Case Study: Surface-controlled Formation Isolation Valves and Their Application as a Barrier for Temporary Well Suspension

摘要

The industry trend of E&P operationsfrom deep water subsea wells is increasing the demand for deepwater drilling rigs. Toincrease rig availability, operators are resorting to a new strategy of transferring the subsea tree installation responsibilityfrom the offshore drilling rig to a subsea equipment support vessel. The installation from a rig can take 1 to 3 weeks;transferring this responsibility to the support vessel enables the rig to move to the next well sooner and offers significant rigtime savings.This paper introduces a fit-for-purpose surface-controlled formation isolation valve (SFIV) designed for the temporary wellsuspension that is required as a part of this strategy. The valve was developed, tested, and manufactured in accordance withthe ISO-28781 standard. A case study demonstrates the operational time savings achieved by suspending a subsea well withthe and landing the tree on heave-compensated wire, call the tree-by-wire technique. Temporary well suspension can beachieved by using plugs or mechanical barrier valves. If plugs are used, the rig must return to remove them after the verticaltree installation, which would partially negate the benefits of the new strategy. Therefore, to fully realize the potential of thisnew strategy, the SFIV was designed to provide a mechanical barrier that could be remotely opened from the support vesselthrough application of pressure in the hydraulic control lines without loss of actuation capacity. It’s a true fail-as-is valve thateliminates the risk of loss of well control in case of a system failure, which has critical importance in well suspensionapplications.Starting in November 2010, several subsea wells around the world were successfully suspended with the SFIV valves.Besides using the SFIV as a suspension valve, operators can use it to perform production build-up tests, downhole lubricatorvalve for deployment of long production loggin or pereforating guns. This is possible since the valve could be openedmultiple times with high differential pressure across the ball valve without any adverse affects on its sealing capacity.