Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CASING REMOVAL TOOL AND METHODS OF USE FOR WELL ABANDONMENT
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a patent cooperation treaty (PCT) application that
claims priority
to United States Provisional Application having Serial Number 62/105,130,
entitled
"Casing Removal For Well Abandonment", filed January 19, 2015, U.S. Patent
Application Serial No. 15/001,055, entitled "Casing Removal Tool And Methods
of
Use For Well Abandonment, filed January 19, 2016, and United States Patent
Application having Serial Number 14/930,369, entitled "Setting Tool For
Downhole
Applications", filed November 02, 2015.
FIELD OF THE INVENTION
[0002] The present application relates, generally, to the field of downhole
tools. More
particularly, the application relates to methods and tools for removing casing
from a
wellbore, which can be usable for the abandonment, or partial abandonment, of
the
well.
BACKGROUND
[0003] When an oil and/or gas well, or a portion of the well, ceases to become
economically
viable, that well or portion of the well may be abandoned. Abandoning a well
involves sealing the intervals of the well to prevent the migration of oil,
gas, brine and
other substances into freshwater and preventing the migration of water or
other
contaminants into the oil and gas reservoirs.
[0004] A wellbore is very often drilled to depths many thousands of feet from
the surface.
The resulting disruption of geologic formations can cause contamination of
otherwise
useful fluid reserves when a fluid from one formation flows through the
wellbore to a
different formation. Well owners and operators have long known of these
potential
risks, but have increasingly become aware of the changes that can occur within
a
wellbore over very long periods of time. Past preferred methods of properly
abandoning and preventing leakage between fluid reserves included placing
cement
plugs within the wellbore, across and on top of hydrocarbon bearing or aquifer
zones.
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That cement placement forms a long-term seal and isolation of the formations
of
interest. The interval to be cemented may be up to several hundred feet in
length.
[0005] The wellbore, however, may include fissures running on the outside of
the outermost
casing. Leakage between formations may thus occur on the outside of the casing
even
if the inside of the casing is sealed by a cement plug. The industry has
increasingly
l)(-1 jib, become aware of the need to remove the casing entirely from
within wellborc. When
the casing is completely removed, the cement plug directly contacts the
formation.
Using existing equipment, operators generally remove the outermost casing
using
mechanical milling techniques; however, there are many drawbacks to the milIin
process. The operation is slow and may take a month or more to complete. The
contaminated metal cuttings of the casing must be returned to the surface for
proces.sing and disposal. The milling drill must be large and powered by heavy
rigs ai
the surface of the wellbore. Furthermore, if there is any interior casing or
productiori
tubing strings left in the wellbore, those must be removed before any drilling
of the
external casing. Therefore, a need exists for a long-term seal of a wellbore
while
minimizing time and financial resources used in pulling casing and/or
production
tubing strings from a wellbore and milling the outermost casing.
[0006] Alternatively to milling the casing, some abandonment projects consider
perforation
of the casing to be adequate. Operators typically use explosive perforating
techniques
to form holes in the casing throughout the zone(s) to be plugged. As known in
the art;
a perforating gun containing a series of shaped charges is lowered into the
wellbore
and the charges are ignited through electrical or mechanical means. The
perforations
provide a flow-path for cement between the interior of the casing and the
annulus: =
;
[0007] While perforation is typically easier than complete removal of the
casing, perforation
has several drawbacks. It is often difficult to achieve an adequate flow-path
between
the interior of the casing and the annulus, in some instances. Inadequate or
inconsistent explosive perforation through the casing prevents cement from
adequately flowing between the interior of the casing and the annulus. Under
those,
conditions, the cement may not completely seal the annulus. These problems
have
been addressed, in some instances, by implementing a "cement squeeze," into
the
targeted area. A cement squeeze is a technique in which the cement ,is highly
pressurized as it is forced into the wellbore. The pressurization is believed
to ensure'
that cement fills any and all cracks in the casing or surrounding formation. A
cemeni
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squeeze may be especially employed in wellbores which have multiple layers of
piping and/or casing. That is, the inner tube string(s) may be perforated with
a
perforating gun and cement squeezed into the area. The cement is forced
through the
perforations in the inner tube string and fills the annulus between the inner
tube string
and the outer casing layer.
[0008] In a properly formed cement squeeze, cement hardens on both sides of
the casing,
ostensibly sealing that zone of the wellbore. Long term studies of wellbores
have
revealed, however, that after a few years the casing itself starts to
deteriorate. In
many circumstances, a deteriorating casing leaves fissures through which
fluids may
leak. Even a properly implemented cement squeeze does not address the problem
of
casing deterioration. Furthermore, cement squeeze techniques typically still
require
heavy equipment capable of producing the high pressures.
[0009] Therefore, a need exists for a wellbore sealing and isolation technique
that does not
require milling, explosive perforation, or tubing string extraction.
[0010] A need exists for sealing and isolation techniques which do not require
a drilling rig;
or a high pressurizing rig, to be transported to the wellbore site.
[0011] A need exists for sealing and isolation techniques that are not
susceptible to fissures
caused by deterioration of the casing after a cement plug has been
established, which
can lead to contamination issues.
[0012] Given the drawbacks associated with mechanical milling and with the
explosive
perforation, there is a need in the art for additional techniques for removing
sectionA
of casing or for creating adequate flow paths within the casing to facilitate
abandonment operations.
SUMMARY
[0013] The present application relates, generally, to methods and tools for
removing casing
from a wellbore, which can be usable for the abandonment, or partial
abandonment, of
the well.
[0014] The present application includes a casing removal tool for a rigless
removal of a
portion of a wellbore casing from a wellbore that includes a tubular body
configured
to contain a thermite fuel mixture configured to initiate into a molten
thermite fuel,
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and a nozzle array including a plurality of densely packed nozzles positioned
on an
external surface of the tubular body. The nozzle array can be configured to
impinge
the molten thermite fuel onto a section of the wellbore casing so that the
molten
thermite fuel, from each of the nozzles in the plurality of nozzles, can at
least partially
overlap the molten thermite fuel from each adjacent nozzle in the plurality of
nozzles.
The casing removal tool can further include an orientation lug configured to
anchor
into a downhole orientation tool.
[0015] Other embodiments of the casing removal tool can have an orientation
lug that can be
configured to be set by an operator at a specific orientation before entering
the
wellbore. The casing removal tool, in some embodiments, may include a seconq
nozzle array that can be configured to impinge the molten thermite fuel onto a
seconq
section of the wellbore casing. The casing removal tool, in some embodiments,
may
have area of the nozzle array that takes up one quarter of a total area of the
external
surface. That area may include up to a 90 or more rectangular area, and the
plurality
of nozzles can be uniformly spaced within the rectangular area.
[0016] The casing removal tool, in some embodiments, can include a spacer that
can be
configured to offset the nozzle array by a linear offset distance from the
downhole
orientation tool. In an embodiment, a centralizer can be configured to orient
the
casing removal tool relative to a radial center of the wellbore, and to
maintain the
casing removal tool in the center of the wellbore during operations.
[0017] The disclosed embodiments also include a method of removing casing from
a
wellbore with a casing removal tool. The steps of the method can include
lowering
the casing removal tool into the wellbore and orienting the casing removal
tool within
the wellbore at a first linear orientation and a first azimuthal orientation.
The casing
removal tool includes a tubular body configured to contain a thermite fuel
mixture.
[0018] The steps of the method can further include initiating a burn of the
thermite fuel
mixture to produce a molten thermite fuel, projecting the molten thermite fuel
through
a nozzle array that comprises a plurality of nozzles positioned adjacent to
one another,
and impinging the molten thermite fuel onto a section of the casing to melt,
vaporize,
and/or disintegrate the casing. The molten thermite fuel, from each of the
nozzles in
the plurality of nozzles, can at least partially overlap the molten theimite
fuel from
each adjacent nozzle in the plurality of nozzles to uniformly melt, vaporize
or
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disintegrate a desired section (e.g., continuous section) of the casing. The
steps of the
method can further include retrieving the casing removal tool from the
wellbore.
[0019] The method, in certain embodiments, can further include lowering an
additional
casing removal tool into the wellborc and orienting, while lowered into the
wellborc,
the additional casing removal tool within the wellbore. The additional casing
removal
t tool can be oriented at a combination of linear orientation and
azimuthal orientation,
which is different from the linear orientation and azimuthal orientation of
any
previously lowered casing removal tool.
[0020] The steps of the method can further include initiating a burn of the
thermite fuel
mixture within the additional casing removal tool to produce a molten thermite
fuel
and impinging the molten thermite fuel onto an additional section of the
casing. Each
,
additional section of the casing is at least partially different from each
previous
7
section of the casing to which the molten thermite fuel is applied. The method
cart
= include retrieving the additional casing removal tool from the wellbore
before
4,
lowering a next additional casing removal tool.
[0021] In certain embodiments, the method includes lowering and setting a
downhole
orientation tool prior to lowering the casing removal tool. Each of the casing
removal
tools is configured to linearly and azimuthally orient based on the downholl
orientation tool.
[0022] In certain embodiments, the method includes lowering a spacer with each
of, the
,
casing removal tools to linearly offset each of the casing removal tools from
thq
downhole orientation tool. The spacer may include a length to linearly
position the
y.t
casing removal tool relative to a zone of the casing, and the casing removal
tool may
remove at least a portion of the casing in the zone prior to adjusting the
length of the
spacer for the additional casing removal tool or the next additional casing
removal
tool.
[0023] Setting the downhole orientation tool may include perforating holes
into the casing
with a perforating torch and securing anchor dogs of the downhole orientation
fool
into the perforated holes, setting a sleeve hanger or a post-positioner with a
setting
= ;
tool, or combinations thereof.
=
[0024] In certain embodiments, orienting the casing removal tool further
includes offsetting
the casing removal tool from a radial center of the wellbore towards the
casing. The
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casing removal tool may be offset toward the section of the casing impinged by
the
molten thermite fuel.
[0025] In certain embodiments, lowering the casing removal tool into the
wellbore includes
using a wirelinc, a slickline, other rigless tool lowering strings, or
combinationg
thereof. Lowering and orienting the casing removal tool may include lowering
and
pt 1 I orienting the casing removal tool by attaching the casing
removal tool to an end of a
production tubing drill string.
[0026] The disclosed embodiments also describe and support a system for
removing
wellbore casing from a wellbore that can include a downhole orientation . tool
configured to be secured within the wellbore, wherein the downhole orientation
tool
can have a linear and azimuthal orientation keyway, and a plurality of casing
removal
tools. Each casing removal tool can include an orientation lug that can be
configurecl
to orient within the keyway of the downhole orientation tool. An operator can
change,
a position of the orientation lugs before lowering the casing removal tools
into the
'1
wellbore. The system can further include a nozzle array having a plurality of
densely
packed nozzles configured to impinge molten thermite fuel onto a continuous
section
of the wellbore casing after the casing removal tool is lowered into the
wellbore, and a
spacer configured to offset the nozzle array a linear distance from the
downhole
orientation tool.
[0027] In certain embodiments, the system can include a second spacer
configured to offset
µ.
=
the nozzle array a second linear distance from the downhole orientation tool.
;
The downhole orientation tool may have a sleeve hanger, a post-positioner, 01
combinations thereof. In an embodiment, each casing removal tool, in the
plurality of
casing removal tools, can include a nozzle array that is approximately 6 to 7
meters or
more in length and about 90 degrees around an external surface of the casing
removal
tool.
[0028] In certain embodiments, the system can include a centralizer that is
configured td
orient the casing removal tool relative to a radial center of the wellbore,
and maintain
'
the casing removal tool centrally within the wellbore.
[0029] In certain embodiments, the system above includes small splinters of
the wellbore
casing that can be retrieved from the wellbore, removed from the wellbore, or
allowed
to fall down the wellbore. The small splinters (e.g., small sections) of the
wellborc
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casing are located between the continuous sections of the wellbore casing,
onto which
the molten thermite fuel is, or has been, projected.
[0030] The disclosed embodiments can further include a method of removing
casing from a
wellbore that includes lowering a casing removal tool into the wellbore
through a first
wellbore tubing having a first diameter, wherein the wellbore includes the
first
wellbore tubing and a second wellbore casing. The steps of the method can
continue
by including the lowering of the casing removal tool through the second
wellbore
casing, having a second diameter. In this embodiment, the second diameter is
larger
than the first diameter, and the second wellbore tubing is downhole from the
first
wellbore tubing. The steps of the method can further include orienting the
casing
removal tool within the second wellbore casing, initiating the casing removal
tool to
remove casing from the second wellbore casing, and retrieving the casing
removal
tool from the wellbore.
[0031] In certain embodiments, orienting the easing removal tool can include
offsetting the
casing removal tool from a radial center of the wellbore towards the casing.
Also,
orienting the casing removal tool may include anchoring the casing removal
tool to an
orientation tool that remains secured within the wellbore after the casing
removal tool
has been retrieved from the wellbore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 illustrates an embodiment of a casing removal tool, as
described herein.
[0033] Figure 2 illustrates a nozzle array of a casing removal tool.
[0034] Figure 3 illustrates a liner orientation tool.
[0035] Figure 4 illustrates radial indexing multiple deployments of a casing
removal tool.
[0036] Figure 5 illustrates a casing removal tool configured with a spacer for
removing
casing from multiple zones within a wellbore.
[0037] Figure 6 illustrates a four-way perforating torch, usable for setting
the orientation
tool.
[0038] Figures 7A - 7C illustrate deploying a four-way perforating torch and a
liner
orientation tool in a single trip.
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[0039] Figure 8 illustrates a casing removal tool having multiple slotted
nozzle arrays.
[0040] Figure 9 illustrates a casing removal tool having a helical pattern of
nozzle arrays.
[0041] Figure 10 illustrates an embodiment of an alternative orientation tool.
[0042] Figure 11 illustrates an embodiment of an alternative orientation tool.
I I.if=
DETAILED DESCRIPTION
[0043] Before describing selected embodiments of the present disclosure in
detail, it is to be
understood that the present invention is not limited to the particular
embodiments
described herein. The disclosure and description herein is illustrative and
explanatory
of one or more presently embodiments and variations thereof, and it will be
appreciated by those skilled in the art that various changes in the design,
organization,
means of operation, structures and location, methodology, and use of
mechanical
equivalents may be made without departing from the spirit of the invention.
t't I
[0044] It should be understood, as well, that the drawings are intended to
illustrate and
plainly disclose embodiments to one of skill in the art, but are not intended
to be
manufacturing level drawings or renditions of final products and may include
simplified conceptual views to facilitate understanding or explanation. As
wel15, the
relative size and arrangement of the components may differ from that shown and
still
operate within the spirit of the invention.
[0045] Moreover, it will be understood that various directions such as
"upper", "lower",
"bottom", "top", "left", "right", and so forth are made only with respect to
explanation in conjunction with the drawings, and that components may be
oriented
differently, for instance, during transportation and manufacturing as well as
operation;.
Because many varying and different embodiments may be made within the scope of
the concept(s) herein taught, and because many modifications may be made in
the
embodiments described herein, it is to be understood that the details herein
are to be
interpreted as illustrative and non-limiting.
=
[0046] The methods and tools described herein use an exothermic, thermite
reaction to
controllably remove large, complete sections of casing or to penetrate the
casing with
holes of adequate size to provide a reliable flow-path for
plugging/abandonment
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operations. Rather than making small holes for extraction of production fluid,
or for
aligning tools within the wellbore, the methods and tools described herein are
used to
remove continuous and uniform sections of casing from the wellbore. A casing
removal tool is deployed into the cased wellbore. Several types of casing
removal
tools may be employed to remove casing from the wellbore. Each of which may
have
a small cross-sectional diameter such that the casing removal tool may be
lowered
through tubing of a narrow width and remove casing from tubing at a wider
width.
The casing removal tool may include, for example, thermite that may be
initiated and
projected upon the casing. The molten thermite impinges onto the steel casing
and
.
i
melts, vaporizes, and/or disintegrates the casing. The destruction of the
casing is
caused both by the heat of the molten thermite and by the pressure (e.g., jet)
of the
thermite exiting the casing removal tool. The molten thermite and casing
typically fall
downward within the wellbore immediately after the reaction has completed.
[0047] Figure 1 illustrates an embodiment of a casing removal tool 100
deployed within an
interval 101 of a wellbore. The interval 101 of the wellbore may be located
downhole
from a narrow production tubing. The casing removal tool 100 is shown as
relatively,
close in width to the casing, but in certain embodiments the casing removal
tool 1001
may be narrower than the interval 101 of the casing being removed. The casing
removal tool 100 is small enough to fit through the narrow production tubing
because
the techniques disclosed herein are compact and do not require the use of a
rig to
power the removal of the casing. In fact, in certain embodiments, the casing
removal
tool is used with a wireline, a slickline, other rigless tool lowering
strings, or
= combinations thereof to deploy the casing removal tool, fire, and
retrieve the casing
removal tool before a typical rig could even be transported to the wellbore.
[0048] The casing removal tool 100 includes a tubular body 102 and a focused
nozzle array)
103. As explained in more detail below, the tubular body 102 contains solid
the .7ite:
fuel. The solid thermite fuel may be located within the tubular body 102
adjacent the
nozzle array 103, or may occupy internal space within the tubular body 102 for
several meters above or below the nozzle array 103. The nozzle array 103 is an
area
of an external surface 108 of the casing removal tool 100 that includes a
plurality of
nozzles 104. The area of the nozzle array 103 may vary in size (e.g., length,
width,
and/or shape). For example, the nozzle array may be about 6.1 meters (twenty
(20)
feet) in length but the tubular body 102 that houses the fuel may be about
3.0, 6.1;
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9.14, 12.19 meters or more (about 10, 20, 30, 40 or more feet) in length. When
the
solid thermite fuel is initiated, molten thermite is expelled through the
nozzles 104 of
the nozzle array 103.
[0049] The focused nozzle array 103 is illustrated in more detail in Figure 2.
The plurality
of nozzles 104 provide a path for molten thermite contained on the inside of
tubular
body 102. The nozzles can be less than an inch in diameter and can be less
than half-
inch in diameter. According to some embodiments, the nozzles can be about
3/16"
inches in diameter. However, any diameter of nozzle is within the scope of the
disclosure.
[0050] The focused nozzle array 103 can be densely packed with nozzles 104.
Densely
packed nozzles 104 means that the nozzle array 103 has nozzles 104 in which
the
projection of molten thermite from each nozzle 104 at least partially overlaps
the
projection of molten thermite from each adjacent nozzle 104. The result from
such a
nozzle array 103 is a uniform annihilation of a continuous section of the
casing in
front of the nozzle array 103. For example, a densely packed nozzle array 103
may
have an area that is more than fifty percent (50%) occupied with nozzles 104.
That is,
the area within the nozzle array 103 that is occupied by a nozzle 104 (e.g., a
hole in
the tubular body 102) is greater than the area within the nozzle array 103
that is
between the nozzles 104. According to some embodiments, when the nozzles 104
are
about 4.5 mm (about 3/16 inches) in diameter, the nozzles 104 are also spaced
about
4.5 mm (about 3/16 inches) from each other. Ideally, and without limitation,
when
the thermite is initiated, the casing removal tool 100 provides a hole in the
casing that
is roughly the same size and shape of the nozzle array 103, rather than
providing
discrete holes corresponding to each nozzle 104. For example, if the nozzle
array 103
is 25.4 mm (2 inches) wide and 6.1 meters (20 feet) long, the casing retnoval
tool 100
will provide a 25.4 mm (2 inch) by 6.1 meters (20 foot) hole in the casing.
[0051] For removing casing over a long interval, a longer tubular body 102 is
desirable. Any
length of tubular body 102 is within the scope of the disclosure. However,
practical
considerations, such as issues with uniformly initiating the solid thermite
fuel, may
limit the length of the tubular body 102 to about 15.24 meters or less (about
fifty (50)
feet or less), for example. The embodiment illustrated in Figure 1 has a
tubular body
102 that is about 6.1 meters (20 feet) in length.
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[0052] The nozzle array 103 may cover any radial area the circumference of the
tubular body
102. For example, nozzles 104 may be distributed upon a 3600 area of tubular
body
104. With such a configuration, the casing removal tool 100 removes an entire
longitudinal section of the casing with a single deployment and initiation.
More
generally, however, the nozzle array 103 covers less than the entire
circumference of
the tubular body 102. For example, the nozzle array 103 may cover a 90 area
of the
tubular body 102. According to that embodiment, four deployments of the casing
removal tool 100 is needed to remove a continuous interval of casing, with
each
deployment having the nozzle array 103 rotated along a different 90 section
of casing
to remove the entire 360 of casing. In certain embodiments, the nozzle array
103
may include a 360' ring around the external surface 108 of the casing removal
tool
100.
[0053] To properly orient the casing removal tool 100, a liner orientation
tool 105 may be
secured or set within the wellbore. The orientation tool 105 may include a
keyway
"t
106 for engaging with a location/orientation lug 107 on the casing removal
tool 100.
The orientation lug 107 may be adjusted by an operator at the surface of the
wellbor
to change the azimuthal angle at which the orientation lug 107 interacts with
the
keyway 106, changing the section at which the casing removal tool 100
impinges.
The orientation tool remains fixed in the wellbore and allows multiple
deployments
and orientations of the casing removal tool 100. An embodiment of a liner
orientation
tool 105 is illustrated in more detail in Figure 3. The liner orientation tool
105
comprises a positioning sleeve 201 configured with spring-loaded anchor dogs
202.
As the liner orientation tool is deployed, the anchor dogs 202 are held in a
retracted
position by the inside diameter of casing 203. When the liner orientation tool
encounters appropriately spaced anchor holes 204 within the casing, the anchor
dogs
202 can extend and engage within the anchor holes 204.
;
[0054] In another embodiment, the orientation tool 105 can be secured in place
using a
setting tool that forces teeth or dogs against the casing itself. These types
of
orientation tools 105 may include sleeve hangers (illustrated, for example, by
positioning sleeve 201), or may include post-positioners where the casing
removal
tool 100 slips around the exterior of a post that has been secured within the
wellborc.
A post-positioner will often be positioned below the area of casing that is
being
targeted for removal. In an embodiment in which the orientation tool 105 is
secured
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into place by the use of a setting tool, the orientation tool 105 can comprise
a first
plurality of grooves, which define a first selected profile that is defined by
a selected
spacing of the first plurality of grooves. Upon lowering a casing removal tool
inside
the wellbore, the casing removal tool, comprising a first plurality of
protruding
members, can be positioned and locked into place within the wellbore by the
first
plurality of protruding members forming a first complementary profile that is
i'= ' I
configured to lock only within the first selected profile of the orientation
tool, thus
positioning and locking the casing removal tool into place within the
wellbore. This
embodiment is further described in relation to figure 10.
=
[0055] Once deployed and installed, the liner orientation tool 105 can be used
to anchor
multiple modular deployments of casing removal tools 100, assuring that the
casing
removal tools each return to the desired depth within the wellbore each time
and align
in the correct orientation. For example, the casing removal tools 100, as
illustrated in
Figure 1, can be used to remove a 6.1 meter (20-foot) section of casing. In
this
embodiment, the nozzle array 103 covers a 6.1 meter (20 foot) length of the
casing
removal tool 100 and covers a 900 radial area. As explained above, changing.
the
azimuthal orientation of the casing removal tool 100 over four separate
deployments
enables 360 removal of that section of casing. Generally, this method of use
would
require four different casing removal tools 100, as each tool may be consumed
once
the thermite is initiated.
[0056] Each casing removal tool has a location/orientation lug 107 positioned
to engage with
the keyway 106 of the liner orientation tool 105. Since the keyway 106 of the
liner
orientation tool 105 remains in a constant radial/azimuthal orientation (i.e.,
it does not
shift within the wellbore), the location/orientation lugs 107 of each of the
four
different casing removal tools 100 are indexed to a different position about
the
circumference of the casing removal tool, with respect to the nozzle array
103.
Specifically, each of the location/orientation lugs 107 are positioned, such
that the
casing removal tool 100 orients to such that the nozzle array 103 covers a
different
90 quadrant of the casing with each deployment. Figure 4 illustrates a second
deployment of the casing removal tool 100. The casing removal tool 100 has
been
indexed to a second position 90 rotated from the first position. A section of
casing;
represented by the dashed line 401, was removed during the first deployment of
the
casing removal tool 100.
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[0057] Depending on the particulars of a given casing removal operation, more
or fewer
deployments of a casing removal tool 100 may be required. This will be
dependent
on casing size, wall thickness and overall volume that can be reliably removed
per
thermite system deployed. For example, a larger or thicker casing might
require more
sustained contact with the molten thermite fuel. In such a case, a casing
removal tool
100, having a nozzle array 103 covering an area of 60 instead of 90 , might
be used,
!'
thus requiring six deployments. Alternatively, the casing removal tools 100
may be
deployed in such a way that the radial areas, swept by the nozzle array 103
during
each subsequent deployment, overlap somewhat. In each of those scenarios, the
radial or azimuthal orientation of the casing removal tool within the wellbore
is
determined by indexing the position of the location/orientation lug 107 with
respect to
the nozzle array 103 on each of the casing removal tools 100. In addition to
linear
and azimuthal orientations, the casing removal tool 100 may be oriented away
relative
to a radial center of the wellbore through centralizers positioned along the
casing
;S removal tool 100. The centralizers may be located next to the
orientation tool 105, of
may be integrated such that the
[0058] By deploying the system in a modular manner, sections of the casing can
be removed
over time. The overall length of casing removed can be accomplished by
increasing
the number of deployments. There is no practical limit to the overall length
that can
be achieved following this method. Casing lengths of 600 feet and greater can
be
removed using casing removal tools 100 that are 20 feet in length by simply
repeating
the process described above and stepping the casing removal tool 100 to a
different
vertical location within the wellbore as the previous vertical section is
'removed. For
example, Figure 5 illustrates a casing removal tool 100 offset from the liner
orientation tool 105 by a spacer 501. The spacer 501 may be used for each
casing
removal tool 100 until all of the casing is removed from that "zone." A zone.
of
casing means the entire circle of casing for a length of the wellbore equal to
one
length of the casing removal tool. As explained above, the zone may be 20 feet
(about 3 meters) or more depending on the size of the nozzle array 103. The
casing
removal tool 100 is illustrated in the first indexed position in FIG. 5.
Assuming.that
the nozzle array 103 covers a 90 radial area, as described above, four
deployments of
a casing removal tool 100 (each with a different 90 indexing) would be needed
to
remove all of the casing from Zone 1. Once the casing is entirely removed from
Zone'
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1, the length of the spacer 501 can be decreased to allow removal from Zone 2.
The
process can then be repeated for Zones 3 and 4.
[0059] Depending on conditions, it may be necessary to remove shorter sections
of casing
sequentially. But, conveniently, the liner orientation tool 105 can be
positioned at the
most upper section of the wellbore where casing is to be removed. The first
section of
;)1 ' casing removed is typically lowermost portion of the overall
interval so that falling
slag and by-products from the removal process does not complicate removal of
subsequent sections. Each zone may require a single deployment or multiple
azimuthally indexed deployments to complete the removal process.
[0060] As shown in Figures 1-5, the liner orientation tool 105 allows for
modular
deployments of a casing removal tool 100 to remove sections of casing at
multiple
radial angles at a given depth within a wellbore and also at different depths
within a;
wellbore. Figure 6 illustrates a process for cutting anchor holes 204 in
casing 203.
using a four-way perforating torch 601. The four-way perforating torch uses
molten
=
thermite fuel ejected through nozzles 602 to cut holes 204 in the casing 203.
The four-
way perforating torch 601 can be deployed via a tool string 603, for, example.
Examples of four-way perforating torches 601, as well as other suitable
torches are
available from MCR Oil Tools (Arlington, TX). Once the anchoring holes 204 are
cut, the liner orientation tool 105 can be deployed, as explained above.
[0061] Figures 7A-7C illustrate an alternative method of deploying the liner
orientation tool
105, wherein the four-way perforating torch 601 and the liner orientation tool
105 are
,
both deployed on the same tool string 603 in a single trip. The liner
orientation ,totzl
105 is positioned above the four-way perforating torch 601 during the run in
hole
configuration with the four anchor dogs 202 in a retracted position but with
their
spring force acting on the ID of the casing. The four-way perforating torch
601 is
initiated and creates the four anchor holes at 90 orientation. Once the
anchor holes
204 are cut, the tool string 603 is lowered and the spring loaded anchor dogs
202 are
allowed to seek and locate the anchor holes 204 (Figure 7B). Over-pull is then
applied to verify that the liner orientation tool 105 is anchored. Additional
over-pull
is applied to shear a predetermined weak point, freeing the four-way
perforating torch
601 and tool string 603 from the liner orientation tool 105. Figure 7C
illustrates the
process whereby the tool string 603 and four-way perforating torch 601 are
retrieved
from the wellbore leaving the liner orientation tool 105 in position. It
should be noted
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that the liner orientation tool 105 could also be configured below the four-
way
perforating torch 601 on the tool string 603.
[0062] Figure 8 illustrates another embodiment whereby the casing removal tool
801 is
provided with a slot pattern of multiple nozzle arrays 802 within one tool
configuration. Each nozzle array 802 contains a plurality of densely-packed
nozzles,
=:-; configured in rows and columns on an area of an external surface of
the tubular body:
As shown in FIG. 8, the molten thermite from each row of nozzles at least
partially
overlaps the molten thermite fuel from each adjacent row of nozzles, and each
of the
columns of nozzles at least partially overlaps the molten thermite fuel from
each
adjacent column of nozzles in the plurality of nozzles. Each nozzle array 802
impinges on a continuous section of the wellbore casing, as described in
detail above,
for uniform annihilation of the continuous section of the wellbore casing. The
casing
removal tool 801 provides a series of predetermined slots or holes in the well
casing
so that the cement barrier material can be easily and adequately displaced all
around
the casing without the need for high-pressure circulation. The same liner
orientation
tool 105 can be utilized for depth positioning within the wellbore and tool
anchoring.
Generally, the casing removal tool 801 does not need the indexing capability
described above.
[0063] Figure 9 illustrates another embodiment of a casing removal tool 901
similar to 801,
but wherein the slot pattern is a spiral or helical arrangement of nozzle
arrays 902
The same liner orientation tool 105 can be used to achieve depth positioning
within
the wellbore and tool anchoring; although in this application, it is not
necessary tq
utilize the indexing capability. Possible techniques for utilizing the casing
removal
tools 801, 901 that have multiple nozzle arrays include making several linear
deployments without changing the azimuthal orientation. By changing only the
linear
orientation, an operator leaves strips of casing lengthwise along the
wellbore. After
the strips have been cut into the wellbore, additional 360' horizontal
deployments
may be used to cut the top and the bottom of the strips of remaining casing,
creating
splinters of free-floating casing. These splinters may fall down the wellbore
without
any further interaction. In certain cases, the splinters remain fixed to
cement and/or
geologic formation bchind the casing. In these cases, a fluid wash may be used
to
agitate the splinters and any remaining cement from the wellbore. This creates
a
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wellbore that is similar to a just-drilled wellbore, which may enable greater
fixation of
the cement plug for abandonment.
[0064] As described above, the casing removal tools disclosed herein use an
exothermic
reaction of thermite (or a modified thermite mixture) fuel to remove casing
material'.
The thermite fuel may be in any form, but is typically loaded into the casing
removal
tool as solid pellets. The thermite can include pressed pellets of a powdered
(or finely
divided) metal and a powdered metal oxide. The powdered metal can be aluminum,
magnesium, etc. The metal oxide can include cupric oxide, iron oxide, etc. A
particular example of the thermite mixture is cupric oxide and aluminum. When
initiated, the thermite material produces an exothermic reaction. The thermite
material may also contain one or more gasifying compounds, such as one or more
hydrocarbon or fluorocarbon compounds, particularly polymers.
[0065] The tubular body 102 of the casing removal tools described herein may
be adapted tq
withstand the exothermic reaction of the thermite mixture. For example, it may
be
configured with a reaction-resistant coating, such as graphite or another
material.
[0066] The thermite fuel load disposed within the tubular body 102 will
generally be
cylindrical in shape. According to certain embodiments, the thermite fuel load
is
initiated along the center of the longitudinal axis of the fuel load. Thus,
the fuel load
reacts from the inside out. An advantage of that reaction geometry is that the
material
closes to the inner diameter (ID) of the tubular body 102 is the last material
to react;
and therefore, this material provides some thermal insulation against the
proceedinq
exothermic reaction. That thermal insulation, as set forth above, can help,
maintain
structural integrity of the tool during the course of the reaction. However,
it should be
noted that other initiation/reaction geometries can be used. For example,
according to
certain embodiments, an off-center initiation provides increased expulsion
velocity
through the nozzle array.
[0067] Figure 10 illustrates an alternative embodiment of an orientation tool
1005 that is set
within the wellbore. The orientation tool 1005 includes lower cones 1001 and
upper
cones 1002 that squeeze a sealing member 1003, maintaining a fluid-tight seal.
Upppt
slips 1007 and lower slips 1009 are likewise forced into position and maintain
the
cones 1001, 1002 in position by biting into the wellbore with teeth.
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[00681 Orientation tools, such as the orientation tool 1005 illustrated in
Figure 10, can be
deployed within a wellbore using a setting tool. The setting tool can carry
the
orientation tool 1005 to the desired location within the wellbore. To deploy
an
orientation tool within a wellbore, a setting tool is typically connected to
the
orientation tool, and the setting tool and orientation tool arc run down the
wellbore
using a slickline, wireline, coiled tubing, or other conveying method. The
setting tool
: =
typically includes a sleeve that rides on the outside 1011 of a mandrel 1013
and
applies push force to the slips 1007. The setting tool also typically engages
a mandrel
1013 by a threaded connection or by a shear stud, for example, allowing the
setting
tool to apply pull force to the mandrel 1013. Once the setting tool reaches
the desired
depth within the wellbore, the setting tool deploys the orientation tool 1005
by
actuating forces onto the upper slips 1007, which force is conveyed to the
lower coneSµ
;
1001, upper cones 1002, sealing member 1003, and lower slips 1009.
[0069]The embodiment of Figure 10 illustrates that the orientation tool 1005
includes a cone
, .
1015 that contains an inside diameter profile 1017, with a groove or a
plurality of
grooves 1019 into which a complementary projected profile of the casing
removal
tool 100 may engage. While Figure 10 depicts grooves 1019 for mechanical
engagement with complementary protrusions of an apparatus and/or string, it
should
be understood that in various embodiments, the grooves 1019, and/or the
complementary protrusions for engagement therewith, can include one or more
magnets for providing magnetic adhesion, and/or one or more chemicals (e.g.,
adhesives, epoxies, or similar substances) to provide a chemical adhesion.
. =
= [00701 In further embodiments, other orienting techniques may be used to
secure the casing
removal tool 100. For example, figure 11 illustrates an embodiment of an
orientation
tool 1105 that utilizes a post-positioner 1107. The orientation tool 1105 can
be set
with a setting tool in a similar manner as described above with regard to
figure 10;
After the orientation tool 1105 is set, the casing removal tool 100 may be
lowered
onto a post area 1109 and secured to a post head 1111. The post head 1111 is
located
at the distal end of a post 1113 which may be a few centimeters to a meter or
more in
length. The post head 1111 includes an orientation nub 1115 which the casing
removal tool 100 may orient by in a reversal of roles to the keyway 106 and
orientation lug 107 described above. The post head 1111 may also include a
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complementary profile that fits into grooves (e.g., grooves 1019) as described
above
in regards to figure 10.
[0071] The foregoing disclosure and the showings made of the drawings are
merely
illustrative of the principles of this invention and are not to be interpreted
in a limiting
sense.
r. :=
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