Wells – Processes – Assembling well part
Patent
1995-02-17
1997-05-13
Tsay, Frank
Wells
Processes
Assembling well part
166 99, E21B 1916, E21B 3108
Patent
active
056283660
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to protective arrangements, and relates more particularly but not exclusively to protective arrangements for downhole tool assemblies employed in the drilling of wells.
In the drilling of wells intended for exploration of subterranean formations and/or the eventual recovery of hydrocarbons or other minerals, much of the work involves drilling of the well. However, from time to time it is necessary to lower a tool assembly down the well for the accomplishment of related operations. For example, a liner running and cementing operation may be necessary in the course of drilling a well. Such tool assemblies have varying degrees of complexity, and frequently involve fluid flow passages and/or relatively movable components or sub-assemblies.
DESCRIPTION OF THE PRIOR ART
Proper functioning of such tool assemblies can be disrupted by the entry of drilling debris into the mechanism or fluid passages. A form of protective arrangement for obviating such debris-induced disruption is known as a "junk bonnet", and takes the form of a cap intended to shield the tool assembly from descending debris. However, known forms of junk bonnet do not provide a fluid seal, and are liable to be dislodged by movement of the drill pipe as part of operation of the tool assembly. These problems allow debris to enter the tool assembly, and result in failure of the protective arrangement. Further, the known forms of junk bonnet have a relatively large outside diameter which restricts fluid circulation in the annulus between the drill pipe and the casing, and which hinders easy removal of the tool assembly from the well when a large amount of cuttings and drilling debris has accumulated in the annulus.
It is therefore an object of the invention to provide a protective arrangement for a downhole tool assembly which obviates or mitigates these problems.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a downhole tool assembly comprising a sleeve member, a tube member axially movable with respect to and at least partially located within said sleeve member, a seal member mounted within a lower end of said sleeve member providing a sliding fluid seal to the exterior of said tube member or to the exterior of a tubular extension member thereof and having an external diameter substantially equal thereto, a downhole tool sub-assembly and a protective arrangement comprising an annular seal means characterised in that said annular seal means has an inner surface dimensioned to fit around said tube member and an outer surface dimensioned to fit within at least an upper end of said sleeve member, said inner surface being provided with an inner fluid seal means for forming a sliding fluid seal to the exterior of said tube member, said outer surface being provided with an outer fluid seal means for forming a sliding fluid seal to the interior of said sleeve member and the downhole tool sub-assembly being located within an annular Volume (C) between the seal member and said annular seal means, the Volume (C) being constant nothwithstanding movement of the tube member relative to the sleeve member.
The annular seal means preferably includes a fluid passage linking axially opposite ends of said annular seal means, and fluid flow control means selectively operable either to open said fluid passage to the flow of fluid therethrough between said axially opposite ends of said annular seal means or to close said fluid passage to the flow of fluid therethrough between said axially opposite ends of said annular seal means.
Said fluid flow control means may comprise a valve means fitted in said fluid passage or on one end thereof; said fluid flow control means more preferably comprises a plug insertable into said fluid passage for retention therein to block said fluid passage to fluid flow therethrough between said axially opposite ends of said annular seal means.
Said annular seal means preferably comprises a body which is axially divided into a plurality of mutuall
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Nodeco Limited of International Base
Tsay Frank
LandOfFree
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