Wells – Processes – Operating valve – closure – or changeable restrictor in a well
Patent
1996-06-19
1999-07-06
Tsay, Frank
Wells
Processes
Operating valve, closure, or changeable restrictor in a well
166330, E21B 3402
Patent
active
059186763
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to safety valves with subsea trees and particularly horizontal subsea trees.
BACKGROUND OF THE INVENTION
The use of horizontal trees is rapidly becoming the norm for subsea completions because of the cost reduction offered over conventional technology. As subsea completions enter deep water the cost saving increases dramatically up to 25% as reported in an article entitled "Horizontal Trees Provide Quick Well Bore Access, 25% Cost Savings", edited by Leonard Le Blanc, Offshore International Magazine November 1993. Horizontal wellheads also allow for larger completions to be utilised in conventional technology, allowing a field to be exploited by fewer wells. However, the conventional method of isolating the horizontal wellhead after workover and before production, which may be a period of several years, is by situating wireline plugs in the tubing hanger. This is viewed by some major oil companies as a less than ideal method. One particular problem with this is that it is very difficult and indeed dangerous to extract the plugs prior to production. It has frequently been found that such plugs are often very difficult to remove which can add considerably to the cost of the exercise.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved apparatus and method for providing well isolation and to mitigate or obviate at least one of the disadvantages associated with the existing apparatus and methods.
This is achieved by using a two-part safety valve system. A first part containing a valve mechanism remains in the wellhead and is normally biased to a closed position. The valve remains in the wellhead at all times during production and can be actuated to an open position by latching in a second part which contains control cables and a moveable valve actuator operable from the surface during workover to actuate the valve in the wellhead portion open. This provides for greater safety during the workover phase in comparison to a wire set plug and also allows safer re-entry to the well.
According to one aspect of the invention, there is provided a horizontal tree safety valve system comprising, element moveable between an open and a closed position, portion and having a moveable valve element actuating means whereby when said first and second valve portions are secured together, said valve element actuating means is responsive to a control signal to actuate said valve element to move from a closed to an open position.
Accordingly in another aspect of the present invention there is provided a horizontal tree safety valve comprising: tree, first resiliently biased means located in said first valve portion and coupled to moveable valves means for urging said moveable valve means to a closed position, first valve portion by latch means, said latch means having respective first and second latching portions coupled to said first and second valve portions, coupled to said moveable valve means when said first and second safety valve portions are secured together, said resiliently biased element being responsive to an actuating force applied thereto to urge said moveable valve means to an open position when said actuating force is present, said first resiliently biased means and said resiliently biased element urging said valve means to a closed position in the absence of said actuating force.
Preferably said moveable valve means is an apertured ball valve, said apertured ball valve having a central through-hole when being moveable in response to an actuating force between the closed position and through 90.degree. to the open position.
Conveniently, said first portion resiliently biased means is implemented by a coil spring.
The ball valve is located in a ball cage and the ball has a pair of slots machined in faces thereof for receiving pins about which the ball moves axially and rotatably. The slots are disposed at 45.degree. to the axis of aperture through the ball.
Preferably the latch means is implemented by a plurality of pivot
REFERENCES:
patent: 4325409 (1982-04-01), Roberts
patent: 4372391 (1983-02-01), Barrington et al.
patent: 4560004 (1985-12-01), Winslow et al.
patent: 4569397 (1986-02-01), Brakhage, Jr. et al.
patent: 4577692 (1986-03-01), Reardon
patent: 4703807 (1987-11-01), Weston
patent: 5575336 (1996-11-01), Morgan
Expro North Sea Limited
Tsay Frank
LandOfFree
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