High Performance Water-Based Drilling Fluids - An Environmentally Friendly Fluid System Achieving Superior Shale Stabilization While Meeting Discharge Requirement Offshore Cameroon

Abstract

Abstract Historically, invert-emulsion drilling fluids are the system-of-choice for drilling offshore Cameroon due to minimum NPT, high ROPs, ease of maintenance, robust performance under various downhole conditions, and the resulting lower drilling costs. However, with a regulatory environment moving toward zero discharge, the cost of the waste management associated with invert-emulsion drilling fluids is diminishing their attractiveness. Therefore, when the operator was planning to drill their next development well offshore Cameroon (BaF field, Douala Basin), they evaluated high-performance water-based mud system (HPWBM) alternatives. HPWBM systems offer the potential advantage of offshore discharge of drilled cuttings and effluents due to absence of oil contamination and lowered waste management costs. This paper documents the advantages of the selected HPWBM, and its design and performance characteristics in stabilizing reactive clays/shale. Specially designed chemical components in the HPWBM formulation created an efficient osmotic membrane, thereby minimizing pore pressure transmission under downhole conditions. This HPWBM system is one of the first commercial applications of nanotechnology in drilling fluids. The field recap demonstrated that the selected high performance water-based drilling fluid met expectations by achieving the required drilling performance and high shale stabilization with zero environmental impact. Finally, the paper reviews the cost reduction in waste management when switching to the environmentally friendly high performance water-based mud system.