U.S. patent application number 13/097471 was filed with the patent office on 2011-11-03 for continuous rod pump drive system.
This patent application is currently assigned to OIL LIFT TECHNOLOGY INC.. Invention is credited to VERN HULT, MARK WIDNEY.
Application Number | 20110266005 13/097471 |
Document ID | / |
Family ID | 44857361 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110266005 |
Kind Code |
A1 |
HULT; VERN ; et al. |
November 3, 2011 |
CONTINUOUS ROD PUMP DRIVE SYSTEM
Abstract
In a downhole rod-driven pump, continuous rod is used to drive
the pump. The continuous rod is connected directly to the drive
eliminating the need for a polish rod and an uphole coupling. A
coupling is used to connect the continuous rod to the pump reducing
restrictions in the production annulus and wear on the production
tubing. Further, clean out tubing can be inserted into the
production tubing beside the continuous rod and can extend therein
to the pump without restriction. When the coupling is a threaded
coupling, the continuous rod can be rotated in an appropriate
direction to release the continuous rod from the pump when the pump
is stuck. When the coupling is a shear coupling, the shear coupling
can be sheared for releasing the pump from the continuous rod. When
the pump is a progressing cavity pump and the coupling is a shear
coupling, the continuous rod can be reverse rotated for changing
the direction of pumping and if the rotor thereafter remains stuck,
the shear coupling can be sheared.
Inventors: |
HULT; VERN; (Calgary,
CA) ; WIDNEY; MARK; (ARDROSSAN, CA) |
Assignee: |
OIL LIFT TECHNOLOGY INC.
Calgary
CA
|
Family ID: |
44857361 |
Appl. No.: |
13/097471 |
Filed: |
April 29, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61330095 |
Apr 30, 2010 |
|
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|
Current U.S.
Class: |
166/378 ;
166/105; 166/68.5 |
Current CPC
Class: |
E21B 43/126 20130101;
E21B 33/047 20130101; E21B 33/085 20130101 |
Class at
Publication: |
166/378 ;
166/105; 166/68.5 |
International
Class: |
E21B 19/00 20060101
E21B019/00; E21B 43/00 20060101 E21B043/00 |
Claims
1. A method for installing and driving driven component of a
rod-driven pump, the pump being fluidly connected at a bottom of a
string of production tubing fluidly connected to a wellhead at
surface, the method comprising: providing a continuous rod;
coupling a downhole end of the continuous rod to an uphole end of
the driven component; running the continuous rod and driven
component downhole through a bore of the production tubing;
ensuring the continuous rod is of sufficient length to be
operatively connected to the pump in the wellbore and drivingly
secured to a drive at surface; and driveably securing the
continuous rod to the drive at surface, wherein the continuous rod
is driven by the drive for pumping produced fluids to surface
through the bore of the production tubing.
2. The method of claim 1 wherein the pump is a rotary pump having a
rotor and a stator, the rotor being the driven component, and the
drive is a drive head, the method comprising: coupling the downhole
end of the continuous rod to an uphole end of the rotor; running
the continuous rod and rotor downhole through a bore of the
production tubing; landing the rotor in the stator of the rotary
pump for operatively engaging the rotor therein; and once the rotor
is engaged with the stator, cutting the continuous rod above the
drive head for driveably securing the continuous rod thereto,
wherein the continuous rod co-rotates with the drive shaft for
rotation of the rotor in the stator in a first pumping direction
for pumping produced fluids to surface through the bore of the
production tubing.
3. The method of claim 2 further comprising coupling the downhole
end of the continuous rod to the uphole end of the rotor using a
threaded coupling.
4. The method of claim 3, when the continuous rod is to be
disconnected from the rotor without removal of the rotor from the
stator, the method further comprising; rotating the continuous rod
in a reverse direction for unthreading the downhole end of the
continuous rod from the rotor.
5. The method of claim 2 further comprising driveably coupling the
downhole end of the continuous rod to the rotor using a shear
coupling.
6. The method of claim 5, when the rotor cannot be rotated in the
stator in the first direction, the method further comprising:
rotating the continuous rod and the rotor in a reverse direction
for pumping particulates downhole into the wellbore for freeing the
rotor in the stator and thereafter rotating the continuous rod and
the rotor in the first pumping direction for pumping produced
fluids to surface.
7. The method of claim 6 wherein, after rotating the rotor in the
reverse direction, the rotor cannot be reverse-rotated in the
stator, further comprising: axially shearing the shear coupling for
freeing the downhole end of the continuous rod from the rotor.
8. The method of claim 2 further comprising: coupling the downhole
end of the continuous rod to the rotor using a length of sucker
rod, the sucker rod being welded, at an uphole end, to the downhole
end of the continuous rod and having the threaded coupling at the
downhole end for threaded connection to the rotor.
9. The method of claim 1 wherein the pump is a reciprocating pump,
the driven component being a plunger, and the drive is a pumpjack,
the method further comprising: coupling the downhole end of the
continuous rod to the uphole end of the plunger using a threaded
coupling.
10. The method of claim 9, when the continuous rod is to be
disconnected from the pump, the method further comprising; rotating
the continuous rod for unthreading the downhole end of the
continuous rod from the plunger.
11. The method of claim 1 wherein the pump is a reciprocating pump,
the driven component being a plunger, and the drive is a pumpjack,
the method further comprising: coupling the downhole end of the
continuous rod to the plunger using a shear coupling.
12. The method of claim 11 wherein the continuous rod is to be
disconnected from the pump, further comprising: axially shearing
the shear coupling for freeing the downhole end of the continuous
rod from the plunger.
13. The method of claim 1, when particulates deposit in the pump,
further comprising: inserting a cleanout tubing string into the
bore of the production tubing in a production annulus formed
between the continuous rod and the production tubing; passing the
cleanout tubing string substantially unrestricted through the
production annulus to the coupling of the continuous rod to the
driven component of the pump; and providing fluid through the
cleanout tubing string for cleaning particulates from the pump.
14. A method for installing and driving a rotor in a stator of a
rod-driven rotary pump, the pump being fluidly connected at a
bottom of a string of production tubing fluidly connected to a
wellhead at surface, the method comprising: providing a continuous
rod; coupling a downhole end of the continuous rod to an uphole end
of the rotor; running the continuous rod and rotor through a bore
of the production tubing; landing the rotor in the stator of the
rotary pump for operatively engaging the rotor therein; and once
the rotor is engaged with the stator, locking the continuous rod in
the wellhead; cutting the continuous rod at a length calculated to
extend above a drive head when installed on the wellhead;
installing the drive head to the wellhead, the continuous rod
passing through a hollow drive shaft in the drive head; and
driveably securing the continuous rod thereto above the drive head,
wherein the continuous rod co-rotates with the drive shaft for
rotation of the rotor in the stator in a first pumping direction
for pumping produced fluids to surface through the bore of the
production tubing.
15. The method of claim 14 further comprising coupling the downhole
end of the continuous rod to the uphole end of the rotor using a
threaded coupling.
16. The method of claim 15, when the continuous rod is to be
disconnected from the rotor without removal of the rotor from the
stator, the method further comprising; rotating the continuous rod
in a reverse direction for unthreading the downhole end of the
continuous rod from the rotor.
17. The method of claim 14 further comprising coupling the downhole
end of the continuous rod to the rotor using a shear coupling.
18. The method of claim 17, when the rotor cannot be rotated in the
stator in the first direction, the method further comprising:
co-rotating the continuous rod and the rotor in a reverse direction
for pumping particulates downhole into the well for freeing the
rotor in the stator and thereafter co-rotating the continuous rod
and the rotor in the first pumping direction for pumping produced
fluids to surface.
19. The method of claim 18 wherein after co-rotating the continuous
rod and the rotor in the reverse direction, the rotor cannot
thereafter be co-rotated in the stator in the first pumping
direction, further comprising: axially shearing the shear coupling
for freeing the downhole end of the continuous rod from the
rotor.
20. The method of claim 14 further comprising: coupling the
continuous rod to the rotor using a length of sucker rod welded, at
an uphole end, to the downhole end of the continuous rod and having
a threaded end at the downhole end for threaded connection to the
rotor.
21. The method of claim 14, when particulates deposit in the stator
inhibiting co-rotation of the rotor, further comprising: inserting
a cleanout tubing string into the bore of the production tubing in
a production annulus formed between the continuous rod and the
production tubing; passing the cleanout tubing string substantially
unrestricted through the production annulus to the coupling of the
continuous rod to the rotor; and providing fluid through the
cleanout tubing string for cleaning particulates from the pump.
22. A method for servicing a rod-driven pump fluidly connected to a
bore of a production tubing in a wellbore comprising: driveably
connecting an uphole end of a continuous rod to a drive at surface,
the continuous rod extending through the bore of the production
tubing from the drive to the pump; providing a coupling for
driveably connecting between a downhole end of the continuous rod
and the pump; inserting a cleanout tubing string into the bore of
the production tubing in a production annulus formed between the
continuous rod and the production tubing, the cleanout tubing
string passing within the production annulus, substantially
unrestricted by the continuous rod therein, to the coupling at the
downhole end of the continuous rod; and circulating cleanout fluids
through the cleanout tubing string.
23. The method of claim 22 further comprising: providing a threaded
coupling for connecting between the downhole end of the continuous
rod and the pump.
24. The method of claim 22 further comprising: providing a shear
coupling for connecting between the downhole end of the continuous
rod and the pump.
25. A rod-driven pumping system comprising: a drive positioned at
surface; a continuous rod driveably connected to the drive and
extending downhole through a bore of a production tubing to a pump,
forming a production annulus therebetween; and a coupling
connecting between the continuous rod and the pump, the production
annulus having a maximized pass-by 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
unrestricted therethrough.
26. The rod-driven pumping system of claim 25 wherein the coupling
is a threaded coupling.
27. The rod-driven pumping system of claim 25 wherein the coupling
is a shear coupling.
28. The rod-driven pumping system of claim 25 wherein the system
further comprises a length of sucker rod welded at an uphole end to
a downhole end of the continuous rod and having threads at a
downhole end for connection to the coupling.
29. The rod-driven pumping system of claim 25 wherein the pump is a
rod-driven progressing cavity pump having a stator and a rotor
operatively engaged within the stator for rotation therein and
wherein, the drive comprises a drive head having a hollow drive
shaft supported on a wellhead at surface, the continuous rod being
driveably connected through the hollow drive shaft of the drive
head; and the coupling connects between the continuous rod and the
rotor.
30. A rod string for driving a pump in a wellbore, the rod string
comprising: a continuous rod having an uphole end for drivingly
connecting to a drive at surface and a downhole end for connection
to the pump; and a coupling for connecting between the downhole end
of the continuous rod and the pump.
31. The rod string of claim 30 further comprising a length of
sucker rod having an uphole end welded to the downhole end of the
continuous rod and having a downhole end for connection to the
coupling.
32. The rod string of claim 30 wherein the coupling is a threaded
coupling.
33. The rod string of claim 31 wherein the coupling is a threaded
coupling and wherein the downhole end of the length of sucker rod
is threaded for connection to the coupling.
34. The rod string of claim 30 wherein the coupling is a shear
coupling.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a regular application claiming priority
of U.S. provisional application 61/330,095 filed Apr. 30, 2010, the
entirety of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Embodiments of the invention relate to systems and apparatus
for driving a downhole pump using continuous rod, and more
particularly, for eliminating a polish rod and couplings thereto
and couplings along a length of the continuous rod until at least a
top of the pump for reducing wear on production tubing through
which the continuous rod extends and for providing annular space
thereabout for insertion of at least cleanout tubing.
BACKGROUND OF THE INVENTION
[0003] One of skill in the art will appreciate that there are many
types of pumps which are actuated by rotation or reciprocation of a
rod string. Examples of such pumps, used for pumping fluids in a
wellbore, are plunger pumps (reciprocating) and progressing cavity
pumps (rotary).
[0004] Plunger pumps typically comprise pistons or plungers which
are reciprocated for pumping fluids through production tubing to
surface. The pump typically comprises a standing valve, which opens
on an upstroke for drawing fluids 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
pump and into the production string.
[0005] Progressing cavity pumps (PC pumps) comprise a stator and a
rotor, the rotor being rotated within the stator for pumping fluids
therethrough. The stator is generally connected at the bottom of
production tubing.
[0006] 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 axially through the production tubing
from surface to the pump. The production tubing is hung from a
tubing hanger in a wellhead at surface and extends downhole in a
cased wellbore. A production annulus is formed between the rod
string and the 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 a downhole end to
a plurality of sucker rods therebelow, the sucker rods being
connected end-to-end by couplings for forming the rod string.
Typically each of the plurality of sucker rods is typically about
25 to 30 feet in length. There can be hundreds of such connections
along the length of the rod string.
[0007] As one of skill in the art will appreciate, each of the
couplings, being of larger diameter than the sucker rods, creates a
localized restriction in the production annulus.
[0008] At a minimum, it is known to connect an uphole end of the
rod string to 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 diameter which is
larger than the outer diameter of the sucker rod string. For
example, in the case of a sucker rod having a 1'' pin end, the
couplings have an outer diameter of 2- 3/16'' or in the case where
the couplings are designed for slim hole, the couplings have an
outer diameter of about 2''. In the case of a sucker rod having a
7/8'' pin end, the couplings have an outer diameter of 1- 13/16''
or in the case where the couplings are designed for slim hole, the
couplings have an outer diameter of about 1-5/8''.
[0009] Alternatively, the rod string is a continuous rod string,
such as PRO-ROD.RTM. available from C-Tech Oilwell Technologies
Inc. of Edmonton, Alberta, Canada. Use of continuous rod permits
couplings to be eliminated along a length of the rod string,
however the continuous rod requires at least a coupling at the
polish rod and at the connection to the rotor.
[0010] The polish rod extends through a rotary drive and a rotary
seal at the wellhead, typically called a stuffing box, and for a
short distance into the production tubing, forming a production
annulus therebetween. The polish rod is generally a rod of known
and consistent dimensions for unrestricted and sealable movement
through the stuffing box and through the rotary drive, as
necessary.
[0011] In the case of a PC pump, some axial movement of the polish
rod, and the rod string connected thereto is required to enable
manipulation of the rotor during setting and removal of the rotor
from the stator. Thus, the polish rod must have a length sufficient
to enable manipulation of the rotor from the stator, typically 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 between the polish rod and the rod string to
ensure that the polish rod is properly located through the wellhead
and wellhead drive. In the case of a reciproxating pump, the rod
string must have sufficient length to ensure that the rod string,
when connected between the pump jack and the pump provides
sufficient length to ensure a full stroke of the pump while sealing
at the stuffing box. As noted above, each coupling forms a
localized restriction in the production annulus.
[0012] 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 worst case scenario where the pump
seizes.
[0013] The two or more couplings, spaced apart between the polish
rod and the pump, reciprocate or rotate with the rod string. IN the
case of a PC pump, the 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 couplings
act as point loads on the wall of the production tubing and can
cause significant wear thereto. Eventually, the point loading of
the production tubing may result in a wearing through of the tubing
causing leaks therein and a loss of production.
[0014] Additionally problematic is the reduction in the production
annulus at each of the couplings. In instances where the pump
becomes blocked with particulates, such as sand, it is known to
lower a small diameter cleanout tubing string, generally coiled
tubing, through the production annulus to the pump so as to 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 bypass of the cleanout tubing through
the production annulus. It is known to pass the cleanout tubing
into the production tubing, through ports in the wellhead such as
taught in Canadian Patent 2,310,236 to Titus Tools Inc.,
Lloydminster, Alberta, Canada.
[0015] In the case of a PC pump, due to the threaded coupling
connections, 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 risking
loss of the rod string in the production tubing. Even in the case
where a continuous rod is used, reverse rotation will result in an
unthreading of the uphole coupling at the polish rod resulting in
dropping of the rod string.
[0016] 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 couplings and which can enable the
passage of a cleanout tubing therealong.
SUMMARY OF THE INVENTION
[0017] Continuous rod is connected directly to a drive or through a
stuffing box eliminating the need for the polish rod and an uphole
coupling. As a result, the 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 tubing is
minimized as there is only one location at which wear might occur.
Further, the production annulus remains unrestricted from the
wellhead to the top of the pump permitting cleanout tubing and the
like to pass therethrough to the pump.
[0018] 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 bottom of a string of production tubing
fluidly connected to a wellhead at surface. The method comprises
providing a continuous rod and coupling a downhole end of the
continuous rod to an uphole end of the driven component. The
continuous rod 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 pump in the
wellbore and drivingly secured to a drive at surface. The
continuous rod is driveably secured the to the drive at surface,
wherein the continuous rod is driven by the drive for pumping
produced fluids to surface through the bore of the production
tubing.
[0019] In the case of a progressing cavity pump the driven
component is a rotor. In the case of a reciprocating pump the
driven component is a plunger.
[0020] In another broad aspect, a method for servicing a rod-driven
pump fluidly connected to a bore of a production tubing in a
wellbore comprises: driveably connecting an uphole end of a
continuous rod directly to a drive at surface, the continuous rod
extending through the bore of the production tubing from the drive
to the pump. A coupling is provided for driveably connecting
between a downhole end 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
continuous rod and the production tubing, the cleanout tubing
string passing within the production annulus, substantially
unrestricted by the continuous rod therein, to the coupling at the
downhole end of the continuous rod. Cleanout fluids are provided
through the cleanout tubing string.
[0021] In another broad aspect, a rod string for driving a pump in
a wellbore comprises a continuous rod having an uphole end for
drivingly connecting to a drive at surface and a downhole end for
connection to the pump; and a coupling for connecting between the
downhole end of the continuous rod and the pump.
[0022] 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 extending downhole through a bore of a
production tubing to a pump, forming a production annulus
therebetween; and a coupling connecting between the continuous rod
and the pump, the production annulus having a maximized pass-by
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 unrestricted therethrough.
[0023] In an embodiment, the coupling is a threaded coupling. In
the case of a PC pump, should the rotor become stuck in the stator,
such as due to particulate deposition therein, the direction of
rotation can be reversed for unthreading the threaded coupling at
the rotor, freeing the continuous rod from the rotor. In the case
of the reciprocating pump, the rod can be rotated in an appropriate
direction for unthreading the threaded coupling at the pump for
freeing the continuous rod from the reciprocating pump.
[0024] In an embodiment, the coupling is a shear coupling.
Advantageously, in the case of a PC pump, as the shear coupling is
not a threaded coupling, the direction of rotation of the
continuous rod and the rotor can be reversed for pumping 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 again for pumping to
surface.
[0025] In the case of both a PC pump and a reciprocating pump,
should cleaning operations be unsuccessful, an axial shearing of
the shear coupling can be performed for releasing the continuous
rod from the pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a partial longitudinal sectional view of prior art
couplings connecting adjacent sucker rods, for forming a rod string
in production tubing;
[0027] FIG. 2A is an elevation view of a wellhead installation and
PC pump showing a cross-section of a wellbore portion, the
installation implementing an embodiment of the invention in a
production mode;
[0028] FIG. 2B is a partial longitudinal sectional view according
to FIG. 2A, illustrating a continuous rod connected to an uphole
end of a pump rotor therein;
[0029] FIG. 2C is a cross-sectional view according to FIG. 2B
illustrating a production annulus about the continuous rod in
production tubing hung in a wellbore casing;
[0030] FIG. 2D is an elevation view of a wellhead installation and
reciprocating pump showing a cross-section of a wellbore portion,
the installation implementing an embodiment of the invention in a
production mode;
[0031] FIG. 3A is a partial longitudinal sectional view of one
embodiment of a threaded coupling for connecting between continuous
rod and a pump rotor;
[0032] FIG. 3B is a partial longitudinal sectional view of one
embodiment of a shear coupling for connecting between continuous
rod and a pump rotor;
[0033] FIG. 4A is a longitudinal sectional view of a drive head of
the wellhead installation of FIG. 2A, the continuous rod being
operatively connected to a drive shaft above the production
tubing;
[0034] FIG. 4B is a partial elevation view of a polished rod liner
installed on the continuous rod;
[0035] FIG. 5A is an elevation view of a wellhead installation and
PC pump, the installation implementing a Y-access service adapter
for a running a service coil tubing into the production annulus in
a service mode;
[0036] FIG. 5B is an elevation view of a wellhead installation and
PC pump, the installation implementing an integrated Y-access
service adapter installed below a wellhead drive for a running a
service coil tubing into the production annulus in a service
mode;
[0037] FIG. 5C is a partial longitudinal sectional view according
to FIGS. 5A and 5B illustrating the continuous rod connected to an
uphole end of the pump and the service coil tubing positioned in
the production annulus thereabout;
[0038] FIG. 5D is a cross-sectional view according to FIG. 5C
illustrating the service coil tubing in the production annulus;
[0039] FIG. 6 is a side elevation, cross-sectional view of an
embodiment of a rod lock-out clamp for engaging the continuous
rod;
[0040] FIG. 7 is a plan view of the rod lock-out clamp according to
FIG. 6;
[0041] FIG. 8 is a side elevational, cross-sectional view of a
blowout preventer having an integrated rod lock-out clamp for
engaging the continuous rod;
[0042] FIG. 9 is a plan view of the integrated rod lock-out clamp
of FIG. 8; and
[0043] FIG. 10A is a plan view of a piston of a rod-lock clamp
illustrating a gripping profile suitable for use with continuous
rod according to an embodiment of the invention; and
[0044] FIG. 10B is a detailed plan view of the gripping profile
according to
[0045] FIG. 10A.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] Having reference to FIG. 1, prior art couplings 10 are used
for connecting between adjacent lengths of sucker rod 12 for
forming a rod string 14. 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
of production tubing 16, a plurality of rod-to-rod couplings create
localized restrictions in a production annulus 18 between each
coupling 10 along a length of the rod string 14 and the production
tubing 16.
[0047] 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 cavity pump (PC pump), the rod string 14 is
rotated by a rotary drive at surface. In the case of reciprocating
pumps, such as a plunger pump, the rod string 14 is reciprocated,
such as by a pump jack at surface.
[0048] 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 for the polish rod and the prior
art plurality of rod-to-rod couplings 10 therealong. Instead, a
continuous rod 30 extends from a drive D at surface to the pump P.
A coupling 10 is used to couple the continuous rod 30 to the pump P
at a downhole 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 coupling 10 is
referred to herein in the singular, one or more couplings 10 may be
used adjacent the downhole end 38 of the continuous rod 30 leaving
the production annulus 18 substantially unobstructed
therealong.
[0049] As shown in FIGS. 2A-2C, in the case of a PC pump P, a
stator 20 is fluidly connected to the production tubing 16 in a
wellbore 22. A rotor 24 is installed within the stator 20.
According to embodiments of the invention, the continuous rod 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 continuous rod 30 to the rotor 24.
[0050] Having reference to FIG. 2D, in the case of a reciprocating
pump P, the continuous rod 30 extends from a pumpjack drive D,
through a stuffing box S 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.
[0051] FIGS. 3A and 3B illustrate embodiments of couplings 10 which
may be used to connect between the continuous rod 30 and the rotor
24.
[0052] In embodiments of the invention, the continuous rod 30 is
driveably 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 prior art uphole
coupling.
[0053] Further, in the case of a PC pump P, a plurality of pony
rods and couplings 10, as required in the prior art to permit
manipulation of the rotor 24 for 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 20 in a PC pump P Only after installation of the rotor
24 into the stator 20 is the continuous rod 30 cut above the drive
head 26.
[0054] In the case of a reciprocating pump P, the continuous rod 30
has sufficient length to permit connection between the pumpjack D
and the plunger T for permitting a full stroke of the pump before
the continuous rod 30 is connected to the pumpjack and is cut.
[0055] Advantageously, the continuous rod 30 and production tubing
16 diameters can be optimized for further benefits as described
below.
[0056] In greater detail, and with reference to FIGS. 2A and 4A,
for use with a PC pump P, the continuous rod 30, extends from the
drive head 26 and through a 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 directly
to the drive head 26, such as by extending through a hollow drive
shaft 32 of the drive head 26, thereby eliminating the conventional
polish rod. A variety of different sealing arrangements are known
at the drive head 26, such as those avoiding a dynamic seal to the
continuous rod 30.
[0057] The continuous rod 30 is coupled to the rotor 24 using a
coupling 10, such as shown in FIG. 3A or 3B. The continuous rod 30
and the rotor 24 are run downhole through a bore in the production
tubing 16 until the rotor 24 is inserted through the stator 20 to a
tag pin or bar therebelow (not shown). The continuous 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 above the drive head 26. Co-rotation of the drive
shaft 32, the continuous rod 30 and the rotor 24 in a first,
pumping direction, results in pumping of produced fluid through the
production tubing 16 to surface.
[0058] In one embodiment, prior to installation of the drive head
26, the continuous rod 30 is coupled to the rotor 24 using the
coupling 10 and is run into the production tubing 16. Once the
rotor 24 is manipulated into the stator 20, the 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 to pass through the drive head 26, once installed
on the wellhead, and to extend thereabove. The drive head 26 is
then mounted to the wellhead 27 with the continuous rod 30 passing
through the hollow drive shaft 32 and the continuous rod 30 is
driveably secured, such as by clamping, above the drive head 26 for
co-rotation with the drive shaft 32.
[0059] Having reference again to FIGS. 2D and 4B, in the case of a
reciprocating pump P, the continuous rod 30 is coupled to the
driven component of the reciprocating pump P, which is typically
lowered through the production tubing using the 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 components 28 and the stuffing box S and extend to the
bridle 60 of the pumpjack D when the pumpjack D is at the top of
the pump stroke. Once cut, a polished rod liner 70 and stuffing box
S are typically lowered over the continuous rod 30 and the 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, a variety of different sealing
arrangements are known at the stuffing box S, such as those
avoiding a dynamic seal to the continuous rod 30. One such sealing
arrangement comprises static seals which seal to the continuous rod
and dynamic seals which seal to the polished rod liner 70 in the
stuffing box S.
[0060] In an embodiment, having reference to FIG. 2B, a connection
between 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 shown and described in the context
of a PC pump P, the interface of sucker rod 34 can also be used to
connect between the continuous rod 30 and the driven component of a
reciprocating pump. The sucker rod interface 34 is truncated at an
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 conventional rod male threading.
[0061] Further, in an embodiment, the coupling 10 is a conventional
threaded coupling (FIG. 3A), which is threaded between the downhole
end 40 of the interface 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 the continuous
rod 30 upon some failure, such as sanding-in of the rotor 24 in the
stator 20 or blockage of the travelling valve T. Unlike a rod
string 14 comprising a plurality of threaded sucker rod 12 lengths,
the entirety of the continuous rod 30 can 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 cases where the pump P is stuck.
[0062] In an embodiment, the coupling 10 is a shear coupling, such
as shown in FIG. 3B, which can transmit driving torque yet is
susceptible to axial shearing. IN the case of a PC pump, connecting
the continuous rod 30 to the rotor 24 with a driveable coupling 10
which enables bi-direction co-rotation, when the rotor 24 is stuck
in the stator 20, generally as a result of sand or other
particulates, the 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 can be
returned to the first direction for pumping produced fluid to
surface. Should efforts to free the rotor 24 fail, axial shearing
of the shear coupling 10 is used to release the continuous rod 30
from the rotor 24. Similarly, in the case of a reciprocating pump,
axial shearing of the shear coupling 10 is used to release the
continuous rod 30 from the pump P.
[0063] Having reference to FIG. 4B, in the case of both rotary and
reciprocating pumps P, a polished rod liner 70 may be installed
over the continuous rod 30 for providing a larger diameter or
improved surface for sealing, such as in the 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 bearing support and a smoother surface for
sealing.
[0064] In a production mode, through the elimination of couplings
10 along a length of the continuous rod 30, the production annulus
18 is freed of restrictions. 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 passage
of at least another small diameter tubing 50 thereby. For example,
where 3-1/2'' production tubing would normally be used with
conventional rod string 14, the use of 1'' continuous rod 30
without rod-to-rod couplings could instead enable use of 2-7/8''
production tubing 16. The smaller diameter production tubing 16 is
less expensive and also increases the "rise velocity" of produced
fluids for retention of suspended solids therein. With 7/8''
continuous rod 30, one might reduce the 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 casing in which 3-1/2'' production tubing 16 can no
longer be run downhole through the damaged area.
[0065] In embodiments, the smaller diameter tubing or cleanout
string 50 is 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 equipment D or
through service ports 52 provided in the wellhead 28.
[0066] Having reference to FIGS. 5A-5D, wellhead installations 28,
fluidly connected to the production tubing 16, can comprise the
service ports 52, such as 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 the production
annulus 18. PC pumps may require servicing, such as cleaning out by
flowing cleanout fluids therethrough. As a result of maximizing the
pass-by clearance in the production annulus 18, the smaller
diameter tubing 50, such as 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
production annulus 18 until the coiled tubing 50 reaches the
coupling 10 adjacent the uphole end 42 of the rotor 24. The coiled
tubing 50 is inserted into the production 18 annulus through the
variety of service ports 52 in the wellhead 28 and is lowered
therein adjacent the uphole end 42 of the rotor 24 after which
clean out fluids are provided therethrough.
[0067] Rod lock-out clamps, in most cases include BOP seals for
sealing the well from release of well fluids and gases as taught in
Applicant's issued Canadian patent 2,349,988, the entirety of which
is incorporated herein by reference, are known for gripping a
polished rod in a conventionally-driven pump installation. Relevant
aspects from Canadian Patent 2,349,988 have been extracted and
applied as follows.
[0068] Having references to FIGS. 6-9 and in embodiments of the
invention, 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 pump P connected thereto during
installation or servicing of the pump and drive components or
during connection of drive and other wellhead components
thereto.
[0069] The rod lockout clamp 160, 180 generally comprises a clamp
body 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 30 in the bore 164 and
manipulating means 184, such as bolts, for moving the clamp members
182 into gripping engagement with the continuous rod 30.
[0070] As shown in FIGS. 6 and 7, it may be preferable not to
restrict the 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 are prefereably made
undersize relative to the continuous rod 30 to enhance gripping
force. The pistons 182 further include O-rings 223 to provide a
better seal in the bore 164.
[0071] Having reference to FIGS. 8 and 9, where the clamp 180 is
integrated with a blow out preventer, the pistons 182 are made
substantially of metal so as to allow the pistons 182 to be forced
into engagement with the continuous rod 30 to 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 that of the continuous rod 30. Enhanced gripping
force is achieved if the arcuate recess diameter is undersized
relative to the continuous rod 30. A narrow elastomeric seal 188 is
provided which runs across the vertical flat surface of the 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 only the lower portion of the
piston if desired. The seal 188 compresses into grooves which
permit the pistons 182 to engage the continuous rod 30 in
metal-to-metal contact. The seals 188 seal between the pistons 182,
between the pistons 182 and the continuous rod 30 and between the
pistons 182 and the bores in which the pistons 182 are
installed.
[0072] Having reference to FIGS. 10A and 10B, gripping of the
continuous rod 30 with less surface damage can be accomplished by
several modifications, including minimizing a gap between the
pistons 182 in the gripping position, making 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 gripping surface tangential to the
gripping arc at about a 15 to 20 degree angle g and then forming
another arc tangential to the straight gripping surface at a radius
equal to the smallest continuous rod 30 to be gripped.
* * * * *