Customized HPWBM Using Dual Brine System to Provide Wellbore Stability in Exploration North Madura Offshore Indonesia

Abstract

The Water-Based Mud (WBM) system was planned to be used in drilling at Offshore North Madura, Indonesia. However, a review of offset wells found they experienced issues while drilling and running the casing. Designing a proper WBM is the key to successfully drill into problematic clay. This paper shares the optimization done by using a combination brine in High-Performance Water Based Mud (HPWBM) to minimize the potential risk of time dependent shale in the North Madura area. A series of shale reactivity and WBM performance tests such as CEC, CST, Shale Erosion Test, Shale Accretion Test, Swelling Test, and Lubricity Test were performed using the representative cutting samples from the offset wells. The testing used a combination of KCl & NaCl and a single NaCl, with an inhibitor combination added of polyamine, encapsulation, and non-ionic polymer blended with glycol to give the optimum results. This fully formulated HPWBM to provide the most effective inhibition and lubrication was tested and evaluated prior to drill the exploration campaign. The HPWBM with dual brine combination was successfully implemented in the well. The formulation facilitated the execution of the exploration well and provided good penetration rate, wellbore stability, and lubricity. There was an unexpected occurrence whereby the Driller Cyber System malfunctioned, causing the draw works to be unable to move and stay in the same position which suspended operation for 96 hours. However, the mud system proved to be stable during the troubleshooting of this problem. There was no issue related to the mud system during the drilling and casing job. The cementing job proceeded smoothly with no excessive cement required which meant that the well was still within acceptable hole-gauge range. No Non-Productive Time (NPT) was recorded related to the mud execution. By executing the HPWBM properly, the company saved around 7% of the planned mud cost to drill the section, from a reduced system maintenance of the HPWBM which required less dilution compared to a regular WBM. This paper shares the novel approach of using a brine combination formulation in designing the HPWBM system to provide a better result than the previously formulated WBM.