Abstract
This paper discusses the successful design, laboratory testing, and performance of an innovative, low solids, organophilic clay-free invert emulsion fluid (OCF-IEF) used to drill the reservoir section of an extended reach drilling (ERD) well. This specially designed drill-in fluid helped maintain the key ERD factors within the specifications necessary and set new limits for drilling performance, thus maximizing the horizontal section displacement/reservoir drainage and production output. ERD wells necessitate extensive design, planning, and close monitoring of various parameters to successfully complete the drilling and completion phases and deliver production expectations. While evaluating the feasibility of drilling the longest well in the UAE, establishing appropriate fluid system properties was a key focus area. The rheology profile was optimized for hydraulic management, hole cleaning, and fluid stability. The ground marble bridging package was designed to be minimally damaging. Lubricity and rate of penetration (ROP) maximization was also addressed by designing a low solids OCF-IEF in which the base brine was calcium bromide (CaBr2). This paper discusses the processes used during the planning phase, including laboratory testing and hydraulic simulations, and the procedures followed during the execution phase, which helped ensure trouble-free performance during drilling operations. Proper planning and execution using the best-available drilling practices helped enable the drilling of this record-breaking well, without significant issues that could impact rig time. The selection of an OCF-IEF to provide low equivalent circulating density (ECD) performance in a fragile gel fluid, with low sag risk, was fundamental to achieve the necessary fluid properties. The low solids design helped improve deployment of the weighting material (ground marble) compared to similar fields in which more conventional organophilic clay-based fluids were used. More than 18,000 ft were drilled in nine days with an average ROP of 2,000 ft/D, which set a record ROP in this field. As a result, the drilling operations were completed ahead of schedule and below the authorized financial expenditure (AFE). Additionally, the production rate was five times greater than estimated, thus confirming the anticipated nondamaging property of this OCF-IEF. The OCF-IEF design and performance brought within reach reserves not easily accessible using conventional mud systems and drilling techniques. The increased reservoir drainage resulted in significant productivity gains. This fluid can also be used during other operations to reach new target depths to maximize production.
