A Multi-Parameter While-Drilling Process for Detecting Abnormal Pore Pressure in Ultra-Deep Carbonate Formations: A Case Study from the Tarim Basin

Formation pore pressure is a critical parameter controlling drilling safety and wellbore stability, and its prediction in ultra-deep carbonate formations is challenging due to extreme temperature–pressure conditions, complex geological settings, and strong lithological heterogeneity. This study develops a multi-parameter while-drilling process that integrates drilling engineering parameters, mud logging gas measurements, cuttings-based elemental logging data, and drilling fluid performance indicators to investigate the processes governing abnormal overpressure and its real-time responses. By combining elemental logging parameters, rock drillability indices, and gas logging responses, a predictive framework for detecting abnormal pore pressure is established. The results show that structural position strongly controls overpressure distribution; secondary fault zones preferentially host abnormal overpressure; synchronous enrichment of S and Sr in cuttings-derived elemental data provides precursor signals; and gas logging indicators, including total hydrocarbon peaks and hydrocarbon migration velocity, are highly sensitive to overpressure. Application of the proposed while-drilling process to three ultra-deep wells (Fudong-101, Hade-18, and TKe-1) generated nine real-time pressure warnings, eight of which were confirmed, yielding a prediction accuracy of 88.89%. These results demonstrate that the proposed process effectively improves real-time identification of abnormal overpressure in ultra-deep carbonate formations, enhancing drilling safety and operational efficiency.