Abstract Drilling horizontal wells through weak and thermally sensitive shale formations requires addressing wellbore instability challenges, including equivalent circulating density (ECD) fluctuations and mechanical disturbances. This study focuses on engineering solutions that mitigate these issues in an unconventional hot shale reservoir, improving drilling efficiency and reducing non-productive time. The study employed a multidisciplinary approach combining geological analysis with engineering practices to address wellbore instability. Formation properties, such as mineralogy, natural fractures, bedding plane weakness, and mechanical behavior, were thoroughly evaluated to identify wellbore instability risks. To mitigate lateral wellbore instability, the drilling fluid design, managed pressure drilling (MPD) techniques, and bottom-hole assembly (BHA) optimization were assessed and refined. The enhanced hole cleaning protocols and effective cuttings management strategies, supported by real-time monitoring and optimized connection and tripping practices were implemented to further reduce risks of hole pack-off and stuck pipe and ensure an efficient drilling operation. The implemented measures significantly improved drilling efficiency and addressed wellbore instability challenges in the hot shale formation. Non-productive time (NPT) was reduced from 40.1% to 12.8%, reflecting more efficient operations. The use of flat rheology oil-based mud (OBM) generated low and stable ECD, which minimized stress on wellbore and reducing cavings, lost circulation, and pipe sticking events. The motorized rotary steerable system (RSS) BHA reduced mechanical vibrations, enhancing stability during drilling. MPD ensured precise pressure control and minimizing ECD fluctuation, further mitigating wellbore instability risks. The implementation of enhanced hole cleaning protocols and optimized connection and tripping practices improved cuttings management, reducing the incidence of hole packing and ensuring consistent wellbore conditions for subsequent logging and completion activities. These engineering interventions not only improved operational safety but also provided a replicable framework for horizontal drilling in thermally sensitive shale formations. The integration of advanced monitoring systems and optimized practices demonstrated that wellbore stability could be effectively managed, even in challenging geological conditions. The study highlights the importance of a multidisciplinary approach to address the complex mechanical and geomechanical challenges posed by unconventional formations, offering valuable insights for future drilling campaigns in similar reservoirs. This outcome validates the strategies’ effectiveness and underscores the need for continuous evaluation and adaptation of drilling techniques to maximize efficiency and minimize operational risks. This study advances the understanding of horizontal drilling in hot shale formations. Areas for further exploration include continuous circulation systems (CCS) and casing centralizer optimization, offering potential improvements in operational safety and efficiency.
Hong-jun et al. (Tue,) studied this question.