The industry trend of E&P operations from deepwater subsea wells is increasing the demand for deepwater drilling rigs. To increase rig availability, operators are resorting to a new strategy of transferring the subsea tree installation responsibility from the offshore drilling rig to a subsea equipment support vessel. The installation from a rig can take from 1 to 3 weeks; transferring this responsibility to the support vessel enables the rig to move to the next well sooner and offers significant rig time savings.

A fit-for-purpose, surface-controlled formation isolation valve (SFIV) was designed for temporary well suspension as a part of this strategy. The valve was developed, tested, and manufactured in accordance with the ISO-28781 standard. A case study demonstrates the operational time savings achieved by suspending a subsea well with the landing tree on heave-compensated wire—the tree-by-wire technique. Temporary well suspension can be achieved by using plugs or mechanical barrier valves. If plugs are used, they must be removed after the vertical tree installation, which would partially negate the benefits of the new strategy. To fully realize the potential of this new strategy, the SFIV was designed to provide a mechanical barrier that could be remotely opened from the support vessel by applying pressure in the hydraulic control lines. This fail-as-is valve eliminates the risk of losing well control if the system fails, which is critically important in well suspension applications.

Starting in November 2010, several subsea wells around the world were successfully suspended with the SFIV valves. They can be used as suspension valves to perform production buildup tests, as downhole lubricator valves to deploy long production logging, or as perforating guns. The valves can be opened multiple times with high differential pressure across the ball valve and no adverse affects on sealing capacity.