Patent Application
20070181346
This invention relates to a connector which establishes a fluid tight connection to a drill-string and preferably establishes a fluid tight connection between a drill-string and a top-drive.
It is known in the oil and gas industry to use a top drive motor and a drill-string to drill wells. It is the top drive motor that provides the torque to rotate the drill-string, which in turn rotates the drill bit at the bottom of the well. The drill-string itself consists of a series of hollow pipes, typically 30 ft (9.14 m) in length, and these are attached to each other via a threaded connection. The top drive is also attached to the drill-string via a threaded connection.
During the drilling process, drilling-mud is pumped through the connection between the top drive and the drill-string. This drilling-mud travels through the drill-string and ensures sufficient lubrication, cooling and the removal of cuttings. It is often necessary to remove the drill-string from the well (to replace the drill bit for example) and under such circumstances drilling-mud is pumped through the drill-string to displace and support the retreating drill-string and maintain hydraulic balance in the well bore. This ensures that a vacuum is not created and that the force required to remove the drill-string is minimised, allowing the removal to occur more quickly. In a conventional arrangement, the drilling-mud is pumped through the same connection, between the top drive and drill-string, as used when drilling.
When removing a drill-string from a well (which in the industry is known as tripping-out), successive sections of the drill-string have to be disconnected from the remaining sections of the drill-string. Furthermore, the section being removed also has to be disconnected from the top drive. A new connection is then established between the top drive and the remaining sections of the drill-string. However, making and breaking these threaded connections is-very time consuming and slows down the process of removing a drill-string from a well. This has a serious impact on the productivity of the well.
Previous attempts have been made at speeding up the process of tripping-out. GB2156402A discloses methods for controlling the rate of withdrawal and the drilling-mud pressure to maximise the tripping-out speed. However, the time taken to connect and disconnect each section of the drill-string to the top drive is not addressed. Other attempts include removing several sections at a time, as discussed in GB2156402A. However, this approach is limited by the height of the derrick holding the top drive.
According to the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drill-string, the connector comprising a body portion and an extendable seal portion, the seal portion having a seal which is adapted to sealingly engage the drill-string when the seal portion is at least partially extended from the body portion.
The seal may comprise a tapered bung, which may be forced into the open end of the drill-string, when the seal portion is at least partially extended from the body portion.
The seal portion may comprise a piston-rod having a cap and a shaft which are joined together, the shaft being slidably mounted within the cylinder. The cap and part of the shaft may be located inside the cylinder.
The connector may further comprise a piston, the piston being slidably mounted on the shaft within the body portion. The body portion may comprise a cylinder. The piston and cap may divide the cylinder into two chambers: a first-chamber and a second-chamber. The first chamber may contain drilling-mud, whilst the second chamber may contain air.
In one embodiment, the piston-rod may have a central flow passage which provides a flow communication path between the first-chamber and the drill-string. Furthermore, a flow communication path from the inside of the hollow shaft to the cylinder may be provided by a hole in the piston-rod. The inside of the hollow shaft is not in flow communication with the cylinder when the piston covers the hole in the piston-rod.
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which:
With reference to
With reference to
The shaft 30, cylinder 15, bung 60 and cap 40 shown in
The connector 10 further comprises a piston 50. The piston 50 is slidably mounted on the shaft 30 inside the cylinder 15 and is free to move between the cap 40 and the end-cap 110. The whole assembly 20, 40, 50 and 60 is also able to slide in the cylinder 15. The inside of the cylinder 15 is divided by the piston 50 to form a first chamber 80 and a second chamber 70. The first and second chambers 80 and 70 preferably hold air and drilling-mud respectively. The piston 50 is sealed against the shaft 30 and cylinder 15, for example by means of O ring seals 52 and 54, to ensure no flow communication between the two chambers 70 and 80. The first chamber 80 is in flow communication with an air supply via a port 100 and the second chamber 70 is provided with drilling-mud via a socket 90. The top drive 2 is connected to the connector 10 via a conventional thread in the socket 90.
In the disposition of components shown in
In operation of the connector 10, the pressure of the air in the first chamber 80 is kept at a constant value of approximately 100 psi. By contrast, the pressure of the drilling-mud in the second chamber 70 is varied and it is this pressure that controls the operation of the connector 10.
When the pressure of the drilling-mud pressure is sufficiently low, so that (accounting for the differences in the projected areas of the two sides of the piston 50), the force exerted on the piston 50 by the drilling-mud is less than the force exerted on the piston 50 by the compressed air, the piston 50 is biased towards the cap 40 and socket 90. The piston 50 forces the retraction of the piston-rod 20 into the cylinder 15. The piston 50 also abuts the cap 40, thereby closing the holes 120 and ensuring no drilling-mud flows out of the connector 10. When the piston-rod 20 is retracted, the bung 60 and the seals 130 are disengaged from the drill-string 4 and the top most section of the drill-string 4 can be removed.
To extend the piston rod 20, so that the bug 60 and seal 130 engage the drill-string 4, the pressure of the drilling-mud is increased. Once this pressure exceeds a certain threshold, the force exerted by the drilling mud on the piston 50 exceeds the force exerted by the compressed air on the piston 50, so that the cap 40 is forced toward the end-cap 110 and the piston-rod 20 extends. As the projected area of the cap 40 is greater than the projected area of the piston 50 and the air pressure is only exposed to the piston 50, the piston 50 remains abutted to the cap 40. Thus, whilst the piston-rod 20 is extending, the holes 120 are not exposed and drilling-mud cannot flow.
Once the bung 60 and seals 130 are forced into the open threaded end of the drill-string 4, thereby forming a fluid tight seal between the piston-rod 20 and the open end of the drill string 4, the piston-rod 20, and hence cap 40, are no longer able to extend. By contrast, as the piston 50 is free to move on the shaft 30, the piston 50 is forced further along by the pressure of the drilling-mud. The holes 120 are thus exposed and drilling-mud is allowed to flow from the second chamber 70, through the piston-rod 20 and into the drill-string 4. The drill-string 4 can then be lifted by clamping the elevators 6 to the drill-string 4 and raising them.
As described above, the connector 10 replaces the traditional threaded connection between a top drive 2 and drill-string 4 during the removal of a drill-string 4 from a well. With this connector, the connection between the top drive 2 and drill-string 4 can therefore be established in a much shorter time and great savings can be achieved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0602565.4 | Feb 2006 | GB | national |
