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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.
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.
Lost circulation while drilling across vugular or naturally fractured limestone formations is a costly challenge and has financial impacts including nonproductive time and remedial operational expenses. Many fields in the UAE are encountering notorious lost circulation complications, which are difficult to control with conventional lost circulation solutions while drilling surface sections. Novel lightweight thixotropic cement has proven beneficial to take control of severe losses in these vugular and naturally fractured limestone formations. The main challenge while drilling across the surface section in UAE offshore field is the heavy or total loss of returns. Drilling performance is affected due to poor hole cleaning, a risk of stuck pipe, surface fluid handling problems, and well control risks. Conventional extended cement slurries have been widely used to cure losses while drilling but with limited success. A new lost circulation solution combines lightweight (10.5- lbm/galUS) high solids fraction cement (trimodal system) and a thixotropic agent, which develop fast gels with high compressive strength. Thus, it enables plugging of large voids and fractures to deliver the wellbore integrity required to continue drilling with enhanced performance and efficiency. Intensive laboratory qualification tests focusing on static gel strength and compressive strength development was performed to tailor the new solution. The results were promising with more than 100 lbf/100 ft2 of static gel strength in 10 minutes and compressive strength development of 1,000 psi within 24 hours at low surface temperature. In addition, a transition time (TT) on-off-on test demonstrated more rapid gel strength development when the shear is reduced and regained fluidity with reapplication of shear. In one of the wells, heavy losses were encountered while drilling across surface section. The lightweight thixotropic solution was pumped for the first time worldwide and it was shown that the innovative lost circulation solution was effective in significantly reducing the losses and enabled the operator to continue drilling to section TD. This case study demonstrates that this advanced system is effective in curing losses and reducing nonproductive time. The unique properties of faster rapid gel strength and high compressive strength make this solution effective for treating a wide range of lost circulation events while drilling. Furthermore, the advanced lightweight thixotropic cement lost circulation solution exhibits strong performance in curing heavy losses and establishing well integrity with reliability.
One of the greatest historically unsolved challenges to date in the United Arab Emirates is the failure to effectively cure the severe losses due to poor zonal isolation during drilling and cementing aquifer formations in particular the Dammam, UER & Simsima formations in the BAB field. Continuous efforts have been made to seek and pilot new technologies in UAE land operations to overcome drilling operation challenges, specifically chronic lost circulation in aquifer formations with the commitment to drive a more cost-effective operation and reduce the risk of Non-Productive Time (NPT). The current practice was not providing proper zonal isolation in the surface and intermediate sections. Most of the time aerated drilling was utilized while drilling the lost zones and conduct a top-up cement job to improve zonal isolation, but this results in limited reliability. It was necessary to identify a different approach to cure or significantly reduce the losses which would enable the hole section to be drilled successfully while minimizing operational risks, in a cost-effective manner. A technique combining two different technologies was selected: a swelling polymer lost-circulation material (LCM) that hydrates and helps reduce flow velocity into the formation, followed by a shear-rate rheology-dependent cement system. This cement system is a tunable and tailored slurry with thixotropic properties and has shown very cost-effective results with high success rates. It was then decided to tailor this approach to Abu Dhabi land operations to maximize wellbore asset value. After four subsequent trials targeting two different aquifer formations, the technique has shown tremendously promising results by successfully curing the losses providing above 80% returns. These combined technologies aim to eliminate or reduce effect of losses during cementing by performing the primary cementing job with complete returns or minor losses across aquifers thus enhancing wellbore integrity during the lifecycle of the well. It is hoped that this will eliminate, or at a minimum reduce production deferrals and subsequently improve plug and abandon (P&A) operations at end of field life. This paper aims to describe the challenges faced on the first three trials utilizing this technique and the solutions assigned for each trial based on the inputs, such as loss rate, formations interval exposed, design and lab testing for the pumped treatments as well as job execution details along with lesson learned for future jobs.
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