Information
-
Patent Grant
-
6167961
-
Patent Number
6,167,961
-
Date Filed
Thursday, May 20, 199925 years ago
-
Date Issued
Tuesday, January 2, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Bagnell; David
- Dougherty; Jennifer R.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 166 1175
- 166 1176
- 166 298
- 166 313
- 166 556
-
International Classifications
-
Abstract
A whipstock assembly 10 for setting within a casing C on an anchor A diverts a cutting mill M to cut a window in the casing. The whipstock assembly is passed through a restriction positioned above the location where the whipstock assembly is set, is lowered past the restriction in a run in position, and is set within the casing in a set position. The whipstock assembly includes an upper whipstock body 20 having a ramp surface 22, 26, a middle lower whipstock body 60 having a concave guiding face 72, and a lower whipstock body 110 having a concave whipstock diversion face 112. A lower hinge member 118 is provided for positioning the concave whipstock diversion face for diverting the cutting mill, and at least one whipstock positioning member 80, 100 engages the casing when in the set position for positioning the middle whipstock body guiding face. Accordingly the method of the invention, the cutting mill and at least a portion of the a downhole motor may be positioned adjacent the guiding face of the middle whipstock body when initiating rotation of the cutting mill. The whipstock and method of the present invention are particularly well suited for conducting a thru tubing operation, with the tubing OD being less than the ID of the casing which the whipstock assembly is set.
Description
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 before activating the downhole motor to insure that the cutting mill is out of engagement with the lower whipstock body diversion surface when the mill is first rotated. The rotating mill may be then be lowered for engagement with the whipstock diversion surface.
It is an object of the present invention to provide an improved whipstock assembly and an improved method for cutting a window in a casing after passing the whipstock assembly through a substantial restriction in a wellbore. The whipstock assembly and the method of the present invention are particularly well suited for use in thru tubing operations, wherein a tubing having an outer diameter less than an inner diameter of the casing is positioned within a well, and the whipstock assembly is lowered through the tubing while in a run in position then lowered below the tubing and set within a casing for diverting a mill to cut a window in the casing.
It is a related object of the present invention to improve the reliability of cutting a window in a casing after passing a whipstock assembly through a restriction positioned above the location where the window is cut. The whipstock assembly is provided with a concave guiding face for guiding the cutting mill prior to engaging the concave whipstock diversion face which diverts the cutting mill to cut the window in the casing.
It is a significant feature of the present invention that the whipstock assembly may be reliably set within a large diameter casing after passing through a small diameter restriction positioned above the location where the whipstock assembly is set. The whipstock assembly may be retrievable so that, after cutting the window in the casing and drilling a lateral from the wellbore, the whipstock assembly may be returned to the surface by raising the whipstock assembly through the restriction.
It is an advantage of the present invention that the whipstock may include a ratchet mechanism which ensures that the whipstock assembly remains in the set position until it is intentionally disabled for releasing the whipstock assembly.
It is another advantage of the present invention that the lower end of the upper body of the whipstock assembly may be designed to remain out of engagement with the casing, thereby enhancing the reliability of the whipstock assembly moving from the run in position to the set position.
Yet another advantage of the invention is that the whipstock positioning member may be provided with a stop surface for limiting movement of the whipstock upper body relative to the whipstock middle body.
Still another advantage of the invention is that the reliability of the whipstock setting operation is enhanced by utilizing a rod to move the whipstock assembly components to the set position, with the rod first initiating movement of the lower components of the whipstock assembly and subsequently initiating movement of upper components of the whipstock assembly.
These and further objects, features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A
,
1
B,
1
C,
1
D,
1
E and
1
F illustrate successively lower portions of a whipstock assembly, partially in cross section, in the run in position for passing through a restriction in a wellbore.
FIGS. 2A
,
2
B,
2
C and
2
D illustrate the whipstock assembly in the set position within a casing.
FIG. 3
illustrates an exemplary anchor for securing the position of the whipstock assembly within a casing.
FIG. 4
is a cross section taken along lines
4
—
4
in FIG.
1
A.
FIG. 5
is a cross section taken along lines
5
—
5
in FIG.
2
C.
FIG. 6
is a cross section taken along lines
6
—
6
in FIG.
2
C.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1
consists of
FIGS. 1A
,
1
B,
1
C,
1
D,
1
E and
1
F, which are successively lower portions of suitable whipstock assembly
10
according to the present invention. The whipstock assembly
10
as shown in
FIG. 1
is in the run in position. In the following description, the whipstock assembly
10
is discussed for positioning within a vertical wellbore. Those skilled in the art will appreciate that the whipstock assembly and method of the present invention are conventionally used in inclined or deviated wellbores, although for ease of explanation the wellbore axis for following description will be considered vertical. Also, those skilled in art will appreciate that the terms “upper” and “lower” are used herein with reference to such typical orientation, and should not be construed in the limiting sense.
The primary components of the whipstock assembly are a setting tool
12
shown in
FIG. 1A
, and upper whipstock body
20
shown in
FIGS. 1A
,
1
B, a middle whipstock body
60
shown in
1
B,
1
C and
1
D, a lower whipstock body shown in
FIGS. 1D and 1E
, and a latch assembly
140
shown in
FIGS. 1E and 1F
. According to the present invention, this entire assembly may be lowered into a wellbore through a restriction, which in a typical application will be a tubing string T, a portion which is shown in FIG.
1
A. Once passed through the lowermost end of the tubing string T, the whipstock assembly
10
of the present invention may be set within a casing C, which is shown in FIGS.
2
A-
2
D. Those skilled in the art will appreciate that the outer diameter of the tubing T is less, and in many applications is significantly less, than the inner diameter of the casing C. The whipstock assembly of the present invention is thus well suited for a thru tubing application wherein the whipstock assembly is passed through a small diameter tubing and out the lowermost end of the small diameter tubing, is set within a much large diameter casing for cutting a window in the casing, and then optionally retrieved to the surface by passing upward through the tubing string T. A suitable embodiment in the present invention may include a upper whipstock body, a middle whipstock body, and a lower whipstock body which each have a nominal diameter of from 3.5 to 3.8 inches, and that the whipstock assembly may be set within a casing having an inner diameter of from 8 inches to 9 inches.
Those skilled in the art will appreciate that a wellbore may have significant restrictions other than a tubing string already in the well, and that considerable cost savings may be realized by passing a whipstock assembly through the small diameter restriction and then setting the whipstock assembly below the restriction in a large diameter casing. Those skilled in the art will thus appreciate that restrictions other than a tubing string may exist within a well such that it is beneficial to pass the whipstock assembly of the present invention through the restriction and then set the whipstock assembly in a casing having an interior diameter much larger than the restriction. Accordingly, the term “restriction” as used herein means a passageway whose average diameter is less than approximately 65% of the interior diameter of the casing in which the whipstock assembly is set, more typically it is in the range of from about 40% to 65% of the diameter of the casing string in which the whipstock assembly is set.
The whipstock assembly
10
may be passed through the tubing string T in the wellbore by lowering the assembly from a work string WS as shown in
FIG. 1A. A
suitable setting tool
12
according to the present invention is a hydraulically activated setting tool of the type well know in the art. The setting tool
12
includes an outer sleeve
14
and an inner rod
16
which is movable relative to the outer sleeve upon actuating the setting assembly. More particularly, an exemplary actuation of the setting tool raises the rod
16
with respect to the sleeve
14
, or alternatively pushes the sleeve
14
downward relative to the rod
16
. A lower end of the setting sleeve
14
engages a shoulder surface
25
on the upper whipstock body
20
and the rod
16
extends downward within the bore
28
of the upper body to the connector
30
.
Referring to
FIGS. 1A
,
1
B and
4
, the upper whipstock body
20
has top concave ramp surface
22
, which is preferably angled at about 15 degrees relative to a central axis of the whipstock assembly, a concave ramp surface
26
which is discussed in further detail below, and a casing engaging surface
24
also discussed further below. The concave ramp surface
26
of the upper whipstock body may be considered the front surface of the upper body, and accordingly the casing engaging surface
24
which is radially opposite the front or high side surface
26
may be considered the back or low side surface of the upper whipstock body. The whipstock back surface
24
of the whipstock body may be machined as shown in
FIG. 4
to match the ID of the casing in which the whipstock will be set, so that the upper portion of the upper whipstock body
20
will be in planar engagement with the casing C when the whipstock assembly is set.
The connector
30
may be shear pinned in the run in position to the upper whipstock body
20
by pin
32
. A shear stud
34
may be extend downward from the connector
30
and to a ratchet assembly
40
. The ratchet assembly
40
includes a ratchet retainer and ratchet ring or subassembly
42
and a ratchet assembly mandrel
44
. The ratchet assembly is discussed further below, and is of the type known in the art for use in whipstock assemblies to retain a set whipstock in that condition. A guide body
46
is provided at the lower end of the bore
28
in the upper body, and as explained subsequently is movable within the bore of the upper body. The lowermost end
48
of the upper body
20
not need contain a bore, but may contain a backside slot
47
for allowing movement of the upper link
56
.
The lower end of the upper body
20
is pivotally connected with the upper end of the middle whipstock body
60
by an upper hinge member
50
. The hinge member
50
is pivotally connected at
49
to the upper whipstock body and similarly is pivotally connected at
51
to the middle whipstock body. The upper hinge member
50
includes a front or high side surface
52
, and a back or low side surface
70
for engagement with a stop surface
71
on the middle whipstock body
60
. A shear pin
63
is provided for maintaining the position of the upper hinge member
50
in the run in position while the whipstock assembly
10
is lowered in the well. The lower end of the hinge member
50
includes a curved surface
66
and a short planar surface
64
. One of these surfaces is continually in engagement with the planar surface
65
in the upper end of the middle whipstock body
60
. The engaging surfaces
64
and
65
are positioned as show in
FIG. 1B
to the right of the centerline of the pin
51
, thereby ensuring that, when the shear pin
63
is severed, the upper hinge member
50
can only rotate in the desired direction to achieve setting of the whipstock assembly. The rotational force which rotates the hinge member
50
is downward through the sleeve
14
and the upper whipstock body
20
then to the pin
49
, which as shown in
FIG. 1B
is slightly to the left of pin
51
, thus achieving rotation of the hinge member
50
. The uppermost end of the hinge member
50
also includes a concave ramp surface
52
which may be parallel with the concave ramp surface
52
of the upper hinge member when the whipstock assembly is in the set position. The middle whipstock body has a concave guiding surface
72
which extends downward from the lowermost end of ramp surface
53
to the lower end of the middle whipstock body
60
.
The middle whipstock body
60
also has aback side slot
62
for receiving the upper rod
58
and the middle rod
90
as discussed below.
Upper link
56
is pivotally connected at
52
to guide body
46
. Upper rod
58
extends down from link
56
into slot
62
. The lower end of the rod is connected to an upper middle link member
74
. A lower middle link member
76
is pivotally connected at
75
to the upper middle link
74
, and middle rod
90
extends downward from the lower middle link
76
. A whipstock positioning member
80
is pivotally connected to the middle whipstock body
60
at pin
81
and is retained in the run in position by shear pin
82
. The middle whipstock body
60
thus has a narrow through slot
83
extending from the concave surface
72
to the opposing back surface of the middle whipstock body. The whipstock positioning member
80
is also pivotally connected to the upper middle link
74
by pin
84
, which slides within slot
86
provided in the upper middle link
74
. The lower end of the middle rod
90
is similarly connected to a similar assembly comprising another upper middle link
92
, a lower middle link
94
, and a pivot connection
105
between these members. Another whipstock positioning member
100
is pivotally connected at
101
to a lower end of the middle whipstock body
60
. The pivot member
100
is moveable within through slot
163
, and is retained in the run in position by shear pin
102
. Pin
104
is connected to the positioning member
100
, and slides within the slot
106
. The lower rod
96
extends downward from the lower middle link
94
and, when in the run in position, fits within back slot
114
in the lower whipstock body
110
. The lower link
97
is threadably connected to the lower rod
90
and pivots about pin
128
mounted on lower connector
126
.
A conventional tongue in groove hinge connector
98
is provided for pivotally connecting the lowermost end of the middle body
60
with the uppermost end of the lower whipstock body
110
. The lower whipstock body
1
10
includes a front concave whipstock diversion face
112
and a rear slot
114
for receiving the lower rod
96
. A conventional lug
116
is provided at the uppermost end of the lower whipstock body
110
. A lower hinge member
118
is pivotally connected at
120
to the lowermost end of the lower whipstock body
110
and is pivotally connected at
122
to a lower connector
126
. Connector
126
includes threads
130
for mating with the latch assembly
140
. The lower hinge member pivots about the axis of pin
122
mounted on lower connector
126
. The lower hinge member
118
is retained in the run in position by shear pin
124
.
A latch assembly
140
is a type conventionally provided for securing the whipstock assembly to an anchor which is set in a well, and includes an upper bushing
132
with threads for mated engagement with threads
130
, retaining nut
133
surrounding orientation sub
134
, overshot bushing
136
in threaded engagement with overshot
138
, and lower latch housing
142
. A key
141
is provided for securing the latch housing
142
in a selected position so that when the whipstock assembly is secured to the anchor, the faces of the whipstock assembly which engage the mill will be properly aligned.
The whipstock assembly
10
discussed above may thus be lowered in the well in the set position until the latch assembly
140
is secured to a conventional anchor, such as anchor
150
shown in
FIG. 3
set within the casing C. The anchor
150
includes a plurality of upper slips
152
and a plurality of lower slips
154
. Each of these slips may be moved radially outward into engagement with the inner wall of casing C by a plurality of circumferentially spaced wedge members
156
and
158
, respectively. Sub
160
extends upward from the slips, and the upper end of the sub
160
is provided with a orientation surface
162
which cooperates with the latch assembly
140
to achieve the desired orientation of the whipstock assembly in the well so that the mill will drill a window and a lateral at the desired azimuth. Further details with respect to suitable anchor assembly
150
are discussed in U.S. Pat. No. 5,595,247, hereby incorporated by reference.
Once the whipstock assembly position has been secured on the anchor
150
, the whipstock assembly is moved from the run in position to the set position. To initiate this action, fluid may be pumped through the work string WS to activate the hydraulic setting tool
12
, which then raises the rod
16
with respect to the sleeve
14
and thus the upper whipstock body
20
. Those skilled in the art will appreciate that the hydraulic setting tools of this type are well known in the prior art, and thus the details of the setting tool
12
are not discussed herein. Also, those skilled in the art will appreciate that other types of setting tools may be used to activate the rod
16
for setting the whipstock assembly. If the whipstock assembly is lowered in the well from a wire line rather than a work string, an explosive charge setting tool may be used to move the rod
16
to set the whipstock assembly.
In a preferred embodiment of the invention, the activation of the setting tool
12
first shears the pin
32
which interconnects the connector
30
and the upper whipstock body
20
, thereby allowing movement of the rod
16
. Movement of the rod
16
thereafter preferably activates components of the whipstock assembly starting with the lowermost end of the whipstock assembly
10
and moving upward to set the whipstock assembly. Thus the activation of the setting tool may next shear the member
124
which retains the lower pivot member
118
in the run in position. Further raising of the rod
114
will thus rotate the pivot member in the clockwise direction from the run in position as shown in
FIG. 1E
to the set position as shown in FIG.
2
D. Once flilly rotated to the set position, movement of the pivot member
118
brings the lower whipstock body
110
into engagement with the casing C. More particularly, a concave surface
112
on the whipstock assembly
110
runs out at point
113
, and a lower surface
111
on the whipstock assembly below point
113
is configured for planar engagement with the casing C, as shown in FIG.
2
D. Also, the pivot member
118
may include a rearward casing engaging surface
127
for engaging the casing at a location opposite the location where the window will be cut. If desired, both the surface
111
of the whipstock assembly
110
and a front surface
119
of the pivot member
118
may engage the casing.
Raising of the rod
96
causes the pin member
104
as shown in
FIG. 1D
to engage in the bottom of the slot
106
in the upper middle link
92
. In a preferred embodiment, the pin
104
bottoms out on this slot after rotation of the pivot member
118
is initiated, but prior to movement of the rod
96
causing the pivot member
118
to reach its fully set position. Thus as the pivot member
118
is in the process of moving toward the set position, the pin
104
bottoms out in the slot
106
so that further upward movement of the rod
90
shears the pin
102
which holds the lower whipstock positioning member
100
in the run in position. After shearing the pin
102
, the lower whipstock positioning member
100
will then begin to rotate about pin
101
in the clockwise direction, moving from the position as shown in
FIG. 1D
to the position as shown in FIG.
2
C. The whipstock positioning member
100
has a rearward surface
103
for engaging the casing C, thereby positioning the lower end of the middle whipstock body
60
in its desired position within the casing C. As shown in
FIG. 6
, the whipstock positioning member
100
is a plate like member which is straddled by the lower end of the upper middle link
92
, and accordingly each end of the pin
104
moves downward in a respective slot
106
in the member
92
during the setting operation. Referring to
FIG. 2B
, upward movement of the rod
90
also moves the upper whipstock positioning member
80
from the position as shown in
FIG. 1C
to the position as shown in FIG.
2
B. This movement is similarly accomplished by first raising the upper middle link
74
so that pin
84
bottoms out in the slot
86
, at which point pin
82
which retains the upper positioning member
80
in the run in position is sheared. The upper positioning member
80
then rotates in the clockwise direction about the axis
81
until the rear surface
83
engages the casing.
Movement of the upper and the lower whipstock positioning member is controlled by limiting upward movement of the rod
96
, which in turn occurs when surface
119
and
127
on the lower hinge
118
engage opposing sides of the casing C. The position of the guiding face
72
on the middle whipstock body with respect to the high side of the casing is thus determined by the limit of the upward travel of rod
96
. Each of the positioning members may also include a stop surface, such as stop surface
99
on positioning member
100
(see FIG.
2
C), which would engage the upper surface of the slot in the whipstock body to prevent over-rotation of the positioning member.
When the upper whipstock member
80
moves from the run in position as shown in
FIG. 1C
to the set position as shown in
FIG. 2B
, the middle whipstock body
60
is inherently moved toward the center of the casing C. As discussed above, a downward force is transmitted through the upper body to move the pivot member from the run in position as shown in
FIG. 1B
to the set position as shown in FIG.
2
B. The desired movement is accomplished by first shearing the pin
63
so that the lower end of the upper pivot
50
moves toward the center of the casing, thereby causing the curved surface
66
at the lower end of the upper pivot member
50
to come into engagement with the upper surface
65
of the middle whipstock body
60
. The positioning of the middle whipstock body
60
with respect to the upper whipstock body
20
is limited when the back surface
70
of the upper pivot member
50
engages the stop surface
71
on the middle whipstock body. At this set position, the concave ramp surface
53
at the upper end of the middle whipstock body
60
cooperates with the ramp surface
52
to serve as the transition from the lowermost end of the concave surface
26
of the upper whipstock body
20
to the guide surface
72
on the middle whipstock body
60
.
Referring now to
FIG. 2A
, it should be understood that during this setting operation, the uppermost end of the upper whipstock body
20
normally rests against the “low side” of the casing C. In a typical application, the window may be drilled on the “high side” of the casing. It should be remembered that the casing C in which the whipstock assembly is set in most applications is not truly vertical, and thus the affects of gravity acting on the whipstock assembly normally tends to keep the whipstock assembly against the low side of the casing, which is the left side of the casing shown in FIGS.
2
A-
2
D. The back side
24
of at least the uppermost end of the upper whipstock body
20
may be machined for providing planar engagement with the ID of the casing, as discussed above. Preferably the lowermost end of the upper whipstock body
20
will be spaced slightly from the low side of the casing, as shown in
FIGS. 2A and 2B
, thereby ensuring the reliable setting of the whipstock assembly
10
to accommodate tolerance variations in the various components of the whipstock assembly.
During the upward movement of the rod
16
, the ratchet rod
44
moves upward with respect to the retainer and sleeve subassembly
42
, moving from the position as shown as in
FIG. 1B
to the position as shown in FIG.
2
A. The ratchet assembly
40
functions to ensure that the whipstock assembly is retained in the set position by preventing any downward movement of the rod
58
with respect to the upper whipstock body
20
. Once the whipstock assembly
10
is fully set, further upward force applied to the rod
16
will shear the stud
34
, thereby separating the rod
16
from the ratchet mandrel
44
. Once the stud
34
shears, the hydraulic setting tool including the rod
16
, the sleeve
14
and the connector
30
may be retrieved to the surface by raising the work string, thereby leaving the whipstock assembly set in the well.
A work string may then be used to lower a cutting mill in a well to drill the window in the casing. The cutting mill will similarly be influenced by gravity, and will typically thus first engage initial ramp surface
22
on the upper whipstock body
20
as shown in FIG.
2
A. Further downward movement of the cutting mill will move the cutting mill along the upper whipstock body concave surface
26
, which may have a slight taper of approximately 3° degrees with respect to the central axis of the casing string. Once the cutting mill is lowered to reach the lowermost end of the upper whipstock body, the mill will be forced toward the high side of the casing as it moves along the ramp surface
52
of the upper member
50
and the parallel ramp surface
53
of the middle whipstock body
60
. A particular feature of the present invention is that the concave guiding surface
72
of the middle whipstock body
60
preferably is not tapered with respect to the central axis of the casing, and accordingly this concave surface is a straight concave surface with no taper. The cutting mill may be then lowered along the middle whipstock body with the concave guiding surface
72
of the middle whipstock body retaining the mill trapped between the middle whipstock body and the casing C as shown in FIG.
5
. The length of the middle whipstock body
60
is preferably controlled so that at least a portion of the downhole motor MO as shown in
FIG. 2B
is also effectively trapped between the middle whipstock body and the casing. The downhole motor MO thus typically has a diameter slightly less than the diameter of the mill M, and preferably both the mill M and at least a portion of the downhole motor MO which may be used to rotate the mill are effectively trapped between the concave guiding surface
72
the middle whipstock body and the casing C. This trapping of the motor is substantially reduces any likelihood of the mill rotating out of engagement with the concave surface
72
. The motor and the mill may thus be lowered in the well until the mill M engages the lug
116
on the lower whipstock body
110
. Engagement of the mill M with the lug
116
may be sensed at the surface since further lowering of the work string is not possible. Once the operator senses that the mill has engaged a lug
116
, the operator may raise the mill a short distance, e.g. 2 feet, so that the mill is positioned along the guiding surface
72
of the middle whipstock body. The mill is preferably not raised any further than necessary to ensure that the mill is positioned along a lower end of the middle whipstock body
60
, since preferable the motor MO is also trapped between an upper end of the middle whipstock body and the casing. At this stage, hydraulic fluid may be pumped downhole to activate the motor MO, thereby initiating rotation of the cutting mill M. The cutting mill M will thus begin rotating with both the mill and the motor being effectively trapped between the middle whipstock body
60
and the casing. While the mill is rotating, the work string may be lowered to bring the rotating mill to engagement with the lug
116
, thereby commencing cutting of the window. Those skilled in the art will appreciate that the lug
116
serves to begin cutting of the window in the casing and prevents the mill from merely cutting into the whipstock body. Once an initial hole has been made in the casing, the rotating mill is lowered and as it is lowered the window is widened and lengthened as the mill moves downward along the inclined face
112
of the lower whipstock body
110
. The inclination of the concave diversion face of the lower whipstock body may vary, but in a typical application may be approximately 3° degrees.
Once the mill M has completely formed the window in the casing, another mill may be lowered in the well from a work string to pass through the window cut in the casing and begin drilling a lateral into the formation. The set whipstock assembly
10
thus serves to guide both the mill which cuts the window and the mill which extends the lateral into the formation during a side tracking operation.
Depending on the desires of the operator, the set whipstock assembly may be retained in the set position in the well. Alternatively, however, the whipstock assembly may be unset and retrieved to the surface through the restriction, such as the small diameter tubing T. The retrieval of the whipstock assembly
10
may be accomplished by positioning the lower end of a retrieving tool within the bore
28
of the upper whipstock body
20
, as shown in FIG.
1
. An upward force on the whipstock body
20
may then shear the pin
36
, thereby effectively disabling the ratchet assembly
42
which retained the whipstock body in the set position. Upward movement of the upper whipstock body
20
will thus effectively collapse the set whipstock assembly, returning the whipstock assembly to the run in position. The whipstock assembly may then be retrieved while in the run in position to the surface through the tubing string T. Those skilled in the art will appreciate that if problems are encountered using a conventional retrieving tool to engage the upper whipstock body
20
as discussed above, an overshot tool or die collar may be lowered to engage the threads
23
on the outside of the upper end of the upper whipstock body, and the overshot tool then used to exert the upward force on the set whipstock assembly to return the whipstock assembly to the run in position for retrieval to the surface.
It should be understood that the length of the upper whipstock body, the middle whipstock body and the lower whipstock body will depend upon the desires of the operator. In a exemplary application, the upper whipstock body
20
may have an axially length of 3 or 4 feet. The middle whipstock body
60
may have an axial length of from 12 to 20 feet, and the lower whipstock body may have an axial length of from 20 to 40 feet. Those skilled in the art will appreciate that a fill length of the middle whipstock body and the lower whipstock body are not shown in the figures since a complete showing of each of these whipstock bodies is not necessary for an understanding of the invention. It is preferred, however, that the middle whipstock body
60
have a length of at least twelve feet so that the mill may be raised out of engagement with the lug on the lower whipstock body, as explained above, with both the mill and at least a portion of the downhole motor still trapped by the guiding surface
72
on the middle whipstock body. In one embodiment of the invention, a sleeve may be provided at an upper end of the downhole motor, with this sleeve having a diameter of approximating the diameter the cutting mill. For this application, the length of this upper middle whipstock body thus would typically have to be much longer than twelve feet to ensure that both the mill and the sleeve at the upper end of the motor were in engagement with the guiding surface
72
of the middle whipstock body when initiating rotation of the cutting mill. In other applications, guide pads or sleeves may be positioned at a lower end of the downhole motor, and for these applications the length of the middle whipstock body may be reduced.
In a preferred embodiment to the invention, the lower hinge
118
as shown in
FIG. 2D
not only positions the lower whipstock body into engagement with the casing C, but also acts to stabilize the lower end of the whipstock body by engaging the casing at a location circumferentially opposite the location where the window will be cut. The rear surface
127
on the lower pivot member
1
18
thus essentially forces the lower end of the whipstock body
110
into engagement with the casing. Since the ratchet assembly
40
does not allow the rod
96
to move downward when the whipstock assembly is in the set position, the lower pivot member
118
effectively acts as a cam to force the lower end of the whipstock body into engagement with the casing, thereby stabilizing the position of the lower whipstock body
110
within the casing. Also, the opposing end
119
of the lower pivot member
118
may also engage the casing to further stabilize the lower pivot member
118
when in the set position. In a less preferred embodiment, the set anchor
150
in the well may provide sufficient rigidity to maintain the lower end of the lower whipstock body
110
in engagement with the casing when the rod
96
is pulled upward, so that the pivot member
118
need not engage the casing.
During the above discussion of the operation of the whipstock assembly, it was noted that a component, such as the lower pivot member
118
or the whipstock positioning members
80
,
100
, may engage the casing at a location circumferentially opposite the location where the window will be cut. It should be understood that the term “circumferentially opposite” should not be construed to be limited to a location which is 180° degrees opposite the bottom of the concave surface of the lower whipstock body (and thus not necessarily 180° degrees circumferentially opposite the location where the window will be cut). Instead, the term “circumferentially opposite” as used herein is meant in a broader sense to indicate that these components contact a side of the casing which is on the opposing side from where the window will be cut. For example, it should be understood that the rear surface
127
and the lower pivot member
118
may contact the casing at a location 170° degrees opposite the point
113
where the concave surface runs out, but that the surface
127
is nevertheless circumferentially opposite the location where the window will cut. Those skilled in the art will also appreciate that each of the various components which contact the casing at a location opposite the location will where the window will be cut need not have a single surface contact, and instead may use two or more casing contact surfaces which are spaced apart. For example, in another embodiment, the whipstock positioning member
80
may not be a plate like member but instead may have a Y-configuration, so that the two legs of a positioning member straddle the upper middle link with the rearward end of each of these straddle members then engaging the casing at a position which is circumferentially opposite the location where the window will be cut.
The upper hinge member
50
in a preferred embodiment pivotally connects a lower end of the upper whipstock body and an upper end of the lower whipstock body. The upper concave surface
53
on the middle whipstock body, when moved to the set position, effectively serves as an extension of the ramp surface on the upper body for guiding the cutting mill into position along the guiding surface
72
of the middle whipstock body. Other arrangements may be used for initially positioning the cutting mill and subsequently the motor along the guide surface
72
of the middle whipstock body. Those skilled in the art will appreciate that various types of setting tools and mechanisms may be used for setting the whipstock assembly, for ensuring that the set whipstock assembly is retained in the set position until it is intentionally released, and for releasing the whipstock assembly to be retrieved to the surface. As previously noted, a setting tool may be used to move a rod upward with respect to a setting sleeve which is engagement with the upper whipstock body, but other arrangements will be readily apparent to those skilled in the art for achieving this purpose. Also, the whipstock positioning member
80
and
100
as discussed herein may be pivotally connected to both the upper end and the lower end of the middle whipstock body. In other arrangements, a single positioning member rather than two positioning members may be employed, or three or more positioning members could be utilized. If two positioning members are utilized, the lower positioning member could alternatively be provided at an upper end of a lower whipstock body. Also, these positioning members may be moved to a set position by components other than by movement of a rod responsive to a setting tool. For example, positioning members could be hydraulically actuated to move from the run in position to the set position, and then released to return to the run in position.
Offset centralizers could be used to position the whipstock upper body against the casing at a location opposite where the window will be cut if gravity cannot be relied on for this function. The cutting mill and the motor may have similar offset centralizers to ensure that the mill, when lowered in the well, engages the whipstock upper body so that it enters and is trapped between the middle whipstock body and the casing. While the invention has been particularly desired for embodiments wherein the mill is powered by a downhole motor, the whipstock assembly may also be used to guide a mill which is rotating by rotating a drill string at the surface to turn the mill.
The foregoing disclosure and description of the invention are thus explanatory of preferred embodiments. It would be appreciated by those skilled in the art that various changes in the size, shape and materials, as well as in the details of the illustrated construction and system, the combination of features, and the methods as discussed herein may be made without departing from the invention. Although the invention has thus been described in detail for various embodiments, each should be understood that this explanation is for illustration, and the invention is not limited to these embodiments. Modifications to the apparatus and methods as described herein will be apparent to those skilled in the art in view of this disclosure. Such modifications may be made without departing from the invention, which is defined by the claims.
Claims
- 1. A whipstock assembly for setting within a casing on an anchor for securing the set whipstock assembly within the casing after having passed the whipstock through a restriction positioned above the location where the whipstock assembly is to be set, the whipstock assembly being set within the casing to divert a cutting mill to cut a window in the casing, the whipstock assembly comprising:a lower whipstock body having a concave whipstock diversion face for diverting the cutting mill to cut the window in the casing; a lower hinge member at a lower end of the lower whipstock body for pivoting the lower whipstock body from a run in position for passing the whipstock assembly through the restriction to a set position for positioning the concave whipstock diversion face for diverting the cutting mill; a middle whipstock body above the lower whipstock body, the middle whipstock body moveable relative to the lower whipstock body from a run in position for passing the whipstock assembly through the restriction to a set position, the middle whipstock body having a concave guiding face for guiding the cutting mill when in the set position; a whipstock positioning member above the lower hinge member for moving from a run in position for passing the whipstock assembly through the restriction to a set position for positioning the middle whipstock body guiding face for guiding the cutting mill, the whipstock positioning member having a casing engaging surface for engaging the casing when in the set position at a location circumferentially opposite the location where the window will be cut; and an upper whipstock body positioned above the middle whipstock body, the upper whipstock body movable relative to the middle whipstock body from a run in position for passing the whipstock assembly through the restriction to a set position, the upper whipstock body having an upper body ramp surface for moving the cutting mill when in the set position into engagement with the middle whipstock body guiding face.
- 2. The whipstock assembly as defined in claim 1, wherein the middle whipstock assembly concave guiding face has a substantially zero degree taper when the middle whipstock body is in the set position, thereby trapping the mill between the casing and the concave guiding face.
- 3. The whipstock assembly as defined in claim 1, further comprising:an upper hinge member pivotally connecting a lower end of the upper whipstock body and an upper end of the middle whipstock body; and the upper hinge member movable with respect to the middle whipstock body from a run in position to a set position for radially spacing the middle whipstock body guiding face from the upper whipstock body ramp surface.
- 4. The whipstock assembly as defined in claim 1, further comprising:another whipstock positioning member above the lower hinge member for moving from a run in position for passing the whipstock assembly through the restriction to a set position for positioning the middle whipstock body guiding face for guiding the cutting mill, the another whipstock positioning member having another casing engaging surface for engaging the casing when in the set position at a location circumferentially opposite the location where the window will be cut.
- 5. The whipstock assembly as defined in claim 4, further comprising:each of the whipstock positioning member and the another whipstock positioning member are pivotally connected to the middle whipstock body; and an elongate rod axially moveable relative to the lower whipstock body for moving the whipstock positioning member from the run in position to the set position.
- 6. The whipstock assembly as defined in claim 5, wherein the elongate rod moves both the lower hinge member and the another whipstock positioning member form the run in position to the set position.
- 7. The whipstock assembly as defined in claim 1, wherein the lower hinge member when in the set position moves a portion of the lower end of the lower whipstock body into engagement with the casing.
- 8. The whipstock assembly as defined in claim 7, wherein the lower hinge member includes a lower hinge member engaging surface for engagement with the casing when in the set position at a location circumferentially opposite where the window will be cut.
- 9. The whipstock assembly as defined in claim 1, wherein of the concave guiding face on the middle whipstock body is sufficiently long such that both the cutting mill and at least a portion of a downhole motor for rotating the cutting mill are guided by the middle whipstock body concave guiding face during rotation of the cutting mill.
- 10. The whipstock assembly as defined in claim 1, wherein the whipstock body includes a retrieval surface for engagement with a retrieval tool to retrieve the whipstock assembly to the surface.
- 11. The whipstock assembly as defined in claim 1, further comprising:a stop member for preventing movement of the whipstock positioning member with respect to the middle whipstock body when in the set position.
- 12. A method of cutting a window in a casing after passing a whipstock assembly through a restriction in a well bore, the whipstock assembly being movable from a run in position for passing through the restriction to a set position for anchoring the whipstock assembly within the casing to divert a cutting mill to cut a window in the casing, the method comprising:providing a whipstock assembly having a lower whipstock body with a concave whipstock diversion face, a middle whipstock body movable relative to the lower whipstock body and having a concave guiding face, and an upper whipstock body movable relative to the middle whipstock body and having a ramp surface; lowering the whipstock assembly in the wellbore past the restriction while the whipstock assembly is in the run in position; thereafter anchoring the whipstock assembly within the casing; pivoting a lower end of the lower whipstock body from a run in position for passing the whipstock assembly through the restriction to a set position for positioning the whipstock diversion face for engagement with the cutting mill to cut the window in the casing; moving a whipstock positioning member from a run in position for passing through the restriction to a set position for positioning a middle whipstock body guiding face for guiding the cutting mill, the whipstock positioning member engaging the casing when in the set position at a location circumferentially opposite the location where the window will be cut; moving a lower end of the upper whipstock body relative to an upper end of the middle whipstock body from a run in position for passing through the restriction to a set position for positioning the middle whipstock body guiding face for guiding the cutting mill; lowering the cutting mill for engagement with the ramp surface on the upper whipstock body; thereafter lowering the cutting mill to a position axially adjacent the middle whipstock body guiding face; rotating the cutting mill while positioned axially adjacent the middle whipstock body guiding face; and thereafter lowering the cutting mill into engagement with the lower whipstock body diversion face for cutting the window in the casing.
- 13. The method as defined in claim 12, further comprising:pivotally connecting a lower end of the upper whipstock body and an upper end of the middle whipstock body; and moving the middle whipstock body from a run in position to a set position for radially spacing the middle whipstock body guiding face from the upper whipstock body ramp surface.
- 14. The method as defined in claim 12, further comprising:raising the cutting mill while positioned axially adjacent the middle body guiding face and thereafter rotating the cutting mill.
- 15. The method as defined in claim 12, further comprising:after cutting the window in the casing, retrieving the whipstock assembly to the surface.
- 16. The method as defined in claim 12, further comprising:moving another whipstock positioning member from a run in position for passing the whipstock assembly through the tubing string to a set position for positioning the middle whipstock body guiding face for guiding the cutting mill, the another whipstock positioning member engaging the casing when in the set position at a location circumferentially opposite the location where the window will be cut.
- 17. The method as defined in claim 16, further comprising:pivotally connecting each of the whipstock positioning member and the another whipstock positioning member to the middle whipstock body.
- 18. The method as defined in claim 12, further comprises:engaging each of the lower whipstock body and a lower hinge member with the casing when the whipstock assembly is in the set position.
- 19. The method as defined in claim 12, further comprising:moving an elongate rod axially relative to the lower whipstock body for moving each of a lower hinge assembly and the whipstock positioning member from the run in position to the set position.
- 20. The method as defined in claim 19, further comprising:activating a setting tool to move the elongate rod; and separating the elongate rod after the whipstock assembly is in the set position; and thereafter retrieving the setting tool to the surface.
- 21. The method as defined in claim 12, further comprising:providing a stop for preventing movement of the whipstock positioning member with respect to the middle whipstock body when the whipstock assembly is in the set position.
- 22. The method as defined in claim 12, further comprising:lowering the whipstock assembly through a tubing string while in the run in position, the tubing string having an outer diameter less than an inner diameter of the casing in which the whipstock assembly is set, such that the tubing string forms the restriction in the wellbore.
US Referenced Citations (6)