Since the Bureau of Safety and Environmental Enforcement (BSEE) released and implemented the updated version of the Code of Federal Regulations (CFR) in recent years, Operators now have the need to reenter wells that had been deemed as abandoned in the 1980’s, and perform operations to comply with the updated regulations. All of these wells have surface plugs (either cement plugs or cast iron bridge plugs) that require milling in order to access the wellbores to be abandoned. The use of a pulling unit is generally the method used for these abandonment operations. However, the risks of having pressure trapped below those surface plugs, and the ability to maintain well control during milling operations with the pulling and jacking units (PJU) poses a great concern to the Operators. Upon evaluation, Shell decided to use large outside diameter (OD) coiled tubing (CT) to mill the surface cement plugs and the cast iron bridge plugs. The use of CT enabled several operational advantages, such as the ability to handle potentially live well situations safely and efficiently, faster operations to mobilize (mob) from well to well, the use of larger bottom hole assemblies (BHA) with mills manufactured to drift the different casings 7", 9 5/8" and 10 ¾" inner diameter (ID), ensure optimal downhole motor (DHM) performance and to provide efficient removal of solids from the wellbore back to surface. This paper describes the CT operations performed on two shallow waters platforms projects in the GoM for Shell, where a total of 9 wells were intervened using 2 3/8" and 2 7/8" OD CT. The challenges encountered together with the developed solutions, equipment used, lessons learned are also discussed. Full compliance with BSSE regulations for well abandonment was the final result.
Demand for subsea well intervention work has continued to be strong for the last 10 years. Even though subsea well interventions from an intervention vessel represent only a fraction of the total well workover activity in the Gulf of Mexico (GoM), its operating environment poses challenges in meeting economic goals for the Operators. The Q4000, a purpose-built, multi-service dynamically positioned (DP) vessel, was first introduced in the GoM in April 2002 and has been extensively used to meet demand of subsea well intervention and abandonment. Coiled tubing (CT) intervention, along with Slickline and Electric Wireline, has been instrumental in supporting the Q4000 ability to maintain safe, reliable, and cost efficient subsea through tubing well interventions in such a demanding operating environment. This paper will summarize the operational experience and will focus on the CT-specific best practices and lessons learned that have resulted from over than 10 years of continuous operations on the Q4000. The document will highlight critical stages in the learning curve, standardized procedures, synergies between the CT and the Q4000 crews, and their impact on safety, efficiency and cost reduction. The paper will also discuss the needs for further improvements that will be required to meet the new challenges that subsea well intervention will be facing in the future.
The future of exploration and production (E&P) operations in the Gulf of Mexico (GoM) is focused on deep water, that is, >5,000 ft [1,524 m] water depth. As the industry pushes the envelope to reach deeper reservoirs, subsea wells have become an important part of the offshore production. Although subsea completions may offer significant economic and environmental advantages over seafloor-founded structures, they require floating drilling or well intervention vessels to enable wellbore access should a workover operation be required to maintain production at an economic level or even to plug and abandon (P&A) the wells once they become uneconomical to produce. Interventions and P&A operations are very costly and may involve multiple services. The P&A of subsea wells represents no financial upside to the operators, other than the possible recycling of the subsea trees. Consequently, reducing costs and avoiding future environmental liability are the prerequisites for successful subsea decommissioning. Riserless subsea P&A operations are often completed by setting the plugs with drillpipe after the production tubing is removed with the rig. As part of the operational improvement process, a coiled tubing (CT) service company evaluated the option of performing this task using the riserless CT technique from a multiservice vessel (MSV) after the zonal and casing isolation packer had been successfully set and tested. This technique would allow the operator to save time to complete these operations, thus reducing the cost. Between 2010 and mid-2015, the CT service company has successfully completed 18 riserless subsea interventions at well depths ranging from 4,900 ft to 21,000 ft [1,494 m to 6,400 m] and water depths from 4,600 ft to 7,000 ft [1,402 m to 2,133 m]. Riserless wellbore access with CT has proved to be an efficient P&A method that has helped reduce operating time by up to 40% as compared to riserless workover rig-based operations. Detailed engineering and planning as well as continuous improvements have allowed implementing the CT riserless technique in accordance with the Bureau of Safety and Environmental Enforcement regulations.
Objectives/Scope The latest developments in well construction demand equipment that defies the current industry limits to access the full length of the pay zones in 40,000+ ft wells. With the growing trend of drilling horizontal wells in the mega reach category and beyond, there is a need for a new level of engineering design of Coiled Tubing (CT) strings and downhole technology with a specific approach to reach these new and expanding requirements. Methods, Procedures, Process Extended reach conveyance of CT is a challenge that service companies and operators have progressively addressed as wells are drilled deeper into the mega reach area. Advanced CT string designs and materials, as well as systematic variations of parameters affecting friction coefficients between CT and wellbore completions, provide benefits to operators in extending the reach of the horizontal sections. Special downhole tools and engineering testing are required to plan the best outcome from the available downhole force technology to increase wellbore coverage while maintaining well underbalance, reducing operational footprint, and safely deploying the heaviest 40,000 ft 2-3/8 in CT pipe offshore. Results, Observations, Conclusions This paper describes the systematic process used to address the mega reach challenges, as CT is required to reach Total Depth (TD) in wells longer than 40,000 ft in one offshore oil field in Abu Dhabi. It summarizes the considerations taken to design the right string for the project and describes the multiple technologies used to extend the reach of the CT in the horizontal sections while remaining underbalanced. Additionally, this paper discusses the implementation of a surfactant-based Friction Reducer (FR) system to extend the CT reach and the friction matching analysis performed while calculating the extended lock-up depth. In addition, the special transportation solutions to deploy the CT reel to the wellhead are discussed, along with the track stack required to make these operations possible. Novel/Additive Information Detailed data collected throughout the campaign enabled the operating company and the service company to benchmark the results of the operations, drawing better conclusions well after well and enabling a positive loop of improvement leading to economic gains as the campaign was executed. Technical challenges, downhole tools, and fluid solutions to reach TD Transportation solutions for mega reach CT string deployment
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.