Wells – Conduit wall or specific conduit end structure – Downhole coupling or connector
Reexamination Certificate
1998-08-11
2001-04-10
Neuder, William (Department: 3672)
Wells
Conduit wall or specific conduit end structure
Downhole coupling or connector
C166S377000
Reexamination Certificate
active
06213206
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention refers to a hydraulically releasable coupling, in particular for use together with equipment which is lowered into an oil or gas well.
When working in an oil or gas well, there is a need for introducing different tools and other items into the well. In wells that deviate strongly from the vertical, the tool is often attached to the end of a coiled tube, which in addition to guiding the tool, also enables circulation of the fluid in the well.
It may happen that a tool gets stuck in the well, and special equipment has to be introduced to extract the tool from the well. Before such equipment can be introduced into the well, the coiled tube must be disconnected from the stuck tool and withdrawn from the well. To enable such disconnection of the coiled tube, it is customary to fit a releasable coupling between the coiled tube and tool. Couplings of this kind comprise two sleeve-shaped main parts releasably connected, and secured in coupled position by a releasable lock. A through fluid channel allows fluid to flow from the coiled tube through the coupling, and on to the tool.
The simplest couplings are held together by shear pins which are arranged to break whenever they are subjected to a predetermined force. Detachment from a stuck tool is done by pulling on the coiled tube with sufficient force, so as to make the shear pins break. In deep wells, where there may be a considerable friction between the coiled tube and the wall of the well, it has proved difficult to transmit sufficient power to break the shear pins, and therefore they must be dimensioned to break by a relatively small force. This easily results in the shear pins breaking unintentionally, for example by vibrations and shock caused by the tool working in the well. To alleviate this problem, it is known to lock the two main parts of the coupling together by means of a locking device, which is kept in locking position by a displaceable locking sleeve, and in which the locking sleeve is kept in position by shear pins. In such known arrangements the shear pins are not subjected to shear forces when the tool is in ordinary use. Disconnecting is done by dropping a sealing body, typically a ball, through the coiled tube and down into the coupling, where the ball lands on a seat, assigned to the locking sleeve, and blocks the through fluid channel. Increasing the fluid pressure in the coiled tube, gives rise to a hydraulic force against the sealing body, and thus against the sleeve. If the fluid pressure is sufficiently increased, the force will be great enough to break the shear pins and displace the locking sleeve, so that the coupling is released. Such hydraulically releasable couplings have, because of their functional reliability, become widely used.
Some of the hydraulic tools require hydraulic control signals in addition to hydraulic power, and it is common to use a coiled tube, prefitted with two internal thin tubes, for the transmission of such hydraulic control signals. In addition the coiled tube often carries an electric cable for the transmission of electric signals to or from the tool. In such cases there is no room for dropping a sealing body through the coiled tube, and known couplings which are released by means of a sealing body, can, therefore, not be used. Thus, couplings released through pull is the only possibility left, as mentioned above.
SUMMARY OF THE INVENTION
The object of the invention is to provide a hydraulically releasable coupling, which may be used whenever hydraulic signal lines are being carried in the coiled tube to the tool, which is connected to the coiled tube by the coupling.
The object is achieved through the characteristics given in the description below and the following claims.
As mentioned, it is customary to lead at least two hydraulic signal lines through a coiled tube to hydraulic tools. The signal lines are used in a known manner, as pressure line and return line, alternately, for hydraulic fluid, to allow a hydraulic function to be reversed. Two hydraulic signal lines which alternately act as pressure line and return line, are each, according to the present invention, lead to a hydraulic piston or a defined area of a common hydraulic piston in the hydraulically releasable coupling.
The invention is based on the fact that at any time there will be an axial force acting on the locking sleeve, as a consequence of the hydraulic pressure in the hydraulic pressure line acting on one area, and a substantially smaller hydraulic pressure in the return line, acting on another area. The shear pins holding the locking sleeve in position, are dimensioned in a manner that makes the overall hydraulic force too small for the shear pins to break. The situation will be the same if the hydraulic function is reversed, so that the pressure line and the return line exchange roles. By pressurizing both hydraulic lines at the same time, a greater axial force will act on the locking sleeve, and the shear pins are dimensioned to break from such increased force.
REFERENCES:
patent: 4526233 (1985-07-01), Stout
patent: 5086844 (1992-02-01), Mims et al.
patent: 5323853 (1994-06-01), Leismer et al.
patent: 5984006 (1999-11-01), Read et al.
patent: 2224525 (1990-05-01), None
patent: 942136 (1995-12-01), None
Andrus Sceales Starke & Sawall LLP
Neuder William
Transocean Petroleum Technology AS
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