Riserless coiled tubing intervention cuts time and cost by half

HEIN KRISTIAN JACOBSEN, TechnipFMC 

Operators are turning increasingly to riserless solutions, using vessels for subsea light well intervention (LWI), instead of traditional rig-based operations with risers. Riserless light well intervention (RLWI) saves time and reduces costs for operators, whether in shallow or deep water. LWI vessels offer simpler and faster deployment, and when combined with riserless systems, they deliver safer and more reliable performance. 

Until now, RLWI was limited to wireline or slickline for operations such as well logging, perforating, setting and pulling plugs, other maintenance tasks, and decommissioning. When coiled tubing (CT) was required, operators had no choice but to revert to costly, complex riser-based systems, forfeiting the benefits of RLWI. 

EXPANDING RLWI TO COILED TUBING 

Fig. 1. The Island Constructor vessel, outfitted with Pivotal Riserless Intervention service and coiled tubing before transit.

TechnipFMC has recently introduced the comprehensive Pivotal Riserless Intervention service, adding CT capability to the riserless toolbox. By eliminating the need for risers, this innovation delivers numerous advantages: 

• Up to 50% cost savings, compared with traditional methods 
• Nearly 75% emissions reduction, advancing operational sustainability 
• More than 25% fewer personnel on board (POB), reducing exposure risk 
• Reduction in rig-up time, down from days to hours. 

WALKING THE RLWI WALK ON THE PATH TO INNOVATION 

For more than two decades, TechnipFMC has established a solid presence in RLWI operations, where they service more than 1,000 wells. Average RLWI operational time has dropped by nearly two-thirds, with interventions over the past nine years averaging less than seven days per well. RLWI typically uses a monohull vessel equipped with remotely operated well control systems to perform seabed operations, including production enhancement, data acquisition and advanced services for plug and abandonment (P&A). 

Building on this foundation, TechnipFMC pioneered riserless coiled tubing (RLCT), initially for core retrieval and pilot-hole drilling and later expanded to logging, milling and jetting and P&A. Working closely with CT provider Halliburton, we developed seamless transitions between wireline and slickline conveyance to CT—making the switch in just hours, as often as needed. This dual capability enables operators to select the most efficient conveyance method for each live well operation from the same vessel, optimizing performance and cost, Figs. 1 and 2.

Fig. 2. TechnipFMC’s riserless intervention equipment deploying Halliburton’s coiled tubing subsea from the Island Constructor vessel.

IMPROVING ON TRADITIONAL RISER-BASED CT  

RLCT combines vessel mobility, wireline agility and CT for a full range of riserless well intervention and P&A operations. Operators retain all the benefits of rig-based CT, including: 

• Effective fluid circulation 
• Precise cement plug placement with minimal contamination 
• Perforating/washing/cementing (PWC) operations for P&A. 

Unlike riser-based CT, RLCT requires no tension frame or rigid connection to the seabed. Active heave compensation (AHC) is engaged only when the bottomhole assembly (BHA) is ready for lubrication. BHA rig-up and rig-down occur at the moonpool level, eliminating the need for personnel at hazardous heights in the tension frame. 

Because RLCT transmits less force to the subsea tree and wellhead, it significantly reduces integrity risks—especially in shallow-water environments or during decommissioning of older wells. RLCT operates with higher efficiency and safety by using the vessel’s dynamic positioning, as opposed to the need for mooring or blowout preventer (BOP) tethering, which becomes a requirement for riser-based solutions in shallow water. 

KEY TECHNOLOGY FEATURES 

At the heart of the RLCT’s capabilities are TechnipFMC’s subsea stripper and injector, which replace the pressure control head (PCH) used for wireline or slickline operations. The subsea stripper (Fig. 3) uses three duplicate sealing elements—similar to those used for surface CT applications—to provide redundant, effective sealing around the CT, even in worst-case scenarios. The subsea master injector works with the surface injector to maintain CT tension between vessel and seabed. 

Because the stripper and injector are retrieved to surface when changing the BHA, the sealing elements can be replaced, as needed, between runs. 

The subsea master injector pushes the CT into the well by overcoming stripper friction and extrusion force caused by borehole pressure acting on the CT cross-section. Working in tandem with the surface injector, it maintains CT tension between the vessel and the seabed. 

A standard CT injector at surface is mounted on a heave-compensated platform that runs along the rails of the tower cursor system. The CT injector and cursor system are suspended from the tower’s winch and are actively and passively heave-compensated. The remaining components of the CT spread are standard equipment, configured to meet the specific requirements for each project. 

The RLCT system also integrates advanced capabilities, including real-time data acquisition, high- and low-cycle CT fatigue prediction and monitoring and continuous measurement and recording of forces acting on the stack via sensors. 

A PROVEN TRACK RECORD OF RLCT  

Pivotal Riserless Intervention was developed in the demanding conditions of the North Sea, where nimble vessels are essential for exploiting narrow weather windows, and where the ability to pivot seamlessly between wireline and CT operations delivers unmatched flexibility. 

The first deployment of RLCT took place in 2014, when the technology was used to drill and recover core samples from hard-rock deposits of granite, quartz and schist at a fjord outlet. In water depths up to 300 m, 52 RLCT runs were made within three wellbores, along a future tunnel route with 2 7/8-in CT over four weeks. Maximum deviation of the wellbores drilled was 55°. A 5 7/8-in rock bit was used for obtaining 150-m cores, across a total drilled length of 537 m in the wells. 

After coring, the wells were abandoned by filling with cement. Successfully obtaining core samples to verify rock quality also eliminated the need for a drilling rig, improving project efficiency and economics. 

SHALLOW WATER? NO PROBLEM FOR RLCT, UNLIKE RISER-BASED OPERATIONS  

In 2015, Centrica contracted TechnipFMC to drill a critical pilot well for shallow gas detection in Butch field on the Norwegian Continental Shelf (NCS). Given the location, the project required compliance with stringent regulations from the Norwegian Petroleum Safety Authority (PSA), but an additional complication was the shallow water depth of only 66 m. Rig-based riser drilling in such conditions is complex, often requiring fixed platforms, jackups or moored rigs, which drive up costs and safety risks. 

It took only four-and-a-half days on location to easily conduct two 2 ⅞-in CT runs in the 351-m pilot hole. After drilling the pilot well with a 5 ⅞-in tricone bit, RLCT was used to obtain a gamma ray, resistivity, pressure, directional inclination and sonic logging suite. The well was then cemented and abandoned, in compliance with strict regulatory requirements.  

ULTRADEEPWATER RLCT CORING OPERATION CONQUERS HARD VOLCANIC ROCK 

Mineral resources on the NCS were initially mapped by the Norwegian Petroleum Directorate (NPD), using geophysical data and seabed samples collected by ROVs. However, data gaps remained, concerning the thickness of potentially economic deposits of seabed massive sulfides (SMS) and iron-manganese (Fe-Mn) crusts, for estimating resources in place. To obtain this necessary information, NPD awarded a contract to TechnipFMC, to collect core samples via RLCT in multiple locations along Mohns Ridge. 

TechnipFMC outfitted an anchor-handling tug supply (AHTS) vessel with a dedicated vertical cursor, attached to the AHC winch cable for effective compensation of vessel motion, while BHA movement was controlled with the CT surface injector. A pipe-handling and make-or-break unit for connecting and disconnecting the coring BHA was also installed. 

Fourteen gravity-fed RLCT coring runs were executed in water depths between 2,780 and 3,085 m in just 26 days. Although four runs returned empty, a total of 54.6 m was cored, of which 9.9 m was recovered for an average recovery rate of 18%. While this may seem modest, it represents a significant success, given the extreme conditions, and is more than 40% higher than obtained by the Ocean Drilling Program, using drill pipe coring in a comparable environment. 

RLCT’s robustly efficient and effective operation was completed in only 46 days from mobilization to demobilization, despite extended waiting-on-weather time during the deteriorating autumn weather conditions. The entire coring project was executed from receipt of the tender to completion of coring operations in less than five months  to provide critical data to the NPD.  

World’s first riserless CT intervention in a live well returns suspended well to production in just 33 days. An operator sought to bring a 4,000-m deep North Sea well back online, after several years’ suspension. Concerns included protecting the fragile, older wellhead—limited to 2,500-psi casinghead pressure—and avoiding further formation damage.  

The Pivotal Riserless Intervention service was configured to perform all necessary intervention steps by seamlessly switching from braided line for fishing, to CT for suspension plug milling, acid wash and scale cleanout and nitrogen lift, to e-line for perforating and safety valve installation. 

Despite this broad scope, the equipment was significantly lighter than that used by conventional rig-based CT interventions, which reduced transmitted forces and safeguarded the wellhead throughout operations. 

To ensure flawless execution, TechnipFMC conducted extensive rig-up and testing quayside. After installation on the vessel, system integration testing (SIT) was completed onboard prior to departure, including skidding and lifting the subsea stripper and injector into the module handling tower. 

Offshore, a full test program was executed successfully by the lean, cross-trained crew of 86, which numbered 25% fewer personnel than the 120 typically required for riser-based intervention. 

The rigorous preparation enabled completion of the world’s first riserless CT intervention in a live well in just 33 days—including mobilization, transit, intervention activities and demobilization—roughly half the time required by conventional riser-based operation. Switching from CT to wireline was similarly accelerated and took just over six hours, thanks to the multiskilled crew and the optimized equipment setup. 

The riserless result: a safer, more efficient intervention that reduced time, cost, emissions and personnel exposure, while meeting the operator’s technical requirements. 

RLWI replacement of gas lift valves cuts intervention time and cost by 47%. The failure of downhole gas lift valves in several wells in a Norwegian Barents Sea field was causing numerous shut-ins and lost production. The operator chose TechnipFMC RLWI to replace the valves in six wells by using a light intervention vessel, instead of deploying a sixth-generation semisubmersible rig, for which the day rates for this operation would have been $800,000/day.  

All six valves were successfully replaced, without any hiccups, to reestablish the well barrier envelope and restore production. With an average replacement time of six days per well, RLWI saved 47% in time and cost, compared with rig-based operations. 

INDUSTRY-RECOGNIZED INNOVATION 

In its first year, Pivotal Riserless Intervention earned recognition from leading industry organizations for its groundbreaking accomplishments. The awards encompass the versatility of RLWI, including the OWI Global Awards for Well Intervention Excellence, naming RLCT as the “Best Example of P&A Innovation,” as well as selection for the “Innovation and Technology Award,” at the 2024 Intervention & Coiled Tubing Association (ICoTA) annual conference. 

 RLCT has continued to receive accolades in 2025: 

• SPE Offshore Achievements Award 2025 - Field Proven Technology  
• ICoTA Global Intervention Technology Award 2025 
• ICoTA Curtis Blount Outstanding Paper Award 2025  
• UTC Award 2025. 

Whether the goal is to unlock new oil recovery opportunities or to reduce the decommissioning backlog and associated regulatory challenges, this industry recognition emphasizes how Pivotal Riserless Intervention provides subsea well operators in all offshore environments, with new efficiencies, improvements in safety and OpEx reductions. 

HEIN KRISTIAN JACOBSEN is managing director, TIOS, at TechnipFMC. He has been in the energy industry for 23 years, working in Malaysia, Singapore and Norway. He previously worked in subsea drilling systems and has been part of TechnipFMC’s RLWI team since 2007, as an operational engineer, operational manager and operational director. He holds a master’s degree in offshore engineering from the University of Stavanger and an Executive MBA from BI in Oslo.