U.S. patent application number 14/481840 was filed with the patent office on 2015-03-12 for self-aligning, fluid-driven pumping unit.
The applicant listed for this patent is Pine Tree Gas, LLC. Invention is credited to Joseph A. Zupanick.
Application Number | 20150071794 14/481840 |
Document ID | / |
Family ID | 52625808 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150071794 |
Kind Code |
A1 |
Zupanick; Joseph A. |
March 12, 2015 |
SELF-ALIGNING, FLUID-DRIVEN PUMPING UNIT
Abstract
A reciprocating well pumping unit includes a fluid-driven
cylinder to drive a reciprocating rod assembly. A valve controls
fluid delivery to the cylinder, the valve having a valve spool
capable of being positioned in a first position or a second
position, the valve in the first position causing fluid flow that
allows the lifting rod to extend, the valve in the second position
causing fluid flow that allows the lifting rod to retract. A detent
assembly provides resistance to movement of the valve spool between
the second and first positions. A control rod is coupled to and
moves with the lifting rod. A spring is capable of storing energy
as the control rod is moved in the first direction and a rod stop
engages the spring, the spring engaging the valve spool as energy
is stored in the spring to urge the valve spool toward the first
position.
Inventors: |
Zupanick; Joseph A.;
(Pineville, WV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pine Tree Gas, LLC |
Pineville |
WV |
US |
|
|
Family ID: |
52625808 |
Appl. No.: |
14/481840 |
Filed: |
September 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61875561 |
Sep 9, 2013 |
|
|
|
Current U.S.
Class: |
417/362 ;
417/555.2 |
Current CPC
Class: |
F04B 47/028 20130101;
F04B 47/14 20130101; F04B 49/22 20130101 |
Class at
Publication: |
417/362 ;
417/555.2 |
International
Class: |
F04B 47/02 20060101
F04B047/02; F04B 49/22 20060101 F04B049/22; F04B 47/14 20060101
F04B047/14 |
Claims
1. A reciprocating well pumping unit comprising: a fluid-driven
cylinder adapted to be coupled to a reciprocating rod assembly, the
cylinder having a lifting rod capable of traveling between an
extended position and a retracted position; a valve capable of
controlling fluid delivery to the cylinder, the valve having a
valve spool capable of being positioned in a first position or a
second position, the valve in the first position causing fluid flow
that allows the lifting rod to extend, the valve in the second
position causing fluid flow that allows the lifting rod to retract;
a detent assembly providing resistance to movement of the valve
spool between the second position and the first position; a control
rod coupled to the lifting rod such that movement of the lifting
rod in a first direction results in movement of the control rod in
the first direction; a rod stop coupled to the control rod; and a
spring carried on the control rod and capable of engagement with
the rod stop, the spring capable of storing energy as the control
rod is moved in the first direction and the rod stop engages the
spring, the spring engaging the valve spool as energy is stored in
the spring to urge the valve spool toward the first position.
2. The reciprocating well pumping unit of claim 1, wherein when a
threshold amount of energy is stored in the spring, the detent
assembly permits the movement of the valve spool into the first
position.
3. The reciprocating well pumping unit of claim 1 further
comprising: a dampener operably associated with the valve spool or
the control rod to control a velocity of the valve spool or the
control rod.
4. The reciprocating well pumping unit of claim 1, wherein the
detent assembly further comprises: a detent seat having at least
one detent stop; at least one detent arm supporting a detent
bearing and being pivotally movable between an engaged position in
which the detent bearing engages the at least one detent stop and a
disengaged position in which the detent bearing becomes disengaged
from the at least one detent stop; a detent spring to bias the at
least one detent arm toward the engaged position.
5. The reciprocating well pumping unit of claim 4, wherein the at
least one detent stop is a recess or a projection disposed on the
detent seat.
6. The reciprocating well pumping unit of claim 1 further
comprising: a second rod stop coupled to the control rod; a second
spring carried on the control rod and capable of engagement with
the second rod stop, the second spring capable of storing energy as
the control rod is moved in the second direction and the second rod
stop engages the second spring, the second spring engaging the
valve spool as energy is stored in the second spring to urge the
valve spool toward the second position; wherein the detent assembly
provides resistance to movement of the valve spool between the
first position and the second position.
7. The reciprocating well pumping unit of claim 6 further
comprising: at least one dampener operably associated with the
valve spool or the control rod to control a velocity of the valve
spool or the control rod.
8. The reciprocating well pumping unit of claim 6, wherein the
detent assembly further comprises: a detent seat having a first
detent stop and a second detent stop; at least one detent arm
supporting a detent bearing and being pivotally movable between an
engaged position in which the detent bearing engages one of the
first and second detent stops and a disengaged position in which
the detent bearing becomes disengaged from the one of the first and
second detent stops; a detent spring to bias the at least one
detent arm toward the engaged position.
9. A reciprocating well pumping unit comprising: a beam assembly
pivotally attached to an anchor member that is fixed relative to a
well; a fluid-driven cylinder having a cylinder housing and a
cylinder rod, the cylinder rod capable of extending from or
retracting into the cylinder housing; and a traveling assembly
adapted to be coupled to a reciprocating rod assembly extending
into the well, the traveling assembly coupled to one of the
cylinder rod and the cylinder housing; wherein the beam assembly is
capable of pivoting during operation of the fluid-driven
cylinder.
10. The reciprocating well pumping unit of claim 9, wherein an axis
of rotation about which the beam assembly is capable of pivoting
intersects a longitudinal axis of the reciprocating rod
assembly.
11. The reciprocating well pumping unit of claim 10, wherein the
beam assembly is capable of lateral movement along the axis of
rotation during operation of the fluid-driven cylinder.
12. The reciprocating well pumping unit of claim 9, wherein the
anchor member is a wellhead of the well and the pivotal coupling
between beam assembly and the wellhead is located at a fluid port
of the wellhead.
13. The reciprocating well pumping unit of claim 12, wherein a
conduit is fluidly connected to the fluid port to allow fluid
communication between the conduit and a wellbore of the well.
14. The reciprocating well pumping unit of claim 9, further
comprising a fluid source fluidly connected to the cylinder
housing.
15. The reciprocating well pumping unit of claim 9, wherein the
beam assembly further comprises: a beam; and a base coupled to the
beam.
16. The reciprocating well pumping unit of claim 15, wherein the
beam is coupled to another of the cylinder rod and the cylinder
housing.
17. The reciprocating well pumping unit of claim 15, wherein the
base is coupled to another of the cylinder rod and the cylinder
housing.
18. The reciprocating well pumping unit of claim 15, wherein the
traveling assembly further comprises: a traveling head; a plurality
of rollers rotatingly coupled to the traveling head, the plurality
of rollers engaging the beam to allow the traveling head to travel
along the beam in a direction substantially parallel to the
movement of the reciprocating rod assembly.
19. The reciprocating well pumping unit of claim 15, wherein the
beam is an I-beam having a first flange and a second flange joined
by a transverse member.
20. The reciprocating well pumping unit of claim 19, wherein the
traveling assembly further comprises: a traveling head; and a
plurality of rollers rotatingly coupled to the traveling head, the
plurality of rollers engaging the beam to allow the traveling head
to travel along the beam; wherein a first and a second of the
plurality of rollers are each positioned on an opposing side of the
first flange of the beam.
21. The reciprocating well pumping unit of claim 9, wherein the
traveling assembly further comprises: a rotating member rotatingly
coupled to the one of the cylinder rod and the cylinder housing; a
flexible linkage having a first end coupled to the beam assembly
and a second end coupled to the reciprocating rod assembly; wherein
the rotating member engages the flexible linkage such that
extension or retraction of the cylinder rod moves the rotating
member thereby resulting in the lifting or lowering of the
reciprocating rod assembly.
22. The reciprocating well pumping unit of claim 21, wherein: the
rotating member is a sheave or a sprocket; and the flexible linkage
is a cable, a rope, or a chain.
23. The reciprocating well pumping unit of claim 9 further
comprising: a counter weight coupled to the beam assembly to
counteract at least a portion of the weight of the beam assembly
about the pivotal coupling of the beam assembly.
24. A reciprocating well pumping unit comprising: a fluid-driven
cylinder having a cylinder housing and a cylinder rod, the cylinder
rod capable of extending from or retracting into the cylinder
housing, one of the cylinder rod and the cylinder housing being
coupled to a reciprocating rod assembly extending into a well,
another of the cylinder rod and the cylinder housing being fixed
relative to the reciprocating rod assembly; a heat exchanger having
a first fluid pathway fluidly connected to the fluid-driven
cylinder, the first fluid pathway receiving a first fluid used to
drive the cylinder rod, the heat exchanger having a second fluid
pathway to receive a production fluid from the well; and a
temperature determination unit operably associated with either the
first or the second fluid pathway downstream of the heat exchanger
to determine a temperature of the production fluid following exit
of the production fluid from the heat exchanger; wherein the flow
of the first fluid to the fluid-driven cylinder is adjusted in
response to the temperature determination.
25. The reciprocating well pumping unit of claim 24, wherein the
temperature determination unit further comprises a temperature
sensor.
26. The reciprocating well pumping unit of claim 24, wherein the
temperature determination unit further comprises a temperature
switch.
27. The reciprocating well pumping unit of claim 24, wherein the
temperature switch is configured to turn off a pumping circuit,
thereby ceasing reciprocation of the reciprocating rod
assembly.
28. The reciprocating well pumping unit of claim 24, wherein when
the temperature is greater than or equal to a threshold
temperature, an operator is notified that pumping operations should
be ceased.
29. The reciprocating well pumping unit of claim 24, wherein the
one of the cylinder rod and the cylinder housing is coupled to the
reciprocating rod assembly by a traveling assembly.
30. The reciprocating well pumping unit of claim 24, wherein the
flow adjustment of the first fluid further comprises ceasing
delivery of the first fluid to the fluid-driven cylinder.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Application No. 61/875,561, filed Sep. 9, 2013, which
is hereby incorporated by reference.
BACKGROUND
[0002] The present disclosure relates to an improved type of
oilfield pumping unit used to reciprocate a down-hole rod pump.
Historically, conventional oilfield pumping units used a "walking
beam" pivoting on a ground-based support frame. The beam is rocked
back and forth by a crank arm connected to a rotary gear-drive. The
beam is typically connected to the rod string via a wire rope, and
the reciprocating motion of the beam provides the reciprocal
lifting and lowering of the rod string. These pumping units were
relatively large, massive structures, necessitated by the overhung
lifting loads.
[0003] More recently, hydraulically powered pumping units have
become increasingly popular. In one configuration, a linear motion
system employs a single hydraulic cylinder centered above or below
the polished rod. Often, a mast is used to suspend a single
hydraulic cylinder above the polished rod. The polished rod is
directly coupled to the cylinder, and hydraulic pressure applied to
the ring side of the piston causes the cylinder to retract, thus
lifting the rods. The mast can be attached to the ground, the
casing, or the tubing. Other configurations have employed an offset
cylinder with one or more pulley wheels are attached to the rod-end
of the cylinder. A wire rope passes across the pulley wheel such
that one rope end is attached to the rod string and the other end
is dead-lined. As the cylinder extends, the wire rope transmits a
lifting motion to the rod string.
SUMMARY
[0004] Described herein is a compact artificial lift hydraulic
pumping system providing simplified installation, longer life and
ease of maintenance. A beam is pivotally mounted to a wellhead,
ground, or other anchor structure, and one or more hydraulic
cylinders are asymmetrically mounted with respect to the beam. The
mounting is designed to pivot and slide about the pivot so as to
provide self-aligning lift forces to the down-hole pump rod string.
The self-aligning nature of the pump system eliminates side loads
on both the hydraulic cylinder and polished rod.
[0005] In some embodiments, the system comprises a beam
asymmetrical and parallel to the polished rod. The base of the beam
is pivotally or rigidly attached to the wellhead, tubinghead or
casing and one or more hydraulic cylinders are mounted parallel but
axially offset from the center of the pivoting beam. In some
embodiments, the end of the hydraulic cylinder is attached to a
traveling assembly that comprises a traveling head that rolls along
a track formed by the profile of the beam. The polished rod is
attached to the traveling head such that the reciprocating movement
of the hydraulic cylinders is thus coupled to cause a similar
movement of the rod string. In one embodiment, the traveling
assembly comprises a rotating member, such as a sprocket or sheave,
connected to the rod end of the hydraulic cylinder. The traveling
assembly further includes a flexible linkage, such as a chain,
cable, wire, or rope passing over the rotating member and providing
a lifting force to the polished rod.
[0006] Some embodiments require no elevated mast to suspend a
hydraulic cylinder above the polished rod. The entire pumping unit
may be assembled at ground-level, and then pivotally erected into
place. This can be done without the use of overhead lifting
equipment such as a crane or boom truck. Some embodiments may be
configured to lift the rods when hydraulic pressure is applied to
cap end of the hydraulic cylinder and the cylinder is extending. In
the prior art utilizing a single cylinder suspended above the well,
the ring side of the cylinder must be used to lift the rods on the
up-stroke. Since the ring side of the cylinder piston has less
surface area than the cap side, this configuration requires higher
hydraulic pressure to develop the force required to lift the
rods.
[0007] In some embodiments, it may be desirable to suspend the
hydraulic cylinder above the polished rod, using the retracting
cylinder force to lift the rods from the well. Here again, the unit
may be assembled at ground level and pivotally erected into
place.
[0008] The embodiments described herein also have a number of
inherent advantages over traditional hydraulic pumping units
configured with wire rope sheaves. In the prior art, the wire rope
often become a high wear item due to the physical limitations of
the size of the sheave. While conventional "walking beam" pumping
units are configured with a wire-rope bending radius of 70 inches
or more, the prior art hydraulic units are typically configured
with rope sheaves with a bending radius of 12 inches or less. This
small diameter bending radius severely reduces the life of the wire
rope, thus increasing maintenance cost, and increasing HSE risk due
to frequency of wire rope failures. In contrast, to the rigidly
mounted cylinders provided in the prior art, the embodiments
described herein allow use of larger radius sheaves due to the
freely pivoting nature of the cylinder attachment to the well
structure. In such a case, the angle of the cylinder with respect
to the polished rod would infinitely change as the cylinder passes
between the retracted and extended position.
[0009] Other advantages are present with respect to multiple
symmetrically arranged hydraulic cylinders. Some hydraulic pumping
units require two or more specially designed hydraulic cylinders
rigidly attached between upper and lower mounting plates, the
illustrative embodiments may utilize a single cylinder
configuration. Fewer cylinders would inherently reflect lower
initial cost, as well as lower future maintenance cost. Further
still, regardless of the number of hydraulic cylinders, these
embodiments may utilize low-cost, commodity type hydraulic cylinder
configured with pin and clevis end connections. These cylinders are
less expensive than custom-manufactured cylinders with a ridged
mounting base arrangement required in the prior art. In some
embodiments, the cylinders may be rigidly attached to a vertical
mounting beam at multiple points. Thus able to are better able to
handle column loading than the base-mounted cylinders found in the
prior art.
[0010] Still other advantages are present with respect to rigid
mounted cylinder configurations, whether that be single or multiple
cylinder configurations. Rigid mounting of the cylinders with
respect to the polished rod requires a high degree of accuracy in
manufacturing and installation so as to cause the lifting force to
be aligned parallel and congruent with the polished rod. Yet even
with such care, there may still be some slight misalignment. Such
misalignment of rigidly mounted cylinders will inherently cause
side loads and wear between the polished rod and the stuffing box,
and between the hydraulic cylinder rod and the cylinder rod
bushings. The gimbaled mounting presented in this illustrative
embodiment overcome these deficiencies by providing pivoting and
sliding degrees of freedom with respect to the wellhead mounting
pins, thus allowing the lifting force to be always transmitted
parallel to the polished rod.
[0011] The illustrative embodiments also overcome problems
associated with low pressure wellhead fixtures. In contrast to the
bolted flanged face tubing holder utilized in high pressure
wellheads, many low pressure wellheads utilize hammer union
pack-off assemblies, thus lacking any flat faced surfaces to which
a base plate or cylinder mounting assembly could be bolted or
fastened. The illustrative embodiments overcome that problem by
utilizing existing, symmetrically opposed wellhead piping ports as
a means of attachment.
[0012] Hydraulic pumping units require a directional shifting valve
to cyclically change the flow of oil and the directional motion of
the hydraulic cylinders. An electric limit switch that senses the
end of each stroke of the hydraulic cylinder may be used to shift a
solenoid operated hydraulic valve from one position to another. In
an improved system, mechanical controls linked to the movement of
the hydraulic cylinder travel may be utilized to shift a valve
spool from either the "up" or "down" position to the other. A
spring detent mechanism is required to snap the valve from one
position to the other so as to prevent the hydraulic directional
valve from being stuck in a center position where no oil flows to
the cylinder, preventing completion of the stroke. Unfortunately,
sudden reversal of direction of the cylinder caused by the snap
action of a spring detent mechanism on the valve can cause tensile
or buckling fatigue and failure of the down-hole rod string, in
addition to accelerated wear from the shock loads on the hydraulic
system. Soft shifting valve configurations can be used to reduce
the acceleration and deceleration forces at the beginning and end
of each stroke.
[0013] Hydraulic systems typically have an overall energy
efficiency of between 75%-85%. The loss of motive energy is
translated into heating of the hydraulic fluid. This heat must be
removed in order to prolong the life of the hydraulic components.
Fan-powered heat exchangers may be used to cool the hydraulic
fluid. In certain applications, particularly in shallow well
pumping applications, the volume of fluid pumped from the well may
be sufficient to dissipate this excess heat. In this situation, a
tube and shell heat exchanger may use the fluid pumped from the
well as a medium to dissipate the heat from the hydraulic fluid. A
temperature switch in the production fluid downstream of the heat
exchanger could be used as a "pump-off" controller. Production
fluid pumped from the well is normally at a constant temperature.
As such, a higher than normal temperature reading after the heat
exchanger would signal that the volume rate of the production fluid
from the well is decreasing, thus indicating the well is
approaching a pumped-off condition. This may trigger a control
circuit to set the pumping unit to an idle or off state.
Alternatively, a similar temperature monitoring circuit could
monitor the hydraulic fluid temperature for the same purpose. In
either case, a reset timer would be used to re-start the pump cycle
at a pre-determined interval.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following figures are included to illustrate certain
aspects of the present disclosure, and should not be viewed as
exclusive embodiments. The subject matter disclosed is capable of
considerable modifications, alterations, combinations, and
equivalents in form and function, without departing from the scope
of this disclosure.
[0015] FIG. 1 illustrates a profile view of a hydraulic pumping
unit in a vertical operating position according to an illustrative
embodiment, a traveling head assembly of the pump unit being near a
top of the stroke;
[0016] FIG. 2A illustrates a profile view of the pumping unit of
FIG. 1 in an assembly or well maintenance position;
[0017] FIG. 2B illustrates a top view of a mounting base attached
to a wellhead according to an illustrative embodiment;
[0018] FIGS. 3A, 3B and 3C illustrate front, partial front and
enlarged, and top views of a traveling head assembly according to
an illustrative embodiment;
[0019] FIGS. 4A and 4B illustrate profile and side views of a
pumping unit utilizing a roller chain to lift rods according to an
illustrative embodiments;
[0020] FIGS. 5A and 5B illustrate a profile view of a pumping unit
utilizing a mechanical spring and counter balance arrangements to
reduce the supplied energy to lift the rods according to an
illustrative embodiment;
[0021] FIGS. 6A and 6B illustrate profile views of a hydraulic
pumping unit in an operating position according to an illustrative
embodiment, the hydraulic pumping unit of FIG. 6A having a larger
diameter sheave or sprocket than that of FIG. 6B;
[0022] FIGS. 7A and 7B illustrate profile and top views a shifting
system for a hydraulic pumping unit;
[0023] FIG. 8 illustrates an enlarged exploded view of the shifting
system of FIG. 7A;
[0024] FIG. 9A illustrates an enlarge profile view of a plurality
of stationary components associated with the shifting system of
FIG. 7A;
[0025] FIG. 9B illustrates a top view of a mounting frame used to
mount the shifting system of FIG. 7A to a beam;
[0026] FIG. 9C illustrates an enlarged profile view of the shifting
system of FIG. 7A; and
[0027] FIG. 10 illustrates a schematic of a hydraulic circuit
associated with the shifting system of FIG. 7A.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0028] In the following detailed description of the illustrative
embodiments, reference is made to the accompanying drawings that
form a part hereof. These embodiments are described in sufficient
detail to enable those skilled in the art to practice the
invention, and it is understood that other embodiments may be
utilized and that logical structural, mechanical, electrical, and
chemical changes may be made without departing from the spirit or
scope of the invention. To avoid detail not necessary to enable
those skilled in the art to practice the embodiments described
herein, the description may omit certain information known to those
skilled in the art. The following detailed description is,
therefore, not to be taken in a limiting sense, and the scope of
the illustrative embodiments is defined only by the appended
claims.
[0029] Unless otherwise specified, any use of any form of the terms
"connect," "engage," "couple," "attach," or any other term
describing an interaction between elements is not meant to limit
the interaction to direct interaction between the elements and may
also include indirect interaction between the elements described.
In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to".
Unless otherwise indicated, as used throughout this document, "or"
does not require mutual exclusivity.
[0030] As used herein, the phrases "hydraulically coupled,"
"hydraulically connected," "in hydraulic communication," "fluidly
coupled," "fluidly connected," and "in fluid communication" refer
to a form of coupling, connection, or communication related to
fluids, and the corresponding flows or pressures associated with
these fluids. In some embodiments, a hydraulic coupling,
connection, or communication between two components describes
components that are associated in such a way that fluid pressure
may be transmitted between or among the components. Reference to a
fluid coupling, connection, or communication between two components
describes components that are associated in such a way that a fluid
can flow between or among the components. Hydraulically coupled,
connected, or communicating components may include certain
arrangements where fluid does not flow between the components, but
fluid pressure may nonetheless be transmitted such as via a
diaphragm or piston.
[0031] FIG. 1 shows one embodiment of the hydraulic pumping unit 10
configured in the operating position. The base 11 is pivotally
attached to a rigid part of the well structure 12. Shown here, the
base is pivoting on lugs 13 that are installed in unused ports of
the wellhead 14. These lugs 13 typically screw into wellheads 14
with 2 inch pipe threads. These threads can easily support the
reactive force generated by the hydraulic pumping unit in most
shallow well applications. Symmetrically opposed ports in the
tubing head 9 may be used as well. The hydraulic pumping unit 10
may also be supported by symmetrically opposed pipe nipples
carrying flow products from the well. For added strength, these
nipples can be thick-wall Schedule 80 or stronger pipe.
Alternatively, similar types of lugs can be welded or fastened to
the well casing or a ground mounted structure so as to provide an
alternate support to the pivoting base. The mounting lugs may be
positioned close to the ground so as to facilitate easy access for
installation and maintenance.
[0032] An upright beam 15 is rigidly attached to the base 11. In
the operating position, the beam is horizontally offset, but
approximately parallel with the polished rod 16. Typically, a
standard 6 or 8 inch wide-flange I-beam would be used for most
shallow well applications. In some embodiments, the beam 15 merely
acts as a guide for the traveling head assembly 17 and is not
subject to column loading. Light strength material such as aluminum
or fiberglass composite can be used instead of steel.
[0033] One or more hydraulic cylinders 18 are connected between the
base 11 and the head assembly 17. The length of the hydraulic
cylinder 18 determines the stroke of the pumping unit. The polished
rod load determines the required diameter of the hydraulic cylinder
and the system pressure. In some long stroke applications,
limitations on the buckling strength of the hydraulic cylinder rod
19 may be design criteria. Typically, a single 4 inch diameter
hydraulic cylinder would meet the design criteria for most shallow
well applications. Alternately, multiple cylinders can be
symmetrically arranged about the beam 15 to provide additional lift
capacity.
[0034] FIG. 2A shows a configuration of the hydraulic pumping unit
in the out-of-service position. When well-work is required, the
head assembly 17 may be detached from the polished rod 16, and the
pumping unit 10 allowed to pivot out of the way of any down-hole
operations. Initial assembly and future periodic maintenance of the
pumping unit would similarly occur in this lay-down position as
well. The unit would then be rotated back into the operating
position using either man-power, or a simple winching device.
[0035] FIG. 2B shows the top view of the base 11 pivoting on lugs
13. Pivot bushing 19 can be of any suitable bearing material, such
as brass or steel. Alternatively, other configurations may employ
roller or ball bearings to reduce wear. While the base 11 is
designed to pivot about one axis, a small amount of lateral
movement perpendicular to the pivot axis may be provided so as to
also accommodate small misalignment in that axis as well. The
movement of the base 11 about the non-pivoting axis may be through
sliding of the pivot bushing 19 along the pipe lugs 13, or through
a gimbaled or linear bearing assembly. As such, the entire pumping
unit has multiple degrees of freedom.
[0036] FIG. 3A shows the profile view of the head assembly of one
configuration of the pumping unit. This head assembly 17 is used to
transmit the force of the hydraulic cylinder rod 19 to the polished
rod 16. The head 17 assembly travels along a track formed by the
beam 15. Typically, rollers 20 would be used to reduce friction as
the head moves up and down along the beam 15. The rollers 20 can be
flanged so as to keep aligned with the edge of the beam 15.
Alternate configurations may include rollers that roll against both
front and back flanges of beam 15. The rollers 20 can be steel,
aluminum, polyurethane, nylon, or any other suitable material. To
minimize maintenance cost, replaceable rollers are preferably
designed to wear ahead of the beam 15.
[0037] FIG. 3B shows the detail of the attachment of the polished
rod 16 to the head assembly 17. In one configuration, a spherical
bearing 21 is used between the rod clamp 22 and the base plate 23
to allow for any misalignment in the travel of the head assembly
17. The base plate 23 is configured with a bearing holder 24 such
that bearings 21 may be easily replaced if necessary. Alternate
head bearing assembly configurations may also be employed to
similarly provide freedom of movement in either one or two axis.
The use of this head bearing assembly, in combination with the
pivot and slid bearing of the base, provide the geometry necessary
to eliminate side loads while lifting the polished rod 16.
[0038] FIG. 3C illustrates the top view of the head assembly 17. In
the illustrated configuration, normally the weight of the down-hole
rod string acting on the polished rod 16 keeps the rollers in
contact with the beam 15. At times when downward force is not
present, such as during installation or when the down hole pump
becomes "stacked-out", guide 25 and back-plate 26 serve to keep the
head assembly 17 from rotating beyond the flange face of the
rollers 27. Other roller or guide configurations could provide
similar function to keep the head assembly 17 aligned with the beam
15 at all times.
[0039] FIG. 4A shows an alternate configuration to the track
mounted traveling head arrangement previously described. Here, one
or more hydraulic cylinders 28 are rigidly attached to the beam 15.
Freely turning sprockets 29 or sheaves are attached to the
traveling portion of the cylinder 28. Because the entire hydraulic
pumping unit 30 can pivot in relation to the well structure, the
diameter of the sheave or sprocket 29 has no bearing on the angle
of force applied to the polished rod 16. In one embodiment, roller
chain 31 is connected to the bridle 32 to lift the polished rod 16.
The other end of the roller chain is "dead-lined" 33 and fastened
to the beam 15.
[0040] FIG. 4B reflects the front view of sprocket or sheave head
assembly. The vertical spacing of the rod clamp 34 to the polished
rod 16 is achieved through adjusting the point of attachment of the
cylinder mounting bracket 8 to the beam 15, and through changing
the length of the roller chain 31 attached to the bridle 32. In the
event of a failure of a single roller chain or wire rope, load
sensing circuits can be used to shut off the supply of hydraulic
fluid so as to prevent asymmetrical forces to the pumping unit.
[0041] FIG. 5A illustrates the counter-balancing of the off-center
mass of the pumping unit. For safety reasons, it is important to
provide some restraint of the pumping unit 34, in the event the
polished rod 16 fails, or some other instance that could allow the
pumping unit to unexpectedly fall away from the upright position. A
spring 35 may be used to counteract and balance the overhung load
of the pumping unit about the pivot point 37. This counter-balance
force may also be in the form of a counter weight 36 on the
opposite side of the pivot point 37. Alternately, if minimal pivot
movement is desired, a ridged or semi ridged attachment may be
employed in place of the spring 35 to restrain the hydraulic
pumping unit 34 to the well structure 12.
[0042] Energy efficient hydraulic circuits may be employed with the
hydraulic pumping units described herein. A charge of compressed
gas such as nitrogen may be used in the form of an accumulator to
balance the dead weight of the rod string. Another form of energy
savings applicable in this and other hydraulic pumping units is to
use one or more coil springs 38 to serve the same balancing
function as the hydraulic accumulator. In one embodiment, the
springs would be sized such that the average hydraulic energy
necessary to lift the polished rod 16 on the upstroke is identical,
but opposite that required to retract the pump on the down stroke.
For example, if the polished rod load is 10,000 lbs. during the
upstroke, and the dead weight of the rod string in the well is
5,000 lbs., the springs 38 would be sized to provide an average
lifting force of 7,500 lbs. This simple example ignores the
difference in force developed on the ring side and cap side of the
hydraulic cylinder. In practice, the ideal mechanical spring
configuration would attempt to make the hydraulic horsepower equal
on both the up stroke and the down stroke.
[0043] FIG. 5B illustrates how multiple springs 38 could be
installed to provide a lifting force to the head assembly 17 in
order to more evenly distribute the duty cycle of the hydraulic
system. Springs may be stacked, or concentrically arranged to
provide the desired force. Center core 39 provides lateral support
for the springs. Die springs are able to provide the millions of
cycles necessary for this type of application.
[0044] FIG. 6A illustrates the significant pivot motion of a
hydraulic pumping unit throughout the stroke cycle when using a
large diameter sheave or sprocket. Large diameter sheaves provide
longer life for wire rope. FIG. 6B illustrates a hydraulic pumping
unit with a sheave or sprocket sized to minimize pivot motion.
[0045] In contrast to the prior art, a simplified shifting and
control system is now presented. As illustrated in FIG. 7A, a
control rod 40 is attached through linkage 50 to the head assembly
47 so as to be indexed with the travel of hydraulic cylinder 28.
The control rod 40 is used to transmit the mechanical motion
necessary to shift the directional control valve 55 from one
position to the other. Adjustable position stops 44 attached to
control rod 40, acting on shift springs 43, are used to set the
actual point of directional change in relation to the stroke of
cylinder 28. In the up-stroke valve position, the pressurized
hydraulic line 57 delivering fluid from the hydraulic pump 58 and
is fluidly coupled to the lower end of the hydraulic cylinder 28,
causing the cylinder to extend. In the down-stroke valve position,
the lower end of the hydraulic cylinder 28 is fluidly connected to
the hydraulic fluid return path 59, thus returning hydraulic fluid
to the reservoir tank and allowing the cylinder to retract. The
speed of the up-stroke cylinder movement is dependent on the volume
rate of the hydraulic pump 58. Independently, the speed of the
falling cylinder may be controlled with a needle valve 60, an
over-balance valve, or other hydraulic control mechanisms.
[0046] FIG. 7B illustrates a top view through cross section AA of
FIG. 7A. As illustrated here, control rod 40 is connected to head
assembly 47 through linkage 50. The control rod 40 may be
positioned to run along any point of beam 15, here illustrated as
traveling within the flanges of an "I" beam.
[0047] FIG. 8 illustrates an exploded view of one embodiment
showing various components of a spring detent snap-action shift
mechanism. As illustrated, control rod 40 travels up and down
through shift tube 62, which in turn is free to travel within guide
tube 63. As the travel of control rod 40 begins to approach the
point representing the end of the hydraulic cylinder stroke,
control rod stop 44 begins to force the shift spring 43 against the
shift tube 62. Shift tube 62 in turn applies force, either directly
or indirectly to valve spool 41. To minimize wear on the valve
spool resulting from the millions of cycles of repeated shifting,
and in recognition of potential slight miss-alignment of the
shifting components, a non-ridged coupling of the shifting tube 62
to the valve spool 41 may be preferred.
[0048] Valve spool 41 is held in place by spring detent assembly
42, illustrated here in prospective view showing only one half of
the symmetrically arranged roller bearings that will seat in either
the upper detent seat or lower detent seat, each seat corresponding
to a respective valve position. The travel of control rod 40 causes
shift spring 43 to be compressed until such time there is
sufficient force to suddenly unseat detent mechanism. Once
unseated, compressed shift spring 43 begins to force valve spool 41
from the present position to the other. Instead of snapping quickly
to the alternate valve position, velocity control devices 45,
coupled to valve spool 41, dampens the stored energy of the
shifting spring 43, thus allowing the valve spool to travel slowly
and smoothly from one position to the other. Velocity control
device 45 may be an adjustable, variable orifice shock absorber,
commercially available to control the velocity of an object being
acted upon with an applied force. In a preferred embodiment, the
amount of time involved in the shifting process is between 1-5
seconds.
[0049] FIG. 9A illustrates one embodiment of a preferred mounting
arrangement of the various components of the hydraulic shifting
system. In this arrangement, stationary components including
directional control valve 55, guide tube 63, and velocity control
device 45 are rigidly attached to mounting frame 49, which in turn
mounts to a ridged structure of the hydraulic pump beam. As
illustrated, hydraulic directional control valve 55 is mounted to
the front face of mounting plate 52, while guide tube 63 is mounted
behind. FIG. 9B illustrates the mounting frame 49 attached to the
beam 15. Set screws 53 may be used to provide adjustable attachment
of mounting frame 49. As illustrated, mounting frame 49 is shown
mounted within the flanges of an "I"-beam. Control rod 40 is
illustrated passing behind mounting frame 49. FIG. 9C illustrates
the operation of the shift control mechanism with the addition of a
control lever 54 for manual activation of directional control valve
55.
[0050] While one embodiment of "soft" mechanical shifting of a
hydraulic directional control valve has been described herein, it
should be noted that other types of mechanical hydraulic control
could provide additional beneficial results. For instance, a valve
spool profile can configured so as to provide taper so as to create
a variable Cv factor as it travels from one position to the next.
In such a case, both valve spool position within the valve body and
valve spool geometry can provide non-linear velocity control as the
spool changes from one flow path to the other.
[0051] In yet another embodiment, two separate valves can be linked
to the movement of the hydraulic cylinder stroke such that one
valve provides variable flow control, and another separate valve
provides directional control. For instance, as the hydraulic
cylinder approaches the end of a stroke, a flow control valve
begins to progressively reduce the volume rate of fluid flowing to
the directional shifting valve. Based on the design of the control
valve, the reduction in flow can be in direct or variable
relationship to the position of the cylinder with respect to the
desired reversal point. An adjustable stop on the flow control
valve is used to set a minimum fluid volume rate so as to allow the
cylinder to "creep" slowly to the point where direction is
reversed. Similar to the function as previously described, a detent
used in combination with shifting springs would be used to shift a
separate directional control valve. Upon shifting direction, the
control valve would progressively open from "creep" for full open
position.
[0052] FIG. 10 illustrates one embodiment of a simplified hydraulic
circuit using a minimal number of hydraulic component. Electric
motor or other prime mover 69 is connected to drive hydraulic pump
58. Relief valve 71 is provided, but provides no operational
function other than for over-pressure safety issues. Two position
directional control valve 55 is positioned for either extending the
cylinder, or allowing the cylinder to retract. The valve is
illustrated in the extend-cylinder position. In this configuration,
fluid from reservoir tank 80 flows into the suction of the
hydraulic pump 58. It is noted that the reservoir tank 80 can be
either open to atmosphere, or a nitrogen charged accumulator so as
to assist with lifting the dead weight of the downhole rod string.
In either case, hydraulic fluid is discharged from the pump 58 and
flows through the by-pass of needle valve 74 into the base of
hydraulic cylinder 75, causing the cylinder to extend. For the
retract-cylinder phase of the cycle, directional control valve 55
shifts to a second position allowing hydraulic fluid from the
extended cylinder to return through needle valve 74, through valve
55, then ultimately to reservoir tank or accumulator 80. While
directional control valve 55 is in this retract position, hydraulic
fluid from the pump is similarly directed to the same common return
path as the fluid from the retracting hydraulic cylinder. As such,
the motor 69 and pump 58 are unloaded when hydraulic pressure isn't
needed, thus eliminating the need for expensive pressure
compensated, variable displacement pumps, as well as eliminating
repeated starting and stopping the motor pump combination.
[0053] The heat exchanger 76, necessary to maintain oil temperature
within operating limits, may be of tube and shell construction. In
contract to conventional air cooled-radiator type oil coolers,
tube-and shell oil coolers can be designed to handle the high
operating pressure of the hydraulic system. In one embodiment,
fluid pumped from the well may be used as the coolant. As
illustrated, heat exchanger 76 is located just prior to the
accumulator or tank 80. It is noted that the heat exchanger can be
located in most any flow path in the system.
[0054] While the embodiments described herein refer to the term
"hydraulic" when describing the motive fluid used to raise and
lower the cylinders, it should be noted that any type of fluid or
mechanical energy could be similarly employed to achieve the same
results, including pneumatic sources of energy. For example, an
internal combustion engine may be located at or near the location
of the pumping unit. In such a case, waste heat from the engine may
be converted into steam, either alone or combined with additional
input energy. This steam could be used to provide the fluid power
necessary to raise and lower the pumping unit. Alternate forms of
mechanical linear actuators may also be used to provide the lifting
force described herein as that produced by a hydraulic
cylinder.
[0055] It should be apparent from the foregoing that an invention
having significant advantages has been provided. While the
invention is shown in only a few of its forms, it is not limited to
only these embodiments but is susceptible to various changes and
modifications without departing from the spirit thereof.
* * * * *