Wells – Means for guiding insertable element laterally of well axis – Secured in operative position by movable means engaging well...
Utility Patent
1999-05-20
2001-01-02
Bagnell, David (Department: 3672)
Wells
Means for guiding insertable element laterally of well axis
Secured in operative position by movable means engaging well...
C160S298000, C160S313000, C160S055000
Utility Patent
active
06167961
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to whipstocks and methods for setting a whipstock of the type commonly used for setting in a casing, cutting a window in the casing and then drilling a lateral from the casing in a formation. More particularly, this invention relates to a relatively small diameter whipstock which may be run in the well and then reliably set in a large diameter casing while minimizing the risk of the window mill rotating out of engagement with the concave whipstock surface. The present invention is thus well suited for a “thru tubing” operation wherein the whipstock is run in the well through a small tubing and is set within a large diameter casing to perform the window cutting operation and the drilling of a lateral. The whipstock may also then be retrieved to the surface through the small diameter tubing.
BACKGROUND OF THE INVENTION
A whipstock is a downhole diversion tool inserted into a well bore and used for deflecting a drill bit, mill, or other tool in a direction that is angularly offset with respect to the orientation of an original well bore. The deflected mill may thus establish a new or additional drilling path. A whipstock set in a casing string on an anchor thus provides an angled whipstock face at the desired depth in the well bore to conduct side track or lateral drilling operations thru the casing string.
It is frequently desirable to cut or mill a window in a casing string that includes therein a smaller diameter tubing or other significant restriction that is positioned above the desired position of the casing window. Since the removal of the tubing string or the removal of this restriction may require considerable rig time and expense, “thru tubing” whipstock assemblies have been developed for passing through a tubing string and then setting in the casing string at the desired depth for milling or cutting the window in the casing. Once the window has been properly cut in the casing, a side track or lateral drilling operation may proceed, using the whipstock face as the diversion tool for the drilling bit. In some applications, the whipstock face is oriented to drill the lateral in a desired azimuthal direction relative to the casing. Thru tubing whipstocks are disclosed in U.S. Pat. Nos. 5,595,247 and 5,769,167. A suitable anchor at the lower end of a whipstock for setting within the casing is disclosed in U.S. Pat. No. 5,595,247.
In many thru tubing whipstock operations, the diameter of the whipstock body and the diameter of the window cutting mill effectively prevent the mill, once positioned against the whipstock concave deflecting surface, from rolling out of engagement with this concave surface during the window cutting operation. In other applications, however, the restriction above the location where the whipstock is set is sufficiently small that the combined diameter of both the whipstock body which is passed thru this restriction and the diameter of the mill which is also passed through this restriction for engaging the whipstock are less than the interior diameter of the casing in which the whipstock is set. The mill may still be used to cut a window in the casing since the lower end of the whipstock is spaced radially from the side wall of the casing opposite the circumferential location where the window is to be cut. In these applications, however, the mill may tend to rotate or roll out of engagement with the concave whipstock surface, so that the mill can then become positioned on the side of the whipstock body rather than against the front concave face of the whipstock body, thereby effectively terminating the intended window cutting operation. Moreover, special problems are presented when attempting to reliably set and reliably retrieve a whipstock in a large diameter casing when the whipstock body has a diameter markedly less than the interior diameter of the casing.
The disadvantages of the prior art are overcome by the present invention, and an improved whipstock and method are hereinafter disclosed which allow a relatively small diameter whipstock to be run into a well, set within a relatively large diameter casing, reliably mill a window in the casing by engaging a cutting mill with the whipstock, drill a lateral into the formation and, if desired, thereafter retrieve the whipstock to the surface.
SUMMARY OF THE INVENTION
A whipstock assembly for setting in a casing on an anchor includes a lower whipstock body having a concave whipstock diversion face for diverting a cutting mill to cut a window in the casing, a lower hinge member for pivoting the lower whipstock body with respect to the anchor, a middle whipstock body moveable relative the lower whipstock body, at least one whipstock positioning member, and an upper whipstock body moveable relative to the middle whipstock body. The whipstock assembly may be run into a wellbore through a substantial restriction positioned above the location where the whipstock assembly is to be set, and accordingly the whipstock assembly is movable from a run in position for passing through the restriction to a set position for cutting the window in the casing. The middle whipstock body has a concave guiding face for guiding the cutting mill when in the set position, and the upper whipstock body has a ramp surface for moving the cutting mill when in the set position into engagement with the middle whipstock guiding face. The whipstock positioning member engages the casing when in the set position at a location circumferentially opposite the location wherein the window will be cut, thereby positioning the middle whipstock body for guiding the cutting mill.
In a preferred embodiment, the middle whipstock body concave guiding face has a substantially zero degree taper when in the set position, such that the middle whipstock body may guide both the cutting mill and at least a portion of the a downhole motor used to rotate the cutting mill. An upper hinge member may be used for pivotally connecting a lower end of the upper whipstock body and upper end of the middle whipstock body. One or more whipstock positioning members may be pivotally connected to the middle whipstock body for reliably positioning the whipstock assembly when in the set position. A setting tool may be used to move a rod which activates the hinge member and the one or more whipstock positioning members to the set position. A stop member may be provided for preventing movement of the whipstock positioning member with respect to the middle whipstock body when in the set position.
According to the method of the invention, the whipstock assembly is lowered in the wellbore past the restriction while in the run in position. The whipstock assembly is then secured to on anchor already positioned within the casing. The lower whipstock body, the middle whipstock body, and the upper whipstock body are each moved from a run in position to a set position, with the whipstock positioning member engaging the casing to position the middle whipstock body. A cutting mill is then lowered for engagement with the ramp surface on the upper whipstock body, and thereafter lowered to a position axially adjacent the middle whipstock body guiding face. The cutting mill may then be rotated while positioned axially adjacent the middle whipstock body guiding face, and the rotating cutting mill then lowered for engagement with the lower whipstock body diversion face for cutting the window in the casing.
According to a preferred embodiment of the invention, a lower end of the upper whipstock body and an upper end of the middle whipstock body may be pivotally connected. A pair of whipstock positioning members may be provided each for engaging the casing at a location circumferentially opposite the location where the window will be cut. Each whipstock positioning member may be pivotally connected to the middle whipstock body. Both the lower whipstock body and the lower hinge member may engage the casing when in the set position. A setting tool may be used to move the whipstock assembly to the set position. The cutting mill may be raised
Braddick Britt O.
Pollard Michael E.
Bagnell David
Bushman Browning
Dougherty Jennifer R.
TIW Corporation
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