Note: Descriptions are shown in the official language in which they were submitted.
CA 02738500 2011-04-29
1 "A CONTINUOUS ROD PUMP DRIVE SYSTEM"
2
3 FIELD OF THE INVENTION
4 Embodiments of the invention relate to systems and apparatus for
driving a downhole pump using continuous rod, and more particularly, for
6 eliminating a polish rod and couplings thereto and couplings along a length
of the
7 continuous rod until at least a top of the pump for reducing wear on
production
8 tubing through which the continuous rod extends and for providing annular
space
9 thereabout for insertion of at least cleanout tubing.
11 BACKGROUND OF THE INVENTION
12 One of skill in the art will appreciate that there are many types of
13 pumps which are actuated by rotation or reciprocation of a rod string.
Examples of
14 such pumps, used for pumping fluids in a wellbore, are plunger pumps
(reciprocating) and progressing cavity pumps (rotary).
16 Plunger pumps typically comprise pistons or plungers which are
17 reciprocated for pumping fluids through production tubing to surface. The
pump
18 typically comprises a standing valve, which opens on an upstroke for
drawing fluids
19 into the pump and closes on a downstroke, and a travelling valve, which is
closed
on the upstroke and which opens on the downstroke, for forcing fluid out of
the
21 pump and into the production string.
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1 Progressing cavity pumps (PC pumps) comprise a stator and a rotor,
2 the rotor being rotated within the stator for pumping fluids therethrough.
The stator
3 is generally connected at the bottom of production tubing.
4 The driven components, typically the plunger of the reciprocating
pump and the rotor of the PC pump, are driven using a string of rods which
extend
6 axially through the production tubing from surface to the pump. The
production
7 tubing is hung from a tubing hanger in a wellhead at surface and extends
downhole
8 in a cased wellbore. A production annulus is formed between the rod string
and the
9 production tubing. Produced fluids, from the pump, flow up the production
annulus
to surface. The rod string comprises a polish rod at the wellhead which is
coupled at
11 a downhole end to a plurality of sucker rods therebelow, the sucker rods
being
12 connected end-to-end by couplings for forming the rod string. Typically
each of the
13 plurality of sucker rods is typically about 25 to 30 feet in length. There
can be
14 hundreds of such connections along the length of the rod string.
As one of skill in the art will appreciate, each of the couplings, being of
16 larger diameter than the sucker rods, creates a localized restriction in
the production
17 annulus.
18 At a minimum, it is known to connect an uphole end of the rod string to
19 the polish rod using a coupling and to connect a downhole end of the rod
string to
the pump, such as to the rotor, using a coupling The couplings have an outer
21 diameter which is larger than the outer diameter of the sucker rod string.
For
22 example, in the case of a sucker rod having a 1" pin end, the couplings
have an
23 outer diameter of 2-3/16" or in the case where the couplings are designed
for slim
2
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1 hole, the couplings have an outer diameter of about 2". In the case of a
sucker rod
2 having a 7/8" pin end, the couplings have an outer diameter of 1-13/16" or
in the
3 case where the couplings are designed for slim hole, the couplings have an
outer
4 diameter of about 1-5/8".
Alternatively, the rod string is a continuous rod string, such as PRO-
6 ROD available from C-Tech Oilwell Technologies Inc. of Edmonton, Alberta,
7 Canada. Use of continuous rod permits couplings to be eliminated along a
length of
8 the rod string, however the continuous rod requires at least a coupling at
the polish
9 rod and at the connection to the rotor.
The polish rod extends through a rotary drive and a rotary seal at the
11 wellhead, typically called a stuffing box, and for a short distance into
the production
12 tubing, forming a production annulus therebetween. The polish rod is
generally a
13 rod of known and consistent dimensions for unrestricted and sealable
movement
14 through the stuffing box and through the rotary drive, as necessary.
In the case of a PC pump, some axial movement of the polish rod, and
16 the rod string connected thereto is required to enable manipulation of the
rotor
17 during setting and removal of the rotor from the stator. Thus, the polish
rod must
18 have a length sufficient to enable manipulation of the rotor from the
stator, typically
19 from about 25 to about 36 feet long. Further, so as to properly locate the
rotor
relative to the stator, one or more short pony rods are connected and coupled
21 between the polish rod and the rod string to ensure that the polish rod is
properly
22 located through the wellhead and wellhead drive. In the case of a
reciproxating
23 pump, the rod string must have sufficient length to ensure that the rod
string, when
3
CA 02738500 2011-04-29
1 connected between the pump jack and the pump provides sufficient length to
2 ensure a full stroke of the pump while sealing at the stuffing box. As noted
above,
3 each coupling forms a localized restriction in the production annulus.
4 Additionally, a shear coupling is normally provided between the rod
string and pump to ensure that the rod string can be released from the pump in
a
6 worst case scenario where the pump seizes.
7 The two or more couplings, spaced apart between the polish rod and
8 the pump, reciprocate or rotate with the rod string. IN the case of a PC
pump, the
9 couplings remain at substantially the same elevation in the well throughout
their
service. As the couplings are localized diameter changes along the rod string,
the
11 couplings act as point loads on the wall of the production tubing and can
cause
12 significant wear thereto. Eventually, the point loading of the production
tubing may
13 result in a wearing through of the tubing causing leaks therein and a loss
of
14 production.
Additionally problematic is the reduction in the production annulus at
16 each of the couplings. In instances where the pump becomes blocked with
17 particulates, such as sand, it is known to lower a small diameter cleanout
tubing
18 string, generally coiled tubing, through the production annulus to the pump
so as to
19 deliver washing fluids thereto to clear sand. Each coupling, including the
uphole
coupling between the polish rod and the rod string, is a potential obstruction
to the
21 bypass of the cleanout tubing through the production annulus. It is known
to pass
22 the cleanout tubing into the production tubing, through ports in the
wellhead such as
4
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1 taught in Canadian Patent 2,310,236 to Titus Tools Inc., Lloydminster,
Alberta,
2 Canada.
3 In the case of a PC pump, due to the threaded coupling connections,
4 typically right hand threads, the direction of rotation of the rotor cannot
be changed
because, if reversed, the threading, at one or more of the couplings, can
unthread
6 risking loss of the rod string in the production tubing. Even in the case
where a
7 continuous rod is used, reverse rotation will result in an unthreading of
the uphole
8 coupling at the polish rod resulting in dropping of the rod string.
9 Therefore there is a need for a system which avoids these limitations
and, in particular, which can minimize wear of the production tubing, rod and
rod
11 couplings and which can enable the passage of a cleanout tubing therealong.
12
5
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1 SUMMARY OF THE INVENTION
2 Continuous rod is connected directly to a drive or through a stuffing
3 box eliminating the need for the polish rod and an uphole coupling. As a
result, the
4 continuous rod utilizes one or more couplings at the downhole end of the
continuous rod for connection to the pump. Localized wearing of the production
6 tubing is minimized asthere is only one location at which wear might occur.
Further,
7 the production annulus remains unrestricted from the wellhead to the top of
the
8 pump permitting cleanout tubing and the like to pass therethrough to the
pump.
9 In a broad aspect, a method is provided for installing and driving a
driven component of a rod-driven pump, the pump being fluidly connected at a
11 bottom of a string of production tubing fluidly connected to a wellhead at
surface.
12 The method comprises providing a continuous rod and coupling a downhole end
of
13 the continuous rod to an uphole end of the driven component. The continuous
rod
14 and driven component are run downhole through a bore of the production
tubing
ensuring the continuous rod is of sufficient length to be operatively
connected to the
16 pump in the wellbore and drivingly secured to a drive at surface. The
continuous rod
17 is driveably secured the to the drive at surface, wherein the continuous
rod is driven
18 by the drive for pumping produced fluids to surface through the bore of the
19 production tubing.
In the case of a progressing cavity pump the driven component is a
21 rotor. In the case of a reciprocating pump the driven component is a
plunger.
22 In another broad aspect, a method for servicing a rod-driven pump
23 fluidly connected to a bore of a production tubing in a wellbore comprises:
driveably
6
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1 connecting an uphole end of a continuous rod directly to a drive at surface,
the
2 continuous rod extending through the bore of the production tubing from the
drive to
3 the pump. A coupling is provided for driveably connecting between a downhole
end
4 of the continuous rod and the pump. A cleanout tubing string is inserted
through the
bore of the production tubing in a production annulus formed between the
6 continuous rod and the production tubing, the cleanout tubing string passing
within
7 the production annulus, substantially unrestricted by the continuous rod
therein, to
8 the coupling at the downhole end of the continuous rod. Cleanout fluids are
9 provided through the cleanout tubing string.
In another broad aspect, a rod string for driving a pump in a wellbore
11 comprises a continuous rod having an uphole end for drivingly connecting to
a drive
12 at surface and a downhole end for connection to the pump; and a coupling
for
13 connecting between the downhole end of the continuous rod and the pump.
14 In yet another broad aspect, a rod-driven pumping system comprises
a drive positioned at surface, a continuous rod driveably connected to the
drive and
16 extending downhole through a bore of a production tubing to a pump, forming
a
17 production annulus therebetween; and a coupling connecting between the
18 continuous rod and the pump, the production annulus having a maximized pass-
by
19 clearance along a length of the continuous rod from the wellhead to the
coupling at
the pump and being sufficient to permit a cleanout tubing to pass
substantially
21 unrestricted therethrough.
22 In an embodiment, the coupling is a threaded coupling. In the case of
23 a PC pump, should the rotor become stuck in the stator, such as due to
particulate
7
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1 deposition therein, the direction of rotation can be reversed for
unthreading the
2 threaded coupling at the rotor, freeing the continuous rod from the rotor.
In the case
3 of the reciprocating pump, the rod can be rotated in an appropriate
direction for
4 unthreading the threaded coupling at the pump for freeing the continuous rod
from
the reciprocating pump.
6 In an embodiment, the coupling is a shear coupling. Advantageously,
7 in the case of a PC pump, as the shear coupling is not a threaded coupling,
the
8 direction of rotation of the continuous rod and the rotor can be reversed
for pumping
9 the particulates downhole for freeing the rotor without risk of separating
the
continuous rod from the rotor. Thereafter, the direction of rotation can be
reversed
11 again for pumping to surface.
12 In the case of both a PC pump and a reciprocating pump, should
13 cleaning operations be unsuccessful, an axial shearing of the shear
coupling can be
14 performed for releasing the continuous rod from the pump.
16 BRIEF DESCRIPTION OF THE DRAWINGS
17 Figure 1 is a partial longitudinal sectional view of prior art couplings
18 connecting adjacent sucker rods, for forming a rod string in production
tubing;
19 Figure 2A is an elevation view of a wellhead installation and PC pump
showing a cross-section of a wellbore portion, the installation implementing
an
21 embodiment of the invention in a production mode;
22 Figure 2B is a partial longitudinal sectional view according to Fig. 2A,
23 illustrating a continuous rod connected to an uphole end of a pump rotor
therein;
8
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1 Figure 2C is a cross-sectional view according to Fig. 2B illustrating a
2 production annulus about the continuous rod in production tubing hung in a
wellbore
3 casing;
4 Figure 2D is an elevation view of a wellhead installation and
reciprocating pump showing a cross-section of a wellbore portion, the
installation
6 implementing an embodiment of the invention in a production mode;
7 Figure 3A is a partial longitudinal sectional view of one embodiment of
8 a threaded coupling for connecting between continuous rod and a pump rotor;
9 Figure 3B is a partial longitudinal sectional view of one embodiment of
a shear coupling for connecting between continuous rod and a pump rotor;
11 Figure 4A is a longitudinal sectional view of a drive head of the
12 wellhead installation of Fig. 2A, the continuous rod being operatively
connected to a
13 drive shaft above the production tubing;
14 Figure 4B is a partial elevation view of a polished rod liner installed on
the continuous rod;
16 Figure 5A is an elevation view of a wellhead installation and PC pump,
17 the installation implementing a Y-access service adapter for a running a
service coil
18 tubing into the production annulus in a service mode;
19 Figure 5B is an elevation view of a wellhead installation and PC pump,
the installation implementing an integrated Y-access service adapter installed
below
21 a wellhead drive for a running a service coil tubing into the production
annulus in a
22 service mode;
9
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1 Figure 5C is a partial longitudinal sectional view according to Fig. 5A
2 and 5B illustrating the continuous rod connected to an uphole end of the
pump and
3 the service coil tubing positioned in the production annulus thereabout;
4 Figure 5D is a cross-sectional view according to Fig. 5C illustrating the
service coil tubing in the production annulus;
6 Figure 6 is a side elevation, cross-sectional view of an embodiment of
7 a rod lock-out clamp for engaging the continuous rod;
8 Figure 7 is a plan view of the rod lock-out clamp according to Fig. 6;
9 Figure 8 is a side elevational, cross-sectional view of a blowout
preventer having an integrated rod lock-out clamp for engaging the continuous
rod;
11 Figure 9 is a plan view of the integrated rod lock-out clamp of Fig. 8;
12 and
13 Figure 10A is a plan view of a piston of a rod-lock clamp illustrating a
14 gripping profile suitable for use with continuous rod according to an
embodiment of
the invention.; and
16 Figure 10B is a detailed plan view of the gripping profile according to
17 Fig.1OA.
18
19
CA 02738500 2011-04-29
1 DESCRIPTION OF THE PREFERRED EMBODIMENTS
2 Having reference to Fig. 1, prior art couplings 10 are used for
3 connecting between adjacent lengths of sucker rod 12 for forming a rod
string 14.
4 As can be seen, a diameter of the couplings 10 is greater than a diameter of
the
sucker rods 12 such that when the rod string 14 is positioned in a bore 15 of
a string
6 of production tubing 16, a plurality of rod-to-rod couplings create
localized
7 restrictions in a production annulus 18 between each coupling 10 along a
length of
8 the rod string 14 and the production tubing 16.
9 Embodiments of the invention can be used to drive rotary driven
pumps or reciprocating pumps. In the case of rotary pumps, such as a
progressing
11 cavity pump (PC pump), the rod string 14 is rotated by a rotary drive at
surface. In
12 the case of reciprocating pumps, such as a plunger pump, the rod string 14
is
13 reciprocated, such as by a pump jack at surface.
14 As shown in Figs. 2A-2D, continuous rod 30 is utilized as the rod
string 14 to replace the prior art lengths of sucker rod string 12,
eliminating the need
16 for the polish rod and the prior art plurality of rod-to-rod couplings 10
therealong.
17 Instead, a continuous rod 30 extends from a drive D at surface to the pump
P. A
18 coupling 10 is used to couple the continuous rod 30 to the pump P at a
downhole
19 end 38 of the continuous rod 30. The continuous rod 30 is connected to a
driven
component of the pump P. As will be appreciated by one of skill in the art,
while the
21 coupling 10 is referred to herein in the singular, one or more couplings 10
may be
22 used adjacent the downhole end 38 of the continuous rod 30 leaving the
production
23 annulus 18 substantially unobstructed therealong.
11
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1 As shown in Figs. 2A-2C, in the case of a PC pump P, a stator 20 is
2 fluidly connected to the production tubing 16 in a wellbore 22. A rotor 24
is installed
3 within the stator 20. According to embodiments of the invention, the
continuous rod
4 30 extends from a drive head 26 installed on a wellhead 28 at surface to the
rotor
24, which is the driven component. The coupling 10 is used to couple the
6 continuous rod 30 to the rotor 24.
7 Having reference to Fig. 2D, in the case of a reciprocating pump P,
8 the continuous rod 30 extends from a pumpjack drive D, through a stuffing
box S
9 which is fluidly connected to the wellhead 28 at surface to a driven
component of
the reciprocating pump P, typically a plunger T containing a travelling valve.
11 Figs. 3A and 3B illustrate embodiments of couplings 10 which may be
12 used to connect between the continuous rod 30 and the rotor 24.
13 In embodiments of the invention, the continuous rod 30 is driveably
14 connected directly to the drive D, as will be discussed in greater detail
below,
eliminating the need for a conventional polish rod and eliminating the need
for a
16 prior art uphole coupling.
17 Further, in the case of a PC pump P, a plurality of pony rods and
18 couplings 10, as required in the prior art to permit manipulation of the
rotor 24 for
19 installing in the stator 20, are not required as the continuous rod 30 has
sufficient
length to permit the rotor 24 to be raised and lowered for installation into
the stator
21 20 in a PC pump P Only after installation of the rotor 24 into the stator
20 is the
22 continuous rod 30 cut above the drive head 26.
12
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1 In the case of a reciprocating pump P, the continuous rod 30 has
2 sufficient length to permit connection between the pumpjack D and the
plunger T for
3 permitting a full stroke of the pump before the continuous rod 30 is
connected to the
4 pumpjack and is cut.
Advantageously, the continuous rod 30 and production tubing 16
6 diameters can be optimized for further benefits as described below.
7 In greater detail, and with reference to Figs. 2A and 4A, for use with a
8 PC pump P, the continuous rod 30, extends from the drive head 26 and through
a
9 wellhead 28 at surface, to the rotor 24 positioned in the stator 20
downhole. As
shown in Fig. 4A, in an embodiment, the continuous rod 30 is driveably
connected
11 directly to the drive head 26, such as by extending through a hollow drive
shaft 32
12 of the drive head 26, thereby eliminating the conventional polish rod. A
variety of
13 different sealing arrangements are known at the drive head 26, such as
those
14 avoiding a dynamic seal to the continuous rod 30.
The continuous rod 30 is coupled to the rotor 24 using a coupling 10,
16 such as shown in Fig. 3A or 3B. The continuous rod 30 and the rotor 24 are
run
17 downhole through a bore in the production tubing 16 until the rotor 24 is
inserted
18 through the stator 20 to a tag pin or bar therebelow (not shown). The
continuous
19 rod 30 is lifted to properly locate the rotor 24 in the stator 20 after
which the
continuous rod 30 is driveably secured, such as by clamping, and cut to length
21 above the drive head 26. Co-rotation of the drive shaft 32, the continuous
rod 30
22 and the rotor 24 in a first, pumping direction, results in pumping of
produced fluid
23 through the production tubing 16 to surface.
13
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1 In one embodiment, prior to installation of the drive head 26, the
2 continuous rod 30 is coupled to the rotor 24 using the coupling 10 and is
run into the
3 production tubing 16. Once the rotor 24 is manipulated into the stator 20,
the
4 continuous rod 30 is locked to the wellhead 27, such as by a ram BOP
therein. The
continuous rod 30 is then cut to a length calculated based upon the length
required
6 to pass through the drive head 26, once installed on the wellhead, and to
extend
7 thereabove. The drive head 26 is then mounted to the wellhead 27 with the
8 continuous rod 30 passing through the hollow drive shaft 32 and the
continuous rod
9 30 is driveably secured, such as by clamping, above the drive head 26 for co-
rotation with the drive shaft 32.
11 Having reference again to Fig. 2D, in the case of a reciprocating pump
12 P, the continuous rod 30 is coupled to the driven component of the
reciprocating
13 pump P which is typically lowered through the production tubing using the
14 continuous rod 30. Once the reciprocating pump P is positioned in the
wellbore, the
continuous rod 30 is cut to a sufficient length to pass through the wellhead
16 components 28 and the stuffing box and extend to the bridle 60 of the
pumpjack D
17 when the pumpjack D is at the top of the pump stroke. Once cut, a polished
rod liner
18 70 and stuffing box S are typically lowered over the continuous rod 30 and
the
19 polished rod liner 70 is secured to the continuous rod 30. The continuous
rod 30 is
then typically connected to the bridle 60. As with the drive head 26 for the
PC pump,
21 a variety of different sealing arrangements are known at the stuffing box
S, such as
22 those avoiding a dynamic seal to the continuous rod 30. One such sealing
14
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1 arrangement comprises static seals which seal to the continuous rod and
dynamic
2 seals which seal to the polished rod liner 70 in the stuffing box S.
3 In an embodiment, having reference to Fig. 2B, a connection between
4 the continuous rod 30 and the driven component of the pump P can comprise a
short length or interface of sucker rod 34, such as about 2 feet in length.
While
6 shown and described in the context of a PC pump P, the interface of sucker
rod 34
7 can also be used to connect between the continuous rod 30 and the driven
8 component of a reciprocating pump. The sucker rod interface 34 is truncated
at an
9 uphole end 36 and is joined, such as by butt-welding directly to a downhole
end 38
of the continuous rod 30. A downhole end 40 of the interface 34 comprises
11 conventional rod male threading.
12 Further, in an embodiment, the coupling 10 is a conventional threaded
13 coupling (Fig. 3A), which is threaded between the downhole end 40 of the
interface
14 34 and an uphole threaded end 42 of the driven component. Using this
embodiment, a conventional shear coupling 10 is not required to enable
retrieval of
16 the continuous rod 30 upon some failure, such as sanding-in of the rotor 24
in the
17 stator 20 or blockage of the travelling valve T. Unlike a rod string 14
comprising a
18 plurality of threaded sucker rod 12 lengths, the entirety of the continuous
rod 30 can
19 be reverse-rotated to predictably unthread only the threaded coupling 10
from the
rotor 24. Thus, the rod string 14 cannot be lost and retrieval is easily
available in
21 cases where the pump P is stuck.
22 In an embodiment, the coupling 10 is a shear coupling, such as shown
23 in Fig.3B, which can transmit driving torque yet is susceptible to axial
shearing. IN
CA 02738500 2011-04-29
1 the case of a PC pump, connecting the continuous rod 30 to the rotor 24 with
a
2 driveable coupling 10 which enables bi-direction co-rotation, when the rotor
24 is
3 stuck in the stator 20, generally as a result of sand or other particulates,
the
4 continuous rod 30 and rotor 24 can be reverse co-rotated to attempt to pump
the
particulates downhole into the formation for freeing the rotor 24. Thereafter,
rotation
6 can be returned to the first direction for pumping produced fluid to
surface. Should
7 efforts to free the rotor 24 fail, axial shearing of the shear coupling 10
is used to
8 release the continuous rod 30 from the rotor 24. Similarly, in the case of a
9 reciprocating pump, axial shearing of the shear coupling 10 is used to
release the
continuous rod 30 from the pump P.
11 Having reference to Fig 4B, in the case of both rotary and
12 reciprocating pumps P, a polished rod liner 70 may be installed over the
continuous
13 rod 30 for providing a larger diameter or improved surface for sealing,
such as in the
14 drive head 26 or the stuffing box S, to prevent the leakage of well fluid
from around
the continuous rod 30 at surface. Further, the polished rod liner 70 provides
better
16 bearing support and a smoother surface for sealing.
17 In a production mode, through the elimination of couplings 10 along a
18 length of the continuous rod 30, the production annulus 18 is freed of
restrictions.
19 Further, one can implement production tubing 16 having a smaller bore 15
and still
maximize a pass-by clearance in the production annulus 18 sufficient to permit
21 passage of at least another small diameter tubing 50 thereby. For example,
where
22 3-1/2" production tubing would normally be used with conventional rod
string 14, the
23 use of 1" continuous rod 30 without rod-to-rod couplings could instead
enable use of
16
CA 02738500 2011-04-29
1 2-7/8" production tubing 16. The smaller diameter production tubing 16 is
less
2 expensive and also increases the "rise velocity" of produced fluids for
retention of
3 suspended solids therein. With 7/8" continuous rod 30, one might reduce the
4 production tubing 16 further, to 2-3/8" for example. Smaller production
tubing 16 can
further have the advantage of enabling re-commissioning of wells having
damaged
6 casing in which 3-1/2" production tubing 16 can no longer be run downhole
through
7 the damaged area.
8 In embodiments, the smaller diameter tubing or cleanout string 50 is
9 inserted into the bore 15 of the production tubing 16. The cleanout string
50 can be
inserted through a stuffing box mounted to the well after removal of the drive
11 equipment D or through service ports 52 provided in the wellhead 28.
12 Having reference to Figs. 5A-5D, wellhead installations 28, fluidly
13 connected to the production tubing 16, can comprise the service ports 52,
such as
14 Y-access service adapters (Figs. 5A and 5B) or integrated Y-access service
adapters installed below the drive head 26 (Figs 5C and 5D) to provide access
to
16 the production annulus 18. PC pumps may require servicing, such as cleaning
out
17 by flowing cleanout fluids therethrough. As a result of maximizing the pass-
by
18 clearance in the production annulus 18, the smaller diameter tubing 50,
such as
19 coiled tubing, can be passed through the service ports 52 and into the
production
annulus 18. Passage of the coiled tubing 50 is substantially unrestricted
within the
21 production annulus 18 until the coiled tubing 50 reaches the coupling 10
adjacent
22 the uphole end 42 of the rotor 24. The coiled tubing 50 is inserted into
the
23 production 18 annulus through the variety of service ports 52 in the
wellhead 28 and
17
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1 is lowered therein adjacent the uphole end 42 of the rotor 24 after which
clean out
2 fluids are provided therethrough.
3 Rod lock-out clamps, in most cases include BOP seals for sealing the
4 well from release of well fluids and gases as taught in Applicant's issued
Canadian
patent 2,349,988, are known for gripping a polished rod in a conventionally-
driven
6 pump installation. Relevant aspects from Canadian Patent 2,349,988 have been
7 extracted and applied as follows.
8 Having references to Figs. 6-9 and in embodiments of the invention,
9 such rod lock-out clamps 160,180 may be used to grip the continuous rod 30
for
temporarily suspending the continuous rod 30 in the wellbore and spacing out
the
11 pump P connected thereto during installation or servicing of the pump and
drive
12 components or during connection of drive and other wellhead components
thereto.
13 The rod lockout clamp 160, 180 generally comprises a clamp body
14 having a bore 164 formed therethrough for receiving the continuous rod 30.
clamp
members 182, such as two opposing radial pistons, for gripping the continuous
rod
16 30 in the bore 164 and manipulating means 184, such as bolts, for moving
the
17 clamp members 182 into gripping engagement with the continuous rod 30.
18 As shown in Figs. 6 and 7, it may be preferable not to restrict the
19 diameter through the bore 164 so that the continuous rod 30 can be pulled
through
the clamp 160. The continuous rod 30 is gripped by arcuate recesses 186, which
21 are prefereably made undersize relative to the continuous rod 30 to enhance
22 gripping force. The pistons 182 further include O-rings 223 to provide a
better seal
23 in the bore 164.
18
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1 Having reference to Figs. 8 and 9, where the clamp 180 is integrated
2 with a blow out preventer, the pistons 182 are made substantially of metal
so as to
3 allow the pistons 182 to be forced into engagement with the continuous rod
30 to
4 prevent movement of the continuous rod 30 therein. An inner end of the
pistons 182
is formed with an arcuate recess 186 with a curvature corresponding
substantially to
6 that of the continuous rod 30. Enhanced gripping force is achieved if the
arcuate
7 recess diameter is undersized relative to the continuous rod 30. A narrow
8 elastomeric seal 188 is provided which runs across the vertical flat surface
of the
9 piston 182, along the arcuate recess 186, along a mid-height of the piston
182 and
circumferentially around the piston 182. The circumferential seal can
encompass
11 only the lower portion of the piston if desired. The seal 188 compresses
into
12 grooves which permit the pistons 182 to engage the continuous rod 30 in
metal-to-
13 metal contact. The seals 188 seal between the pistons 182, between the
pistons
14 182 and the continuous rod 30 and between the pistons 182 and the bores in
which
the pistons 182 are installed.
16 Having reference to Figs. 1 OA and 1 OB, gripping of the continuous rod
17 30 with less surface damage can be accomplished by several modifications,
18 including minimizing a gap between the pistons 182 in the gripping
position, making
19 a gripping arc starting at an inward edge of the piston 182 at a radius of
about 0.025
inches smaller than the largest continuous rod 30 to be gripped, making a
straight
21 gripping surface tangential to the gripping arc at about a 15 degree angle
and then
22 forming another arc tangential to the straight gripping surface at a radius
equal to
23 the smallest continuous rod 30 to be gripped.
19
