Wells – Conduit wall or specific conduit end structure – Downhole coupling or connector
Patent
1996-12-05
1998-08-04
Dang, Hoang C.
Wells
Conduit wall or specific conduit end structure
Downhole coupling or connector
166377, 285 3, 285315, E21B 1706, E21B 2304
Patent
active
057879826
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a hydraulically releasable disconnecting device, particularly for use together with equipment carried down into an oil or gas well.
When operating in an oil or gas well, there exists a need for carrying various tools etc. down into the well. The tool is attached to the end of a coil pipe which, in addition to carry the tool, also gives an opportunity of circulating liquid within the well.
It happens that tools get stuck in the well and that it is necessary to convey down special equipment in order to bring it up. Therefore, the coil pipe must be capable of being disconnected from the tool and to be pulled out of the well. In order to have a controlled disconnection, a disconnecting device is placed between tool and coil pipe.
Disconnecting devices have a through-going liquid channel and consist of two main parts releasably coupled together by means of a locking mechanism. When the disconnecting device is released, the two main parts are disconnected.
There are simple disconnecting devices which release upon the occurence of a predetermined traction force, but it is more common to use disconnecting devices which release hydraulically. When releasing hydraulically, a sealing body is first pumped through the coil pipe until it lands in a valve seat in the disconnecting device. The sealing body blocks the liquid flow through the disconnecting device, and continued pumping gives a hydraulic pressure increase and a force releasing the locking mechanism.
In known disconnecting devices, springy finger-like catchers having external enter hooks on the one main part are adapted to be conducted into a hole having an internal catching groove in the other main part. When the enter hooks which are disposed along the periphery of a cylinder, are conducted into the hole, the enter hooks on the catchers mesh with the catching groove. Then, a safety sleeve is guided in between the catchers and prevents these from springing back; then, the enter hooks can not leave the catching groove. The safety sleeve is attached by means of shear pins, and the two main parts of the disconnecting device are locked to each other. The safety sleeve has a passage for liquid and is provided with a seat adapted to receive a sealing body. When the sealing body, normally a steel ball, is carried in and rests against the seat in the safety sleeve, the passage for liquid is closed. When the liquid pressure increases, an axially directed force acts on the sealing body and the safety sleeve. Upon the occurence of a predetermined force, the shear pins are broken, and the safety sleeve is displaced such that it no longer prevents the catchers from leaving the catching groove. Then, the two main parts of the disconnecting device may be separated from each other.
The finger-like catchers are subjected to breakage. A reason to this is the use of rotational and striking tools which give vibrations and fatigue. Bending forces lead to that one of the catchers or a few of them transfer all forces between the two main parts of the disconnecting device, some of the catchers, thus, being overloaded. When an acidizing of a well is carried out, acid is pumped through the disconnecting device. The catchers exhibit a large surface and are, thus, subjected to acid attack. The catchers are corroded, the cross-section thereof being reduced. In order to increase the strength of the catchers and the resistance to acid thereof, the dimensions of the catchers have been increased, and various types of material have been tried out. The result is disconnecting devices having vigorous and relatively rigid catchers requiring a large force to mount and release the locking mechanism. Even with said improvements the catchers are subjected to breakage. Also, disconnecting devices have been made where said catchers are shielded from the liquid flow, but a disadvantage of such shielding is that the area of the through-going channel of the disconnecting device is reduced.
An object of the invention is to provide a disconnecting device having great strength and
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Bakke Oil Tools AS
Dang Hoang C.
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