Study on In-Situ Rock Mechanical Behavior and Wellbore Stability of Ultra-Deep Carbonate Formations in A 10000-Meter Well

The ultra-deep formations are characterized by complex geological structures and harsh downhole environments, resulting in frequent wellbore instability that has become one of the major technical problems restricting the exploration and development of ultra-deep oil and gas resources. In particular, the ultra-deep carbonate formations face even more complex and severe wellbore instability problems due to their highly-developed fractures and complicated geomechanical characteristics affected by the coupled effect of ultra-high temperature and pressure. Aiming at the ultra-deep carbonate strata of Sinian Dengying groups in the 10000-meter ultra-deep well with the most complex geological conditions and the highest drilling difficulty in China, this paper explores the variation law of rock mechanics properties under ultra-high temperature and pressure conditions. Based on the in-situ rock mechanical behavior and porous thermo-elastic theory, a wellbore stability analysis model for ultra-deep carbonate rocks has been developed. This study is helpful in solving the problem of wellbore instability in ultra-deep carbonate formations and can provide support for safe and efficient drilling in ultra-deep formations.