achieves an MAE of 5.78%. Notably, the new method is more stable, with its prediction error envelope remaining within ±5%, whereas the dc-indexʼs error extends to ±10%. Given its theoretical compatibility with modern PDC bits and its demonstrated high accuracy, this surface-based and real-time scheme has the potential to overcome the conventional limitations of Pp estimation from surface data, providing a robust safeguard for well control in HTHP environments.

The gas kick represents a major risk in deepwater oil and gas exploration. Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control. In this paper, we introduce a transient wellbore multiphase flow model specifically developed to simulate gas kick in deepwater dual-gradient drilling, incorporating a downhole separator. The model accounts for the variable mass flow within the annulus and heat exchange between the annular fluid and the formation. Using this model, we analyzed the multiphase flow and thermodynamic behavior during the gas kick. Simulation results reveal a progressive increase in bottom-hole temperature, underscoring its potential as a key indicator for gas kick early detection. Additionally, variable gradient parameters affect not only the annular equivalent circulating density (ECD) profile but also the evolution of the gas kick. The inclusion of a downhole separator alters the annular ECD profile, creating a “broken line” shape, which enhances adaptability to the multi-pressure systems typically encountered in deepwater formation. By adjusting factors such as hollow sphere concentration, separator position, and separation efficiency, the annular ECD profile can be effectively customized. This study provides important theoretical insights and practical applications for utilizing dual-gradient drilling technology to address challenges in deepwater formation drilling.