Note: Descriptions are shown in the official language in which they were submitted.
CA 02534883 2006-10-04
51488-4D
CASING MILL WITH CORE BREAKING MECHANISM
BACKGROUND OF THE INVENTION
Field of Invention. The present invention relates generally to methods and
apparatus
for milling windows in well casings in the downhole environment whenever the
trajectory of a well should be modified after a casing or liner has been set
in a well or
when one or a plurality of branches are built from a parent well. More
particularly,
the present invention concerns a method and apparatus for milling casing
windows
which ensures predictable milling so that the resulting casing window will be
of
predetermined dimension, contour geometry; location and orientation. Even more
specifically, the present invention provides for stabilized rotation and
efficiently
controlled guiding of a pilot mill having articulated and rotary driven
relation with a
substantially rigid string mill, especially during initiation of casing
milling, to ensure
efficient deflector controlled guiding of the pilot mill and guiding of the
string mills
by the pilot mill, to ensure precisely controlled formation of a casing window
by the
pilot mill and string mills. The present invention also concerns a casing
window
milling system incorporating an articulated pilot mill having the capability
for
controlling its amplitude of relative misalignment with a substantially rigid
milling
shaft and having rotary driven relation with the milling shaft during
initiation of
casing milling and during initial pilot boring into the subsurface formation
from the
casing window.
Related Art. Casing windows are required whenever the trajectory of a well
should
be modified after a casing or a liner has been set in a well or when one or a
plurality
of branches are built from a parent well.
A casing window is generally performed with a combination of mills mounted on
a
mandrel at the bottom end of a drill string and wedging between the casing and
a
deflection tool called the whipstock. The whipstock is generally set in the
hole in
combination with the first milling run. 1'he window may be completed in one
single
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operation in the hole or in multiple runs. The peripheral surface of mills is
generally
covered with abrasive or cutting inserts made of hard material such as
sintered
tungsten carbide compounds brased on a steel mandrel. The hardness of the
whipstock is generally designed so minimum wear will be generated by the
rotation of
mills peripheral surface onto the whipstock face while the assembly is pushed
and
rotated against the casing wall under deflecting action of the whipstock.
However the
milling action generally results from unbalanced pressures between
respectively the
mills) and the whipstock on one hand and the mih(s) and the casing wall on the
other
hand.
In high inclination condition; the whipstock face is generally oriented upward
and
therefore forces applied by the mills) onto the whipstock face increase with
the
increasing weight component of the milling string. Although a whipstock is
expected
to support some milling damage, how much whipstock material is left after
milling
has been preformed is difficult to predict. In such case the success of
whipstock
retrieval may become risky and lead to lost time and additional contingency
and
sometimes to the loss of the bottom section of the well.
The lack of control on the window geometry is another major disadvantage of
conventional window milling techniques and makes some lateral branching
techniques inapplicable or more complex. Most windows show a lower section
directed sideways with respect to the hole axis. How much this "walk away"
affects a
window is hardly predicable and depends on several factors like well
inclination, pilot
mill size and shape, mill cutting structure, weight on bottom hole assembly,
whipstock hardness and orientation.
When the formation surrounding the well casing being penetrated by the window
bore
is well consolidated, it is desirable that the pilot mill have a geometry
enabling it to be
efficiently guided along an intended trajectory by the wall surface of the
wellbore
being formed. When the formation surrounding the wellbore is not well
consolidated,
a pilot mill which has a freely articulated and rotary driven connection with
a
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substantially rigid milling shaft could be subject to forces that might tend
to change its
course from the intended trajectory. If the pilot mill should be suddenly
articulated
when encountering some unusual structure in the downhole environment, the
pilot
mill or its articulated connection with the milling shaft could become
damaged,
S perhaps to the extent of being separated from the milling shaft. It is
desirable
therefore to provide a casing window milling system having an articulated
pilot mill
and also having a mechanism for controlling the amplitude of relative
misalignment
of the pilot mill relative to the axis of rotation of the milling shaft. This
pilot mill
amplitude control feature will permit the pilot mill to be efficiently
deflected so as to
follow the slope of the deflecting tool without damaging the deflecting tool
and will
permit the pilot mill to be constrained in a coaxial relationship with the
milling shaft
so as to be guided by the milling shaft after the pilot mill has passed a
point on the
deflecting tool where self guiding of the pilot mill can no longer be ensured.
Thus it
is desirable to provide a casing window milling tool which incorporates a
locking or
restraining mechanism which can be actuated mechanically or hydraulically to
lock
the pilot mill in co-axial, stabilized relation with the milling shaft.
SUMMARY
It is a primary feature of the present invention to provide a novel method and
apparatus for predictable milling of casing windows which employs a rotary
milling
tool having an articulated pilot mill provided with cutting means only on its
forward
axial end so that the pilot mill is capable of cutting only on the forward
axial end
thereof and will not cut or substantially erode away a deflection element that
is
utilized to guide the pilot cutter;
It is another feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which utilizes an articulated pilot
mill not
only for pilot hole cutting but also for efficiently guiding other milling
cutters of the
apparatus during milling activities so that the geometry and location of the
resulting
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casing window will conform specifically to plan and will not be varied by
other
factors during milling;
It is also a feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which employs guide means such as a
tubular guide bearing to render the pilot mill extremely stable during initial
forming
of the casing window;
It is another feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which utilizes an articulated pilot
mill
having a non-milling periphery for guided engagement with an inclined guide
surface
of a deflecting device and having a forward milling end for milling a pilot
window
bore through the well casing and into the surrounding formation;
It is also a feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows wherein a pilot mill is employed
which has
articulated driven connection with a substantially rigid string mill and which
is
adapted for non-milling engagement with an inclined guide surface and is
adapted for
pilot window milling engagement with the casing of a well;
It is a feature of the present invention to provide a well casing milling
system
incorporating a pilot mill having articulated driven connection with a
substantially
rigid string mill shaft wherein the articulated driven connection comprises a
universal
joint which transmits torque and axial load from the substantially rigid
string mill
shaft to the pilot mill;
It is also a feature of the present invention to provide a novel casing window
milling
system having a pilot mill that has articulated rotary driven connection with
a
substantially rigid milling shaft by means of a universal joint and wherein
the
universal joint incorporates an articulation control mechanism for adjusting
the
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amplitude of angular misalignment of the pilot mill relative to the milling
shaft
between a maximum allowable angle and a coaxial relationship and for locking
the
pilot mill at the selected amplitude of angular misalignment;
It is another feature of the present invention to provide a well casing
milling system
incorporating a pilot mill and a substantially rigid string mill shaft and
means for
decoupling the bending moment that would otherwise be transmitted between the
pilot mill and string trill shaft as the pilot mill is diverted from the
longitudinal axis of
the well casing to the inclined path of the guide surface of the deflector
tool;
It is an even further feature of the present invention to provide a well
casing milling
system incorporating a deflecting tool having an upper guide bearing to
provide an
articulated rotary driven pilot mill of a milling assembly with precise
guiding during
initial casing window milling to ensure rotary stabilization of the pilot mill
and ensure
proper orientation and direction of the pilot bore;
It is a feature of the present invention to provide a well casing milling
system
incorporating a pilot mill having articulated driven connection with a
substantially
rigid string mill shaft and wherein the articulated rotary driving connection
defines a
flow passage through which a suitable fluid may be pumped for cooling or
otherwise
enhancing the casing window milling operation;
It is a feature of the present invention to provide a well casing milling
system
incorporating a pilot mill having articulated driven connection with a
substantially
rigid string trill shaft and wherein the pilot mill defrnes a non-milling
substantially
cylindrical guiding periphery and the articulated rotary driving connection
defines the
axis of rotation of the pilot trill and is located within and intermediate the
axial length
of the pilot mill to provide for stability and guidance thereof;
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it
It is another feature of the present invention to provide a well casing
milling system
incorporating a deflecting tool which is set within the well casing and which
defines
an inclined guide surface for non-milling engagement by an articulated pilot
mill of a
casing window milling assembly and which deflecting tool defines a passage
through
which fluid may be caused to circulate and well tools may be passed for
conducting
other well activities with the deflecting tool in place or for retrieval of
the deflecting
tool from the well casing;
It is a feature of the present invention to provide a well casing milling
system
incorporating a pilot mill having articulated driven connection with a
substantially
rigid string mill shaft and employing a rotary drive means having articulated
driving
connection with the substantially rigid string mill shaft, which rotary drive
means may
take the form of a positive displacement motor, turbine or other equivalent
power
source and which rotary drive means may be rotated by a drill string for
enhancing the
power and/or speed of the milling system;
It is another feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows and has a pilot mill which has
articulated
driven connection with a substantially rigid milling shaft having string mills
and
which provides radial force to the rigid shaft and string mills causing the
string mills
to penetrate into the casing without substantial wear of the guide face of the
deflection
tool;
It is also a feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which incorporates a deflecting tool
which
is set within the well casing and a milling assembly having a substantially
rigid
milling shaft and a pilot mill having articulated rotary driven connection
with the
milling shaft and wherein the milling assembly and the deflection tool may be
releasably interconnected during running operations to ensure single pass
installation
and desired initial relative positioning of both the deflecting tool and
milling assembly
before the casing window milling operation is initiated;
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It is an even further feature of the present invention to provide a novel
method and
apparatus for predictable milling of casing windows which employs an elongate
milling tool having sufficient stiffness to prevent or minimize its deflection
during
milling so that the resulting casing window will have precisely and
predictably
determined characteristics of window dimension, window contour geometry and
location;
It is also a feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which employs deflection tool
establishing
a substantially tubular pilot mill guide or pilot mill and rotary drive motor
guide for
guiding the articulated pilot of the window milling tool and wherein a portion
of the
tubular pilot guide is partially milled by succeeding window mills to form the
deflecting tool with a predictable guide surface geometry that is suitable for
guiding
well tools from the main well bore through a casing window and into a lateral
bore;
and
It is an even further feature of the present invention to provide a novel
method and
apparatus for predictable milling of casing windows which incorporates a
deflecting
tool and milling tool which enable guided movement of the milling tool and its
rotary
drive motor and rotary stabilizer within a guide passage of the deflecting
tool; and
It is also a feature of the present invention to provide a novel method and
apparatus
for predictable milling of casing windows which is design to enable a
deflecting tool
and a casing window milling tool to be run into a well casing as a unitary
assembly
and after milling of a casing window, to be extracted from the well casing as
an
assembly.
Briefly, a downhole casing window milling assembly embodying the principles of
the
present invention is composed of a rotary positive displacement motor, a
hollow
rotary driving articulation connected to the motor bit box on its upper end
and to a
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substantially rigid milling shaft on its lower end, a pilot mill having
articulated
connection with the substantially rigid milling shaft, a deflection tool
releasably
connected to the bottom of the milling tool and an anchoring device at the
very
bottom which additionally provides for location and orientation of the casing
window
milling system within the well casing.
The rotary positive displacement motor drives the milling assembly through an
articulated joint such as a universal joint or a short flex joint which also
defines a flow
passage. The purpose of such articulation or short flex joint is to decouple,
cancel or
minimize bending moments that could be transmitted by the milling assembly to
the
motor bearings while still allowing fluid to circulate to the bottom of the
milling
assembly. If desired, the rotary drive motor can eventually include two power
sections to provide additional torque without creating additional conveyance
constraints in high dog leg severity wells.
The downhole motor can be also a turbine or other alternative downhole rotary
power
I S generation wherever the mechanical power source will be most appropriate
without
noticeably affecting the basic benefit of the milling equipment. The downhole
motor
and its rotational stabilizer can also be adapted for passing through the
deflecting tool
and to be guided by the deflecting tool when the deflecting tool incorporates
a tubular
guide.
Although use of downhole rotating power source such as positive displacement
motors provide better milling performance in deviated or horizontal wells, the
bottom
milling tool may be alternatively powered by or in combination with a
conventional
rotary drill string. While using a downhole power source, the drill string may
be
rotated to provide additional mechanical power to the milling tool and also to
minimize the effect of dragging forces and thus provide better control of
milling tool
penetration.
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The casing window milling assembly is composed of a plurality of string mills
mounted on a substantially rigid hollow milling shaft. A pilot mill is mounted
for
articulation at the bottom end of the milling shaft and is rotated and moved
axially by
the milling shaft. The pilot mill is of generally cylindrical configuration
and defines a
generally cylindrical outer peripheral surface which establishes a non-
milling, guided
relationship with the inclined guide surface of the deflecting tool. The pilot
mill has
a milling face only at its forward. end and has no abrasive material on its
outer
periphery so that the deflecting tool is not subject to significant milling
action by the
pilot mill as the pilot mill is rotated and guided during window milling. The
pilot mill
is articulated within a small angular amplitude relative to the milling shaft
so it can
spin along an axis parallel to the inclined guide face of the deflection tool
and be
guided without milling the guide face of the deflection tool, unlike
conventional
casing window milling tools which typically having milling contact with the
deflection tool and thus tend to remove at least a portion of the guide face
during
milling. The milling shaft is provided with at least one and preferably two or
more
string mills, such as a gauging mill and a reaming mill, for example, which
are each
typically of greater diameter than the diameter of the pilot mill. The initial
string mill
is mounted to the milling shaft at a relatively short distance from the pilot
mill so
most of the opening milled in the well casing will be made with the initial
string mill.
Optionally, one or several reaming mills can also be mounted on the milling
shaft
above the first string mill. In most common situations, casing windows are of
full
size, meaning that the diameter of a cylinder passing through the window is
substantially equal to the casing inside diameter. In this case the outside
diameter of
the pilot mill is smaller than that of the string mills) which typically have
a diameter
that is very close to the drift diameter of the casing. The milling system can
incorporate a locking or restraining mechanism for controlling the amplitude
of
misalignment of the pilot mill relative to the milling shaft from a coaxial
relationship
to a relationship permitting a maximum degree of allowable articulation. This
feature
permits the pilot mill to be efficiently guided along the slope of the
deflecting tool or
whipstock during~initial casing window milling and permits guiding of the
pilot mill
to be controlled by the milling shaft when the pilot mill has moved along the
guiding
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CA 02534883 2000-04-14
78543-43D
face of the whipstock to a point that its efficient self
guiding can no longer be ensured. In one suitable form the
locking or restraining system may take the form of a
hydraulic piston actuated mechanism which is maintained in a
release position by captured hydraulic fluid within a closed
chamber. The hydraulic fluid may be released in any
suitable manner, such as by breaking of a frangible element
or by pressure responsive opening of a release valve to
permit spring urged movement of the hydraulic piston to a
position causing restraint or locking of the articulated
connection between the pilot mill and the milling shaft.
When so restrained, the pilot mill will be guided along the
intended trajectory by its coaxial or axial misalignment
controlled relation with the milling shaft and with its
trajectory being controlled by the milling shaft. Moreover,
under conditions where unusual forces are encountered that
might tend to deflect the pilot mill from its intended
course the locking or restraining mechanism will ensure that
the pilot mill will maintain its intended trajectory.
In the case of undersized windows, meaning that
the diameter of a cylinder passing through the window is
substantially smaller than the casing inside diameter, the
diameter of the pilot mill may be equal to the diameter of
the string mills. This is generally the case of a window
milling in a production liner/casing which requires the
milling tool to be passed through a production tubing.
According to another feature of the present
invention, there is provided a pilot mill, comprising: a
mill head structure; a core breaking mechanism having a core
passage and a breaking mechanism; and the core breaking
mechanism located within the mill head structure.
CA 02534883 2000-04-14
78543-43D
According to another feature of the present
invention, there is provided a method for milling,
comprising: providing a pilot mill having a mill head
structure and a core breaking mechanism, the core breaking
mechanism comprising a core passage and a breaking mechanism
and located within the mill head structure; rotating the
pilot mill; receiving a core of non-milled surface within
the core passage; and breaking the core of non-milled
surface with the breaking mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited
features, advantages and objects of the present invention
are attained and can be understood in detail, a more
particular description of the invention, briefly summarized
above, may be had by reference to the preferred embodiment
thereof which is illustrated in the appended drawings, which
drawings are incorporated as a part hereof.
10a
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It is to be noted however, that the appended drawings illustrate only a
typical
embodiment of this invention and are therefore not to be considered limiting
of its
scope, for the invention may admit to other equally effective embodiments.
In the Drawings:
Fig. 1 is an elevation view of a casing window milling tool constructed in
accordance
with the teachings of the present invention and having parts thereof broken
away and
shown in section and further showing the pilot mill thereof in deflecting
engagement
with an inclined guide of a deflection tool;
Fig. 2 is a sectional view of a well casing and casing window deflection tool
and
showing the casing window milling tool of the present invention located within
the
deflection tool and further showing pilot hole milling and staged casing
window
milling;
Fig. 3 is a sectional view showing a deflection tool and further showing the
pilot mill
of the milling tool of Figs. 1 and 2 being located within a substantially
tubular guide
1 S bearing of the deflection tool;
Fig. 4 is a sectional view taken along line 4-4 of the deflection tool of Fig.
3 showing
the geometry of the guiding face of the deflection tool before milling has
taken place;
Fig. 5 is a sectional view taken along line 4-4 of the deflection tool of Fig.
3 showing
the geometry of the guiding face of the deflection tool after casing window
milling
has been completed;
Fig. 6 is a sectional view taken along line 6-6 of the deflection tool of Fig.
3 showing
the geometry of the pilot mill guide bearing of the deflection tool before
milling has
taken place, showing a pilot null located within the pilot mill guide bearing
and
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further showing fastener means releasably securing the pilot mill within the
pilot mill
guide bearing for installation of the window milling assembly;
Fig. 7 is a sectional view taken along line 6-6 of the deflection tool of Fig.
3 showing
the geometry of the pilot mill guide bearing of the deflection tool after
casing window
milling has taken place and showing the resulting open guiding face that is
formed by
staged milling of the pilot mill guide bearing by staged milling;
Figs. 8-10 are longitudinal sectional views in sequence, showing an accurate
casing
exit operation being carried out according to the teachings of the present
invention;
Fig. 11 is a longitudinal sectional view showing the pilot mill sub-assembly
of the
present invention;
Fig. 12 is a transverse sectional view taken along line 12-I2 of Fig. 11;
Fig. 13 is an end view of the pilot mill sub-assembly of Figs. 11 and 12 and
showing
the milling end face of the pilot mill;
Fig. 14 is a sectional view showing an alternative embodiment of the present
invention located within a well casing at the position for initiating casing
window
milling and wherein the rotary drive motor and the stabilizer are adapted to
be guided
within the guide passage of the deflecting tool along with the pilot mill for
predictable
milling of a casing window and showing deflecting tool geometry for retrieval
thereof
following casing window milling;
Fig. 15 is a sectional view similar to that of Fig. 14 and showing the casing
window
milling operation in progress, with the pilot mill nearing completion of
window
milling and with the string mills having removed a sacrificial portion of the
deflecting
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tool to define a predictable guide configuration for subsequent guiding of
well tools
into the lateral bore;
Fig. 16 is a sectional view showing the deflecting tool of Figs. 14 and 15;
Fig. 17 is a sectional view taken along line 17-17 of Fig. 16;
Fig. 18 is a sectional view taken along line 18-18 of Fig. 16;
Fig. 19 is a sectional view taken along Iine 19-19 of Fig. 16;
Fig. 20 is a partial longitudinal sectional view showing a casing window
milling
system representing an alternative embodiment of the casing window milling
system
of present invention having a pilot mill adapted for controllable articulation
relative to
the milling shaft and showing the pilot mill in a condition for articulating
relationship
with the milling shaft to permit guiding of the pilot mill by the inclined
guide surface
of the deflecting tool;
Fig. 21 is a partial longitudinal sectional view similar to Fig. 20 and
showing the pilot
mill of Fig. 20 being maintained with its longitudinal axis in coaxial
relation with the
Longitudinal axis of the substantially rigid milling shaft to permit guiding
control of
the pilot mill at least in part by the milling shaft;
Fig. 22 is a sectional view showing an alternative embodiment of the
deflection tool
and further showing the pilot mill of the milling tool being located within a
substantially tubular guide bearing of the deflection tool;
Fig. 23 is a sectional view showing an example of a window milled in the
casing
using the alternative embodiment shown in Fig. 22;
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Fig. 24 is a partial sectional view of the pilot mill including one embodiment
of the
core breaking mechanism;
Fig. 25 is a partial sectional view of the pilot mill including a second
embodiment of
the core breaking mechanism;
Fig. 26 is a front view of the pilot mill including the second embodiment of
the core
breaking mechanism;
Fig. 27 is a partial sectional view of the pilot mill secured to the
deflecting tool with
one embodiment of the first retaining mechanism, second retaining mechanism,
and
protection mechanism;
Fig. 28 is a partial sectional view of the pilot mill secured to the
deflecting tool with a
second embodiment of the first retaining mechanism and protection mechanism;
Fig. 29 is a partial sectional view of the pilot mill secured to the
deflecting tool with a
third embodiment of the second retaining mechanism;
Fig. 30 is a sectional view of the retrieving tool inserted in the deflecting
tool;
Fig. 31 is a view taken along line 31-31 of Figure 30;
Fig. 32 is an isometric view of the retrieving tool; and
Fig. 33 is a front view of one embodiment of the resilient member.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and first to Figs. l and 2, a downhole casing
window
milling assembly constructed in accordance with the principles of the present
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invention and representing the preferred embodiment of the present invention
is
shown generally at 10. The casing window milling assembly 10 is comprised of
deflecting tool shown generally at 12, and a milling tool shown generally at
14 and
rotary drive motor assembly shown generally at 16.
S The deflecting tool 10 is defined by an elongate deflecting body 18 which is
adapted
to be run into the main well casing and to be precisely located and oriented
for milling
of a casing window. The deflecting tool 18 may define a longitudinal passage
20
through which fluid may be caused to flow and through which certain downhole
well
operations may be conducted. The longitudinal passage 20 will not interfere
with
deflection of the window milling system during milling operations because, as
will be
explained in detail hereinbelow, the window milling string of the milling tool
will be
caused to precisely traverse a predetermined trajectory to ensure generation
of a guide
surface of predetermined configuration on the deflecting body as the milling
tool is
deflected from the longitudinal axis of the well casing and progresses along a
predetermined inclined path through the wall of the well casing. The
longitudinal
passage 20 will also accommodate a suitably sized spear fishing tool without
compromising the guiding and performance of the deflecting tool. This feature
enables simple and e~cient removal of the deflecting tool from the well
casing. The
Longitudinal passage 20, if desired, may be initially filled with a drillable
material
which is easily removed with the deflecting tool set within the well casing in
the event
the fluid flow or retrievable characteristics of the deflecting tool are
needed. The
deflecting tool 12 may also define a connection geometry to provide e~ciently
for
connection thereof to a retrieval device that is run into the well casing for
connection
to and retrieval of the deflecting tool 12 subsequent to the window milling
operation.
At its lower or forward end the elongate deflecting body 18 defines a
connector
shown generally at 22 which enables connection of various other well equipment
such
as an anchor, bridge plug, selective landing tool or other means that
positively secure
the deflection tool in the well casing. The connector 22 may take the form of
a
connection receptacle 24 into which a connecting section of other well
equipment is
CA 02534883 2000-04-14
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received. Connection may be established by a releasable connector element 26
or by
any other suitable means. Orientation of the deflecting tool 12 with respect
to the
well casing may be established in any suitable manner. For example, the well
casing
may be provided with an orienting coupling within which is located an
orienting slot
or an orienting key of conventional nature. The deflecting tool or any other
apparatus
to which the deflecting tool is connected may be provided with a corresponding
orienting feature for orienting engagement with the orienting slot or key to
thus
provide for precise location and orientation of the deflecting tool with
respect to the
well casing. In the alternative, for weU casings without indexing or orienting
features,
an indexing packer may be set in suitably located and oriented relation within
a well
casing and the diverting tool may be landed and set with respect to the
orienting and
indexing feature of the indexing packer.
At its upper or trailing end the deflecting tool 12 is provided with a pilot
mill guide
which defines a contoured and inclined guide surface 30 representing the
primary
inclined guide surface of the deflecting tool. As is evident from the
transverse
sectional view of Fig. 6, taken along line 6-6 of Fig. 3, the contoured
inclined guide
surface 30 may initially be of partially cylindrical or curved cross-sectional
configuration so that it defines an elongate inclined guide groove or slot
which diverts
a forwardly moving milling assembly from the longitudinal axis of the main
well bore
to the desired exit angle for a lateral bore.
Conventionally, when the initial milling element of a casing window milling
assembly
comes into contact with a deflecting tool, also identified as a whip-stock,
significant
lateral force is imparted both to the whip-stock and to the initial milling
element. This
typically results in significant removal of material forming the guide surface
of the
whip-stock and results in significant application of bending or deflecting
force to the
milling tool and its rotary drive mechanism. Since most conventional casing
window
milling tools are diverted but not significantly guided, the milling tool will
tend to
wander during window milling so that the casing window formed by the milling
operation is typically imprecise from the standpoint of location, orientation,
window
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size and contour geometry. To overcome this disadvantage it is considered
desirable
to ensure precision guiding and controlled orientation of the milling assembly
especially during initial milling contact with the well casing. According to
the
principles of the present invention this precision milling tool guiding
feature is
accomplished by providing the deflecting tool with a guiding and stabilizing
feature
for ensuring the accuracy of milling tool tracking during milling. The
precision
milling feature is also enhanced by eliminating or significantly minimizing
application of lateral forces to the deflecting tool and to the milling
assembly. To
ensure the accuracy of orientation, location, dimension of the contour
geometry of the
casing window being nvlled it is necessary to establish precision guiding and
stabilization of the initial milling element at the outset of the milling
operation. To
accomplish this initial guiding and stabilization feature the elongate body 18
of the
deflecting tool 12 is defined in part by a guide bearing 32 of generally
tubular
geometry which defines a generally cylindrical internal guide surface 33 which
may
form a part of the inclined guide surface or face 30. Thus the inclined
contoured
guide surface 30 is in part of cylindrical configuration so as to define a
pilot mill
guide surface that is oriented along a predetermined inclination relative to
the
longitudinal axis of the well casing that establishes a predetermined lateral
bore
trajectory to be followed by milling apparatus for milling a casing window of
predictable dimension and contour geometry and to establish the trajectory of
a lateral
wellbore which is subsequently drilled along the trajectory that is
established by
window milling equipment.
The milling tool shown generally at 14 incorporates a pilot mill 34 which has
a
substantially cylindrical outer guided periphery 36 defined by a plurality of
lands 38
that are separated by fluid transfer channels 40. The lands 38 are defined by
cylindrical surface segments which establish non-milling guided relation with
the
internal cylindrical surface 30 of the guide bearing 32 and after moving past
the guide
bearing, establish non-milling guided relation with the inclined contoured
guiding
face 30 of the deflecting tool. The internal cylindrical guide surface 33 of
the guide
bearing 32 ensures that the pilot mill is precisely confined to its intended
trajectory
I7
CA 02534883 2000-04-14
ooi63sx1 rc~rntsoonoisi
and ensures precision milling of a pilot bore through the well casing and into
the
formation surrounding the casing. Since only the non-milling cylindrical
guided
surface of the pilot mill 34 will contact the internal cylindrical surface 33
of the guide
bearing 32 or the inclined guide surface 30, the inclined contoured guide
surface will
not be eroded to any significant extent by the pilot mill 34 and thus will
remain after
completion of the milling operation has been completed to serve as a guide
surface for
guiding other well tools through the casing window and into the lateral bore.
As the pilot mill 34 is diverted from the longitudinal axis of the main well
casing to
the trajectory of the branch bore it is desirable that no significant lateral
forces be
imparted either to the pilot mill 34 or to the diverting tool 12. It is also
desirable that
the pilot mill 34 have an efficiently guided and stabilized relationship with
the
internal cylindrical guiding surface of the guide bearing 32 as milling of the
casing is
initiated. It is considered desirable therefore to provide the pilot mill 34
with
pivotally articulated connection with a relative to a substantially rigid
milling shaft, to
be discussed in detail hereinbelow, and to locate its point of pivotal
articulation
internally and intermediate the length of the pilot mill. This feature will
enable the
pilot mill 34 to be readily pivoted so that it will precisely track the
angular inclination
defined by the internal generally cylindrical surface 33 of the guide bearing
32.
Referring now particularly to Figs. 1 l and 12 the pilot mill 34 has a mill
head
structure 35 from which extends an elongate generally cylindrical mill body
37. The
mill body 37 defines an internal connection receptacle 42 within which is
seated a pair
of universal joint inserts 44 and 46 being secured in fixed relation within
the
connection receptacle 42 of the pilot mill structure by connection pins 48 and
SO
which are welded as shown or otherwise fixed to the pilot mill structure. The
connection pins 48 and 50 are received within connection pin receptacles that
are
defined respectively within the universal joint inserts 44 and 46 as shown in
Fig. 11.
It is to be borne in mind that the universal joint inserts may be fixed within
the
connection receptacle 42 by any other suitable means, such as by welding or by
machining partially spherical surface segments within the mill body 37. The
18
CA 02534883 2000-04-14
0 oois3sai rc-rrtrsoona
universal joint inserts 44 and 46 further define internal spherical surface
segments 52
and 54 which, when the inserts are positioned in assembly as shown in Fig. 11,
cooperatively define a spherical receptacle 56 within which is retained a
spherical
universal joint element 58 defining a part of the forward end 60 of an
elongate tubular
milling shaft 62.
To maintain a non-rotatable relationship and to provide for torque
transmission
between the milling shaft 62 and the pilot mill 34 and to also permit
articulation of the
pilot mill relative to the elongate milling shaft the universal joint
receptacles 44 and
46 also define ball receptacle segments 64 and 66 respectively. The ball
receptacle
segments 64 and 66 cooperate with a plurality of ball receptacle segments 68
to define
a plurality of ball receptacles 70 each receiving a torque transmitting ball
72. The ball
receptacles 70 are of greater dimension than the dimension of the torque
transmitting
balls as shown in Fig. 11 to thereby permit the pilot mill 34 to have the
capability for
pivotal articulation relative to the milling shaft 62. The looseness of fit of
the torque
transmitting balls 72 with their respective ball receptacles permits movement
of the
pilot mill 34 about a point P located on the longitudinal axis 74 of the
elongate milling
shaft This feature permits the pilot mill to maintain a predetermined
inclination with
respect to the longitudinal axis of the milling shaft 62 as the pilot mill is
rotated by the
milling shaft. This feature also permits efferent guiding of the pilot null by
the
inclined guiding features of the diverting tool without imparting significant
lateral
force to the diverting tool or bending moment to the substantially rigid
milling shaft
62.
The head swcture 35 of the pilot mill 34 also defines a circular tapered
milling face
76 which intersects with a flat, circular, centrally located mill nose 78. The
milling
face and mill nose is provided with any suitable means for milling or eroding
the well
casing to define a pilot window opening therein. It should be borne in mind
that the
cylindrical outer periphery 36 of the pilot mill 34 is not provided with
milling or
cutting elements or materials so that milling of the well casing occurs only
when the
end face 76 of the pilot mill 34 is moved into contact with the well casing as
the pilot
19
CA 02534883 2000-04-14
oors~szi rc~rn~soonozsi
mill is rotated by the milling shaft 62 via the universal joint
interconnecting the pilot
mill 34 with the milling shaft. The end face and mill nose of the pilot mill
34 is
coated with adequate abrasive inserts such as tungsten carbide compound or
other
suitable abrasive materials that are utilized on casing window mills. The
abrasive
milling material may be brazed or otherwise fixed to the face surface of the
pilot mill
and to the surfaces of string mills that follow the pilot mill. Thus, the
pilot mill 34 is
capable of milling only when its end face 76 is in contact with the well
casing.
Contact by the outer peripheral surface 36 of the pilot mill with the well
casing, the
deflecting tool or any other structural object will not cause erosive wear
thereof. The
outer cylindrical surface 36 of the pilot mill 34 is intended only for guide
purposes to
guide the pilot mill along an intended inclined trajectory with respect to the
longitudinal axis of the well casing so as to perform a pilot opening in the
well casing.
To enhance hulling of the well casing by the pilot mill 34, the pilot mill
defines a
plurality of fluid circulation passages 80 which are disposed in communication
with a
circulation fluid supply manifold passage 82. The manifold passage 82 receives
circulation fluid from a fluid supply passage 84 of the elongate tubular
milling shaft
62. Thus, the universal joint additionally serves for fluid flow transmission
between
the tubular milling shaft and the pilot mill 34. The milling end face 76 of
the pilot
mill 34 also defines fluid circulation channels 86 which transport the
circulation fluid
medium from the circulation passages 80 to the side channels 40 of the pilot
mill.
Although the lands 38 and the side channels 40 of the pilot mill are shown to
be of
helical configuration in Fig. 3 to enhance circulation flow as the pilot mill
is rotated, it
should be borne in mind that the lands and side channels may be of any other
configuration, such as substantially straight and parallel, without departing
from the
spirit and scope of the present invention. To ensure against fouling of the
universal
joint by debris such as particulate milled from the well casing or from the
surrounding
formation the internal connection receptacle 42 may be provided with a seal
assembly
43, such as a bellows seal for example, for excluding any such debris from the
universal joint. In addition to providing a seal between the pilot mill 34 and
the
CA 02534883 2000-04-14
VO 00/63521 PCT/US00/10
milling shaft 62, the seal 43 must also accommodate the pivotal articulation
of the
pilot mill relative to the milling shaft.
Referring now again to Figs. 1 and 2 the elongate tubular milling shaft 62 is
substantially rigid and is provided with at least one milling element 88 and
preferably
a plurality of string milling elements or mills 88 and 90 which are fixed in
spaced
relation along the length of the milling shaft. Although two milling elements
88 and
90 are shown it should be borne in mind that any number of milling elements
may be
located along the length of the milling shaft 62. The initial string mill is
located quite
close to the pilot mill so that most of the window opening that is milled
within the
well casing is formed by the initial string mill. The mill 88, or the first of
the string
mills 88 and 90, will typically have a diameter exceeding the diameter of the
pilot mill
34. In this case the first string mill 88 will be a gauging mill which greatly
enlarges
the much smaller pilot mill bore to roughly the desired diameter necessary for
a
casing window of predetermined dimension and contour geometry. The second of
the
string mills, mill 90, will typically be a reaming mill which finalizes the
dimension
and contour geometry of the window being milled in the well casing. The
diameter of
the string mills is typically very close to the drift diameter of the well
casing. The
string mills 88 and 90 each define a plurality of abrasive covered lands 92
and fluid
circulation channels 94 to provide for milling of the well casing and to
permit fluid
circulation past the string mills during milling activities. If desired, the
fluid
circulation channels of the string mills may be provided with a flow of fluid
from the
internal passage 84 of the milling shaft 62 to thus provide for cooling of the
string
mills and for removal of milled particulate and other debris as a window
milling
operation is in progress.
In the case of undersized casing windows, meaning that the diameter of a
cylinder
passing through the window is substantially smaller than the casing inside
diameter,
the diameter of the pilot mill 34 and the string mills 88 and 90 may be of
equal
diameter. This is generally the case of a window milling operation in a
production
21
CA 02534883 2000-04-14
00/63521 PGT/USOO/1OZ81
Iiner/casing having the requirement that the milling tool must pass through a
production tubing string.
As the casing window milling operation progresses the orientation of the
milling shaft
62 will be translated from a coaxial relation to an inclined relation with the
S longitudinal axis of the main wellbore as shown by angle "d" in Fig. 8. It
is desirable
that the rotary drive means of the casing milling system be isolated or
decoupled from
any lateral forces or bending moments that might cause exceptional wear of the
bearings of the rotary drive mechanism. At its trailing or upper end the
elongate
tubular milling shaft 62 is provided with an articulating connection shown
generally at
96: This articulating connection may be of substantially identical
construction and
function, as compared to the universal joint mechanism of Fig. 1 I, which
establishes
articulating connection of the pilot mill 34 to the forward end 60 of the
milling shaft
62. The articulating connection 96 is established by a spherical end 98 of the
milling
shaft which is captured by universal joint inserts 100 and 102 in the same
manner as
discussed above in connection with the universal joint of Fig. 11.
Driving rotation between the universal joint 96 and the elongate milling shaft
62 is
defined by a plurality of torque transmitting ball elements 104 which are
loosely
received within ball receptacles in the same manner and for the same purpose
as
described above. The universal joint connection 96 also defines a flow passage
such
as shown at 84 in Fig I 1 to permit the flow of circulation fluid into the
milling shaft
passage 84 from the drill string to which the rotary drive mechanism is
connected.
The universal joint connection at the forward end of the milling shaft 62 with
the pilot
mill 34 and the universal joint connection 96 at the trailing end of the
milling shaft
permits orientation of the milling shaft at any point in time to be
established jointly by
its forward and trailing universal joint connections. Moreover, the elongate
tubular
milling shaft 62 is substantially rigid and is decoupled from both the pilot
mill and the
rotary drive mechanism by its universal joint connections so that it is not
deflected
significantly by any of the forces to which it is subjected during milling
operations.
The rigidity of the milling shaft causes the string mills 88 and 90 to be
efficiently
22
CA 02534883 2000-04-14
NO 00/63521 PGT/US00/1t
guided by the pilot mill as the pilot mill 34 is guided along its intended
trajectory by
the inclined guide surface 30 of the body structure 18 of the deflecting tool
12. Since
the milling shaft is oriented by the positions of its universal joints, the
string mills do
not remain concentric with the pilot mill or with the universal joint
connection thereof
with the rotary drive mechanism. This feature causes the string mills to have
controlled milling relation with the primary inclined guiding feature 30 of
the body
structure 18 of the deflecting tool 12 as shown by Fig. 2 and as shown in the
operational views of Figs. 9 and 10. Thus, the string mills change a portion
of the
primary inclined guide surface during milling so that a predetermined
contoured guide
surface will remain after completion of the window milling operation to serve
as a
contoured guiding face for well equipment-that is run into the well casing and
diverted
through the casing window and into the lateral bore.
For rotation of the milling shaft 62 the universal joint 96 for driving and
permitting
articulation of the milling shaft is provided with a threaded pin type pipe
connection
106 which is received by the internally threaded box connection 108 of the
rotary
output shaft of the rotary drive assembly 16. The rotary drive assembly 16
incorporates a rotary drive motor 110 which is positioned by a drill string
extended
from the surface through the well casing. It should be borne in mind that
rotary drive
motor 110 may take any number of suitable forms without departing from the
spirit
and scope of the present invention. For example, the rotary drive motor may
conveniently take the form of a rotary positive displacement motor or a
turbine which
is driven by the flow of a fluid medium being pumped through the drill string
to the
rotary motor. The rotary drive motor 110 may also be powered by a mud motor
that
is connected at the lower end of a drill string extending from the surface.
The drill
string may be fixed during window milling operations or in the alternative, it
may be
rotated at a suitable rotary speed to provide for operation of the casing
window
milling assembly. Additionally, a rotary drill string may be utilized in
combination
with a rotary positive displacement motor, turbine or the like for achieving
desired
rotary speed and torque of the elongate milling shaft to provide for optimum
window
milling.
23
CA 02534883 2000-04-14
~ OU/63521 PGT/~SOO/1U281
It is well known that rotary apparatus such as a fluid energized motor, rotary
drill
string etc. are rotated within a well casing, the rotary apparatus tends to
oscillate or
otherwise become unstable within the well casing. To ensure thax no extraneous
oscillation is transmitted to the milling tool 14 by the rotary drive motor, a
stabilizer
112 is connected between the drive motor 110 and the connection box 108. Thus,
as
it is mtatably driven the upper or trailing end of the elongate tubular
milling shaft 62
is stabilized by the stabilizer element 112 and thus remains essentially free
of
vibration which might otherwise contribute to inaccuracy of casing window
milling.
As is typical with stabilizers, the stabilizer 112 is provided with lands and
fluid
circulation channels as shown.
Referring now again to Figs. 3, 6, and 7 the casing window milling assembly 10
may
be inserted into the well casing as a unitary or integrated assembly. This is
accomplished by positioning releasable fasteners such as shear screws 113 and
114 in
the tubular guide bearing 28 so as to resist both rotary and linear motion of
the pilot
mill 34 and the milling shaft 62 relative to the deflecting tool 12. The shear
strength
of the shear screws 113 and 114 is sufficient to maintain the fixed relation
of the pilot
mill 34 within the tubular bearing 32 and to support the deflecting tool 12 as
the
casing window milling assembly 10 is inserted into and set with respect to the
well
casing. This feature permits both the deflecting tool 12 and the milling tool
14 to be
properly positioned within the well casing in a single pass running operation.
After
the deflecting tool 12 has been properly oriented and set within the well
casing, with
the milling assembly fixed thereto by fastening means, milling operations may
be
initiated by applying suffcient rotational force to the pilot mill 34 by the
milling shaft
62 to cause shearing of the shear screws 113 and 114. After this has been
accomplished the pilot mill 34 is then free of the tubular bearing and may be
rotated
and moved linearly toward the well casing wall as it is guided initially by
the internal
cylindrical surface of the guide bearing 32 and then by the inclined contoured
guide
surface 30 of the elongate deflecting tool body 18 of the deflecting tool 12.
This
feature enables the pilot mill 34 to form a pilot bore along the intended
inclined
trajectory established by the tubular bearing 32 and the inclined guide
surface 30 and
24
CA 02534883 2000-04-14
VO 00/63SZ1 PCT/US00/1.
to cause precision milling of a pilot window in the well casing and a
precisely
oriented and located pilot bore into the immediately surrounding structure,
i.e. casing
cement and formation material as is evident from Figs. 2, 9 and 10.
OPERATION
Preferably the deflecting tool and the milling tool are run into the well
casing as an
integral unit, so that casing window milling can be initiated by a single pass
installation. In this case the shear screws 113 and 114 will maintain the
milling tool
in releasable assembly with the deflecting and will maintain the pilot iiciill
34 secured
within the pilot mill bearing 28 essentially as shown in Figs. 3 and 6. To
release the
pilot mill for milling rotation a suitable force is applied either by rotating
the milling
shaft and pilot mill with the rotary power source 110 or by imparting a linear
force to
the milling shaft. After the casing window milling assembly 10 has been
located
within the well casing with the deflecting tool being oriented and fixed
within the well
casing and the pilot mill 34 rendered rotatable as the result of shearing the
shear
screws 113 and 114 or otherwise releasing suitable fastener means, the
elongate
milling shaft 62 is mtatably driven by the rotary drive means 110 and linear
movement of the milling tool 14 is initiated. As the pilot mill 34 is rotated
and moved
linearly during the initial stage of casing window milling it is rendered
highly stable
by the tubular guide bearing section of the deflecting tool 12. Since the
pilot mill 34
is of essentially cylindrical configuration and is initially rotated within
the
substantially cylindrical internal surface of the guide bearing 32 it is
simply and
efficiently self guided and stabilized by the tubular guide bearing 32 and
pr~isely
oriented for milling a pilot opening of accurately controlled location,
orientation and
contour geometry in the well casing. This self guiding and stabilizing feature
of the
pilot mill 34 is enabled by locating the articulation pivot point of the pilot
mill
internally thereof and intermediate its axial length and along its axis of
rotation.
Stabilization of the pilot mill 34 in this manner enables the pilot mill to
initiate
window milling of the well casing and to generate a precisely controlled pilot
bore
which provides for guiding milling shaft 62 and its gauging and reaming mills
88 and
CA 02534883 2000-04-14
oomszi ~ rc~rwsoono28i
90. As mentioned above, the articulating connection of the pilot mill with the
forward
end of the milling shaft and the articulated connection of the trailing end of
the
milling shaft with the bit box connection of the rotary drive means and
stabilizer
assembly results in stabilized rotation and orientation as well as precision
guiding of
S the milling shaft 62 at both of its ends. Since the milling shaft 62 is
substantially
rigid, this double ended articulation of the milling shaft causes its
progressive
orientation as the pilot mill 34 continues milling a pilot bore of inclined
trajectory
through the well casing and into the surrounding formation, with orientation
of the
pilot bore being determined by the inclination of the internal cylindrical
guide surface
guide surface 30 of the deflecting tool 12. Immediately as the forward end of
the pilot
mill 34 is projected from the tubular guiding and stabilizing surface of the
tubular
guide bearing 32 the inclined trajectory of the pilot mill 34 and its
articulating
connection with the forward end of the milling shaft 62 will cause the milling
end
face 76 of the pilot mill to engage and begin milling a pilot window opening
in the
well casing. Simultaneously, as shown particularly in Fig. 2 the inclined
trajectory of
the pilot mill 34, through its articulated connection with the milling shaft
62 causes
the gauging and reaming milling elements 88 and 90 to be maintained in
controlled
relation with the inclined guide surface of the deflecting tool. This causes
the string
mills 88 and 90 to enlarge and finalize the pilot window in the well casing
and to
establish the initial inclination of an inclined lateral bore while at the
same time
having controlled guide surface forming relation with the elongate body 18 of
the
deflecting tool 12. It should also be noted that the guided relation of the
pilot mill 34
with the tubular bearing structure 32 and the inclined contoured guide face 30
causes
the string mills 88 and 90 to be directed into milling contact with a
sacrificial portion
41 of the tubular bearing structure 32 which is shown in Fig. 6 and is shown
to have
been removed in Fig. 7. When the pilot mill 34 is located within the tubular
guide
bearing 32 the appearance of the tubular guide bearing will be as shown in
Fig. 6.
After the milling operation has been completed the string mills 88 and 90 will
have
milled away a sacrificial portion of the tubular guide bearing 32, leaving an
open
guiding face 116 that is defined by curved lateral segments 118 and 120 having
an
intermediate curved guide surface segment 122 which is located between the
curved
26
CA 02534883 2000-04-14
wo oois~s2i rcr~soont
guide surface segments 118 and 120 and which is defined by the original
cylindrical
configuration of the internal guide bearing surface 30. After the milling
operation has
been completed the open guiding face 116 will serve as a deflecting guide
surface for
guiding various well tools into the lateral branch. .
As shown by the transverse sectional views of Figs. 4 and 5, both taken along
line 4-4
of Fig. 3, the transverse geometry of the deflecting tool body 18 will have
the
configuration shown in Fig. 4 before the casing window has been milled. In the
region of he section line 4-4 the deflecting body 18 will define an open
guiding face
124 which is defined by a substantially cylindrical guiding surface which
intersects
the flow passage 20 and also intersects the outer peripheral surface 126 of
the
deflecting tool at 128 and 130 and thus defines an open guide face or slot
132. After
the milling operation has been completed the sacrificial region 41 of the
tubular guide
bearing 32 and the deflecting body 18 will have been removed, leaving an open
contoured guiding face 134. The contoured open guiding face I34 is defined in
part
by guide surface segments 136 and 138 which form a part of the undisturbed
pilot
guide surface 30. The path of the string mills 88 and 90 will have been
controlled by
the inclined trajectory of the pilot mill 34 so that a central guide surface
segment 140
will not have been contacted or will have been contacted in controlled manner
by the
string mills and will thus remain either at its original geometry or a
predetermined
geometry. After the casing window milling operation has been completed other
well
tools, such as those for drilling, lining, cementing and completing and
otherwise
constructing the lateral branch, will be guided by the original guide surface
segment
140 of the guide surface 30 through the casing window and into the lateral
branch.
It is considered within the scope of the present invention to provide for
guiding of the
pilot mill during its initial milling by a generally tubular guide section of
the
deflecting tool as discussed above in connection with Figs. I-13, as shown in
Figs.
14-19, and to also provide for guiding of the rotary motor and stabilizer
within the
deflecting tool rather than in the well casing. This feature can enable the
milling tool
to be of more compact design as compared with convention milling tool design
and
27
CA 02534883 2000-04-14
~ 00/63521 PCT/~JS00/1028'
can enable the milling system to accomplish milling of a casing window and
tool
guide surface of predictable dimension and configuration. It is also
considered within
the spirit and scope of the present invention to provide the deflecting tool
with a
specific geometry enabling the deflecting tool and the milling tool to be run
into the
well casing as a unit and enabling the deflecting tool and the milling tool to
be
extracted from the well casing as a unit when a window milling operation has
been
completed.
Referring now to Figs. 14-19, an alternative embodiment of the present
invention is
shown generally at 150 which accomplishes the above features. Within the well
casing 152 is set a deflecting tool l 54 which is located and oriented in any
suitable
manner as discussed above. The deflecting tool 154 defines an elongate
generally
tubular section 156 defining an internal guide surface or passage 158 of
generally
circular cross-section which is of inclined and slightly curved configuration
and
which intersects the outer periphery 160 of the deflecting tool an a manner
defining a
lateral guide opening 162. The lateral guide opening 162, the deflecting tool
154
defnes a generally tubular pilot guide section 166 which is slightly offset
with respect
to the internal guide surface 158 and defines a generally cylindrical internal
pilot
guide surface I68 within which the pilot mill 34 is located at the beginning
of window
milling as shown in Fig. 14 to insure proper location of the milling tool 14
when
window milling is initiated, thus insuring that the pilot mill 34 is precisely
oriented by
the internal generally cylindrical guide surface 168 the deflecting tool 154
defines an
end flange 170 defining a transverse shoulder I73 and forming a guide opening
I74.
When casing window milling is initiated, a trailing shoulder 177 of a rotary
drive
motor 110 is normally in engagement with the transverse shoulder I73. This
feature
permits the deflecting tool 154 to be supported by the milling tool system 14
as the
deflecting tool and milling tool are run into the casing as a unit:
Alternatively, and as
described above, the pilot mill 34 may be temporarily secured within the pilot
mill
guide surface 168 by shear screws as described above or by any other suitable
means
for retention and release. The internal opening 174 of the end flange 170 to
pass
through the end flange as window milling operations progress, as shown in Fig.
15.
28
CA 02534883 2000-04-14
wo oois3szi rcr~soon
The end flange I70 also facilitates extraction of the milling tool and the
deflecting
tool as a unit when milling operations have been completed. As the drill stem
180 is
withdrawn upon completion of casing window milling the end shoulder 176 of the
rotary drive motor 178 will eventually come into contact with the transverse
shoulder
173 of the deflecting tool 154. Thereafter, further extracting movement of the
drill
stem 180 will also accomplish extraction of the deflecting tool 154. It should
also be
born in mind that the deflecting tool 154, if intended to remain within the
well casing
as a subsequent guide for well tools from the main well bore into the lateral
bore, the
end flange 170 may be eliminated. In this case the deflecting tool 154 will be
designed with a "pulling geometry" which will enable its subsequent extraction
from
the well casing to be accomplished by any suitable pulling equipment. Since
the
resulting guiding geometry of the deflecting tool 154 will be predictable, the
pulling
geometry of the deflecting tool is also precisely controlled.
The cross-sectional geometry of the deflecting tool 154 is rendered more
evident from
Figs. 17, 18 and 19. As shown in Fig. 17, the internal cylindrical surface 168
is
inclined to establish the desired inclination of the pilot bore that is milled
by the pilot
mill and has an internal diameter shown at I82 within which the outer diameter
of the
pilot mill 34 is closely fitted. It should be born in mind that the pilot mill
34 is
oriented by the internal pilot mill guide surface 168 only at the initial
stage of casing
window milling. After the trailing end of the pilot mill has cleared the
internal
cylindrical guide surface 168, the pilot mill will maintain its angulated
orientation
relative to the main well bore by that portion of the guide surface of the
deflecting
tool which is located forwardly of the pilot mill guide surface 168. Also,
since the
pilot mill 34 is of cylindrical configuration and is provided with a milling
surface only
at its leading end, the cylindrical outer periphery of the pilot mill will
maintain the
orientation that has been pre-established by the pilot mill guide surface 168.
The cross-sectional illustration of Fig. 18 shows a partially tubular internal
guide
surface being an extension of the internal guide surface 158 of the deflecting
tool and
having an internal diameter 184 greater than the internal diameter 182 of the
guide
29
CA 02534883 2000-04-14
'00/63521 PCT/USOO/1OZ81
surface I68 shown in Fig. I7. This greater internal diameter is sufficient to
establish
guiding relation with the rotary drive motor and/or the stabilizer element 112
which is
connected to the rotary drive motor 110.
As shown in the sectional view of Fig. 19, the end flange 170 of the
deflecting tool
S 154 is defined by opposed flange sections 171 and 172.
As mentioned above, casing milling is initiated with the milling tool 14 shown
positioned as in Fig. 14 with the pilot mill 34 disposed in guided relation
with the
internal cylindrical guide surface 168. As the milling tool 14 is moved
forwardly by
movement of the drill stem 180 the drill stem will be guided by the
cylindrical surface
sections of the flange sections 171 and 172 that define the end flange 170. As
this
movement occurs the first string mill 88, which may also be referred to as a
gaging
mill, begins to remove the pilot mill guide section 166 of the deflecting
tool. After
the second or reaming mill 90 of the elongate milling shaft 110 has passed
through the
pilot mill guide section of the deflecting tool, the upper portion of the
pilot mill guide
I 5 section will have been removed, leaving a guide passage essentially being
an
extension of the internal guide surface 158 of the deflecting tool 154.
Consequently
as the rotary drive motor I 10 and its stabilizer 112 are moved along the
internal guide
surface 158 efficient positioning of the rigid milling shaft 162 will be
maintained thus
causing its string mills 88 and 90 to continue milling an inclined, slightly
curved
ZO guide passage along the intended trajectory that is desired for the lateral
bore. Thus,
the rigid milling shaft, being pivotally connected to the pilot mill 34 and to
the rotary
drive motor 110 will be precisely controlled as it follows its intended
milling
trajectory. The deflecting tool 154 will be milled in controlled fashion to
effectively
form the inclined guide surface 158. The result is that the casing window is
milled to
25 precision location, orientation and geometry during casing window milling.
Additionally, the dimension of the bore that is milled by the milling tool
will be
closely controlled so that wandering of the milling tool is minimized during
the
milling operation. The net result is predictable and controlled window milling
which
insures that the deflecting tool achieves a predictable configuration as the
result of the
CA 02534883 2000-04-14
'O 00/63521 PCT/US00/1~
milling operation so that it can function efficiently as a tool guide and can
be
efficiently extracted from the well casing when its use is no longer needed.
Referring now to Figs. 20 and 21 a further alternative embodiment of the
casing
window milling system of the present invention is shown in longitudinal
section
generally at 190. As mentioned above, it is desirable that the pilot mill,
when casing
window milling is initiated, be freely pivotal for articulation or angular
misalignment
relative to the longitudinal axis of the milling shaft to permit efficient
guiding of the
pilot mill along the inclined guide surface of the deflecting tool. After the
pilot mill
has moved free of the tubular guide bearing of the deflecting tool and has
moved
along the inclined guide surface of the deflector to an extent that self
guiding of the
pilot mill can no longer be assured, it is desirable to control the
articulating
mechanism of the pilot mill and milling shaft rotary drive connection so that
the
degree of articulation is limited or minimized to permit the trajectory of the
pilot mill
to be controlled jointly by the deflecting tool and the milling shaft. This
feature
prevents unconsolidated formations from permitting or causing the pilot mill
to be
diverted from its intended trajectory.
The embodiment of Figs. 20 and 21 illustrate the articulating connection
between a
pilot mill shown generally at 192 and a substantially rigid milling shaft
shown
generally at 194, wherein the pilot mill is enabled for substantially free
articulation
relative to the milling shaft when in the condition shown in Fig. 20 and is
maintained
in substantially coaxial relation with the milling shaft when in the condition
shown in
Fig. 21. The pilot mill 192 has a generally circular pilot head 196 to which
is fixed or
secured a generally cylindrical stabilizing sleeve 198 which defines external
grooves
200 and lands 202 to permit the flow of fluid externally of the pilot mill for
purposes
of cooling and for removal of mill cuttings and other debris. The pilot head
196
defines a milling face 204 and also defines one or more fluid distribution
passages
206 through which milling fluid is conducted from an internal fluid chamber
208 to
the milling face 204. Although the milling face 204 is shown to be of planar
configuration in Figs. 20 and 21 it should be born in mind that it may be of
tapered
31
CA 02534883 2000-04-14
00/63521 ' PCT/f3S00/1028i
configuration, essentially as shown at 76 in Fig. 11 or it may be rounded or
of any
other suitable milling face configuration. The outer peripheral lands 202 of
the
generally cylindrical stabilizing sleeve 198 served to stabilize rotation of
the pilot mill
as it is rotatably driven by the generally rigid milling shaft 194. This
feature enables
the pilot mill to be efficiently guided by the inclined guide face 210 of a
deflection
body 212 that is set within the well casing. Preferably the deflecting body
212 is of
the configuration and function shown at 18 in Figs. 1, 2, and 3 and described
in detail
above.
The generally cylindrical stabilizing sleeve 198 is of tubular configuration
and defines
a generally cylindrical internal chamber which is formed by internal
cylindrical
surface segments 214 and 216. The cylindrical surface segment 214 is of
slightly
larger diameter as compared with cylindrical surface segment 216 and at the
juncture
of these surface segments is defined an internal circular shoulder 218. A
tubular
bushing support housing 220 is fixed within the cylindrical surface segment
214 of
the internal chamber of the pilot mill 192 with a circular shoulder 222
thereof being
located in abutment with the internal circular shoulder 218 of the stabilizing
sleeve
198. The pilot head 196 and the bushing support housing 220 define the
internal
chamber 208. The bushing support housing 220 provides for location of
articulation
bushings 224 and 226 which cooperatively define a generally spherical internal
chamber 228 which receives a spherical end member 230 of the milling shaft
194,
thus permitting articulation of the milling shaft in pivotal relation about a
pivot point
"P" and within an authorized angle of mis-alignment shown by angle "A"
relative to
the axial center-line "C" of the milling shaft 194.
The milling shaft 194 defines an end section 232 which tapers from a trilling
shaft
diameter "D" shown in Fig. 21 so that the end section 232 is of smaller
diameter as
compared to the diameter of the milling shaft. This smaller diameter assists
in the
amplitude of authorized mis-alignment of the pilot mill relative to the
milling shaft.
The spherical end member 230 is located at the terminal end of the milling
shaft end
section 232 so that the pilot mill 192 is freely pivotal about pivot point "P"
and thus
32
CA 02534883 2000-04-14
~o oomszi pcrrt~soon
can be positioned by the deflector guide surface 210 to provide essentially
for steering
of the milling shaft 194 along an exit angle for casing window milling as
determined
by the angle of the guide surface 210 of the deflecting body 212.
According to the embodiment shown in Figs. 20 and 21 it is appropriate to
permit
articulation of the pilot mill relative to the generally rigid nuIIing shaft
194 for the
purpose of self steering of the pilot mill by its guided and stabilized
contact with the
inclined guide surface 210. The steering and rotational stability of the pilot
mill 192
is initially achieved by the generally tubular guide bearing of the deflecting
body 18
which is shown at 34 in Figs. 1 and 3. When the deflecting element is of
elongate,
tubular configuration as shown at 154 in Fig. 16, the tubular guide bearing
for the
pilot mill will be as shown at 166. This guide bearing establishes precision
orientation and rotational stabilization of the pilot mill along the exit
angle defined by
the deflecting member so that a precision pilot window opening will be milled
in the
well casing at the initial stage of casing window milling as discussed above
in
connection with Figs. 1- 19. Thus it is intended to be understood that the
pilot mill
192 shown in Figs. 20 and 21 will be initially guided and stabilized in the
same
manner and for the same purpose as discussed above.
According to Figs. 20 and 21, and as stated above, it is desirable that the
pilot mill
192 have freedom of articulation relative to the milling shaft 194 under
conditions of
initial casing window milling and that the pilot mill have the capability of
being
maintained in substantially coaxial relation with the milling shaft when
desired so that
straight milling along the intended trajectory from the casing window can be
readily
controlled. To accomplish this feature, the end section 232 of the milling
shaft 194 is
provided with a circular locking flange or enlargement 234. A tubular locking
piston
236 is located within the internal chamber of the stabilizing sleeve 198 and
is sealed
with respect to an internal cylindrical surface 238 by a circular sealing
element 240
and sealed with respect to an external cylindrical surface 242 of a tubular
extension
244 of the bushing support housing 220 by a circular sealing element 246. The
locking piston 236 functions cooperatively with the tubular bushing support
housing
33
CA 02534883 2000-04-14
p OOI63521 PGT/ETSOO/IOZ8'
220 and its tubular extension 244 and with the internal cylindrical surface
238 of the
stabilizing sleeve 198 to define a hydraulic chamber 248. In the freely
pivotal
condition of the pilot mill 192 relative to the milling shaft 194 shown in
Fig. 20, the
hydraulic chamber 248 will be filled with hydraulic fluid which is introduced
into the
hydraulic chamber through one or more hydraulic fluid passages 250 which are
in
communication with one or more hydraulic fluid passages 252 that are formed in
the
circular pilot head 196. The hydraulic fluid passage or passages 252 is
normally
closed by a frangible closure element 254 shown in Fig. 20. This frangible
closure
element maintains the hydraulic fluid within the hydraulic fluid chamber 248
and thus
prevents movement of the locking piston 236 so that the locking piston
.remains in the
position shown in Fig. 20 with its internal locking surface 256 in axially
displaced
relation with the circular locking flange 234 of the milling shaft end section
232. A
tension spring 258 is located within the internal chamber defined by the
stabilizing
sleeve 198 of the pilot mill 192 with one of its ends 260 and retained
relation with a
cylindrical shoulder 262 of the bushing support housing 220. The opposite end
264 of
the tension spring 258 is fixed within spring grooves defined by a circular
shoulder
266 of the locking piston 236. In the relaxed condition of the tension spring
as shown
in Fig. 21, the locking piston 236 will be positioned with its internal
locking surface
256 in registry with the circular locking flange 234 of the milling shaft. In
this
condition the pilot mill 192 is secured by the locking piston against
articulation
relative to the milling shaft. In this condition the longitudinal axes of the
milling shaft
and the pilot mill will be in coincidence and therefore the pilot mill will
mill a straight
course that is in alignment with the longitudinal axis of the milling shaft.
When casing window milling is initiated and during milling of a pilot window
opening in the well casing it is desirable that the pilot mill 192 be disposed
in
articulating relation with the milling shaft so that the pilot mill is
efficiently guided by
the inclined guide surface 210 of the deflecting body 212. As long as the
frangible
closure member 254 remains intact, the hydraulic fluid that is present within
the
hydraulic chamber 248 will maintain the locking piston positioned as shown in
Fig.
20, thus permitting articulation of the pilot mill about the spherical end
member 230
34
CA 02534883 2000-04-14
~ 00/63521 PCT/IIS00/102
of the milling shaft. When it is desired to lock the pilot mill in non-
articulating or
coaxial relation with the milling shaft the frangible closure 254 is broken
away,
thereby permitting the tension spring force of the locking piston to discharge
some of
the hydraulic fluid from the hydraulic chamber 248 through the passages 250
and 252
and through the opening 266. When this occurs, the tension spring 258 will
shift the
locking piston 236 from the unlocking position of Fig. 20 to the locking
position of
Fig. 21. Thus, the frangible closure 254 functions as a "locking trigger" that
can be
actuated in any suitable manner to release hydraulic chamber 248. The locking
trigger may be actuated mechanically simply by moving the pilot mill into
contact
with certain deflector structure or with casing or formation structure,
depending upon
the configuration thereof. As the pilot mill is moved along the inclined guide
surface
of the deflection body so that the center of the milling head of the pilot
mill is in
registry with the casing, the frangible closure will be broken away by contact
with the
casing, releasing the hydraulic fluid from the chamber 248 and allowing spring
urged
I S movement of the locking piston 236 to the Fig. 21 position. Alternatively,
the locking
trigger may conveniently take the form of a pressure responsive closure,
thereby
permitting it actuation responsive to conditions of downhole fluid pressure.
As a
further alternative, the locking trigger may take the form of a valve closure
that may
be selectively opened by an on-board valve actuator responsive to any suitable
fluid
telemetry signals.
In a further alternative embodiment, shown in Fig. 22, the inclined contoured
guide
surface 30 does not extend to the periphery of the deflecting tool at its
lower end.
Thus, the deflecting tool 12 defines a bearing surface 300 at the lower end of
the
guide surface 30 that extends from the lower end of the guide surface 30 to
the
periphery of the deflecting tool 12. The guide surface 30 is preferably
slightly
convexly arcuate.
In this embodiment, the intent is to mill the window in the casing, then
remove the
milling tool 14 and deflecting tool 12 from the well and to use a drilling
deflector and
drilling tool to complete the drilling of the lateral. At least a portion of
the milling
CA 02534883 2000-04-14
WO 00/63521 PGT/I~S00/10:
tool 14 remains within the casing when using the embodiment of Fig. 22. Thus,
the
guide surface 30 of the deflecting tool 12 defines a milling path that limits
the travel
of the milling tool to substantially prevent the milling tool from exiting the
well
casing. The bearing surface 300 provides a stop to define the bottom of the
milled
window and to stop further milling by the milling tool 14. The convexly
arcuate
milling surface 30 forces the pilot triill 34 out through the casing initially
at a
relatively higher rate. Then, once the pilot mill (or the string mills) is at
the desired
position offset from the centerline of the casing to mill the window of the.
desired
width; such as when the center and widest diameter of the pilot mill 34 (or
string
mills) is aligned with the casing, the milling surface 34 directs the pilot
mill
downward along a milling path that is parallel to the centerline of the casing
or along
a similar path intended to maintain the desired milling width of the pilot
mill 34 and
the trailing string mills. Thereby, the arcuate milling surface 34 facilitates
milling of
a window having a width that has the desired width along a longer length than
if the
1 S milling surface 30 were straight, or linear. In one embodiment, the
centerline of the
pilot mill 34 remains within the periphery of the well casing.
One advantage to maintaining the milling tool 14 at least partially within the
casing is
that the direction and orientation of the pilot mill is maintained and the
pilot mill 34 is
substantially prevented from travelling sideways. Prior efforts that have a
guide
surface 30 that extends to the periphery of the deflecting tool 12 force the
mill further
through the casing reducing the aligning support offered by the casing.
However, the
present invention maintains relatively more of the mill in the casing so that
the casing
provides guiding support to the mill and reduces walk-away suffered by prior
milling
designs. Walk-away, a problem known in the art to be associated with prior
designs,
in which the torque of the mill causes the mill to travel radially as well as
axially,
produces a window in which the centerline of the milled window is not aligned
with
the axial direction of the borehoIe. For example, one common problem resulting
from
walk-away is that the bottom of the milled window is offset from the
centerline of the
main portion window through which the lateral is accessed. Such a window may
affect reentry because many prior designs use the bottom of the milled window
to
36
CA 02534883 2000-04-14
i 00/63521 PGT/US00/1028
hang reentry tools. If the bottom of the window is offset from the main
portion of the
window, the orientation of the reentry tool may be incorrect and prevent
effective
reentry into the lateral.
Further, the milling tool 14 is adapted and designed for milling steel or
other metals or
materials forming the casing, not for drilling in a formation necessarily.
Thus, drilling
tools are better suited for drilling the lateral in the formation once the
window is
formed in the casing. Accordingly, using the embodiment shown in Fig. 22, in
which
the milling tool 14 remains at least partially within the casing, the milling
tool 14 is
used for its optimal purpose (milling a window in the casing) and drilling
tools are
then used to form the lateral. The resulting milled.window using this
embodiment
builds a side pocket suitable for further construction of the lateral.
Additionally, using the embodiment shown in Fig. 22, produces a window 302
having
the general shape as shown in Fig. 23. As discussed, the width of the window
302
widens relatively rapidly at its top and then stabilizes at the desired width.
Further,
the pilot mill 34 mills a bottom narrow portion 304. The narrow portion 304 is
relatively narrow as compared to the portion of the milled window 302 adjacent
the
. narrow portion 304. The narrow portion may be useful for attaching equipment
to the
casing, such as liners, liner hangers, and other completion or downhole
equipment.
Additionally, the bottom of the resulting milled window 302 is relatively flat
as
compared to those milled using the embodiment shown in Fig. 3 for example. The
relatively flatter bottom also facilitates use of the casing for attachment of
other
components.
Alternative Embodiment of the Pilot Mill including Core Breaking Mechanism
An alternative embodiment of the pilot mill 34 is shown in Figures 24 and 25.
In
many milling applications, the center of the relevant mill has a velocity of
zero
relative to the surface to be milled. This creates unfavorable cutting
conditions, often
resulting in the destruction of the central portion of the mill and the
interruption of the
37
CA 02534883 2000-04-14
WO 00/6321 PCT/E1S0011a
milling process. The illustrated embodiment of pilot mill 34 solves this
problem and
increases the rate of penetration and durability of the mill in the casing as
well as the
possibility of milling a window using only one trip of the drill string.
In this embodiment, pilot mill 34 includes a core breaking mechanism 498 that
preferably comprises a core passage 500 and a breaking mechanism 502. Core
passage 500 extends from the mill nose 78 to the outer guided periphery 36 of
the
pilot mill 34. Preferably, core passage 500 is included entirely within mill
head
structure 35. Breaking mechanism 502 is located within core passage 500 and is
adapted to break up solid pieces that travel through core passage 500. In the
preferred
embodiment, breaking mechanism 502 comprises a diverting slope 504~within core
passage 500. The diverting slope 504 diverts the core passage 500 from being
substantially parallel to the axis of rotation of pilot mill 34 to being
directed generally
towards the outer guided periphery 36 of pilot mill 34. In the preferred
embodiment,
diverting slope 504 is constructed from a material that is substantially
harder than the
material to be milled. Preferably, diverting slope 504 is hardfaced with
carbide or
another suitable material.
Core passage 500 can have a variety of configurations, so long as the passage
500
provides communication between the mill nose 78 and the outer guided periphery
36.
In the embodiment shown in Figure 24, core passage 500 comprises a core
opening
506 having a first end 508 at mill nose 78 and a second end 510 at the outer
guided
periphery 36. Alternatively and as shown in Figure 25, core passage 500
comprises a
core channel 512 that is open to the tapered milling face 76.
The core passage 500 is preferably configured on mill head structure 35 so
that it does
not interfere with the operation of the fluid circulation passages 80 or the
fluid supply
manifold passage 82. The embodiment shown in Figure 26 shows five fluid
circulation passages 80 and the core passage 50(? functioning independently
from each
other.
38
CA 02534883 2000-04-14
~ ooi63szZ rcrrt~soonoas~
In the preferred embodiment, the core passage S00 extends from mill nose 78 to
outer
guided periphery 36 in an arcuate radial path. Figure 26 clearly shows that
core
passage 500 does not extend linearly from mill nose 78 to outer guided
periphery 36.
Instead, the core passage S00 follows an arcuate path along the radial
direction from
mill nose 78 to outer guided periphery 36. Also preferably, the curve of the
radial
arcuate shape of core passage 500 extends in the direction of rotation of
pilot mill 34.
In operation, the rotating pilot mill 34 is moved towards the appropriate
surface. The
abrasive inserts on the pilot mill tapered milling surface 76 begin milling
the surface.
The presence of core passage 500 on mill nose 78 creates a core of non-milled
surface
that is received within core passage 500 as pilot mill 34 continues the
milling process.
The core of non-milled surface grows in length within core passage 500 until
it hits
diverting slope 504. Diverting slope 504 acts to continuously break the core
of non-
milled surface into pieces as the core is fed through the core passage 500.
The broken-
up core of non-milled surface is then expelled through the outer guided
periphery 36
end of the core passage 500, at which point it joins the remainder of the
debris that
results from the milling operation.
Alternative Embodiment of the Unitary or Integrated Assembly for
Deployment Purposes
Figures 3, 6, and 7 illustrate one embodiment of the casing window milling
assembly
10 in which the deflecting tool 12 is attached to the milling tool 14 during
the
downhole deployment process. This embodiment includes releasable fasteners
such
as shear screws 113 and 1 I4 in the tubular guide bearing 32 so as to resist
both rotary
and linear motion of the pilot mill 34 and the milling shaft 62 relative to
the deflecting
tool 12.
Figures 27 and 28 illustrate an alternative embodiment of a unitary or
integral casing
window milling assembly 10. This embodiment includes a first retaining
mechanism
600, a second retaining mechanism 602, and preferably a protection mechanism
604.
39
CA 02534883 2000-04-14
wo oomszi rcr~soono
In this embodiment, pilot mill 34 is preferably secured at least partially
within guide
bearing 32.
First retaining mechanism 600 is attached to the drift guide surface 33 so
that it is
adjacent the pilot mill rear end 606. In the preferred embodiment, first
retaining
mechanism 600 comprises a first retaining member 608 (Figure 28) that is
securely
attached to the drift guide surface 33, such as by threading, welding, or by
other
means known in the art. First retaining member 608 is shown in Figure 28 as
having
a ring shape, although first retaining member 608 can have any shape (such as
a half
ring or an arcuate segment) provided that first retaining member 608 supports
pilot
mill 34 in place. In another embodiment as shown in Figure 27, first retaining
mechanism 600 comprises at least one securing screw 610 that is inserted
through
tubular guide bearing 32 so that it protrudes from drift guide surface 33 next
to pilot
mill rear end 606.
Second retaining mechanism 602 is attached to the drift guide surface 33 or
the
inclined guide surface 30 so that it is adjacent the pilot miU front end 612.
In the
preferred embodiment, second retaining mechanism 602 comprises a second
retaining
member 614 that is securely attached to the drift guide surface 33 or the
inclined
guide surface 30, such as by threading, welding, or by other means known in
the art.
Second retaining member 614 is shown in Figures 27 and 28 as having a general
ring
shape, although second retaining member 614 can have any shape (such as a half
ring,
a disc, or a half disc) provided that second retaining member 614 supports
pilot mill
34 in place. In one embodiment and as shown in the Figures, the second
retaining
member rear end 620 mirrors the tapered shape of tapered milling face 76.
Protection mechanism 604 is located intermediate the pilot mill 34 (pilot mill
front
end 612) and the second retaining mechanism 602. Protection mechanism 604
protects the abrasive inserts of pilot mill 34 which are included on tapered
milling
face 76 from hitting the second retaining member rear end 620 during the
deployment
process. In one embodiment as shown in Figure 27, protection mechanism 604
CA 02534883 2000-04-14
00/63521 PCTN~O/102F
comprises a protection screw 622 that is embedded in tapered milling face 76
(or pilot
mill front end 612). Protection screw 622 includes a screw head 624 that
extends
farther from pilot mill front end 612 than the abrasive inserts of pilot mill
34. Screw
head 624 is adjacent second retaining member 620. In another embodiment as
shown
in Figure 28, protection mechanism 604 comprises a resilient member 626 that
is
disposed intermediate tapered milling surface 76 (and abrasive inserts) and
second
retaining member rear end 620. Resilient member b26 is constructed from a
resilient
material such as rubber. In the preferred. embodiment and as shown in Figure
33,
resilient member 626 includes a plurality of cuts or serrations 710 extending
from the
center portion 712 preferably to the outer circumference 714 of the resilient
member
626. Cuts 710 also preferably extend axially through the resilient member 626
and
are spaced about the center portion 712.
In operation, casing window milling assembly 10 is deployed downhole with the
pilot
mill 34 secured to the drift guide surface 33 and/or the inclined guide
surface 30 by
use of the first retaining mechanism 600, the second retaining mechanism 602,
and
the protection mechanism 604. First retaining member 608 aids in maintaining
pilot
mill 34 in its proper place, supports the load of pilot mill 34 as the casing
milling
assembly 10 is deployed downhole, and reacts forces applied to pilot mill 34
that are
in the downward direction. Second retaining member 614 aids in maintaining
pilot
mill 34 in its proper place and reacts forces applied to pilot mill 34 that
are in the
upward direction. Protection mechanism 604 protects the abrasive inserts of
tapered
milling face 76. If the casing window milling assembly 10 is jarred during the
deployment process, pilot mill 34 tends to be forced against second retaining
member
614 which event would damage the abrasive inserts, if not for the presence of
protection mechanism 604. Protection mechanism 604 absorbs the force caused by
the jarring event and thus prevents the abrasive inserts from being damaged.
In the
embodiment including the protection screw 622, protection screw 622 absorbs
the
jarring force since the screw head 624 extends farther from the pilot mill
front end
612 than the abrasive inserts. In the embodiment including resilient member
626,
41
CA 02534883 2000-04-14
WO 00/63521 PCT/US00110
resilient member 626 absorbs the jarring force due to its resilient material
construction.
After the deflecting tool 12 has been properly oriented and set within the
well casing,
the milling operation may be initiated by applying sufficient rotational force
to the
pilot mill 34. The rotation of the pilot mill 34 causes the general
disintegration of first
retaining mechanism 600, second retaining mechanism 602, and protection
mechanism 604. Thus, the elements that comprise first retaining mechanism 600,
second retaining mechanism 602, and protection mechanism 604 are constructed
from
materials that can be easily milled by pilot mill 34 and string mills 88 and
90.
Adequate materials include steel and aluminum, and rubber for resilient member
626.
In the embodiment including resilient member 626 with cuts 710, the cuts 7I0
weaken
resilient member 626 in the direction of rotation enabling the efficient
disintegration
of the resilient member 626. Once first retaining mechanism 600, second
retaining
mechanism 602, and protection mechanism 604 are disintegrated, the milling
operation continues as previously disclosed.
In another embodiment as shown in Figure 29, second retaining mechanism 602
comprises a drillable material plug 630 that extends from adjacent the pilot
mill fmnt
end 612 towards the downhole end of deflecting tool 12. Preferably, drillable
material plug 630 fills the entire area within deflecting tool 12 that is at
least partially
defined by inclined guide surface 30. Drillable material plug 630 preferably
completes the outer cylindrical shape of deflecting tool 12. Drillable
material plug
630 is constructed from a material that can be easily milled by pilot mill 34
and string
mills 88 and 90, such as a plastic or soft steel.
In addition to the utility described above (as second retaining mechanism
602),
drillable material plug 630 also improves the efficiency, control, and
reliability of the
initial phase of the milling operation. First, as is well-known in the art,
milling
operations are more controllable and predictable if the entire milling face of
the mill is
in contact with a millable surface. Second, the fact that the entire milling
face of the
42
CA 02534883 2000-04-14
O 00/63521 PCT/US00/102'
mill is in contact with a millable surface also provides continuous cooling of
the pilot
mill 34 by providing a continuous flow of debris through side channels 40.
After the deflecting tool 12 has been properly oriented and set within the
well casing,
the milling operation may be initiated by applying sufficient rotational force
to the
pilot mill 34. The rotational motion disintegrates first retaining mechanism
600 and
protection mechanism 604. The pilot mill 34 then begins to mill drillable
material
plug 630. At first, the entire milling face of pilot mill 34 contacts and
mills drillable
material plug 630. As pilot mill 34 moves along inclined guide surface 30, at
least a
IO section of the pilot mill 34 contacts the target casing so that the milling
face mills both
the target casing and the drillable material plug 630. Thus, at all times, the
entire
surface of the milling face is in contact with a millable material (either the
casing wall
or the drillable material plug 630) thereby enabling the additional utility
disclosed in
the previous paragraph.
Also in the preferred embodiment, the portion of guide bearing 32 that is
milled away
during the milling process is constructed from a material that is softer than
the
material that comprises the remainder of the deflecting tool 12. In the
preferred
embodiment, such a portion of guide bearing 32 is annealed prior to use.
Retrievability of Deflecting Tool
Once the milling operation is concluded, a retrieving tool 650 may be inserted
into the
wellbore to retrieve deflecting tool I2. The interconnection between
retrieving tool
650 and deflecting tool I2 is illustrated in Figures 30 and 31. It is noted
that the
deflecting tool 12 shown in Figure 30 is hollow, unlike the deflecting tools
12 shown
in the prior figures. Whether deflecting tool 12 is hollow or not is not
critical for the
purposes of this invention and either embodiment is encompassed thereby.
43
CA 02534883 2000-04-14
WO 00/63521 PCT/EJS00/10."
Deflecting tool 12 includes a slot 652 preferably defined on inclined guide
surface 30.
Slot 652 includes a main section 654, preferably rectangular in shape, and a
wedge
section 656. In the preferred embodiment, wedge section 656 is proximate the
uphole
end of deflecting tool 12 so that the wide end 658 of wedge section 656 is
proximate
main section 654 and the narrow end 660 of wedge section 656 is distal
thereto. In
those embodiments in which deflecting tool 12 is not hollow, slot 652 should
extend
from the inclined guide surface 30 to the outer surface of the deflecting tool
12.
Retrieving tool 650 includes a hook member 662 extending therefrom. In the
preferred embodiment, hook member 662 is selectively removable from retrieving
tool 650. The selective removability of the hook member 662 is enabled by any
means known in the art, such as fasteners to retrieving tool 650 or a tongue
and
groove system with a lock. The removability of hook member 662 facilitates the
transportation and cleaning, among others, of the hook member 662.
Hook member 662 comprises a first section 664 and a second section 666. First
section 664 extends from retrieving tool 650, preferably radially therefrom,
towards
second section 666. Second section 666 is connected to first section 664,
preferably
distal to deflecting tool 12. Hook member 662 is sized and constructed so that
it may
be selectively inserted into slot 652. Thus, in the preferred embodiment, the
longest
portion of hook member 662 is not longer than the longest portion of main
section
654, and the widest portion of hook member 662 is not wider than the widest
portion
of main section 654.
Second section 666 includes a ramping surface 668 that preferably faces the
deflecting tool 12 and is proximate the uphole end of deflecting tool 12.
Preferably,
the ramping surface uphole end 670 extends past or farther uphole than the
first
section uphole end 672. Also preferably, the ramping surface side ends 676
extend
past or farther laterally than the first section side ends 674. When
deflecting tool 12 is
properly positioned downhole, the uphole edges 696 of slot main section 654
extend
at an angle a from the casing wall. In addition, when retrieving tool 650 is
located
44
CA 02534883 2000-04-14
J 00/6321 PGT/ITSOOnOl
downhole so that the second section distal end 678 (or hook member distal end)
abuts
the casing wall, ramping surface 668 extends at an angle (3 from the casing
wall. In
the preferred embodiment, angle ~ is greater than angle oc. Furthermore, the
retrieving tool 650 is preferably constructed so that the distance between the
second
section distal end 678 and the retrieving tool side 684 that is laterally
opposite the
second section distal end 678 is slightly smaller than the drift diameter of
the casing.
Also in the preferred embodiment, f rst main section 664 is at least partially
tapered
towards the first section uphole end 672. The taper angle 8 of first section
664
preferably matches the angle 8 defined by wedge section 656. It is not
necessary,
although it is possible, for the length of the first section tapered surfaces
680 to equal
the length of the wedge section surfaces 682.
Retrieving tool 650 preferably also includes a cleaning mechanism 686, which
may
comprise a retrieving tool opening 688 and at least one port 690. Retrieving
tool
opening 688 is in fluid communication with a cleaning fluid pressurized source
at the
surface. Each port 690 extends through hook member 662 and provides fluid
communication between the retrieving tool opening 688 and the exterior of
retrieving .
tool 650 adjacent second section distal end 678. A jet nozzle 694 is
preferably
included within each port 690.
Figure 32 illustrates an isometric view of retrieving tool 650. Retrieving
tool 650
includes a longitudinal axis 700, a first perpendicular axis 702 from
longitudinal axis
700, and a second perpendicular axis 704 from longitudinal axis 700. First
perpendicular axis 702 extends from longitudinal axis 700 so that a plane
including
first perpendicular axis 702 and being perpendicular and transverse to
longitudinal
axis 700 passes through hook member 662_ Second perpendicular axis 704 extends
from longitudinal axis 700 so that it is perpendicular to first perpendicular
axis 702.
Retrieving tool 650 is preferably constructed so that the moment of inertia
with
respect to the second perpendicular axis 704 is substantially greater, and
preferably at
CA 02534883 2000-04-14
wo oomszi Pcr~soono~
least three times greater, than the moment of inertia with respect to the
first
perpendicular axis 702.
In operation, once the milling operation has been completed, the retrieving
tool 650 is
inserted downhole. The cleaning mechanism 686 is activated so that cleaning
fluid is
injected from the surface through retrieving tool opening 688 and out through
each
port 690. The pressure monitored at the fluid pressurized source located at
the surface
remains constant until the retrieving tool 650 is adjacent the deflecting tool
12. At
this point, the monitored pressure will decrease somewhat as the retrieving
tool 650
continues along the inclined guide surface 30. This change in pressure alerts
the
operator that the retrieving tool 650 has reached the deflecting tool 12. The
monitored pressure will bottom out when the hook member 662 is adjacent the
slot
652 since the flow of cleaning fluid immediately out of ports 690 is not
obstructed by
the casing wall or the inclined guide surface 30, as before. The large
pressure drop
indicates to the operator that the hook member 662 is adjacent the slot 652.
The jet
nozzles 682 will of course clean the slot 652 as they pass thereby, which
enables the
proper insertion of hook member 662 therein. At this point, the operator may
manipulate the retrieving tool 650 so that hook member 662 is inserted into
slot 652.
The pressurized fluid flowing out of the pressurized fluid source, through the
retrieving tool opening 688 of the retrieving tool body, and through each port
690 as
well as the pressure gauge operatively connected to the retrieving tool
opening 688
comprise a hydraulic signature mechanism. The hydraulic signature mechanism
enables an operator to monitor the pressure of fluid out of ports 690 and
therefore
enables an operator to monitor the location of the retrieving tool 650 in
relation to the
deflecting tool 12, as previously disclosed.
Figures 30 and 31 illustrate the initial insertion position of the hook member
662
relative to the slot 652. Once this initial insertion is achieved, the
operator should
begin to slowly retrieve the retrieving tool 650. This motion enables the
ramping
surface 668 to contact the uphole edges 696 of slot main section 654. Since
second
section distal end 678 abuts the casing wail, continued upward motion of the
46
CA 02534883 2000-04-14
0 oois~s2i ~ rcrnr~oono~~
retrieving tool 650 causes the uphole edges 696 of slot main section 654 to
ramp or
slide on ramping surface 668. And, since the angle ~i of ramping surface 668
is
greater than the angle a of the uphole edges 696, the continued upward motion
of the
retrieving tool 650 causes the uphole end of the deflecting tool 12 to be
lifted away
from the segment of casing wall it was previously abutting. This upward motion
also
results in the first section 664 entering wedge section 656 and the first
section tapered
surfaces 680 mating with the wedge section surfaces 682. Hook member 662 is
thus
secwed within slot 652 by the interaction between ramping surface 668 and
uphole
edges 696 and the interaction between first section tapered surfaces 680 and
wedge
section surfaces 682.
The fact that the uphole end of the deflecting tool I2 is lifted away from the
relevant
segment of casing wall greatly facilitates the retrieval of the deflecting
tool 12.
Without such a lifting motion, the uphole end of the deflecting tool 12 can
easily jam
against a variety of downhole objects, such as collars or debris, during the
retrieval
process. Further complications arise if the wellbore is deviated and the
uphole end of
the deflecting toot 12 must maneuver bends in the casing wall. By lifting the
uphole
end of the deflecting tool 12, the retrieving tool 650 greatly reduces the
chances of the
deflecting tool 12 jamming during the retrieval process.
Furthermore, the fact that hook member 662 and slot 652 are engaged along the
lengths of first section tapered surfaces 680 greatly increases, over the
known prior
art, the amount of surface area that is in contact between the retrieving tool
650 and
the deflecting tool 12. The prior art typically includes a hook and slot
combination
that are engaged only at the portion corresponding to the wedge section narrow
end
660. By increasing the surface area of engagement, a greater amount of lifting
load
may be applied during the retrieval process. In addition, by engaging the hook
member 662 and slot 652 at tapered surfaces, 680 and 682, much less relative
movement between the retrieving tool 650 and the deflecting tool 12 is
exhibited
during the retrieval process.
47
CA 02534883 2000-04-14
vvoooi~szi~~ ' rc~r~rsoona
The fact that the distance between the second section distal end 678 and the
retrieving
tool side 684 is slightly smaller than the drift diameter of the casing also
facilitates the
retrieval of deflecting tool 12. If the difference between the two dimensions
is
substantial, then there is enough space for the hook member 662 to become
disengaged from the slot 652, specially if a jarring event occurs during the
retrieval
process. On the other hand, even if a jarring event occurs while using
retrieving tool
650, the minimal space provided by the relative dimensions of the retrieving
tool 650
and the casing drift diameter greatly inhibits, if not abolishes, the
chances~of
disengagement.
Throughout the use of the retrieving tool 650, the hook member 662 may be
pressed
against the casing wall as shown in Figure 30. Due to the fact that the moment
of
inertia with respect to the second perpendicular axis 704 is substantially
greater, and
preferably at least three times greater, than the moment of inertia with
respect to the
first perpendicular axis 702, the retrieving tool 650 tends to bend about the
second
perpendicular axis 704. This movement facilitates the insertion of hook member
663
into slot 652 as well as the retrieval of deflecting tool 10.
1n view of the foregoing it is evident that the present invention is one well
adapted to
attain all of the objects and features hereinabove set forth, together with
other objects
and features which are inherent in the apparatus disclosed herein.
As will be readily apparent to those skilled in the art, the present invention
may easily
be produced in other specific forms without departing from its spirit or
essential
characteristics. The present embodiment is, therefore, to be considered as
merely
illustrative and not restrictive, the scope of the invention being indicated
by the claims
rather than the foregoing description, and all changes which come within the
meaning
and range of equivalence of the claims are therefore intended to be embraced
therein.
48
