Wells – Means for guiding insertable element laterally of well axis – Secured in operative position by movable means engaging well...
Patent
1997-05-06
1999-06-15
Schoeppel, Roger
Wells
Means for guiding insertable element laterally of well axis
Secured in operative position by movable means engaging well...
E21B 706
Patent
active
059112751
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to apparatus for milling a well casing, and more particularly to apparatus for milling a window at a desired position in one side of a well casing.
In the exploitation of oil and gas wells it is sometimes necessary to form an opening in the steel well casing. For certain applications the orientation of the opening relative to ground co-ordinates is important. It has been proposed to form such an opening by use of one or more milling tools and the present invention, in its preferred embodiment, provides apparatus for forming such an opening (hereinafter referred to as "a window") by means of a milling tool.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided apparatus for milling a well casing including an elongate guide member having a leading end and a trailing end, the guide member having defined thereon a guide track which, in the use position of the guide member, converges with the well casing to be milled from the trailing end of the guide member towards the leading end thereof; a support member which is selectively movable along the guide track in the direction from the trailing end towards the leading end of the guide member to converge with the well casing to be milled; a milling tool having a leading end rotatably supported by the support member and milling means located rearwardly of its leading end; and a releasable coupling initially maintaining the support member and leading end of the milling tool adjacent the trailing end of the guide member and releasable to permit movement of the support member along the guide track towards the leading end of the guide member to bring the milling means into milling engagement with the casing to be milled.
The milling means may be any suitable configuration for milling the material of the well casing. The milling tool may be driven by a motor located adjacent the tool or may be driven by rotation of the drill pipe to which it is connected. In the preferred embodiment of the invention the tool is adapted to be run into a well bore on coil tubing and incorporates a motor located immediately rearwardly of the milling tool for rotating the milling means, a coil tubing connector, a by-pass valve assembly and a blow-out sub. If the tool is embodied to be used with drill pipe which is capable of imparting rotation to the milling means the coil tubing connector, by-pass valve assembly and blow-out sub may be omitted.
The preferred embodiment of the invention offers a number of improvements as compared with prior art systems for window milling. In particular, the use of a support member moveable along the guide track and in which the leading end of the milling tool is rotatable supported offers particularly good support and guidance for the milling tool and reduces the operating torque required to effect milling of the casing. Also, by suitably designing the guide member the overall diameter of the apparatus as it is run into the well can be significantly less than the diameter of the casing to be milled. For example, the preferred embodiment of the invention, in the configuration in which it is run into the well, will pass through a restriction of 3.813 inches (96.85 mm) and yet will be able to mill a window in casing having an inside diameter of 6 inches (152.4 mm) or thereabouts.
In the case of embodiments intended to mill a casing having an inside diameter substantially larger than the initial overall diameter of the apparatus, means are provided for orientating the guide member within the casing such that the trailing end of the guide member rests against the casing adjacent one side thereof and the leading end of the guide member is held adjacent the casing on the diametrically opposite side thereof to the point of engagement of the trailing end with the casing. With the guide member maintained in this orientation the guide track will extend from adjacent one side of the casing obliquely across the casing towards the diametrically opposite side of the casing. The ang
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International Publication No. WO 95/07404 to T. Carter et al., dated Mar. 16, 1995, entitled "Apparatus for Use in a Wellbore".
Lau Werner B.
McGarian Bruce
Tulloch Rory McCrae
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