Note: Descriptions are shown in the official language in which they were submitted.
PUMP JACK ASSEMBLY
FIELD OF THE INVENTION
[0001] The present disclosure relates to pump jack assemblies.
BACKGROUND OF THE INVENTION
[0002] Pump jacks are used to pump oil and fluids out of wells across the
world. Pump jacks are
powered by electric or fuel-powered engines connected to a transmission using
belts or
sheaves. The transmission turns a crank that rocks a horsehead back and forth.
The
rocking horsehead reciprocates a polished rod connected by sucker rods to a
downhole
pump. Oil is returned up the well tubing and gas returns through the annulus
between the
tubing and casing. Vertical stroke pumping systems like the RotaflexTM system
have been
developed as a replacement for pump jacks.
SUMMARY OF THE INVENTION
[0003] The disclosure that follows describes a pump jack assembly having an
improved
hydraulic power system for a driving a pump jack.
[0004] Objects of the present disclosure is to provide a pump jack assembly
with an improved
hydraulic power system that has less moving parts, less hydraulic oil, fewer
hydraulic
hose connections, is more efficient, and is a closed loop hydraulic system as
compared to
an open loop hydraulic system.
[0005] In general, in one aspect, a pump jack assembly is provided. The pump
jack assembly
includes a walking beam pivotally mounted to a frame, a horsehead attached to
a first end
1
Date Recue/Date Received 2021-07-22
of the walking beam, a lever arm attached to a second end of the walking beam,
and a
crank arm operatively attached to the lever arm, the crank arm having one or
more
counter-weights, wherein rotation of the crank arm causes the walking beam to
pivot and
rock the horse head. A hydraulic motor is operatively connected to the crank
arm to
rotating drive the crank arm. A hydraulic pump is operatively connected to the
hydraulic
motor to drive the hydraulic motor by a fluid supply line and a fluid return
line. A prime
mover is operatively connected to the hydraulic pump to drive the hydraulic
pump. And
the hydraulic pump having an internal hydraulic brake that operates to
restrict a flow of
hydraulic fluid through the hydraulic pump to prevent the hydraulic motor from
speeding
up between an upstroke and a down stroke of the crank arm.
[0006] Numerous objects, features and advantages of the present invention will
be readily
apparent to those of ordinary skill in the art upon a reading of the following
detailed
description of presently preferred, but nonetheless illustrative, embodiments
of the
present invention when taken in conjunction with the accompanying drawings.
The
invention is capable of other embodiments and of being practiced and carried
out in
various ways. Also, it is to be understood that the phraseology and
terminology employed
herein are for the purpose of descriptions and should not be regarded as
limiting.
[0007] As such, those skilled in the art will appreciate that the
conception, upon which this
disclosure is based, may readily be utilized as a basis for the designing of
other
structures, methods and systems for carrying out the several purposes of the
present
invention. It is important, therefore, that the claims be regarded as
including such
2
Date Recue/Date Received 2021-07-22
equivalent constructions insofar as they do not depart from the spirit and
scope of the
present invention.
[0008] For a better understanding of the invention, its operating
advantages and the specific
objects attained by its uses, reference should be had to the accompanying
drawings and
descriptive matter in which there are illustrated embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The following drawings illustrate by way of example and are included to
provide further
understanding of the invention for the purpose of illustrative discussion of
the
embodiments of the invention. No attempt is made to show structural details of
the
embodiments in more detail than is necessary for a fundamental understanding
of the
invention, the description taken with the drawings making apparent to those
skilled in the
art how the several forms of the invention may be embodied in practice.
Identical
reference numerals do not necessarily indicate an identical structure. Rather,
the same
reference numeral may be used to indicate a similar feature of a feature with
similar
functionality. In the drawings:
[0010] Figure 1 illustrates side schematic view of a pump jack assembly; and
[0011] Figure 2 illustrates a top, partial view of a connection between a
hydraulic motor and
crank arm of the pump jack assembly.
3
Date Recue/Date Received 2021-07-22
DETAILED DESCRIPTION OF THE INVENTION
[0012] Immaterial modifications may be made to the embodiments described here
without
departing from what is covered by the claims.
[0013] A pump jack (also called a nodding donkey, pumping unit, horsehead
pump, rocking
horse, beam pump, dinosaur, sucker rod pump, grasshopper pump, thirsty bird,
or jack
pump) is the overground drive for a reciprocating piston pump in an oil well.
Pump jacks
are used to mechanically lift liquid out of the well when there is not enough
bottom hole
pressure for the liquid to flow all the way to the surface. Pump jacks are
commonly used
for onshore wells producing little oil.
[0014] Depending on the size of the pump, a pump jack generally produces five
to forty litres of
liquid at each stroke. Often this is an emulsion of crude oil and water. Pump
size is also
determined by the depth and weight of the oil to remove, with deeper
extraction requiring
more power to move the increased weight of the discharge column (discharge
head).
[0015] A pump jack converts the rotary mechanism of a motor to a vertical
reciprocating motion
to drive the pump shaft and is exhibited in the characteristic nodding motion.
The
engineering term for such a mechanism is a walking beam.
[0016] Modern pump jacks are powered by a prime mover, which is an electric
motor or internal
combustion engine. Common off-grid pump jack engines run on casing gas
produced
from the well, but pump jacks have been run on many types of fuel, such as
propane and
4
Date Recue/Date Received 2021-07-22
diesel fuel. In harsh climates such motors and engines may be housed in a
shack for
protection from the elements.
[0017] The prime mover of the pump jack runs a set of pulleys or belts on
sheaves to the
transmission, which drives a pair of cranks, generally with counterweights on
them to
assist the motor in lifting the heavy string of rods. The cranks raise and
lower one end of
an I-beam which is free to move on an A-frame. Positioned on the other end of
the beam
is a curved metal box called a horse head or donkey head, so named due to its
appearance. A cable made of steel or fiberglass, called a bridle, connects the
horse head
to the polished rod, which is a piston that passes through the stuffing box.
[0018] The polished rod has a close fit to the stuffing box, permitting the
rod to move in and out
of the tubing without permitting fluid escape. The tubing is a pipe that runs
to the bottom
of the well through which the liquid is produced. The bridle follows the curve
of the
horse head as the head lowers and raises to create a nearly vertical stroke.
The polished
rod is connected to a long string of rods called sucker rods, which run
through the tubing
to the down-hole pump, usually positioned near the bottom of the well.
[0019] At the bottom of the tubing is a down-hole pump. This pump usually has
two check
valves: a stationary valve at bottom called the standing valve, and a valve on
the piston
connected to the bottom of the sucker rods that travels up and down as the
rods
reciprocate, known as the traveling valve. Reservoir fluid enters from the
formation into
Date Recue/Date Received 2021-07-22
the bottom of the borehole through perforations that have been made through
the casing
and cement.
[0020] When the rods at the pump end are traveling up, the traveling valve is
closed and the
standing valve is open (due to the drop in pressure in the pump barrel).
Consequently, the
pump barrel fills with the fluid from the formation as the traveling piston
lifts the
previous contents of the barrel upwards. When the rods begin pushing down, the
traveling valve opens and the standing valve closes (due to an increase in
pressure in the
pump barrel). The traveling valve drops through the fluid in the barrel (which
had been
sucked in during the upstroke). The piston then reaches the end of its stroke
and begins
its path upwards again, repeating the process.
[0021] Referring to FIGS. 1 and 2, a pump jack assembly 10 is illustrated,
having a horsehead
12, a polished rod 14, and a hydraulic motor 16. Horsehead 12 is mounted to
rock back
and forth on a frame such as an A-frame 18. Horsehead 12 may be connected to
frame 18
through a walking beam 20. Polished rod 14 is connected to horsehead 12 and
may be
inserted through a stuffing box (not shown) into a well 22. Rod 14 may connect
to
horsehead 12 through a carrier bar (not shown) and cables (not shown).
[0022] Hydraulic motor 16 is connected to rock the horsehead 12. In the
example shown,
hydraulic motor 16 connects to crank arm 24, having one or more counterweights
26,
through a belt and sheave assembly having a drive pulley 28, a driven pulley
30, and a
belt 32 connected therebetween. The hydraulic motor 16 is connected to the
drive pulley
28 by a conventional jackshaft 34 that is supported for rotating by bearings
36. While not
6
Date Recue/Date Received 2021-07-22
shown, a transmission may be connected between the hydraulic motor 16 and the
drive
pulley 28 or a transmission may be connected between the driven pulley and the
crank
arm 24. The crank arm 24 may connect to beam 20 through one or more lever arms
38.
[0023] Thus, hydraulic motor 16 is connected to transmit rotational energy to
crank arm 24,
which converts such energy into reciprocal motion of horsehead 12, thus
reciprocating
rod 14 in and out of the well 22.
[0024] Hydraulic motor 16 may form part of a hydraulic power system 40. System
40 may
include a hydraulic pump 42 and fluid supply and return lines 44 and 46,
respectively,
between the hydraulic pump and hydraulic motor 16 in a closed-loop hydraulic
connection. Pump 40 may be driven by a motor 48, which may be a diesel,
natural gas, or
electrical motor. In the example shown motor 48 is powered by gas takeoff from
well 22
through gas line 50. The motor 48 may be connected to the hydraulic pump 42
through a
transmission 52.
[0025] As further depicted, a hydraulic oil reservoir 54 may be connected to
the hydraulic pump
42 to supply hydraulic oil to the hydraulic pump. Additionally, an oil cooler
or radiator
56 may be connected to the hydraulic oil reservoir 54 and the hydraulic pump
42 and
operate to cool hydraulic oil circulating from the hydraulic pump to the
hydraulic oil
reservoir. An oil filter 58 may be connected between the radiator 56 and the
reservoir 54.
Further, a crankcase vent line 60 may be connected between the hydraulic motor
16 and
the hydraulic pump 42.
7
Date Recue/Date Received 2021-07-22
[0026] In certain embodiments, the hydraulic pump 42 may include an internal
hydraulic brake
62 that is operable to restrict flow speed of fluid returning from motor 16 to
the pump. In
a conventional pump jack assembly that contains a non-hydraulic motor,
rotational speed
of crank arm 24 speeds up as counterweights 26 being a downstroke from the
position
shown and slows down as counterweights 30 begin an upstroke. Such imbalanced
rotation wears down the belt and sheave system over time. However, in assembly
10
brake 62 restricts or eliminates motor 16 from speeding up or slowing down as
a result of
crank 24 action, thus serving to correct and restrict rotational imbalances
caused by
counterweights 26. Smoother operation results. The brake may be adjustable,
for example
depending on the balance of the weights 26 compared to the rod weight.
[0027] In certain embodiments, the hydraulic pump 42 may include an internal
flow control
valve 64 to provide variable speed drive. Flow control valve 64 may be used to
speed up
or slow down pump jack speed on demand, for example by adjusting the set
point. Thus,
pump jack speed can be sped up or slowed down in seconds, permitting the pump
speed
to be tailored to match the rate at which the well 22 is producing. By
contrast, speed
changes in a belt and sheave system may require manually changing the size of
the
sheaves. One of ordinary skill in the art can select a suitably powered a
hydraulic pump
42 to operate the hydraulic motor 16 to meet production demands. This
hydraulic pump
may include an internal hydraulic brake and/or a flow control valve. An
example of a
hydraulic pump may be a 90 Series hydrostatic pump made by Sauer.
[0028] Pump jack assembly 10 may be mounted at least partially on a pump jack
66 as shown. In
a conventional pump jack system, pad 66 mounts the prime mover or motor (not
shown).
8
Date Recue/Date Received 2021-07-22
In assembly 10, pad 66 may mount all, some, or none of the components of
hydraulic
system 40, thus providing flexibility in the location of components. In some
cases, the
components of system 40 may be provided on a separate skid or trailer (not
shown).
[0029] In some cases, a conventional pump jack assembly may be retrofitted
with hydraulic
motor 16 to produce assembly 10. For example, an existing non hydraulic pump
jack
motor may be replaced by hydraulic motor 16.
[0030] While the invention has been particularly shown and described with
respect to the
illustrated embodiments thereof, it will be understood by those skilled in the
art that the
foregoing and other changes in form and details may be made therein without
departing
from the spirit and scope of the invention.
9
Date Recue/Date Received 2021-07-22
