Technical Building Blocks for a Resident Subsea Vehicle
Authors: Newell Todd 
Published: April 2018

Inspection and intervention of subsea wells and other assets currently require deployment of manned inspection, maintenance, and repair (IMR) vessels and remotely operated vehicles (ROVs). Recent advances in robotics and automation can now be combined into new, semi-autonomous subsea vehicles that can be left offshore for extended periods and piloted from shore to perform inspection and intervention tasks without a service vessel. Such resident subsea vehicles can create significant value for oil company operators through more frequent inspections, quick responses to problems, and the ability to eliminate the need for an IMR vessel to perform routine maintenance.

The concept and design for the resident subsea vehicle were conceived and refined over a five-year period. During that time, the appropriate tasks for the vehicle were identified and analyzed, and the enabling technologies – the building blocks – for the vehicle were developed, tested, and commercialized. The technologies include autonomous navigation and asset interfacing, remote communications, remote piloting, battery power, connectivity, residency, and mobility. Based on the success in developing these building blocks, the first generation of resident subsea vehicles will be available soon.

Technical building blocks representing subsystems of the resident subsea vehicle Resident Vehicle Task Analysis

The objective of developing a resident subsea vehicle was to have a right-sized inspection/intervention vehicle that would be a permanent part of the offshore architecture, enabling a new level of asset management at an affordable cost.

A necessary step in designing a resident subsea vehicle was identifying tasks that it could perform without being tethered to an IMR vessel. Identifying tasks for the vehicle was more involved than expected. In speaking with offshore personnel, the project engineers found that many details of their day-to-day operations were never conveyed to onshore personnel. These discussions helped define the range of tasks that a resident vehicle should be able to perform. The greatest need for a resident vehicle will likely be in older, brownfield assets that have more maintenance requirements than newer fields.

The project team determined that the resident vehicle should be able to perform visual inspections, along with all intervention tasks that did not require a crane to lift larger components from the seafloor. If the task required a heavy lift, an IMR vessel would be deployed, with tethered ROVs to perform large-scale maintenance.

Smaller ROVs equipped with cameras and other sensors are available to perform inspections, and this functionality is a fundamental requirement of a resident subsea vehicle. However, in addition to identifying problems with subsea assets, the resident vehicle needs to be able to intervene to correct them, make other adjustments, and perform regular maintenance tasks. For example, the resident vehicle should have the capability to turn valves, operate torque tools and manipulators, clean wellheads, and replace small modular components. The project team identified a set of ROV tools that should be available to the resident vehicle at all times to perform these tasks. They also decided that the vehicle should be modular in design so that it could be easily customized to match requirements specific to the asset where it is deployed.