High-Performance Water-Based Drilling Fluids Offshore Cameroon

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 163502, ’High-Performance Water-Based Drilling Fluids: An Environmentally Friendly Fluid System Achieving Superior Shale Stabilization While Meeting Discharge Requirement Offshore Cameroon,’ by Anuradee Witthayapanyanon, SPE, Baker Hughes; Jerome Leleux, SPE, Julien Vuillemet, Ronan Morvan, and Andre Pomian, Perenco; and Alain Denax and Ronald Bland, SPE, Baker Hughes, prepared for the 2013 SPE/IADC Drilling Conference and Exhibition, Amsterdam, 5-7 March. The paper has not been peer reviewed. Historically, invert-emulsion drilling fluids are the preferred system for drilling offshore Cameroon. However, with a regulatory environment moving toward zero discharge, associated costs are rising. Therefore, an operator planning to drill in this environment investigated high-performance water-based-mud (HPWBM) -system alternatives. HPWBM systems offer the potential advantage of offshore discharge of drilled cuttings and effluents (owing to the absence of oil contamination) and lowered waste-management costs. Experience in the field demonstrated that the selected drilling fluid met expectations by achieving the required drilling performance and high shale stabilization with zero environmental impact. Introduction Drilling with an overbalanced pressure is a common operational technique used to prevent formation fluids or gas from entering the wellbore, thereby minimizing the risk of well kick and blowout. However, overbalanced drilling can cause drilling fluid to invade the formation, resulting in formation damage, differential sticking, and sloughing if the formation consists of highly reactive clay and shale. To avoid these consequences, invert-emulsion drilling fluids have always been preferable for drilling highly reactive clays and shale formations. The HPWBM system is formulated with a concept of total inhibition. Unlike a conventional water-based-mud system, designed chemical additives are used explicitly in the formulation to achieve desired drilling characteristics that are similar to those of invert-emulsion mud. The key features of HPWBM systems include high shale stability, clay and cuttings inhibition, rate-of-penetration (ROP) enhancement, minimized bit balling and accretion, torque and drag reduction, and environmental compliance. A complementary benefit of its aqueous base is that HPWBM captures the growing need for more-environmentally- friendly drilling fluids. During the past 10 years, more-stringent regulations on drilling-waste disposal have been implemented worldwide. The industry anticipates that the zero discharge of oil-contaminated drilling wastes will soon be the global standard. By switching from invert-emulsion drilling fluids (oil-/synthetic- based mud) to an HPWBM system, operators can achieve substantial cost savings on waste management and logistics. These savings result from the use of on-site, offshore discharge allowed by an absence of oil contamination.