A Proven and Versatile Coiled Tubing Live-Well Intervention Solution from a Mono-Hull Vessel in the Norwegian Continental Shelf

Abstract

The operator together with intervention-vessel company and several service providers together developed a versatile riser solution for coiled tubing (CT) operations from a monohull vessel already performing riser-less interventions. The solution covers 200 to 500 m water depths and converts back to riser-less after CT operations. From concept selection, a one-team approach was emphasized to drive project performance and involvement among participants and to develop a collective culture. The vessel team collected 3D models of all equipment to check interfaces and to develop a training simulator; physical interface checks were also conducted to verify space on the vessel. Due to harsh weather in the Norwegian Continental Shelf (NCS), a series of analysis and yard tests indicated the need for wellhead load relief systems, an extensive live-well returns and solids removal system, a CT pipe tension process and a CT tension frame (CTTF) for both CT and wireline (WL) together. The CT operations on 3 proof-of-concept wells were successful. The riser deployment and CT packages were rigged up and tested before the operation. During execution, CT was stabbed in the CT injector head after the riser was landed on the well; this eliminated the CT pipe clashing with the V-door during landing joint deployment and eliminated CT reel cycling due to heaves during standby. A rail system inside the CTTF converted from CT to wireline operations in under 3 hours with no crane nor winch. Metocean data indicated 1% of significant wave height (Hs) would exceed operating limits. Some of those waves occurred during CT operation. The experience demonstrated limits for Hs could be expanded above 3.0 m. Trace amounts of oil were recirculated and the operation was simplified when oil-water filters were bypassed. Initially, it took 6 days to run work-over riser, and by the third well this was reduced to under 4 days due to the robust common culture during the operation and a parallel deployment of the riser disconnect package. The CT option was demobilized after the operation and the vessel returned to riser-less operations with zero recordable health, safety, and environmental (HSE) incidents. In the NCS, these were the first CT live-well interventions from a monohull vessel. The 3 operations were performed with zero recordable HSE incidents. The novel vessel compensation system and CTTF demonstrated significant improvements in efficiency when swapping between wireline and CT. The innovative one-team approach was successfully emphasized and enabled fast learning and seamless integration of novel solutions from coiled tubing, wireline, well-test, subsea and other involved parties.