Brine-Based Riserless Fluid: Enabling the World's Most Deviated 24-Inch Section with Cost Optimization and Waste Minimization in Deepwater Malaysia

Riserless drilling is a critical phase in deepwater well construction, particularly in regions with complex shallow hazard environments such as offshore Malaysia. The absence of a riser and blowout preventer (BOP) during this phase necessitates a robust fluid system capable of maintaining wellbore stability, mitigating shallow water and gas flows, and ensuring effective hole cleaning and zonal isolation. Traditionally, freshwater bentonite-based dynamic kill drilling (DKD) mud systems have been employed for this purpose. However, these systems have shown limitations, including severe gumbo formation, hole washouts, and lead to poor zonal isolations, especially in highly deviated top-hole sections. To address these challenges, authors embarked on a multi-campaign initiative to evaluate and implement brine-based DKD mud systems. The objective was to enhance wellbore stability, reduce operational risks, and optimize fluid logistics and cost. This paper presents the journey across four (4) deepwater campaigns in Field-A, detailing the transition from conventional bentonite water-based mud to saturated calcium chloride (CaCl2) brine-based mud and ultimately to super saturated sodium chloride (NaCl) brine-based DKD systems. The study highlights the fluid design, testing, operational execution, and performance outcomes, culminating in the successful drilling and casing of one of the world's most deviated 24-inch top-hole sections. This work also integrates insights from global case studies and SPE literature on riserless drilling, shallow hazard mitigation, and fluid engineering. It demonstrates how brine-based DKD systems, when properly formulated and managed, can serve as a reliable and scalable solution for deepwater riserless operations, offering improved shale inhibition, reduced waste, and enhanced zonal isolation performance.