Wells – Submerged well – Connection or disconnection of submerged members remotely...
Patent
1997-01-27
1999-02-23
Neuder, William
Wells
Submerged well
Connection or disconnection of submerged members remotely...
166368, E21B 3300
Patent
active
058734155
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a completion sub-sea test tree particularly, but not exclusively, to provide tubing and annulus isolation in a production well and the invention also relates to a method of rapid disconnection when completing and testing sub-sea production wells.
2. Description of the Relevant Prior Art
The requirement to perform a well test on a sub-sea well before completion and tree installation is becoming increasingly common. At present, this is performed by running a test string, performing the test and then temporarily suspending the well prior to completion. This procedure has a major impact in three principal areas: it increases cost and rig time during running and retrieving the test string; it creates difficulties when retrieving the well in both terms of time and increased costs, and formation damage may be caused during the suspension and re-entry phases. These problems are particularly relevant with batched drill wells and those with EWT potential.
It is desirable to overcome these problems in such a way which allows a well test/clean up to be conducted through a completion via a conventional production tubing hanger to avoid the need to run and pull the test string and the running and pulling of the suspension system, and associated costs and problems.
An object of the present invention is to provide an apparatus which obviates or mitigates at least one of the aforementioned problems.
A further object of the invention is to provide apparatus which provides isolation of the tubing string and allows disconnection from the well in the event of a rig positioning problem.
A further object of the present invention is to provide isolation of the annulus from the main riser without the requirement to close any of the blow-out-preventer (BOP) rams.
A further object of the invention is to provide the ability to orientate the completion sub-sea test tree, and consequently the attached tubing hanger and completion, into a desired position required to receive the production tree and subsequent tie-backs when deployed.
SUMMARY OF THE INVENTION
This is achieved by providing a completion sub-sea test tree which defines a main bore, an auxiliary or annulus bore and an independently operated valve in the main bore and a further valve in the annulus bore which, in turn, are operated by respective independent control lines acting on the operating mechanism of the respective valves within the test tree. The completion sub-sea test tree provides isolation of the main and/or annulus bore when required. In a preferred arrangement the valves in the main bore and annulus are ball valves and isolation is achieved by metal-to-metal seals between the ball valves and valves seats.
Application of hydraulic pressure provides assist closure to the spring force to cut coil tubing and enabling the valves to be forced closed in the event of an emergency situation requiring rapid disconnect. Hydraulic communication across the tree disconnect is achieved using independent hydraulic stabs which can selectively isolate or allow the hydraulic systems to vent when disconnected. This has the advantage of ensuring that the tubing hanger hydraulic systems are not sensitive to volume changes generated by thermal or pressure effects.
Correct orientation of the tree and tubing hanger assembly is achieved by an orientation slot on the outside diameter of the tree which engages with a pin deployed from the BOP stack.
The independent valves are normally held closed by spring force. Hydraulic pressure applied to the upper face of the operating piston will overcome the spring force to open the valves.
Unlatching from the completion sub-sea test tree is achieved by pressurising a latch control line which overcomes the forces generated by the latch spring lifting the piston allowing the latch body and orientation sleeve to be retrieved. A further safety feature is the sensitivity of the latch piston to valve opening control lines and this ensures the latch piston can only
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Expro North Sea Limited
Neuder William
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