Note: Descriptions are shown in the official language in which they were submitted.
GItAE:005
10 1VIE~D STD APPAI~1''LrS T~ Ci<JT A~ ltElfd~VE ~ASI1~1~
'The present invention is directed generally to a method and apparatus to cut
and remove well casing, and, more specifically, is directed to a method and
apparatus to cut well casing and extract it from the well bore in a single
downhole
trip.
In oil and gas exploration and development operations it is often desirable
to remove casing which has previously been set in the wellbore. Casing removal
requires that the casing string first be severed and the frae end then pulled
to the
surface, to remove the severed portion.
Conventional apparatuses and techniques for extraction of well casing
typically involve the use of multiple trips to move cutting and extracting
equipment
downhole. Thus, in removal operations a casing cutter is first lowered into
the
wellbore to cut the casing at a desired depth after which time the cutter is
returned
to the surface. A spear is then lowered inside the well and engaged to the
free
end of the casing. Once the free end of the casing is engaged, an attempt is
then
made to recover the casing by pulling, or, in the case jars are used, by a
combination of pulling and jarnng. If these attempts to remove the casing are
unsuccessful, the spear assembly is removed from the wellbore and the cutter
reattached to the workstring to sever the casing at a point above or below the
_2_ 2~~2~~$
original cut. The pulling/jarring process is then repeated until the casing is
recovered.
Such prior art apparatuses and techniques for retrieving well casing suffer
from the disadvantage of the overall time and costs involved in completing a
casing extraction. This time and expense is a result of the utilization of
separate
cutting and extraction tools which must be independently run downhole. Even
when casing is retrieved without the need to complete a second cut of the
casing,
at least two trips are necessary for a complete cutting and retrieval
operation.
When a significant length of casing is extracted, considerable rig time must
be
used to move the tools downhole to the site of the cut. Time and expense are
therefore increased when multiple cuts are necessary to retrieve the casing.
Additionally, systems for cutting and removing casing have been proposed
wherein a grapple assembly or "spear" is adapted to be inserted in the top
portion
of the casing, with the degree of insertion of the spear into the casing
limited by a
stop ring. The spear in such systems is a mechanically actuated spear, which
is
actuated through use of interference between the spear grapple and the casing,
and
through manipulation of the workstring. Such systems offer the disadvantages
that
there is a fixed distance between this stop and the cutting elements.
Accordingly,
when the grapple is placed inside the casing (and its depth is established by
the
placement of the stop), there is a fixed depth that which the cutter can be
placed.
Accordingly, if the first attempt to free the casing is not successful, this
type of
tool must be pulled out of the hole, and the distance between the grapple stop
and
cutting elements either lengthened or shortened to facilitate another cut of
the
casing at a different depth.
Accordingly, the present invention provides a new method and apparatus
whereby casing may be cut and pulled with the string in tension, and whereby
the
grapples may be placed at virtually any desired location within the casing,
CA 02062928 2003-03-26
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allowing multiple attempts to cut and pull the casing on a
single trip of the workstring into the wellbore.
In accordance with an embodiment of the present invention
there is provided an apparatus for cutting and retrieving a
casing string, and adapted to be utilized on a workstring. The
apparatus comprises a hydraulically actuable grapple assembly
adapted to be inserted into the casing, a mandrel assembly
extending through the grapple assembly and a cutting assembly
operatively coupled to the mandrel assembly. The grapple
assembly includes a plurality of slips adapted to move between
a first position wherein the slips do not substantially engage
the casing and a second position in which the slips
substantially engage the casing. The slips are moveable
between the first and second positions at virtually any
location within the casing. The slips are moveable from the
first position to the second position in response to fluid
pressure and the slips are oriented to engage the casing and
to place the casing in tension proximate the location at which
the casing is to be cut. The mandrel assembly extends through
the grapple assembly and is mounted in rotatable relation
relative to the grapple assembly
In accordance with another embodiment of the present
invention there is provided an apparatus adapted for use with
a workstring to cut and remove casing from a well, the
apparatus allowing multiple cuts of the casing on a single trip
of the workstring into the well. The apparatus comprises a
spear assembly having a connector to facilitate coupling of the
assembly to the workstring. The spear assembly comprises a
mandrel, a housing assembly rotatably mounted around the
mandrel, and a plurality of grapple slips generally
circumferentially arranged around the body assembly. The slips
are moveable between a first position and a second position,
CA 02062928 2003-03-26
- 3a -
wherein in the second position the slips will engage the casing
and allow tension to be applied to the casing through the
workstring, and wherein in the first position the slips will
substantially be disengaged from the casing and allow movement
of the spear assembly upwardly and downwardly through the
casing, the slips are moveable from the first position to the
second position in response to fluid pressure. The apparatus
further includes a cutting assembly coupled to the mandrel and
adapted to selectively cut the casing.
In accordance with yet another embodiment of the present
invention there is provided a method for cutting and removing
casing from a wellbore on a single trip of a workstring into
the wellbore. The method comprises the steps of: securing a
cutting assembly and a grapple assembly to the workstring, the
cutting assembly being selectively actuable at least partially
in response to hydraulic pressure and the grapple assembly
being actuable at least partially in response to hydraulic
pressured lowering the cutting assembly and the grapple
assembly into the wellbore until the cutting assembly is at a
depth where it is desired to cut the casings applying hydraulic
pressure in the workstring to actuate the grapple to cause the
grapple to engage the casings applying tension to the
workstring to place the casing in tension through the grapple
assembly rotating the workstring to rotate the cutting
assembly, which has been extended in response to hydraulic
pressure, so as to cut the casing; and after the casing has
been cut, applying pull on the workstring to remove the casing
from the wellbore.
In one particularly preferred embodiment, the grapple
assembly will include a plurality of slips generally
circumferentially arranged around the assembly, which slips
will be moved between the engaged and unengaged positions in
CA 02062928 2003-03-26
- 3b -
response to the application of fluid pressure within the
workstring. In this one particularly preferred embodiment, the
application of such fluid pressure will cause movement of the
slips relative to a support member having a generally conical
section, and such movement of the slips relative to such
support member will cause the slips to engage or disengage the
casing.
Fig. 1 illustrates a side, external view of the apparatus
of the present invention.
30
Fig. 2 illustrates a side, partial cutaway view of the cutting and retrieval
apparatus illustrated in Fig. 1,
Fig. 3 illustrates a side, partial cutaway view of the upper assembly of the
spear showing the relative position of the J-groove and the friction 6loclcs.
Fig. 4 illustrates a side detail view of the grapple slips as mounted on the
swivel cone.
Fig. S illustrates a side, detail view of the lower sub and wear collar.
Fig. 6 illustrates a side view of the mandrel.
Fig. 7 illustrates a side partial cutaway view of the tool as it would appear
when lowered into the wellbore prior to cutting operation.
Fig, g illustrates a side view of the tool as it would appear during the
cutting operation.
Fig. 9 illustrates a side view of the tool as it would appear during the
extraction of the casing.
Fig. 10 illustrates a side, partial cutaway, detail view of the latching
assembly of the mandrel sleeve when positioned in the "closed" position.
Fig. 11 illustrates a section view through lines 11-11' in Fig. 10.
Fig. 12 illustrates a side, partial cutaway, detail view of the latching
assembly of the mandrel when in the "engaged'° position.
Fig. 13 is a section view through lines 13-13' in Fig. 12.
-5-
Fig. 14 is a side, detail cross section of the piston tube when positioned in
a °'closed'° configuration.
Fig. 15 is a side, detail cross section of the piston tube when in an
"extended" position.
Fig. 16 is an end cross section of the grapple slips taken through lines 16-
16' of Fig. 7.
Fig. 17 is an end cross section of the grapple slips taken through lines 17-
17' of Fig. 8.
Fig. 18 is an end cross section of the friction blocks taken through lines 18-
18' of Fig. 8.
Fig. 19 is an oblique view of the swivel cone.
Fig. 20 is a side, detail view of the teeth formed along the contact surface
of the slip segments illustrating the tangential angle of inclination of the
teeth
surface.
Fig. 21 is a side, detail view of the slip segments of Fig. 20 illustrating
the
axial angle of inclination of the teeth surface.
Referring now to Fig. 1 in more detail, therein is depicted an exemplary
casing cutting and retrieving assembly 100 in accordance with the present
invention. Casing cutting and receiving assembly 100 includes a body or
mandrel
1 which includes an upper end attachment 1A for coupling to a workstring 105.
An optional drilling jar 104 is depicted in one exemplary configuration
between
mandrel 1 and workstring 105. Drilling jar 104 may be one of any appropriate
and conventional type as will be readily appreciated by those skilled in the
art. As
2~~~~2~
-6-
used herein, the term "workstring" includes any string, whether formed of
drill
pipe, work pipe, production tubing, etc., as may be utilized to perform well
operations. Referring also to Fig. 7, therein is depicted casing cutting, and
retrieving assembly 100 disposed within casing 101. Casing 101 is
conventionally
installed in a formation 102, and is secured in position by cement 103.
Referring again to Fig. 1, mandrel 1 of casing cutting and retrieving
assembly 100 is threadedly coupled to a lower subassembly 49 which may in turn
be connected to a cutting tool via box end 49A as will be further describ~l
herein.
Mandrel 1 defines a bore 52 therethrough to accommodate the passage of well
fluid as will be further described. The uppermost portion of the tool includes
an
outer shield or sleeve 3 which is threadedly disposed about the mandrel 1.
Outer
shield 3 serves to furnish physical protection of mandrel 1 and J-groove 51,
the
function of which will be further described herein. To prevent accidental
unthreading, shield 3 is held in place by a fastener 2. (See Fig. 2). Shield 3
includes a pressure relief valve 4 which covers the access hole to a J-groove
key
6.
A piston tube 8 is disposed about mandrel 1 immediately below shield 3.
Piston tube 8 serves to house J-groove~51 and defines a hydraulic chamber 54,
the
integrity of said chamber being maintained by packing seals 10 and 11. (See
Fig.
2). Contaminants are also prevented from entering J-groove slot 51 by the
inclusion of a wiper seal 9. Piston tube 8 is biased in a closed or upper
position
by a compression spring 15.
A drive sleeve 14 is threadedly connected to piston tube 8 about mandrel 1
and secured by locking screw 13. Accidental unthreading of screw 13 is
prevented by an internal retaining ring 12. Drive sleeve 14 serves to support
friction blocks 19 and house compression spring 15. (See Fig. 2). Drive sleeve
14 also serves as a means to connect piston tube 8 and floating sleeve 24 as
will
be further described herein. An upper ,journal bearing 23, preferably a self
2~~~~2~
-7-
lubricating journal bearing, is disposed between sleeve 24 and sleeve 14 to
permit
axial and radial movement therebetween. A lower bearing 26, ideally an anti-
friction bearing, is disposed below bearing 23 between sleeves 24 and 14.
Bearing
26 serves to limit the travel of floating sleeve 24 and acts as a lower
bearing for
drive sleeve 14 and floating sleeve 24. Contamination of bearings 23 and 26 is
inhibited by upper seal 22 and lower seal 28. Compression spring 15 is mounted
on a ring 16 which constitutes a removable shoulder used to transmit the load
of
spring 15 to an external retaining ring 17. (S~ Fig. 2). Ring 16 also seaves
to
facilitate the assembly of compression spring 15.
A friction block assembly 19 is circumferentially disposed about drive
sleeve 14 as illustrated in Figs. 2 and 18. Friction blocks 19A are outwardly
biased via a plurality of extrusion springs 18. In such a fashion, the outer
contact
surfaces of blocks 19A maintain continuous contact with the interior of the
casing
101. As a result of such contact, friction block assembly 19 serves to provide
resistance when mandrel 1 is rotated relative to tube 8. This rotational
resistance
is necessary to operate the 7-groove 51 lock mechanism as will be further
discussed herein. Friction blocks 19 are axially retained in place by a
friction
block retainer 20 which is circumferentially disposed about mandrel 1.
Retainer
20 is held in place by an eternal retaining ring 21. Sleeve 24 is capable of
axial
movement about mandrel 1. i~Vhen urged downward about the mandrel 1, sleeve
24 forces slips 32 into contact with the inner diameter of the casing 101.
Floating
sleeve 24 also allows drive sleeve 14 to rotate when grapple slips 32 are
situated
in engagement with the casing 100 as will be further described herein.
tirapple slips 32 are disposed immediately below sleeve 24 as illustrated in
Fig. 1. Slips 32 are comprised of a number of segments 32A which are held in
place by slip guide rails 35. {See Figs. 16-17). Sleeve 24 is also adapted to
hold
grapple slip segments 32A in suspension. Slip segments 32A preferably include
a
tongue or T-groove which fits in a complementary tongue or T-groove in
floating
sleeve 24, the overall structural makeup of slips 32 being generally
conventional in
_g_
fashion. Slip segments 32A preferably include tongues or grooves which fit
into
complementary tongues or grooves in rails 35. Rails 35 prevent rotational
movement of segments 32A relative to swivel cone 37.
When actuated, grapple slips 32 serve to engage the inner bore of the well
casing with a sufficient force to support the weight of the casing in addition
to the
overpull necessary to break the casing loose from the formation during
retrieval.
Slips 32 are physically moved into contacting engagement with the inner
diameter
of the casing by swivel cone 37 and floating sleeve 24. Structurally, swivel
cone
37 is located immediately below grapple slips 32 and guide rails 35 as
illustrated
in Fig. 1. Slip guide rails 35 are retained in place by a fastener 34.
Swivel cone 37 comprises an upper cone shaped portion whose exterior
slidably engages the interior of grapple segments 32A. (See Figs. 4, i6 and
17).
In such a fashion, when segments 32A are forced downward along rails 35 by the
downward movement of sleeve 24, segments 32A are interiorly supported by the
tapered wedge shaped surface provided by cone 37. In a preferred embodiment,
cone 37 defines at least two tapered surfaces 37A which may be better seen by
reference to Figure 19. The upper conic portion of cone 37 is disposed
proximate
an upper journal bearing 33, and a lower journal bearing 38. Both bearings 33
and 38 are preferably self lubricating. Bearings 33 and 38 permit rotation of
cone
37 relative to mandrel 1. Bearings 33 and 38 are lubricated via a lubrication
fitting 36 as shown in Fig. 2. Upper wiper seal 61 is retained by a cone
bushing
30, which bushing also serves to protect the small end 112 of cone 37 and
inhibit
the introduction of contaminants therein. A lower wiper seal 39 serves to
inhibit
the introduction of contaminants into swivel cone 37.
The engagement of slips-32 as referenced above is hydraulically actuated.
When the tool is run in the hole and is situated at a desirable depth, mud or
other
fluid is pumped through mandrel bore 52. A majority of this fluid flow is
utilized
to operate the casing cutter tool 56 in a conventional fashion. However,
~~~2'~~~
backpressure in cutting tool 56 forces some fluid through actuation conduit 53
to
hydraulic chamber 54. (See Figs. 14 and 15). Fluid entering chamber 54 forces
piston tube 8 and sleeve 24 downward. The downward movement of sleeve 24
forces grapple slips 32 downward over cone 37. This results in grapple
segments
32A being moved outward in a radial direction by the wedge shaped profile of
cone 37 as earlier described. In such a fashion, grapple slips 32 are forced
downward until slip segments 32A contact and "bite" into the interior of
casing
101.
In order to enhance the contacting relationship between slips 32 and casing
101, it is desirable to increase the axial length of slips 32 without unduly
increasing the length of the entire tool. To accommodate these requirements,
it
has been found that cone 37 should be provided with multiple wedging surfaces
so
that swivel cone 37, when viewed in side cross section, describes two or more
conic sections preferably defining a tapered angle in the range of 4°-
30' with
respect to the axis of the tool, and most preferably defining an angle within
the
range of approximately 4 ° -8 ° . This may be better seen by
reference to Fig. 19 in
which is illustrated a taper angle of 4°.
To additionally insure non-slipping engagement between slips 32 and casing
101, it is desirable to provide slips segments 32A with teeth 60 formed at an
angle
in the range of approximately 5-60° in an axial dir~tion and 0-45' in a
tangential
direction, Preferably teeth 60 will be formed at an angle in the range of
approximately 5-30° in the axial direction and 5-30' in the tangential
direction. In
one embodiment adapted for use in 9-5/8 47 pound casing, teeth formed at an
angle of 12 ° in the axial direction and 8 ° in a tangential
direction have been found
to perform satisfactorily. See Fig. 20-21. In a preferred embodiment, t~th 60
are formed so as to offer nonslip capacity to both pulling tension and
rotation in
either a clockwise or counterclockwise direction. This nonslip capacity is
achieved by the geometry of teeth 60 and their placement on slip segments 32A.
Grapple segments 32A are preferably manufactured from hardened steel, e.g.,
-10-
induction hardened 4140 steel. The surface of teeth 60 may also include other
elements to increase hardness.
Refernng again to Figs. l and 2, an upper thrust bearing 40 is situated
immediately below swivel cone 37 so as to permit rotation between swivel cone
37
and lower sub 49. Bearing 40 rests on an upper bearing race 41 which achieves
even load distribution between disc springs 42 and thrust bearing 40. In an
embodiment designed to cut and retrieve 9 5/8'° casing, a conventional
prestressed
disc spring array incorporating 28 individual segments has been found to be
desirable. Such disc springs will preferably be manufactured to D.LN. spec.
2093.
Disc springs 42 serve to compensate for axial movement of the drilling
sting when the mandrel 1 is rotated under tension. As will be further
described
herein, it is desirable to rotate casing cutter 56 while a moderate to large
tensional
force is applied to the workstring. One reason for applying such tension to
the
workstring is to maintain constant pressure and rate of rotation of the
cutting tool
independent of deflections of the workstring caused by swells (in the case of
a
floating platform), and/or deflection caused by marine currents. Tension drawn
on
the workstring substantially reduces such deflection, thereby enhancing
performance of the cutter tool 56 while reducing wear on the cutter and the
drill
string. Springs 42 behave as a solid member when subjected to a tensional
force
sufficient to place them in a fully collapsed position, e.g., > 35,000 lbs.,
in the
case of the embodiment described above utilizing a 28 disc spring array. Disc
springs 42 are axially disposed above lower bearing race 43 on a lower thrust
bearing 44. Bearing race 43 serves to establish an even load distribution
between
springs 42 and lower thrust bearing 44. Bearing 44 permits rotation of swivel
cone 37 relative to lower sub 49.
Disposed immediately below lower thrust bearing 44 is a wear collar 46..
Collar 46 defines the largest outside diameter of the tool and thus serves as
a
-11-
physical gauge which prevents the tool from entering an overly small diameter
casing. Lower sub 49 is threadedly coupled to mandrel 1 below wear collar 46.
Sub 49 forms an attachment means whereby a casing cutter or the like may be
coupled to the mandrel. Sub locking nut 47 is secured to mandrel 1 with
opposite
hand threads to prevent lower sub 49 from accidentally uncoupling from said
mandrel 1. Internal retaining ring 48 serves to prevent inadvertent
unthreading of
sublocking nut 47. Fluid leakage between bore 52 and the annulus of the casing
is
prevented by seal 45.
The operation of the present invention may be described as follows by
reference to Figs. 1-21 and especially by reference to Figs. 7-9. The overall
spear
assembly is threadedly coupled to a standard workstring via female joint 1A or
other attachment means conventional in the art. To aid in retrieval
operations, one
or more jars (not shown) may be coupled below the workstring and above the
spear. A casing cutter 56, preferably an A-1 big inch cutter or marine cutter
as
described in U.S. Patent No. 3,468,373, is then threadedly attached to sub
assembly 49 via box end 49A. The cutting tool, retrieval tool, jars and
workstring
are then run in the hole to a desired and predetermined depth.
Refernng to Figs. 10-13, when the cutting/retrieval tool has been lowered
to a desired location in the wellbore, the tool is rotated in left-hand
rotation to
disengage J-groove key 6 in J-groove 51. Relative rotation between key 6 and
piston tube 8 is made possible by the resistance provided by friction blocks
19
which frictionally contact the interior of casing 101. Friction blocks 19
prevent
the rotation of piston tube 8 relative to the rotation of the mandrel 1.
Disengaged, key 6 is now free to adopt axial movement along J-groove 51.
~nce key 6 has been released, mud pumps situated on the surface rig or
platform
are engaged, thereby creating fluid pressure through bore 52. A considerable
amount of this fluid passes through bore 52 to cutting tool 56 so as to force
cutting
knives 57 into cutting engagement with the casing. Flow restrictions in
cutting
-12-
tool 56, however, create considerable backpressure so that some fluid is
forced
through activation conduit 53 to hydraulic chamber 54. This pressure overcomes
the upward bias provided by compression spring 15 and forces piston tube 8 and
floating sleeve 24 downward thereby forcing grapple slips 32 down along guide
rail 35 and over swivel cone 37. This downward movement moves slips 32 into
engagement with the interior wail of casing 101. The movement of the drive
sleeve from a "nonengaged" to an "engaged" piston may be seen by reference to
Figs. 14 and 15.
Once slips 32 have engaged the casing, tension is applied to the workstring
in an amount to moderately compress disc springs 42 and to straighten the
workstring. This tension also serves to "set" the slips 32 in the casing.
While the
amount of such tension or overpull will vary on the depth of water in which
the
platform is situated, if any, and the nature of the platform (floating,
stationary,
etc.), it is desirable that an average overpull value of 10,000 lbs. be
maintained on
the workstring and the casing spear. The benefit of such overpull has been
previously discussed in relation to the efficiency of the cutting tool and the
reduction of wear on the workstring: Benefits of overpull also include the
positive
indication that such tension furnishes when the casing has been severed, thus
reducing the chance that the cutting tool 55 will continue to be rotated in
the hole
after the casing has been cut.
Once a desired amount of overpull is achieved on the workstring and the
slips are "set" in the wellbore, the cutting tool 56 is rotated below the
spear in a
conventional manner to effect a severance of the casing. Pump pressure is
maintained during this operation to maintain cutting arms 57 in an extended
position and to circulate cuttings out of the wellbore. Depending on the
manner in
which the casing has been severed in the wellbore, completion of the cutting
operation (and thus severance of the casing) will ordinarily result in the
free end
lOlA of the casing 101 being pulled or jerked a few feet up the wellbore due
to
the overpull maintained on the workstring. This will obviously result in a
~0~~~2~
-13-
noticeable tension drop on the workstring. If a tension release in the
workstring is
not accomplished, completion of the cut will nevertheless result in a
noticeable
drop in fluid pressure. Both events evidence that the casing is severed and
efforts
may be undertaken for retrieval.
When it is established that the casing has been severed, pump pressure is
discontinued and rotation of the cutter 56 is stopped. Reduction of pump
pressure
allows the cutter knives 57 to retract to a folded, relaxed position. Grapple
slips
32 maintain their engaged position in the wellbore independent of pump
pressure
since they have been "set" by workstring tension. If the free end of the
casing
IOlA underwent upward movement as a result of the overpull, this free end 101A
may ordinarily be withdrawn from the wellbore by tension applied through the
platform block. If the casing lOlA does not initially respond to overpull, or
subsequently becomes stuck, it may become necessary to jar the casing through
use of a conventional drilling jar 104. This is accomplished in a conventional
fashion by applying a tensional force in excess of the jar release setting
tension.
To enhance the performance of the jars, it is desirable that this release
tension
exceed the tension needed to compress disc springs 42 to a solid member.
If jarring the workstring is ineffective, the jars may be reset while the tool
remains in the hole. This is accomplished by first lowering the workstring
without
rotation while maintaining pump pressure to hold grapple slips 32 in their
engaged
position. As this occurs, the cutter arms 57 of the casing nutter 56 unfold
out into
the area where the casing 101 has been severed until the cutter arms 57 come
to
rest upon the cut fixed end of the casing 101B. Arms 57 then serve to hold the
workstring while the jars are reset after which time the jarring procedure is
repeated as set forth above.
If the combination of jarnng and pulling is ineffective, it may be necessary.
to withdraw the assembly up the bore and execute a second cut in the casing.
To
recut the casing 10(J, it is necessary to first release grapple slips 32 which
involves
2~~2928
-14-
reducing pump pressure and lowering the workstring (usually a few inches).
This
allows the upward bias in spring 15 to overcome the force in hydraulic chamber
54. The assembly is then rotated in right-hand rotation to reengage key 6 in J-
groove 51. Casing cutter 56 is then adjusted to a different cutting level
whereupon the aforedescribed cutting sequence is repeated.
