Note: Descriptions are shown in the official language in which they were submitted.
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UNIVERSAL CARRIER FOR GRIPPERS IN A COILED
TUBING INJECTOR
FIELD OF THE INVENTION
S The invention relates generally to coiled tubing injectors for handling a
continuous
length of tubing or pipe for insertion into or removal from a well bore, and
for drilling well
bores. More particularly, it concerns gripping elements used by such inj
ectors.
BACKGROUND OF THE INVENTION
Continuous, reeled pipe is generally known within the industry as coiled
tubing and
has been used for many years. It is much faster to run into and out of a well
bore than
conventional jointed, straight pipe.
Coiled tubing is run into and out of well bores using what are known in, the
industry
as coiled tubing injectors. The name dexives from the fact that, in
preexisting well bores,
1S the tubing must be literally forced or "injected" into the well through a
sliding seal to
overcome the well pressure until the weight of the tubing exceeds the force
produced by the
pressure acting against the cross-sectional area of the tubing. However, once
the weight of
the tubing overcomes the pressure, it must be supported by the injector. The
process is
reversed as the tubing is removed from the well
The only method by which a continuous length of tubing can be either forced
against
pressure into the well, or supported while hanging in the well bore or being
lowered or
raised is by continuously gripping a length of the tubing just before it
enters the welt bore.
This is achieved by arranging continuous chain loops on opposite sides of the
tubing. The
continuous chains carry a series of grippers which are pressed against
opposite sides of the
2S tubing and grip the tubing.
Coiled tubing has traditionally been used primarily for circulating fluids
into the well
and other work over operations, rather than drilling, because of its
relatively small diameter
and because it was not strong enough, especially for deep drilling. ~Iowever,
in recent years,
coiled tubing has been increasingly used to drill well bores. For drilling, a
turbine motor
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suspended at the end of the tubing and is driven by mud or drilling fluid
pumped down the
tubing. Coiled tubing has also been used as permanent tubing in production
wells. These
new uses of coiled tubing have been made possible by larger, stronger coiled
tubing.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a
tube
conveying apparatus comprising: a frame; a pair of continuous drive chains
supported on
the frame and revolving in a common plane, the pair of drive chains having
opposed,
elongated parallel runs spaced apart to form a path for engaging tubing
passing
therebetween; and a plurality of grippers carried on each of the pair of drive
chains;
wherein, each gripper includes a carrier mounted to the chain and a pipe
gripping shoe
mounted to the carrier, the shoe including a plurality of tongues for sliding,
in directions
generally perpendicular to the common plane, in corresponding grooves formed
by the
carrier for retaining the shoe on the carrier.
In accordance with another aspect of the present invention, there is provided
a
tubing gripper comprising: a carrier having front and back sides, means for
mounting the
back side of the carrier to a chain, two opposing slots formed on the front
side of the
carrier, each of the slots having an open end and closed end; and a pipe
gripping shoe
removably mounted to the carrier, the shoe including a base portion having
lugs for sliding
into the open ends of the slots, the slots and lugs thereby cooperating to
retain the shoe on
the carrier.
In accordance with yet another aspect of the present invention, there is
provided a
tube conveying apparatus comprising: a frame; a pair of continuous drive
chains supported
on the frame and revolving in a common plane, the pair of drive chains having
opposed,
elongated parallel runs spaced apart to form a path for engaging tubing
passing
therebetween; and a plurality of grippers carried on each of the first and
second drive
chains; wherein, each gripper includes, a carrier mounted to the chain, a pipe
gripping shoe
retained on the carrier, the pipe gripping shoe having a gripping portion
having a rigid
shape that fits around substantially one-half of an outer circumference of
tubing to be
injected, and an elastomeric pad positioned between the Garner and shoe for
floating the
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shoe on the earner; wherein, the carrier has two opposing slots, each of the
slots having an
open end and closed end; and the pipe gripping shoe has lugs for sliding into
the open ends
of the slots, the slots and lugs thereby cooperating to retain the shoe on the
earner.
In accordance with still yet another aspect of the present invention, there is
provided a tube conveying apparatus comprising: a frame; a pair of continuous
drive chains
supported on the frame and revolving in a common plane, the pair of drive
chains having
opposed, elongated parallel runs spaced apart to form a path for engaging
tubing passing
therebetween; and a plurality of grippers carried on each of the pair of drive
chains;
wherein, each gripper includes a earner mounted to the chain and a gripping
shoe connected
to the earner by means of tongues that slide into corresponding grooves in
directions
generally perpendicular to the common plane for retaining the shoe on the
carrier.
In an exemplary embodiment, a coiled tubing injector according to the present
invention includes a quick-release carrier for mounting gripping shoes to
chains of the
injector. The carrier enables removal and replacement of grippers in the field
without tools,
even when the injector is operating. An injector thus may be quickly adapted
to run coiled
tubing within a wide range of diameters, for purposes of a well work over to
drilling.
Furthermore, an injector having grippers according to the present invention
may be used to
run conventional jointed, straight pipe, or a tool string on the end of coiled
tubing. The
diameter of joints are larger than the diameter of the pipe. Tool strings have
various
diameters. The quick-release carrier enables gripping shoes to be easily
removed to
accommodate a joint or a tool as it passes through the injector during
operations. Gripping
shoes can be easily replaced with gripping shoes that have the appropriate
size and shape
for gripping the tool. All shoes are sized so that, when attached to the
injector, they have
same centerline or axis as the other shoes. Thus, gripping shoes of differing
sizes can be
used on the injector to grip a downhole tool or irregularly sized object in
the pipe string as
it is passing through the injector.
These and other aspects and advantages of the invention are discussed below in
connection with a preferred embodiment illustrated by the appended drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a coiled tubing injector intended to be
representative
of coiled tubing injectors generally, but with grippers according to the
present invention.
FIG. 2 is a front elevational view of the coiled tubing injector shown in FIG.
1.
S FIG. 3 is a left side elevational view of the coiled tubing injector shown
in FIGS 1
and 2.
FIG. 4 is an plan view of a drive chain of a coiled tubing injector having
gripper
carriers according to the present invention.
FIG. S is a side, elevational view, partially sectioned, of a gripper with a
first shoe
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type mounted on one of the gripper Garners on the drive chain of FIG. 4.
FIG. 6 is a side, elevational view, partially sectioned, of a gripper with a
second shoe
type mounted on one of the gripper carriers on the drive chain of FIG. 4.
FIG. 7 is a side, elevational view, partially sectioned, of a gripper with a
third shoe
type mounted on one of the gripper Garners on the drive chain of FIG. 4.
FIG. 8 is a perspective view of the gripper carrier and the gripper shoe of
FIG. 6
before as one is being mounted to the other.
FIG. 9 is a side, elevational view of the gripper shoe mounted on the gripper
carrier
of FIG. 8.
FIG. 10 is a top, plan view of the gripper shoe of FIG. 6.
FIG. 11 is a partially sectioned, end view of the gripper shoe of FIG. 10.
FIG. 12 is a partially sectioned, side view of the gripper shoe of FIG. 10.
FIG. 13 is a bottom, plan view of the gripper shoe of FIG. 10.
FIG. 14. is a top, plan view of the gripper Garner shown in FIG'S 4-9.
FIG. 15 is a side view of the gripper carrier of FIG. 14.
FIG. 16 is a cross-section of the gripper carrier taken along section line 16-
16 in FIG.
15.
FIG. 17 illustrates flexing of a leaf spring of the gripper carrier.
DESCRIPTION
In the following description, like numbers refer to like elements.
FIG'S. l, 2 and 3 illustrate an example of a coiled tubing injector 101. It is
intended
to be representative of coiled tubing injectors generally for purposes of
describing the
invention, even though it may differ from other prior art coiled tubing inj
ectors in several
important aspects.
Referring first to FIG. 1, coiled tubing is transported into the top of coiled
tubing
injector 101 from a reel (not shown) on a "goose-neck" support 103. The goose-
neck
support includes a frame 105 supporting a plurality of rollers 107. Bracing
108 extending
from cage 109 positions the goose-neck support 103 in proper relation to the
injector 101.
The cage also supports the injector 101 for transportation. Legs (not shown)
may also be
attached to the corners of the bottom of the cage 101 to stand the injector
above a well head
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(not shown).
Referring now to FIG'S 1, 2 and 3 together, injector 101 includes two,
continuous
loop drive chains generally designated by reference numbers 111 and 113. The
drive chains
revolve generally within a common plane defined by axes 114 and 116, which
plane is
normal to axis 118. Connected to each drive chain is a plurality of grippers
115. The drive
chains 111 and 113 are arranged in a conventional, opposing relationship. Each
drive chain
111 and 113 is mounted on an upper drive sprocket (not shown) and a lower
drive sprocket
119 and 121, respectively. The upper drive sprockets are mounted within drive
housing 117
and are not visible in these views. One set of bearings for the shafts of
upper drive sprockets
are mounted within bearing housings 118 and 120, respectively. The other set
of bearings
on which the shafts of upper drive sprockets are journalled are mounted to the
opposite side
of the drive housing 117.
A box-shaped frame is formed from two, parallel front plates 123 and 125,
separated
by side plate 127 and a second side plate parallel to side plate 127 but not
visible in these
1 S views. This frame supports the drive housing 117 and transmission gear box
131 at its upper
end, and the lower drive sprockets at its lower end.
The lower drive sprockets 119 and 121 are connected to shafts 133 and 135,
respectively. The ends of each shaft is journalled on opposite sides of the
injector frame
within a movable carrier 137. Each carrier is mounted so that it may slide
vertically within
an elongated slot 139 defined in either the front plate 123 or rear plate 125.
A hydraulic
cylinder 141 is inserted between the top of each carrier 137 and a block 143
connected to the
frame at the top of each elongated slot 139. Each cylinder 141 applies a
spreading force
between the stationary block and the moving Garner 137 to push down on the
lower drive
sprockets 119 and 121 and thus tension the drive chains.
Although not visible, coiled tubing injector 101 includes two skates, one for
each
drive chain, for forcing the grippers 115 toward each other as they enter the
area between the
two drive chains through which the coiled tubing passes. Examples of such
skates are
shown in U.S. Patent No. 5,309,990 and are well known in the art. A plurality
of hydraulic
cylinders 145 are used to pull together the skates and maintain uniform
gripping pressure
against coiled tubing (not shown) along the length of the skates. Each
cylinder 145 is
connected at each end through a clevis and pin to an eyelet 147 of a bar
extending behind
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one of the skate and terminating in another eyelet connected to another piston
on the
opposite side of the injector.
At the bottom of the injector, a stripper 149 carried by a stripper adapter
151,
connects the inj ector to a well head. Power for driving the inj ector is
provided by a high
speed, low torque hydraulic motor 153 coupled with the transmission gear box
131 through
brake 155. The hydraulic motor is supplied with a pressurized hydraulic fluid
in a
conventional manner.
Refernng now to FIGS. 4-7, drive chain 111 includes a roller chain having two
strands, 157 and 159, on either side of the row of grippers 115. (Note that in
FIG. 4, the
grippers have their shoes removed, revealing gripper Garners 161.) The roller
chain is of
well-known construction. Rollers 163 are mounted on pins 165 which extend from
an
exterior side of strand 157, through gripper Garner 161, to the exterior side
of strand 159.
Roller links 167 are disposed on opposite sides of each pair of rollers 163.
Pin link plates
169 are outboard of each roller plate and connect pairs of pins.
Mounted to an underside of gripper carriers 161 are a pair of roller bearings
171 and
173 which ride upon the skates of the injector. The roller bearings are
rotatably mounted on
pin 175.
As illustrated by FIG'S 5, 6 and 7, a plurality of different shoes may be
attached to
the same gripper carrier 161. For example, in FIG. 5, "V"-shaped gripper shoe
179 can
support large diameter tubing or pipe, the outer diameter of which is
indicated in phantom
by dashed circle 181. In FIG. 6, it is round-shaped gripper shoe adaptor 183
which may hold
various sizes of rounded gripper shoes disposed therein (not shown) for
gripping smaller
diameter pipes and tubing. In FIG. 7, a comparatively small gripper shoe 185
is shown
mounted to gripper carrier 161. When installed in an injector, the position of
the center line
of the pipe to be gripped by gripper shoe 185 will be the same as the center
line of the larger
diameter pipe to be gripped by gripper shoe 179. This allows different shoes
to be installed
on the same injector in order to accommodate gripping of irregularly shaped
tools or joints
being passed through the injector without changing the relative position of
the skates on
which the gripper Garners roll.
Each of the gripper shoes may be quickly inserted and removed from the gripper
carrier 161 without the use of tools. This is especially useful when running
conventional,
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jointed pipe rather than coiled tubing, or when running a tool string
connected to one end
of the coiled tubing. One or more gripper shoes are removed from each drive
chain to pass
the pipe joint or tool. In FIG. 5, for example, the diameter of a joint is
illustrated by dashed
circle 187 and the outer diameter of the pipe by dashed circle 181.
Referring now to FIG'S 8-17, to mount a gripper shoe to the carrier 161, a
universal
base 189 is integrally formed on the bottom of the gripper shoe. The base
mounts to the
gripper shoe carrier using a tongue and groove type of mounting that allows
the gripper shoe
to be slid onto and out of the mounting in directions that, when the injector
is in an
operational position, are generally parallel to the ground, which directions
are generally
oriented along axis 118, and perpendicular to the directions in which the
chain moves,
which directions are generally oriented along axis 114. Thus, forces exerted
by the pipe
string on the gripping elements, which forces are primarily along axis 114,
tend to act in a
direction along axis 114. along which the grippers shoe is slid into and out
of the gripper
shoe carriers. For purposes of explanation only, the gripper shoe adaptor 183
is chosen to
illustrate this base. The same base is found on each of the gripper shoes 179
and 185. The
universal base 189 includes four mounting lugs, 191a, 191b, 191c and 191d
which function
as tongues that slide into grooves in the form of slots defined by ledges 195
and rails 197
around the periphery of the carrier. When the gripper shoe is lowered toward
the carrier, lug
191a fits into slot 193a defined between ledges 195a and 195c extending from
left side rail
197a. Lug 191b fits in slot 193b defined between ledges 195b and 195c
extending from
right side rail 197b. Lugs 191c and 191d fit over the end of the side rails
197a and 197b,
respectively. The base of the gripper shoe presses against a flat, metal leaf
spring 199,
forcing it down to allow the gripper shoe base 189 to be slid into the base,
toward end rail
201. When base is pushed back to the end rail, the lugs 191a-191d pass under
ledges 195a-
195d, respectively and cooperate with the ledges to retain the gripper shoe on
the carrier.
Leaf spring 199 then pops up, as best shown in FIG. 9, and retain the gripper
show on the
carrier. During normal operation of the injector, lateral forces which would
push the
gripping shoe against the leaf spring are not substantial. Nevertheless, the
leaf spring does
possess substantial lateral strength. To reduce the effect of forces acting as
the gripper shoes
in lateral direction, the orientation of the carriers may be alternated on the
chain, thus
preventing the springs from carrying the lateral load.
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The flat, metal leaf spring 199 is formed of an arched body section 199a and
feet
199b and 199c. The feet of the spring are trapped within open-ended slots 203a
and 203b
formed in the carrier 161. Depressing the leaf spring flattens it and causes
the feet to slide
outward, as illustrated in phantom by FIG. 17. When the feet slide outward,
any dirt or other
debris which may have accumulated in the slots 203a and 203b is pushed out
through their
open ends. The spring force of the spring is such that it may easily be
manually depressed
to release the gripper shoe, or pulled to remove the spring to clean a shallow
channel 205
formed in the carrier between the open slots 203a and 203b for accommodating
the body of
the leaf when it is depressed.
Sandwiched between the gripper shoe base 189 and the Garner 161 is an
elastomeric
pad 206 of high spring rate which allows the gripper shoe to float on the
carrier 161.
Slightly floating the gripper shoe allows the gripper shoe to automatically
make small
adjustments in its alignment with the coil tubing or pipe as it engages the
tubing or pipe, thus
providing a more even distribution of gripping forces across the shoe. The
elastomeric pad
also accommodates manufacturing tolerances that result in slight variations in
the distances
between the skate on which the roller bearings of the gripper Garners ride and
the centerline
of the pipe or other object being gripped. Thus, more of the gripping shoes
will make good
gripping contact with the pipe, improving overall grip. Preferably, only
gripping shoes are
used that have fixed shapes conforming to the normal shape of the pipe, and
that surround
substantially half of the circumference of the pipe. The fixed shape shoes
cause the pipe to
maintain its normal shape as strong forces are applied to the pipe, thus
preventing
deformation. By forcing the pipe to retain its normal shape and floating the
gripper shoe for
better alignment of the shoe with the pipe, contact area between the gripping
shoe and pipe
is increased. Furthermore, greater force may be applied to the pipe without
concern of
deformation. Thus, with greater contact area and force, gripping is improved.
Each shoe Garner 161 is mounted to one of the two drive chains by inserting
one of
the chain pins 165 (Fig. 5) through each of the bores 207a and 207b. Rollers
171 and 173
(Fig's 5-7) are mounted between flanges 209a, 209b and 209c. Roller 175
extends though
openings 211a and 211b in flanges 209a and 209b, and in a similar opening in
flange 209c
which is not visible in these views.
Gripping shoe adaptor 183 includes rims 213a and 213b located at opposite ends
for
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retaining removable gripping elements (not shown). Gripping elements may thus
be
replaced when worn or changed in size or shape, or to accommodate passing of
downhole
tools or other downhole assemblies having different diameters than the pipe.
The forgoing embodiments are but examples of the invention. Modifications,
omissions, substitutions and rearrangements may be made to the forgoing
embodiments
without departing from the invention as set forth in the appended claims.
