Korchagina and Filanovskoe oil fields in the north Caspian Sea have many extended- and mega-reach wells that uses inflow control device (ICD) screen completions with sliding sleeves. This completion technique empowers the operator with the ability to shut off unwanted water/gas breakthrough and allows for more control of injection or inflow with unlimited number of stages or zones. This paper describes a new verified workflow to successfully intervene these wells and manipulate (open/close) these sliding sleeves using coiled tubing (CT). It has proven challenging to shift these sliding sleeves using conventional methods with CT owing to the limitation of available weight on bit (WOB) at the toe end of those extended-reach wells, even when using large-size CT strings. The new proposed workflow uses a well tractor operated in tandem with a hydraulic shifting tool to generate the required shifting force downhole. The bottomhole assembly (BHA) also includes a novel flow control sub, assembled between the shifting tool and the tractor, with the ability to control the flow to selectively activate the tractor, the shifting tool, or both, based on surface commands by manipulating pump rate. To verify the methodology, a realistic well scenario was simulated at a test site by installing two ICD screens with sliding sleeves at the end of a 1,000-ft-long horizontal flow loop. The sleeves on each ICD screen required approximately 4,000 lbf set-down force to open. The available WOB at the end of horizontal loop with 2-in. CT was only 1,000 lbf; applying more than 1,000 lbf set-down load could have detrimental effects, including CT buckling. The 3⅞-in. OD well tractor used for the job was able to generate 6,000 lbf of pulling force downhole, which was more than enough to shift the sleeves open. Both sleeves were successfully opened by tractoring down while maintaining both the tractor and the shifting tool in the on position, which was achieved by manipulating the flow control sub using pump rate cycles. Both sleeves were then successfully closed, one after the other, by pulling with the CT with the tractor turned off while maintaining the shifting tool in the on position, again achieved by manipulating the flow control sub. Live downhole pressure and force measurements were key in confirming proper functionality of the tractor and identifying different tool modes. Having real-time data is also crucial for proper depth correlation using casing collar locators (CCL) or gamma ray measurements to ensure activating the correct sleeves. This marks the first time that a workflow was verified on the use of pull force generated by a well tractor to manipulate completion accessories in extended-reach well interventions using CT. The technology, preparation, results, and prospects of implementation are discussed in this paper.
On the Norwegian continental shelf, well interventions often use wireline's relatively small equipment footprint and weight. However, some operations still require fluid conveyance to specific depths, for which coiled tubing (CT) remains the only possible, economic option. Challenges related to reach and to achieving high annular velocity require the use of large-diameter CT. However, with crane capacity ranging from 30 to 48 t, lifting such strings is not possible. The alternative is joining CT pipes offshore. The conventional way of joining two strings offshore is by creating a butt weld, which connects parts that are nearly parallel and do not overlap. This welding technique, if done onsite, has been long known to decrease CT life by 50% at the weld location. In addition, welding activity offshore raises significant safety issues. Another method of splicing two CT strings consists in using a spoolable dimple connector. Recent engineering advances have addressed several operational challenges related to those connectors, such as fatigue caused by cycling and pressure, ballooning around the dimple area, pressure sealing, and material corrosion. The spoolable dimple connector was used in two CT intervention campaigns to achieve operation objectives in terms of reach and pumping rate. Those operations put forward considerations that must be accounted for during the planning phase. The connector placement was determined by carefully simulating weight distribution to minimize axial load on the dimple area. Several best practices were captured when the equipment was assembled and during interventions to increase integrity of the connector. Detailed measurements allowing for the connector wear and performance monitoring were taken under various work scopes, including cement squeeze and milling, plug setting, perforations, proppant cleanout, and sliding sleeve shifting. Significant improvements in performance with regards to the number of bending cycles and running meters were achieved with this new connector design. For instance, the operations under consideration saw a single connector clocking up to 33,600 running meters in chrome completions. Using a large-diameter CT can now be included as an option for various well intervention work scopes in places where crane lifting capacity is limited. The use of a redesigned spoolable connector allows for more extended reach wells to be drilled and a wider selection of completion size to be installed. It also paves the way for well startup operations that require fluid conveyance, such as proppant fracturing because post-fracturing cleanout can now be performed using CT.
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