Wells – Means for guiding insertable element laterally of well axis – Secured in operative position by movable means engaging well...
Reexamination Certificate
1998-12-18
2001-06-12
Knight, Anthony (Department: 3626)
Wells
Means for guiding insertable element laterally of well axis
Secured in operative position by movable means engaging well...
C166S050000
Reexamination Certificate
active
06244337
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a system for sealing the intersection between a primary borehole and a branch borehole.
BACKGROUND OF THE INVENTION
Numerous systems are known to provide such sealing.
U.S. Pat. No. 2,379,070 discloses a system which comprises a tubular primary casing section which in use is located in the primary borehole in the region of the branchpoint and a branch casing section which is welded to the primary casing section and which in use is located in the branch borehole.
In this known system the primary casing section is a tubular having a curved lower end which forms a lip which can be pulled against an existing casing inside the primary borehole by pulling or pushing the branch casing section into the branch borehole. As a result the tubular wall of the primary casing section is pulled against the wall of the existing casing to provide a seal that covers the window that has been cut into the existing casing at the location where the branch borehole intersects the primary borehole.
Soviet Union patent specification SU-663825 discloses another sealing system where a branch casing is welded to a primary casing section that is formed by a corrugated sleeve which is expanded downhole by an expansion mandrel.
International patent application WO 9403699 discloses the use of a primary casing section that is made of a memory alloy which is expanded by applying heat to provide a fluid-tight juncture.
A disadvantage of the known sealing systems is that they require the use of a primary casing section which is complex and expensive to make, that they require complex installation procedures and that the juncture seal provided can be prone to leakage.
It is an object of the present invention to provide a system for sealing the intersection between a primary and branch borehole which can be made and installed in a cost effective manner and which provides an effective seal.
SUMMARY OF THE INVENTION
The system according to the present invention comprises a primary casing section which in use is located in the primary borehole in the region of the branchpoint and a branch casing section which in use is located in the branch borehole, wherein the branch casing is secured to the primary casing section and the primary casing section is a tubular which defines a slant surface which is adapted to cooperate with a slant surface of a wedge-shaped element.
The presence of said slant surface allows the primary casing section to be pressed towards the area of the wall of the primary borehole surrounding the branchpoint by the wedge-shaped element which is placed in the primary borehole adjacent to the primary casing section at least at the time when the primary casing section is being installed.
Preferably, the system further comprises a wedge-shaped element which is formed by a whipstock which in use is located in the primary well adjacent to the primary casing section such that a slant surface at one end of the wedge-shaped element faces the slant surface of the primary casing section.
The whipstock may be a conventional solid whipstock which is removed or drilled out after the installation procedure. Alternatively, the whipstock may have a soft core which is drilled out or otherwise removed after the installation procedure.
However, it is preferred that the whipstock is a tubular having substantially the same outer diameter as the primary casing section and that it has a slant surface that intersects a central axis of the tubular wall of the whipstock at substantially the same angle as the angle of intersection between the slant surface of the primary casing section and a central axis of the primary casing section.
It is also preferred that when in use the hollow whipstock is located under the primary casing section and the whipstock has a smaller internal width than the outer width of a nose section of the branch casing section and the whipstock is arranged in the primary borehole at least partly under the intersection with the branch borehole and oriented such that when the branch casing section is lowered through the primary well the nose section thereof will be deflected by the slant surface of the whipstock into the branch borehole.
To further improve sealing the outer surfaces of the primary casing section and whipstock may be provided with a sealing agent and during installation the primary casing section and whipstock may be pressed on to each other at a selected axial force. By arranging the slant surfaces of the primary casing section and whipstock at a relatively small acute angle relative to the central axis thereof a wedge is created which maintains a continuous radial force to said section and whipstock also after the exertion of the axial force has stopped. The slant surfaces may be ratchet to aid in the locking process.
These and other features, objects and advantages of the system according to the invention will be described in the following detailed description and drawings.
REFERENCES:
patent: 5311936 (1994-05-01), McNair et al.
patent: 5526880 (1996-06-01), Jordan, Jr. et al.
patent: 5651415 (1997-07-01), Scales
patent: 5730221 (1998-03-01), Longbottome et al.
patent: 5787987 (1998-08-01), Forsyth et al.
patent: 5941308 (1999-08-01), Malone et al.
patent: 5944107 (1999-08-01), Ohmer
patent: 6015012 (2000-01-01), Reddick
patent: 6065543 (2000-05-01), Gano et al.
patent: 6092602 (2000-07-01), Gano
patent: 0 859 121 A2 (1998-08-01), None
patent: 2297779 (1996-08-01), None
patent: 98/09054 (1998-05-01), None
patent: 98/09049 (1998-05-01), None
Cumming Francis Alexander
Fisher Simon Lawrence
Lohbeck Wilhelmus Christianus Maria
Knight Anthony
Schwing Karlena D
Shell Oil Company
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