Note: Descriptions are shown in the official language in which they were submitted.
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1
METHODS AND APPARATUS FOR SEVERING
NESTED STRINGS OF TUBULARS
The present invention generally relates to plugging and abandonment of oil and
gas
wells. More particularly, the present invention relates to the removal of a
tubular from a
wellbore in order to satisfy various environmental regulations. More
particularly still,
the invention relates to severing nested strings of tubulars that are cemented
together in
order to more easily handle the tubulars as they are removed from a wellbore
during or
subsequent to a plugging and abandonment operation.
In the completion of oil and gas wells, boreholes are formed in the earth and
thereafter
are lined with steel pipe known as casing. An annular area formed between the
outside
of the casing and the wall of the borehole is typically filled with cement in
order to
secure the casing in the borehole and to facilitate the isolation of certain
areas of the
wellbore for the collection of hydrocarbons. In most instances, because of the
depth of
a wellbore, concentric strings of tubulars are disposed in the wellbore with
each lower
string of tubulars being necessarily smaller in diameter than the previous
string. In
some cases, especially in offshore oil and gas wells, the strings are run in a
nested
fashion from the surface of the well. In other words, a first string of casing
is cemented
into the wellbore and, subsequently, a second smaller string of casing is
cemented into
the first string to permit the borehole to be lined to a greater depth. This
process is
typically repeated with additional casing strings until the well has been
drilled to total
depth. In this manner, wells are typically formed with two or more strings of
casing of
an ever-decreasing diameter.
When a decision is made to no longer operate a hydrocarbon well, the wellbore
is
typically plugged to prevent formation fluids from migrating towards the
surface of the
well or into a different zone. Various environmental laws and regulations
govern the
plugging and abandonment of wellbores. These regulations typically require
that the
wellbore be filled with some amount of cement. In some instances, the cement
must be
squeezed into the annular area around the cemented casing in order to prevent
fluids
from migrating up towards the surface of the well on the outside of the casing
through
any cement gaps. In offshore wells, regulations typically require not only the
foregoing
steps, but also that a certain amount of wellbore casing be completely removed
from the
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2
wellbore. For example, in some instances, the upper 1,000 feet of casing
extending
downward from the ocean floor into the wellbore must be removed to complete a
plugging and abandonment operation.
Various methods and techniques have been developed and are currently utilized
in order
to remove casing from an offshore wellbore. Most often, some type of cutting
device is
run into the wellbore on a wireline or string of tubulars. The cutting device
is actuated
in order to sever the casing at a predetermined depth, creating separate upper
and lower
strings of casing. Thereafter, the upper string is pulled and brought to the
surface.
Because of the great length and weight of the upper string of casing being
removed, it is
necessary to further sever the upper casing string as it is retrieved at the
surface.
Accordingly, the casing is further severed into predetermined lengths. This
makes
handling and disposal of the removed casing more efficient.
In some instances, the severed upper string of casing includes more than one
set of
tubulars. In other words, there is a first outer string of casing, and then a
second smaller
string of casing nested therein. In one example, the outer casing string is 13
3/8 inches
(34 cm) in diameter, and the smaller casing nested therein is 9 5/8 inches
(24.4 cm) in
diameter. These two strings of severed casing will typically be joined by a
layer of
cement within the annular area. This cement layer adds to the weight of the
severed
casing string, making it even more desirable to cut the retrieved pipe into
manageable
sections.
A casing string is typically comprised of a series of joints that are 30 feet
(9.1 m) in
length. The pipe joints are connected by threaded male-to-female connections.
When
retrieving a severed casing string during a plug and abandonment procedure, it
is
desirable to break the pipe string by unthreading the connected joints.
However, this
process is difficult where the severed string consists of outer and inner pipe
strings
cemented together. Further, there is little incentive to incur the time
necessary to break
the joints apart at the threads, as the pipe joints from an abandoned well
will typically
not be re-used. For these reasons, the severed casing is typically broken into
smaller
joints by cutting through the inner and outer strings at the surface of the
well. The
severed pipe sections are then recycled or otherwise disposed of.
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3
In a conventional plug and abandonment operation, casing strings are severed
generally
as follows:
First, the casing string is severed within the wellbore. Typically, severance
is
accomplished at a depth of around 1,000 feet (305 m). Thereafter, the severed
portion
of casing is "jacked" out of the wellbore and raised to the surface of the rig
platform
using a platform-mounted elevator. As the upper end of the severed casing
section
reaches the floor of the platform, it is lifted to a predetermined height
above a set of
slips. The slips are then set, suspending the severed string of casing above
the rig floor.
A drilling machine then drills a hole completely through the casing, including
any
cement layer and smaller diameter casing which is cemented within the larger
diameter
casing. Thereafter, a pin or other retainer is inserted through the drilled
hole to ensure
that the smaller string of casing is anchored to the larger string. This
method of drilling
a hole through the casing and inserting a retainer pin is necessary to ensure
that the
smaller string of casing does not become dislodged from the larger string due
to some
failure of the cement layer there between.
After the inner casing siring and cement therearound is anchored to the larger
outer
string, a band saw is used to cut the severed tubular into a predetermined
length. The
band saw operates with coolant to avoid the use of high temperature cutters or
the
production of sparks. Typically, a length of approximately ten feet (3 m) is
selected,
with the cut being made above the retention pin. The newly severed, ten-foot
(3 m)
portion of string is then transported to a barge or other transportation means
for disposal
or salvage.
With the slips disengaged, the elevator then raises the severed string of
casing another
length of approximately ten feet (3 m). The slips are then re-engaged and the
drilling,
anchoring and cutting procedure takes place again.
While the foregoing apparatus and method are adequate to dispose of strings of
concentrically cemented casing, the operation necessarily requires personnel
to be at the
drilling mechanism and the band saw during the operation. The presence of
personnel
on a platform inherently carries risk. The risk is magnified when the
personnel must be
in close contact with the operating machinery.
CA 02433362 2005-09-15
.; , , . . , , .
4
There is a need, therefore, for a method and apparatus of disposing of
concentric strings
of tubular during a plugging and abandonment operation which does rat require
personnel to be located directly at the machinery performing the cutting
operations.
There is a further need for a method and apparatus which can be operated
remotely by
S well platform personnel. There is yet a further need for an apparatus and
method that
can more safely and effectively sever strings of casing at a well site.
In accordance with one aspect of the present invention there is provided an
apparatus for
severing casing above a wellbore, comprising.
a clamp assembly constructed and arranged to hold the casing in relation to
the
IO apparatus;
a drill assembly constructed and arranged to form an aperture through the
casir_g
arid through any inner casing string nested within the casing, the aperture
being
dimensioned to receive a zetention member for anchoring the casing to the any
nested
casing string; and
15 a cutting assembly constructed and arranged to sever the casing and the any
other nested casing string by forming a through-cut through the casing;
characterised in that the clamp assembly, drill assembly and cutting assembly
are arranged in proximity to each other.
20 In accordance with another aspect of the present invention there is
provided a method of
severing casing, comprising the steps of:
forming an aperture through .the casing and through any inner casing. string
nested therein, using a drill assembly;
anchoring the casing and the any nested casing string together; and
25 severing the casing using a cutting assembly, the cutting assembly
comprising a
blade to form a cut;
characterised in that the drill assembly and cutting assembly are proximate to
each other so that ihz casing is not moved axially between the steps of
forming the
aperture and severing the casing.
30 In accordance with a further aspect of the present invention there is
provided an
apparatus for severing a casing above a tvellbore, comprising:
.. 04-03=2003 ' Nj~C P> 1~43'WO G 80201339
CA 02433362 2003-06-27
a
a tubular severing assembly;
a support beam; and
a single cantilevered extendable structure having a first end and a second
end,
the extendable structure being attached to the support beam at the first end,
and being
attached to the tubular severing assembly at the second end.
~f~lEI~DED SHEET
CA 02433362 2005-09-15
Thus the present invention generally provides an apparatus and method for
severing
predetermined lengths of nested casing above a drilling rig or workover rig
platform.
The apparatus includes a clamp assembly, a drill assembly and a cutting
assembly. In
S one embodiment, the clamp assembly, the drilling assembly and the cutting
assembly
are disposed at the end of a telescopic arm, and are remotely operated by
personnel
using a control panel. The clamp assembly is positioned adjacent a section of
casing to
be severed, and then clamped thereto. Thereafter, the drilling assembly is
actuated so as
to drill a hole completely through the casing strings. A retention pin is then
inserted
through the newly formed aperture. Finally, the cutting assembly, such as a
band saw,
is actuated so as to severe the casing above the pin. The newly severed
portion of
casing above the pin may then be disposed of.
According to an aspect of the invention there is provided an apparatus for
severing casing
above a wellbore, the apparatus comprising a clamp assembly, the clamp
assembly
constructed and arranged to fractionally engage the casing and hold the casing
in relation
to the apparatus, wherein the pressure applied against the casing by the clamp
assembly
is adjustable, a drill assembly, the drill assembly constructed and arranged
to form an
aperture through the casing and through any inner casing string nested within
the casing,
the aperture being dimensioned to receive a retention member for anchoring the
casing to
the any nested casing string, and a cutting assembly, the cutting assembly
constructed
and arranged to sever the casing and the any other nested casing string by
forming a
through-cut through the casing.
According to another aspect of the invention there is provided an apparatus
for severing
casing above a wel 1 bore, the apparatus comprising a clamp assembly for
holding the
casing in relation to the apparatus, the clamp assembly comprising a frame, at
least two
clamp members for fractionally engaging the casing, a hinge mounted on the
frame, and a
gate movable on the hinge for selectively opening and closing the clamp
assembly, the
gate having at least one clamp member disposed thereon, a drill assembly for
forming an
aperture through the casing and through any other nested casing string within
the casing,
the aperture being dimensioned to receive a retention member for anchoring the
casing to
the any other nested casing string, the drill assembly comprising a drill bit
for boring the
aperture, a rotary motor for rotating the drill bit, and a positioning device
for advancing
CA 02433362 2005-09-15
Sa
the position of the drill bit through the casing during the drilling operation
after the
casing has been clamped by the clamp assembly, a band saw for severing the
casing and
the any nested casing string into manageable lengths by forming a through-cut
through
the casing, the band saw comprising a blade having a plurality of teeth, at
least two
wheels about which the blade is tracked, a housing for the at least two
wheels, the
housing having a first opening through which the blade exits the housing, and
a second
opening through which the blade re-enters the housing, a first pair of roller
members
disposed at the first opening of the housing through which the blade is fed,
and a second
pair of roller members disposed at the second opening of the housing through
which the
blade is received, the first and second pairs of roller members guiding the
blade to cut the
casing at an angle substantially perpendicular to the longitudinal axis of the
casing, and a
positioning device for advancing the position of the blade through the casing
during the
cutting operation after the casing has been clamped by the clamp assembly.
According to a further aspect of the invention there is provided a method of
severing
casing, comprising the steps of clamping an apparatus to casing, forming an
aperture
through the casing and through any inner casing string nested therein, using a
drill
assembly in the apparatus, anchoring the casing and the any nested casing
string together,
and severing the casing using a cutting assembly in the apparatus, the cutting
assembly
comprising a blade to form a cut.
According to a further aspect of the invention there is provided a method of
severing
casing, comprising the steps of clamping a casing severing apparatus to a
section of
casing, the casing severing apparatus comprising a clamp assembly, the clamp
assembly
constructed and arranged to hold the casing in relation to the apparatus, a
drill assembly
having at least one drill bit and a rotary motor to rotate the at least one
drill bit, the drill
assembly constructed and arranged to form an aperture through the casing and
through
any casing string nested within the casing, the aperture being dimensioned to
receive a
retention member for anchoring the casing to the any nested casing string, a
saw, the saw
constructed and arranged to sever the casing and the any nested casing string
by forming
a through-cut through the casing, a positioning device for advancing the
position of the
drill bit through the casing during the drilling operation, after the casing
has been
clamped by the clamp assembly, actuating the drill assembly to form the
aperture through
CA 02433362 2005-09-15
Sb
the casing and through any casing string nested within the casing, inserting a
pin through
the aperture to secure the any nested casing string within the casing, and
actuating the
saw to form a through-cut through the casing above the pin.
According to a further aspect of the invention there is provided a method of
severing
casing, comprising the steps of clamping a casing severing apparatus to a
section of
casing, the casing severing apparatus comprising a clamp assembly for holding
the casing
in relation to the apparatus, the clamp assembly comprising a frame, at least
two clamp
members for frictionally engaging the casing, a hinge mounted on the frame,
and a gate
movable on the hinge for selectively opening and closing the clamp assembly,
the gate
having at least one clamp member disposed thereon, a drill assembly for
forming an
aperture through the casing and through any other nested casing string within
the casing,
the aperture being dimensioned to receive a pin for anchoring the casing to
the any other
nested casing string, the drill assembly comprising a drill bit for boring the
aperture, a
rotary motor for rotating the drill bit, and a positioning device for
advancing the position
of the drill bit through the casing during the drilling operation after the
casing has been
clamped by the clamp assembly, a band saw for severing the casing and the any
nested
casing string into manageable lengths by forming a through-cut through the
casing, the
band saw comprising a blade having a plurality of teeth, at least two wheels
about which
the blade is tracked, a housing for the at least two wheels, the housing
having a first
opening through which the blade exits the housing, and a second opening
through which
the blade re-enters the housing, a first pair of roller members disposed at
the first opening
of the housing through which the blade is fed, and a second pair of roller
members
disposed at the second opening of the housing through which the blade is
received, the
frst and second pairs of roller members guiding the blade to cut the casing at
an angle
substantially perpendicular to the longitudinal axis of the casing, a
positioning device for
advancing the position of the blade through the casing during the cutting
operation after
the casing has been clamped by the clamp assembly, actuating the drill
assembly to form
the aperture through the casing and through the any casing string nested
within the
casing, inserting a pin through the aperture to secure the any nested casing
string within
the casing, and actuating the band saw to form a through-cut through the
casing above the
pin.
CA 02433362 2005-09-15
SC
According to a further aspect of the invention there is provided a method for
pulling concentric
tubulars from an earth wellbore, the method comprising the steps of pulling
the concentric tubulars
upward from the earth wellbore in order to expose a first section of the
concentric tubulars above
the wellbore, coupling the first section of concentric tubulars by forming an
aperture through the
concentric tubulars and inserting a retention member therethrough so that they
are not axially
movable with respect to one another, clamping the concentric tubulars below a
point of severance
in order to provide axial support of the concentric tubulars, and severing the
concentric tubulars at a
location above the point of coupling.
I 0 According to a fizrther aspect of the invention there is provided an
apparatus for severing casing
above a wellbore, the apparatus comprising a clamp assembly, the clamp
assembly constructed and
arranged to hold the casing in relation to the apparatus, a drill assembly
constructed and arranged to
form an aperture through the casing and through any inner casing string nested
within the casing,
the aperture being dimensioned to receive a retention member for anchoring the
casing to the any
I 5 nested casing string, wherein the drill assembly includes at least one
drill bit and a rotary motor to
rotate the at least one drill bit, a cutting assembly, the cutting assembly
constructed and arranged to
sever the casing and the any other nested casing string by forming a through-
cut through the casing,
and a positioning device for advancing the position of the drill bit through
the casing during the
drilling operation, after the casing has been clamped by the clamp assembly.
According to a further aspect of the invention there is provided an apparatus
for severing casing
above a wellbore, the apparatus comprising a clamp assembly, the clamp
assembly constructed and
arranged to hold the casing in relation to the apparatus, a drill assembly,
the drill assembly
constructed and arranged to form an aperture through the casing and through
any inner casing string
nested within the casing, the aperture being dimensioned to receive a
retention member for
anchoring the casing to the any nested casing string, and a cutting assembly,
the cutting assembly
constructed and arranged to sever the casing and the any other nested casing
string by forming a
through-cut through the casing, wherein the cutting assembly defines a band
saw comprising a
blade having a plurality of teeth, at least two wheels about which the blade
is tracked, and a housing
for the at least two wheels, the housing having a first opening through which
the blade exits the
housing.
CA 02433362 2005-09-15
Sd
Some preferred embodiments of the invention will now be described by way of
example
only and with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a tubular severing apparatus in one
arrangement;
Figure 2 is a side, schematic view of the tubular severing apparatus of Figure
l;
Figure 3 is a perspective view of a cross-sectional cut of a casing section,
including an
outer casing string, an inner casing string and a layer of cement
therebetween;
Figure 4 is a side view illustrating a drilling assembly, shown drilling a
hole through a
casing section;
Figure Sa is a top view of an alternative drill assembly;
Figure Sb presents a side view illustrating the drill assembly of Figure Sa;
Figure 6 is a perspective view illustrating the tubular severing apparatus of
Figure 1;
Figure 7 is a perspective view illustrating the tubular severing apparatus of
Figure l;
Figure 8 is au enlarged view of the band saw of Figure 7;
Figure 9 is a perspective view of a control panel as might be used to control
various
portions of the severing apparatus.
CA 02433362 2005-09-15
6
Figure 1 provides a perspective view of a tubular cutting apparatus 100. The
apparatus
100 comprises a clamp assembly 130, a drill assembly I50 and a cutting
assembly 120.
The apparatus I00 is selectively movable. In one aspect, the apparatus 100 is
disposed
at the end of an extendable structure. In Figure l, the extendable structure
is shown as a
cantilevered arm 110. The exemplary arm 110 defines an outer barrel 110 having
at
least one telescoping section 112 extending therefrom. An intermediate
telescoping
section (not shown) may also be incorporated. In such an arrangement, the end
telescoping section 112 is slidably mounted in the intermediate telescoping
section
which is, in turn, slidably mounted in the outer barrel 1 I0.
The arm 110 is supported by a base 114 secured to the floor of a rig platform
(not
shown). The arm 110 is disposed on a vertical support beam 116 vertically
extending
above the base 1 I4. The outer barrel of the arm 110 may be attached to the
support
beam 116 by means of a clamp (not shown in Figure 1) bolted to the top of the
beam
116. A suitable clamp is shown, for example in WO 98/32947, with
IS reference to a telescopic arm for supporting a tong. The clamp maintains
the
arm 110 in position with respect to the beam 116. In one aspect, the arm 110
is pivotally attached to the support beam I 16 to permit the tubular severing
apparatus I00 to pivot about a vertical axis and, alternatively or in
addition, a horizontal
axis. In one aspect, the clamp is releasably attached to the support beam 116.
An additional feature of the arm 110 is that the outer barrel 110 of the arm
itself may be
selectively moved with respect to the support beam 116. This means that the
entire arm
110 may be retracted away from the casing section 200'. When the telescoping
sections
112 are fully contracted, the free end of the arm 110 lies closely adjacent
the support
beam 116. This retracting feature is shown in Figure 4 of the WO 98/32947,
with respect to a tong, but may also be employed in the present application
with
respect to a tubular severing assembly 100.
Tn the arrangement of Figure l, the apparatus 100 is further supported by an
overhead
hoisting system. Cables 160 from the hoisting system are visible in Figure 1.
In one
aspect, the hoisting system maneuvers the tubular severing apparatus 100, with
the
telescoping section 112 of the arm 110 moving in response. In another aspect,
the
telescoping section 112 of the arm 110 is hydraulically powered, causing the
apparatus
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7
100 and the supporting cables 160 to advance and recede in response to
movement of
the arm 110. Alternatively, the arm 110 and the hoisting system may be
independently
powered.
Further details concerning the operation of a suitable telescoping arm are
found in WO
98132947. That application is incorporated by reference herein, in its
entirety.
Also visible in Figure 1 is a section of casing 200'. Casing section 200'
represents an
upper, severed string of casing that is being retrieved from a wellbore (not
shown in
Figure 1). The casing 200' is being further severed into smaller portions for
ease of
manipulation and disposal. The exemplary casing string 200' houses a smaller,
inner
string of casing 205 nested within an outer casing string 200. The inner
string 205 has
been cemented into the outer string 200 in connection with earlier wellbore
completion
operations.
Figure 2 is a schematic view of the apparatus 100, adjacent a section of
casing 200'.
Visible again in Figure 2 is the clamp assembly 130, the drill assembly 150
and the
cutting assembly 120. In this arrangement, the assembly 100 is again disposed
at the
distal end of the telescopic arm 110 and is suspended from above with cables
160. The
telescopic arm 110 again has at least one telescoping section 112.
In Figure 2, the clamp assembly 130 is radially disposed about the section of
casing
200' so as to secure the casing section 200' for severing. The casing 200' is
shown in
Figure 2 in cross-section. Visible in this view are the outer casing string
200, the inner
casing string 205 and a matrix of cured cement 210 in the annular region
between the
two casing strings 200, 205.
Figure 3 is a perspective view showing a cross-section of the casing 200'
after it has
been severed using the apparatus 100 of Figure 2. As previously described,
casing
section 200' defines an outer string of casing 200 which houses a smaller
diameter
casing 205. A matrix of cement 210 is disposed in an annular area between the
two
casing strings 200, 205. In this view, inner casing string 205 is eccentric
relative to the
surrounding outer casing string 200, as is typical in a completed wellbore.
Refernng back to Figure 2, the tubular string 200' is shown being held above a
floor
CA 02433362 2003-06-26
WO 02/075097 PCT/GB02/01339
member 170 by a set of slips 172. The slips 172 permit the tubular string 200'
to be
raised from below the surface of the platform to some height. Typically,
elevators (not
shown) are provided on a rig for maneuvering pipe relative to the wellbore.
The slips
172 hold the casing 200' so that it can be clamped and severed by the
apparatus 100
after positioning of the casing 200' by the elevators.
As noted, the apparatus 100 includes a drill assembly 150. The purpose of the
drill
assembly 150 is to form an aperture through the casing strings 200, 205 for
insertion of
a retention member 165. Preferably, the retention member 165 defines a pin
configured
to be received within the formed aperture. Various pin types may be used,
including,
for example, a cylindrical bar, a cotter pin, or a cotter and key. In FIG. 2,
a simple
tubular pin is shown. The pin 165 serves to anchor any nested casing string
205 and
cement 210 to the outer casing string 200. Preferably, the aperture is formed
completely
through both the front and back walls of the outer casing string 200, and the
pin 165 is
inserted completely through the outer casing string 200.
In the arrangement of Figure 2, the drill assembly 150 is disposed below the
band saw
120. The drill assembly 150 is constructed and arranged to insert a rotating
drill bit 151
essentially perpendicular to the longitudinal axis of the casing string 200'.
In this way,
a suitable aperture is formed. Any known drilling device may be employed for
boring a
through-opening into the casing section 200'. The drill assembly 150 of Figure
2
utilizes a rotary motor (not shown) inside of a housing 153 to rotate a single
drill bit
151. A positioning device is further provided for selectively advancing the
drill bit 151
towards and away from the casing section 200.
An enlarged perspective view of a drill assembly 150 in operation is shown in
Figure 4.
The drill bit 151 can be more clearly seen penetrating the wall of the outer
section of
casing 200. The drill assembly 150 typically operates with a source of coolant
and
advances forward towards the casing 200 by means of a telescoping positioning
device,
shown in FIG. 4 as a cylinder 156. In one aspect, the drill assembly 150 is
operated
remotely from a control panel 125 as is shown in Figure 2. The remote control
panel
125 will be more fully described, inf-~~a.
An alternative arrangement for a drill assembly is presented in Figures Sa and
Sb.
Figure Sa is a top view of the alternative drilling assembly. Figure Sb is a
side view
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9
thereof. In this arrangement, a pair of opposing boring devices 155 are urged
inwardly
towards the center of the casing section 200'. Any drilling assembly 150
capable of
boring an aperture through the casing section 200' for insertion of an
anchoring pin 165
may be employed.
Referring again to Figure 2, it can be seen that the drill assembly 150 has
been actuated
to form an aperture through both casings strings 200, 205. The pin 165 has
been
inserted through the formed aperture to anchor the inner casing 205 to the
outer casing
200.
Figure 6 is a perspective view of the apparatus 100 of Figure 1. In this view,
the clamp
assembly 130 is more clearly seen. The clamp assembly 130 includes a frame 134
that
selectively radially encompasses the casing section 200' in order to secure
the apparatus
100 to the casing section 200'. The clamp assembly 130 further comprises at
least two
clamp members 140 for frictionally engaging the casing 200'. In the
arrangement of
FIG. 6, the clamp members 140 each define a pair of angled support blocks
which are
moved into contact with the casing 200'. However, other arrangements may be
employed, such as a single block having a concave surface.
The clamp assembly 130 includes a gate member 135 that swivels about a hinge
133
mounted on the frame 134. The hinge 133 permits the gate member 135 to be
selectively opened and closed for receiving and for clamping the casing 200'.
In the
view of FIG. 6, the gate member 135 is closed about the casing 200' while the
casing
section 200' is being severed. The gate member 135 includes at least one clamp
member 140 for engaging the casing 200' in its closed position. The gate 135
preferably operated with hydraulic power, and is remotely operated from
control panel
125. A hydraulic arm 136 is shown to aid in remotely opening and closing the
gate 135.
Figure 7 presents the apparatus 100 of Figure 1 in still greater detail. In
this perspective
view, the cutting assembly 120 is more clearly seen. The cutting assembly 120
is
shown as a band saw. The band saw 120 first comprises a housing 122. The
housing
122 houses a pair of wheels (not seen in Figure 7) about which a band saw
blade 121 is
tracked. The band saw blade 121 includes a plurality of teeth. The blade 121
is fed
through pairs of roller members 123 which guide the blade 121 to cut in a
direction
substantially perpendicular to the longitudinal axis of the outer casing 200.
One pair of
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roller members 123 is preferably provided at the housing outlet for the blade
121. In
this respect, the blade 121 is fed through this first pair of roller members
123. A second
pair of roller members 123 is disposed at the opening in the housing 122
through which
the blade 121 is received back into the housing 122. The roller members 123
are more
5 clearly seen in the enlarged view of Figure 8.
Any cutting device 120 known for severing casing may be used, so long as the
cutting
device 120 may be adapted to operate in conjunction with a clamp assembly 130
and a
drill assembly 150. In the exemplary arrangement for a cutting assembly 120 of
FIG. 7,
the cutting assembly defines a band saw 120. Further, the band saw 120
includes a
10 housing 122 that is offset from the angle of cutting by the blade 121. In
other words,
the angle of the housing 122 of the band saw 120 is offset from the angle at
which the
teeth of the blade 121 engage the outer casing 200 during the cutting
operation. The
angle shown is approximately 30 degrees, though other angles may be used. In
addition, an enlarged spacing 129 is provided in the housing 122 between the
wheels.
These features accommodate placement of and access to the drill assembly 150
and
clamp assembly 130. The spacing 129 in the housing 122 is more importantly
sized to
receive the casing 200' as the blade 121 of the saw 120 advances through the
casing
200' during a cutting operation
In the drawings of Figure 7 and Figure 8, the blade 121 of the band saw 120
has been
actuated. In addition, the blade 121 is engaging the casing section 200', and
has
advanced partway through the casing 200' to form a cut that is substantially
perpendicular to the longitudinal axis of the outer casing 200.
Referring again to Figure 2, the band saw 120, the clamp assembly 130, and the
drill
assembly 150 are preferably controlled in an automated fashion from a control
panel
125. Control lines 126 are provided from the control panel 125 to control the
assembly
100, e.g., parts 120, 130, 150, 154, etc.. Figure 9 is a more detailed
perspective view
showing a typical control panel 125 to be utilized with a tubular severing
apparatus 100.
The illustrated control panel 125 in one aspect includes separate controls to
operate the
clamp assembly 130, the drilling assembly 150, and the band saw 120.
The band saw 120 and the drill assembly 150 are typically operated with
similax
controls. For example, the drill assembly 150 and saw 120 each require an
on/off
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control and a rotational speed control to manipulate the rotation of the saw
blade 121 or
the drill bit 151. Corresponding gauges illustrating the rotational movement
of the drill
bit 151 and the band saw 121 as shown in revolutions per minute may optionally
be
provided. In addition, a tool advancing control is provided to control the
speed of
advance of the drill bit 151 into the casing 200' and the blade 121 of the
band saw 120
into the casing 200'. Corresponding positioning devices 126 (shown in FIG. 1)
and 156
(shown in FIG. 4) are provided for the band saw 121 and the drill assembly
150. These
devices permit the drill bit 151 of the drill assembly 150 and the blade 121
of the band
saw 120 to be independently, selectively advanced towards the casing 200'
during the
respective drilling and cutting operations and then withdrawn.
In addition, both the band saw 120 and the drill assembly 150 optionally
include
pressure sensors to determine the amount of pressure placed upon the casing by
the
rotating drill bit 151 or the rotating saw blade 121. Gauges may be provided
at the
control panel 125 indicating pressures on the drill bit 151 or the rotating
saw blade 121.
The clamp assembly 130 also has controls that are located on the control panel
125. For
instance, the clamp assembly 130 includes a panel-mounted control which opens
and
closes the gate 135 located on the clamp assembly 130. Optionally, a gauge
indicating
pressure between the casing 200' and a clamp 140 may be provided and pressure
of the
clamps 140. A corresponding sensor is positioned on at least one of the clamp
members
140 for sensing pressure of the clamp member 140 against the casing 200 when
the gate
135 is closed. Preferably, the sensor is placed on the clamp member 140 on the
gate
135.
In use, the severing apparatus of the present invention operates as follows:
First, a casing cutting means (not shown) is run into a wellbore. The cutting
means is
typically disposed on the end of a run-in string or wireline. The cutting
means is placed
in the wellbore at a predetermined depth, and then actuated. In this way, a
selected
length of casing is severed downhole. Thereafter, the severed portion of
casing 200 is
pulled or "jacked out" of the wellbore and lifted to the rig platform within
an elevator.
A predetermined amount of the severed portion of casing 200' is pulled upwards
past
the slip 172 located at the level of the platform floor. The casing 200' is
held in place
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by the slip 172, exposing the upper portion of the casing 200' above the
platform floor.
Thereafter, a tubular severing apparatus 100 is moved towards the casing 200'
by the
telescopic arm assembly 110 with its extending and retracting sections 112. As
the
apparatus 100 reaches a location proximate to the casing 200', the clamp
assembly 130
is actuated to open the gate 135 and to receive the casing 200'. The gate 135
is then
closed around the casing 200', and the clamp assembly 130 is secured to the
casing 200'
by the clamping members 140. In this way, the severing apparatus 100 is
properly
positioned with respect to the casing 200'.
Thereafter, with the outer casing string 200 clamped in the apparatus 100, the
drill
assembly 150 is operated. Preferably, remote actuation of the drill assembly
150 is
conducted through the control panel 125. The drill bit 151 disposed on the
drill
assembly 150 is rotated and advanced towards the casing 200 to form an
aperture
therein. The aperture is created through at least the front wall of the casing
section 200'
at an angle substantially perpendicular to the longitudinal axis of the outer
casing 200.
A retention mechanism such as a pin 165 is then inserted through the casing
200' to
ensure that any inner string of casing 205 is longitudinally fixed with
respect to the
outer string of casing 200.
The next step involves actuation of the band saw 120. Preferably, actuation of
the band
saw 120 is performed remotely via the control panel 125. The blade 121 of the
band
saw 120 is actuated, and is advanced through the casing 200' at a point above
the pin
165. The retention pin 165 anchors the smaller diameter casing 205 within the
larger
diameter casing 200. In this manner, the inner 205 and outer 200 casing
strings in the
lower section 200" are prevented from separating below the rig floor. The
severed
portion of the casing section 200' is then lifted away, leaving an upper end
of the lower
portion of casing 200" remaining within the clamping assembly 130.
Once the severed piece of casing 200' has been disposed of, an elevator or
other lifting
device works with the slips to lift the casing 200' another predetermined
distance
upwards. The slips 172 are then used to re-grasp the casing 200' for the
operation to be
repeated. Each time a severing operation is completed, the clamp assembly 130
is de-
activated, and the gate 135 is reopened so that the apparatus 100 can move
away from
the severed piece of casing 200'. In addition, it is noted that the pin 165
may be
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retained in the newly lifted section of casing 200' to be severed. A new pin
165 can
then be inserted once a new aperture is formed within the casing 200'.
As demonstrated in the foregoing disclosure, the apparatus 100 of the present
invention
provides a safe and efficient means for severing casing during a plug and
abandonment
operation. In one aspect, the apparatus 100 is operated via a remotely located
control
panel 125.
While the foregoing is directed to embodiments of the present invention, other
and
further embodiments of the invention may be devised without departing from the
basic
scope thereof, and the scope thereof is determined by the claims that follow.
