Wells – Means for guiding insertable element laterally of well axis – Secured in operative position by movable means engaging well...
Patent
1997-04-07
1999-03-23
Neuder, William
Wells
Means for guiding insertable element laterally of well axis
Secured in operative position by movable means engaging well...
175 80, 175 81, F21B 708
Patent
active
058846980
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an assembly for creating borehole branches from a wellbore formed in an earth formation. More particularly the invention relates to an assembly which allows wellbore tools, for example drilling tools or production stimulation tools, to be directed selectively into different deviated borehole branches, and allowing controlled re-entry of the tools.
Whipstocks are commonly used in well drilling in order to deviate the wellbore from an essentially vertical course to a desired inclination. Such whipstocks include tapered sections of round, solid bar which are placed in the wellbore at the desired depth and aligned in the desired direction. They are typically anchored by a slip mechanism, and are used to guide wellbore tools in a selected direction. Generally it is required to mill a window through the casing at the desired kick-off point to permit access to the rock formation around the casing. When only one deviated borehole is drilled, the whipstock is sometimes left in place to act as a guide for re-entry equipment. However, when two or more directional boreholes are drilled from a wellbore it becomes necessary to remove the whipstock from the well so that each of the deviated boreholes can be produced. After removal of the whipstock, selective controlled re-entry into any of the deviated boreholes is difficult and costly since a retrievable whipstock must be placed in the exact position required for re-entry.
It is an object of the invention to provide an assembly for creating deviated borehole branches from a wellbore, which assembly overcomes the aforesaid problems.
In accordance with the invention there is provided an assembly for creating borehole branches from a wellbore formed in an earth formation, comprising a tool guide and positioning means defining a landing position of the tool guide, the positioning means being connected to a casing of the wellbore, the tool guide being positionable at the landing position thereof in at least two different orientations including a first orientation whereby the tool guide guides a tool lowered through the casing in the direction of a first one of said borehole branches and a second orientation whereby the tool guide guides the tool in the direction of a second one of said borehole branches.
The positioning means define an exact landing position for the tool guide, so that repeated positioning of the tool guide in the wellbore at the same position can be achieved without difficulty. The different orientations of the tool guide when in the landing position allow entry of wellbore tools in the different borehole branches. The invention can be used on new wells drilled from surface, or on existing wells which are to be extended.
To create borehole branches of different azimuth angles, suitably the tool guide in the first orientation thereof is oriented in a first angular orientation about the wellbore axis, and the tool guide in the second orientation thereof is oriented in a second angular orientation about the wellbore axis.
Such different angular orientations are suitably achieved if the tool guide includes an upper part and a lower part connectable to said positioning means, the upper part being orientable relative to the lower part in said angular orientations.
Preferably the upper part and the lower part are provided with co-operating splines to facilitate said angular orientations.
To avoid milling windows in the casing to drill the borehole branches, suitably the casing includes at least one window section, each window section being provided with at least one elongated opening, each elongated opening being aligned with one of said borehole branches.
Preferably a removable liner is located inside each window section to temporarily close each opening of the window section during installation of the casing in the wellbore.
The invention will now be described by way of example in more detail with reference to the accompanying drawings in which:
FIG. 1 shows schematically an embodiment of the assembly according to the invention f
REFERENCES:
patent: 3011568 (1961-12-01), Grimm
patent: 5154231 (1992-10-01), Bailey et al.
patent: 5579829 (1996-12-01), Comeau et al.
Hughes John
Konopczynski Michael Robert
Canadian Fracmaster Limited
Neuder William
Shell Research Limited
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