This paper discusses how an organophilic clay-free invert emulsion reservoir drill-in fluid (OCF-IEF-RDF) was customized to successfully break the longest well record in the Middle East and North Africa region and the 4th longest extended-reach drilling (ERD) well globally. The successful design included extensive lab testing to optimize performance of this innovative low-solids OCF-IEF-RDF used to drill the 25,415 ft. horizontal reservoir section. This specially designed drill-in fluid reduced key risks for drilling ERD-type wells and kept parameters within necessary specifications to set new limits for drilling performance, maximizing horizontal section displacement/reservoir drainage, and production output.

Challenges and risks related to drilling extended-reach wells require particular focus on the drilling fluid design in order to meet these challenges and to mitigate the risks. In addition, proper planning beforehand, and close monitoring and control of many fundamentally important parameters when drilling are required in order to execute successfully the drilling and completion phases for such wells. While evaluating the feasibility of drilling this well, establishing appropriate fluid system properties was a key focus area. The rheology profile was optimized for hydraulic management, hole cleaning, and fluid stability, and the ground marble bridging package was designed for minimum damage to the reservoir. Lubricity and rate of penetration (ROP) maximization were addressed by designing a low-solids OCF-IEF-RDF where the base brine was calcium bromide. The paper shall discuss both the processes used during the planning phase, including laboratory testing and hydraulic simulations, and the procedures followed during the execution phase, and how they helped ensure trouble-free performance during drilling.

Proper planning and execution, using best-available drilling practices, enabled drilling of this record-breaking well without encountering significant issues that could impact rig time and increase costs. Selection of an OCF-IEF-RDF to provide low Equivalent Circulating Density (ECD) performance in a fragile gel fluid with low sag risk was fundamental to achieving required fluid properties. The low-solids design improved ease of deployment of the weighting material (ground marble) compared to similar fields where more conventional organophilic clay-based fluids are used. More than 25,415 ft. were drilled in 9 days with an average ROP of 216.8 ft. /hr. and 216.6 Rotating Hours and the best 8.5" daily footage of 4,121 ft. in the field. This resulted in the completion of the drilling operations ahead of schedule. This well is the longest single deployment production liner globally – 25,637 ft. and 4th Longest well drilled globally and longest well drilled in Middle east. In addition, production rate was as expected, confirming the anticipated non-damaging property of this OCF-IEF-RDF.

The OCF-IEF-RDF was specially designed to deliver down-hole properties and behaviors that would deliver low ECD to Equivalent Static Density (ESD) margins. Without this superior control over ECD, the milestones above would not have been possible. It brought innovation to reality, which maximized returns by accessing reserves not easily accessible with conventional mud systems, drilling techniques, and saved on infrastructure costs. This increased reservoir drainage and resulted in significant productivity gains. Pushing the limit of this challenging condition can continue to break records in the future.

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