Subsea Intervention 25 Days Ahead of Schedule | Subsea Services Alliance

Subsea Intervention Program in Five Wells Completed 25 Days Ahead of Schedule

Published: 05/08/2020

Ocean water texture below the surface with sun rays shining through

Intervention operations were required in five wells

An operator offshore Nigeria required intervention services in five subsea wells located in a water depth of 1,210 m [3,970 ft]; the primary objective was to increase production. The scope of work included

  • water shutoff and zonal isolation
  • hydrate milling and cleanup with coiled tubing (CT)
  • remedial safety valve operations.

Purpose-built vessel equipped with premium technologies was an ideal fit

Subsea Services Alliance suggested its newest semisubmersible subsea well intervention vessel, the Q7000. This riser-based intervention vessel is equipped with a fully integrated well services package comprising wireline, slickline, CT, and pressure pumping spreads in an optimized layout. Dedicated service areas increase safety and vessel efficiency.

The Q7000 also features an intervention riser system that enables access to both conventional and horizontal subsea trees at depths down to 3,000 m [10,000 ft]. It can be used for wireline intervention, production logging, CT operations, well stimulation, and full plug and abandonment operations. All equipment and foreseeable spares were loaded onto the vessel in Singapore to enable a fully autonomous operation and avoid importation delays.

Aerial view of Q7000 semisubmersible for riser-based subsea well intervention and decommissioning.
The Q7000 well intervention vessel provided a more rapidly mobilized and cost-effective alternative to a traditional rig.
Intervention riser system at surface being lowered into the sea for subsea well access.
A single 10-week-long deployment of the proprietary intervention riser system across four subsea well hops efficiently enabled achievement of workover objectives on all five wells.

Job executed smoothly, efficiently, and 25 days sooner than planned

On this first job in Nigeria with a newly trained local crew, objectives on all five wells were achieved over a 10‑week period in a single deployment of the subsea well access package—the intervention riser system—with 96.86% uptime. The project was executed with zero lost-time incidents (LTI) and a high level of efficiency, despite the demands of new COVID-19 safety protocols and restrictions.

operating uptime
work-hours with zero LTI
25 d
ahead of schedule
Nigeria, Africa, Offshore

An operator used the Q7000 semisubmersible, intervention riser system, and proprietary downhole tools for intervention operations—including the first use of coiled tubing for hydrate milling in Nigeria—in five subsea wells. Four subsea well hops and >238,000 work-hours were completed 25 days faster than planned, with zero lost-time incidents.

Products Used