Wells – With electrical means
Reexamination Certificate
1998-09-18
2001-01-09
Schoeppel, Roger (Department: 3672)
Wells
With electrical means
C166S385000, C403S375000
Reexamination Certificate
active
06170570
ABSTRACT:
BACHGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sinker bar for a hydrocarbon well apparatus operated by means of a cable.
2. Description of the Prior Art
In the field of oil exploration and extraction, it is often necessary to lower various apparatuses down a hydrocarbon well. Such apparatuses are suspended from a cable driven at the surface by means of a winch.
This applies, for example, when a perforator apparatus is operated to bring a well into operation.
It is also known to perform monitoring or diagnosis functions in hydrocarbon wells that are in operation by lowering measuring apparatuses down such wells. By way of example, one such apparatus is described in French patent application No. 97.03422.
It is also known to use sinker bars whose weight adds to that of the apparatus to make it easier to lower the apparatus down the well. Such sinker bars are often necessary to balance the force, resulting from the pressure prevailing in the well, exerted on the cross-section of the cable.
Sinker bars also make it possible to overcome friction against the inside surface of the well due to the centralizer devices of the apparatus. The cross-section of the apparatus may be smaller than the cross-section of the well and centralizer devices may be used to hold the apparatus on the axis of the well. This applies in particular for inclined wells.
Finally, sinker bars are also effective to exert a sufficient tension on the cable used for operating the apparatus.
Known sinker bars are in the form of a tube provided with a thread at each end. A sinker bar or a set of assembled-together sinker bars is thus screwed at its top end to a cable head and at its bottom end to the apparatus. The operations of screwing and unscrewing sinker bars constitute a first drawback of known devices.
In addition, the cable for operating the apparatus is also used for providing an electrical connection between the apparatus and the surface, e.g. for transmitting data. An electrical connection must therefore be established through sinker bars which are disposed between the apparatus and the cable head. Sinker bars must therefore be fluid-tight and capable of withstanding the pressures prevailing in the well.
As a result, electrical contacts must be present to provide connections between sinker bars, and also between the apparatus and the cable, and seals are required to make the sinker bars fluid-tight. This gives rise to problems of reliability due to loss of insulation or to faulty electrical continuity.
Finally, in inclined wells, a special adapter must be added to provide a ball joint between the sinker bars and the apparatus. Such an arrangement is necessary to avoid the need to center sinker bars, which would require centralizer devices of large mechanical strength.
SUMMARY OF THE INVENTION
There is provided according to the invention a sinker bar for use with a well apparatus connected to an operating cable through a cable head, comprising a bar provided with a longitudinal slot, said slot being adapted to permit lateral engagement of said bar onto said cable, and including first connection means at one of its ends for connection to said cable head.
Thanks to their longitudinal slots, the sinker bars can be mounted on the cable above the member forming the cable head. The cable head can be connected to the apparatus by any appropriate means, in particular by screws, using threads which are provided in existing apparatuses.
A first advantage of the invention is that it eliminates all problems of sealing and electrical contact associated with known sinker bars.
In a particular embodiment, the sinker bar includes at its other end second connection means for connection to a member forming a fishing head.
Fishing heads are known. In the prior art, they comprise members provided with means enabling the apparatus to be extracted without using a cable. Such fishing heads are disposed at the top end of the assembly constituted by the apparatus and its sinker bars, where said assembly is connected to the cable.
Thus, it is also possible to provide for using a fishing head with sinker bars of the invention. Nevertheless, the fishing head is now above the bottom end of the cable, on top of the sinker bars.
Advantageously, the first or second connection means are twist-lock means adapted to engage complementary twist-lock means of said members.
This makes the assembling much simpler and quicker than with the threaded prior art sinker bars.
More particularly, the twist-lock means may comprise a flat twist-lock head adapted to be inserted behind at least one shoulder of said member and to be locked by said shoulder after rotating through about one-fourth of a turn, and locking means for preventing said rotation.
Naturally, the inverse configuration could be adopted, with the twist-lock means then comprising at least one shoulder adapted to receive and lock a twist-lock head of said member.
In practice, it is possible to adopt a combined solution in which the sinker bar is provided with a twist-lock head at one end and with a twist-lock shoulder at its other end. All of the bars are then identical and can be assembled one after another.
Also, in a particular embodiment, said connection means are ball joint means.
There is thus no longer any need, as in the prior art, to provide a ball joint adapter since the axes of two successive sinker bars can be slightly offset in deviated wells.
More particularly, the connection means may include a substantially spherical surface adapted to engage a complementary surface of said member.
When using twist-lock or connection means, the twist-lock means can then possess clearance to make ball joint operation possible.
The invention also provides a method of installing a sinker bar for a hydrocarbon well apparatus operatively connected to a cable through a cable head, comprising the step of engaging the sinker bar laterally onto said cable above the cable head by inserting the cable through a longitudinal slot provided in said bar.
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Aguesse Laurent J.
Chyzak Jean-Pierre
Veignat Eric A.
Jeffery Brigitte L.
Ryberg John J.
Schlumberger Technology Corporation
Schoeppel Roger
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