Eastern Gulf of Mexico: Inhibitive Water-Based Drilling Fluid Sets Ultra-Deepwater Records

摘要

Two record wells were recently drilled in the ultra-deepwater Eastern Gulf of Mexico. The wells were the fastest two wells drilled in water depths greater than 7,000 ft in the GoM. A high-performance water-based mud (WBM) was used to drill the intermediate sections. The fluid had comparable performance to a synthetic-based mud (SBM), with the advantage of cuttings disposal permission in this environmentally sensitive offshore area. Significant savings were realized by not carrying the cuttings to shore for disposal. Other advantages included (a) no losses while running and cementing casing and (b) easier displacements. The fluid was re-used on two consecutive wells and then stored for further applications. The authors will detail the careful planning that coupled with fit-for-purpose solutions allowed setting these records while reducing the overall well cost. The wells were drilled in the Lloyd Ridge area of the Eastern Gulf of Mexico, categorized as "zero-discharge" for SBM cuttings. The use of the high-performance WBM saved the hauling and disposing of approximately 2,000 bbl of cuttings on each well. Cost savings were also accomplished by avoiding fluid losses when running and cementing the casing. On a similar project drilled completely with SBM, 2,156 bbl of mud were lost while running and cementing the 13(5/8)-in. casing. Comparison of drilling and economic performance of the new water-based mud and the synthetic-based mud are included in this paper to offer a comprehensive analysis. Also presented are innovative solutions introduced to optimize hole cleaning and shale inhibition.