Optimized Drilling Performance and Cost Efficiency by Utilizing Enhanced High Performance Water-Based Mud in Reactive Shale Formation, Mahakam Field, Offshore Area, Indonesia

Abstract In offshore drilling operations, particularly in the reactive shale formations of the Mahakam field, achieving optimal drilling performance and cost efficiency remains a significant challenge. Reactive shale formations are characterized by their tendency to swell and disperse when exposed to water-based drilling fluids, resulting in operational issues such as wellbore instability, stuck pipe incidents, and excessive fluid losses. These challenges negatively affect drilling efficiency, increase non-productive time (NPT), and escalate operational costs. To address these issues, a fit-for-purpose solution is required to balance economic considerations while effectively mitigating technical challenges. This study introduces and evaluates an Enhanced High-Performance Water-Based Mud (HPWBM) system, incorporating Enhanced Shale Inhibitor (ESI) as the primary shale inhibitor, as a viable alternative to the existing inhibitor-X. The study of Enhanced Shale Inhibitor (ESI) has been executed as a substitute for the inhibitor-X in the current HPWBM system. Field trials were conducted on two wells, XY-5 and XY-6. By mitigating the adverse effects of reactive shale, the Enhanced HPWBM system successfully reduces shale hydration, enhances cutting integrity, and minimizes bit balling, leading to smoother drilling operations and improved rate of penetration (ROP). The implementation demonstrated significant advantages. The XY-5 well achieved a 22.5% cost saving, equivalent to $101,733.54, compared to the existing mud system with inhibitor-X, while maintaining stable mud weight, effective rheology, and low dilution rates (0.42 m3/m). Similarly, the XY-6 well achieved a 3.5% cost saving, equivalent to $10,900.89, by reusing 240 m3 of treated mud from XY-5 well, highlighting the system's recyclability. This study highlights the economic and operational benefits of deploying the Enhanced HPWBM with ESI as the primary shale inhibitor, presenting it as a promising alternative solution for future drilling operations in challenging environments.