On the Norwegian continental shelf (NCS), coiled tubing (CT) cleanout requires small bites and frequent wiper trips to the surface due to potential sand bedding in a large and deviated completion. A real-time CT downhole measurement system is used to optimize the operation, following a dynamic workflow. Conventionally, the system is powered by downhole lithium battery, which limits CT downhole operating time. A continuous surface-powered system was needed to promote further optimization for such operation. A new hybrid electro-optical cable was introduced to enable continuous power supply from surface to the real-time downhole tool sensors. The system consists of a surface power module that sends power through a layer of low-DC-resistance conductors and optical fibers that enable data telemetry. Conventionally, only three to four trips can be completed before replacement of the downhole battery is required. Battery replacement can take up to 8 hours due to the complexity of that offshore environment. With the continuous power supply, the CT cleanout operation can continue for days without interruption of data from the downhole tool sensors. A three-well CT cleanout campaign in the NCS demonstrated the benefits of this new real-time downhole measurement system by using accurate downhole weight and torque readings to control the penetration through scale and avoid motor stalls. Sections of scale bridges were identified during the cleanout by monitoring fluctuations of downhole torque of the mill. The monitoring allows CT operators to control penetration rate and bite length during the cleanout. When the milled debris are swept, downhole weight is used to detect early signs of solids plugging around the mill. Downhole pressures complement surveillance of the sweeping of solids to the surface by giving a qualitative measurement of solids loading through conversion of the real-time bottomhole pressure reading into equivalent circulating density with changing CT depth. The process of optimizing bite length and sweeping speed is repeated without interruption thanks to continuous power supply from the surface, eventually leading to time reduction. In one of the wells, downhole tools uninterruptedly acquired data for 10 days straight. The CT managed to clean out a total of 40 908 kg of a mixture of scale and sand, with an estimated average time reduction of 25% when compared to CT cleanout without real-time downhole data. Delivery of continuous high-voltage power to downhole tools not only enables reduction in operating time, it also paves the way for extending the capabilities of CT interventions by enabling the operation of more electrically activated application tools. It allows combining multiple work scopes in a single CT run, which reduces operating cost and provides greater operational flexibility. Finally, eliminating the dependency on lithium batteries reduces the carbon footprint for a more sustainable operation.

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The limitations to performing rigless interventions in small platforms and safety concerns of performing multiple heavy lifts to the platform have motivated different locations worldwide to find solutions for accomplishing their objectives by utilizing proven techniques. In Brunei, after more than 8 years of continuous coiled tubing (CT) catenary operations, comprehensive and detailed processes have been strongly established and have created a guide that can be used for implementing similar operations in other locations that do not have such experience. A methodology was implemented to find the bottlenecks in each process involved during the entire cycle of a CT intervention as well as the actions taken by an operator and a service company to eliminate them. Statistical comparisons were used to contrast what was done in the past with what has been implemented in recent years. Additionally, new vessel positioning systems, improved disconnect systems, and proven safety considerations were analyzed, and a streamlined process to operation design, execution, and evaluation (DEE) cycles was developed. As a result of the process improvement documentation has been elaborated which include the flexibility and limitations of the system to cover concerns that are usually present in every stage of the intervention. Checklists and local guidelines will aid workers from other locations to implement catenary operations by using a reference document to cover HSE requirements and well integrity issues including volatile operating conditions and to obtain the information necessary to deliver technically challenging operations. This work supplements the current literature that addresses the "what" of past case histories by providing guidelines for the "how" to achieve an implementation of successful operations while complying with global HSE and environmental regulations. A priority of this work was sharing of knowledge obtained while giving space for continuous improvement related to this type of operation in the future.

Coiled tubing (CT) operations in the Norwegian continental shelf (NCS) often require a long and large-outside-diameter pipe due to big diameter completions, deep wells, and the need for high annular velocity during fluid circulation. However, getting the CT string onboard becomes a challenge when the crane lifting limit is 35 t, and using a standalone crane barge increases the cost of the operation. The alternative is spooling the CT from a vessel to the platform. Boat spooling is done by placing the CT string on a floating vessel with dynamic positioning while the standard CT injector head is secured at the edge of the platform to pull the pipe from the vessel to an empty CT reel on the platform. The boat is equipped with a CT guide; special tension clamps; and an emergency disconnect system, which consists of a standard CT shear-seal blowout preventer. The technique requires careful study of the platform structure for placement of the injector head support frame, metocean data of the field, and equipment placement on the vessel and platform. The boat spooling operation of a 7,700-m long, 58.7-t, 2.375-in.-outside-diameter CT string was successfully executed for a platform at 70-m height from mean sea level. The total operating time from hooking up the vessel to successfully spooling the string only took 12 hours. Historically for the region, the method has been attempted in sea state of up to 4-m wave height and 16 knots maximum wind speed. For this operation, the spooling was carried out during an average sea state of 2-m wave height and 15-knot wind speed. The continuous CT string allows a telemetry cable to be installed inside the pipe after the CT is spooled onto the platform reel, enabling real-time downhole measurements during the intervention. Such installation is not possible or presents high risk if the CT string is taken onboard by splicing two sections of pipe together with a spoolable connector or butt welding. From a cost perspective, the boat-spooling operation had up to 80% direct cost saving for the operator when compared to other methods of lifting a single CT string onboard, such as using a motion-compensated barge crane. The planning for the boat spooling included several essential contingency plans. Performing a CT boat spooling operation in a complex environment is possible and opens new opportunities to use longer and heavier CT strings, with lower mobilization costs. Such strings enable more advanced and efficient interventions, with the option of using real-time CT downhole measurements during the execution of a wide range of production startup work. This, in turn, is critical to support the drilling of more extended reach wells, which allow access to untapped reservoirs.