Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WELL SERVICE PUMP SYSTEM AND METHOD OF OPERATING THE SAME
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001]
This application claims priority to U.S. Provisional Application No.
62/664,080,
filed April 27, 2018, the entire contents of which application are
specifically incorporated by
reference herein without disclaimer.
BACKGROUND
1. Field of Invention
[0002]
The present invention relates generally to pumping assemblies used for well
servicing applications, most particularly pumping assemblies used for well
fracturing
operations.
2. Description of Related Art
[0003]
Oil and gas wells require services such as fracturing, acidizing, cementing,
sand
control, well control and circulation operations. All of these services
require pumps for
pumping fluid down the well. The type of pump that has customarily been used
in the industry
for many years is a gear driven plunger type, which may be referred to as a
"frac pump." The
pump is often powered by a diesel engine, typically 2,000 bhp or larger, that
transfers its power
to a large automatic transmission. The automatic transmission then transfers
the power through
a large driveline, into a gear reduction box mounted on the frac pump. The
frac pump has a
crankshaft mounted in a housing. A plunger has a crosshead that is
reciprocally carried in a
cylinder perpendicular to the crankshaft. A connecting rod connects each
eccentric portion or
journal of the crankshaft to the plunger. The driveline enters the frac pump
at a right angle to
the connecting rods, plungers and pump discharge. A typical pump might be, for
example, a
triplex type having three cylinders, three connecting rods, and three journals
on the crankshaft.
An example of a common type of a well service pump (e.g., plunger pump) is
disclosed in U.S.
Patent No. 2,766,701 to Giraudeau. Typical commercially available pumps
include the
Weir/SPMTm line of pumps, for example, the QWS 2500 ClassicTM Well Service
Pump and the
Destiny TWS2500Tm Well Service Pump.
[0004]
There are a number of known problems with the prior art plunger pumps of the
type
under consideration. These pumps will typically be mounted on a trailer or
skid back-to-back.
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The frac pumps are mounted at a right angle to the engine, transmission and
driveline. Each
pump has an outboard side connected to a manifold with valves for drawing in
and pumping
fluid acted on by the plunger. The inboard sides will be located next to each
other. The overall
width from one manifold to the other manifold should not exceed roadway
requirements,
e.g., Department of Transportation (DOT) rules and regulations. If the pumps
are to be trailer
mounted for highway transport, this distance will be on the order of about
eight and one half
feet. As a result, this necessarily means that the frac units which are
trailer mounted will be
restricted in size by the applicable DOT rules and regulations. The current
plunger stroke
length for present day frac pumps is typically 8 to 10 inches. However, in
order to meet DOT
requirements, some manufacturers have reduced the size of the pump, for
example reducing
the pump stroke, in some cases down to as much as four to six inches.
[0005] However, reducing the stroke length of the plungers is not an
ideal solution to the
problem and, in fact, offers a number of disadvantages in the design. Ideally,
it would be
desirable to lengthen the stroke of these pumps instead of shortening the
stroke length, in order
to reduce cycles per minute in use. This is due to the fact that there is a
tremendous failure rate
in current frac pump fluid ends, due to cyclic fatigue. The increased failure
rate results from
increased demand placed upon today's frac pumps, as compared to the practice
in prior years.
An example of a typical frac job in shale formations today would be a five
hour pump time.
During this pump time the plunger cycles would be, for example, 250 per minute
at 10,000 psi.
There has not been a great deal of change in the design of basic frac pumps
going back some
fifty years. However, the prior art designs of fifty years ago were intended
for frac jobs that
might last up to 2 hours. The unit would then typically be shut down until the
next day. During
today's frac jobs, for example in commonly encountered shale formations, the
units are
pumping 4-8 hours at higher pressures than in the past. The units are then
typically shut down
for an hour or two and then started up again for another stage for
approximately the same
duration. This type of operation may exceed the intended design limits of the
units.
[0006] It has also been attempted in the past, especially with the
larger oil field pumps, to
increase the stroke length by offsetting the crankshaft axis with the cylinder
axis. The offset is
selected so that during the power or output stroke, the centerline of the
crankshaft end of the
connecting rod will be located closer to the cylinder axis than the crankshaft
axis. Matzner et
al. disclose vertically offsetting the cylinder axis from the crankshaft axis
in U.S. Patent No.
5,246,355. It has also been attempted for the axis of the wrist pin of the
connecting rod to be
vertically offset from the cylinder axis to achieve the width requirements. An
example of a
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plunger pump having an offset wrist pin is disclosed in U.S. Patent No.
5,839,888 to Harrison.
However, these designs still suffer from all of the problems of having the
frac pump mounted
at a right angle to the engine, transmission and driveline. They also fail to
reduce the
mechanical complexity of the system and, in fact, likely increase the
complexity.
[0007] With prior art designs, it will be very difficult to increase the
plunger stroke length
much more than 10 to 12 inches. For example, increasing the stroke length by
one inch may
necessitate increasing total length of the frac pump by at least two inches
due to the crankshaft
design. This can put frac pumps in violation of DOT standards regarding the
width of the
trailer mounted frac unit, since the pump sits at a right angle to the engine,
transmission and
driveline.
[0008] Additionally, when one or more of the pump assemblies in prior
art pump arrays
ceased to be operational (e.g., due to binding, corrosion, or the like) such
that the non-
operational pump assembly/ies need to be taken offline, prior control systems
and
methodologies typically would require taking an entire set of pump assemblies
offline.
[0009] For these and other reasons, a need continues to exist for
improvements in oil and
gas well servicing pumps of the type under consideration.
SUMMARY
[0010] The present disclosure includes embodiments of pump systems and
methods.
[0011] Some embodiments of the present well service pump systems (e.g.,
for delivering
fracturing fluid at high pressure to a well) comprise: three or more working
fluid pump
assemblies, each comprising: a working fluid end cylinder having an end
cylinder housing, a
plunger rod configured to reciprocate in the end cylinder housing; and a
hydraulic ram cylinder
having a ram cylinder housing, a ram piston configured to reciprocate in the
ram cylinder
housing, and a piston rod coupled to the ram piston and coupled to the plunger
rod of the
working fluid end cylinder such that piston of the hydraulic ram cylinder can
be actuated to
move the plunger rod of the working fluid end cylinder: in a first direction
to expel working
fluid from the end cylinder housing during a forward stroke of the plunger
rod, and in a second
direction to draw working fluid into the end cylinder housing during a return
stroke of the
plunger rod; and a sensor configured to detect a parameter indicative of the
position of the
plunger rod of the working fluid end cylinder and/or the position of the ram
piston of the
hydraulic ram cylinder; one or more sources of hydraulic fluid configured to
selectively direct
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pressurized hydraulic fluid to each of the hydraulic ram cylinders to drive
the respective ram
piston in at least one of the first and second directions; a control system
coupled to the sensors
and configured to sequentially actuate the hydraulic ram cylinders to deliver
a continuous
output flow of the working fluid from the pump system to the well, the control
system further
configured to: determine how many of the working fluid pump assemblies are
operational; and
adjust the timing of actuation of each of the operational ones of the working
fluid pump
assemblies based on the number of operational working fluid pump assemblies.
[0012] In some embodiments of the present systems, the control system is
configured to:
adjust the timing of actuation of each of the operational ones of the working
fluid pump
assemblies based on the number of operational working fluid pump assemblies
relative to the
total number of working fluid pump assemblies.
[0013] In some embodiments of the present systems, the control system
comprises a
processor or programmable logic controller (PLC) configured to sequentially
actuate the
working fluid pump assemblies such that the hydraulic ram cylinder of a first
one of the
working fluid pump assemblies is beginning its forward stroke as the hydraulic
ram cylinder
of a second one of the working fluid pump assemblies is ending its forward
stroke. In some
embodiments of the present systems, the processor or PLC is configured to
sequentially actuate
the working fluid pump assemblies such that the hydraulic ram cylinder of a
third one of the
working fluid pump assemblies is beginning its forward stroke when the
hydraulic ram cylinder
of the first one of the working fluid pump assemblies is a fraction of the way
through its forward
stroke, where the fraction equals 1/(n-1), and n equals the number of
operational working fluid
end cylinders.
[0014] In some embodiments of the present systems, the three or more
working fluid pump
assemblies comprises six or more of the working fluid pump assemblies, and the
control system
is configured to control the working fluid pump assemblies in two sets each
with three or more
working fluid pump assemblies.
[0015] In some embodiments of the present systems, the control system is
configured to:
determine how many of the working fluid pump assemblies are operational in
each set; and
adjust the timing of actuation of each of the operational ones of the working
fluid pump
assemblies in each set based on the number of operational working fluid pump
assemblies in
the respective set, independently of the timing of the other set. In some
embodiments of the
present systems, the control system is further configured to, if one of the
sets has fewer than a
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threshold number of operational working fluid pump assemblies, not adjust the
timing of the
sets independently, and instead treat all operational working fluid pump
assemblies as a single
set for purposes of adjusting the timing of actuation of the operational ones
of the working fluid
pump assemblies. In some embodiments of the present systems, the threshold
number is 2.
[0016] In some embodiments of the present systems, the control system
comprises a
processor or programmable logic controller (PLC) configured to sequentially
actuate the
working fluid pump assemblies in each set such that the hydraulic ram cylinder
of a first one
of the operational working fluid pump assemblies is beginning its forward
stroke as the
hydraulic ram cylinder of a second one of the operational working fluid pump
assemblies is
ending its forward stroke. In some embodiments of the present systems, the
processor or PLC
is configured to sequentially actuate the working fluid pump assemblies in
each set such that
the hydraulic ram cylinder of a third one of the working fluid pump assemblies
is beginning its
forward stroke when the hydraulic ram cylinder of the first one of the working
fluid pump
assemblies is a fraction of the way through its forward stroke, where the
fraction equals 1/(n-
1), and n equals the number of operational working fluid end cylinders in the
set. In some
embodiments of the present systems, the processor or PLC is configured to
actuate each of the
working fluid pump assemblies, via adjustment of the source of pressurized
working fluid, such
that the duration of the forward stroke is twice the duration of the return
stroke.
[0017] In some embodiments of the present systems, the one or more
sources of hydraulic
fluid comprise: a plurality of bi-directional pumps, each coupled to a
respective one of the
working fluid pump assemblies such that the bi-directional pump is in fluid
communication
with the first hydraulic port and the second hydraulic port of the hydraulic
ram cylinder to
pump hydraulic fluid: from the second hydraulic port directly into the first
hydraulic port to
actuate the ram piston to drive the plunger rod in the first direction; and
from the first hydraulic
port directly into the second hydraulic port to actuate the ram piston to
drive the plunger rod in
the second direction.
[0018] Some embodiments of the present systems comprise a fluid
reservoir configured to
be in fluid communication with each of the plurality of bi-directional pumps
to compensate for
leakage in the system.
[0019] In some embodiments of the present systems, the ram piston of the
hydraulic ram
cylinder reciprocates within the hydraulic ram cylinder, the ram piston is, at
all times, spaced
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a distance from a first end wall of the hydraulic ram cylinder and a second
end wall of the
hydraulic ram cylinder opposite the first end wall.
[0020] Some embodiments of the present systems comprise a motor
configured to drive
each of the bi-directional pumps to direct fluid to the first and second
ports. Some
embodiments of the present systems comprise a pump drive coupled to the motor
and to each
of the bi-directional pumps, the pump drive configured to transfer mechanical
energy from the
motor to each of the bi-directional pumps. In some embodiments of the present
systems, at
least one of the bi-directional pumps is mounted to the pump drive. In some
embodiments of
the present systems, the motor comprises an electric motor and/or a combustion
engine.
[0021] In some embodiments of the present systems, for at least one of the
working fluid
pump assemblies, the ram piston has an actuatable piston surface area that is
at least two times
greater than an actuatable piston surface area of the plunger rod.
[0022] In some embodiments of the present systems, each working fluid
pump assembly
further comprises a coupling member coupled to the plunger rod of the working
fluid end
cylinder and to the piston rod of the hydraulic ram cylinder. In some
embodiments of the
present systems, in each working fluid pump assembly, the piston rod of the
hydraulic ram
cylinder is axially aligned with the plunger rod of the hydraulic ram
cylinder.
[0023] In some embodiments of the present systems, in each working fluid
pump assembly,
the working fluid end cylinder has a cylindrical inner wall and the plunger
rod has an outer
surface that is spaced apart from the cylindrical inner wall such that the
working fluid end
cylinder can pump abrasive fluids without the plunger rod and the cylinder
inner wall
simultaneously contacting individual particles in the working fluid.
[0024] In some embodiments of the present systems, at least one of the
hydraulic pumps
comprises a fixed-displacement hydraulic pump.
[0025] In some embodiments of the present systems, each working fluid pump
assembly
further comprises: an inlet check valve coupled to the fluid end cylinder and
configured to
permit working fluid to be drawn into the fluid end cylinder but prevent
working fluid from
exiting the fluid end cylinder through the inlet check valve; and an outlet
check valve coupled
to the fluid end cylinder and configured to permit working fluid to exit the
fluid end cylinder
while preventing working fluid from being drawn into the fluid end cylinder
through the outlet
check valve.
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[0026] In some embodiments of the present systems, for at least one of
the working fluid
pump assemblies, the working fluid is pressurized when it enters the fluid end
cylinder through
the inlet check valve.
[0027] Some embodiments of the present methods comprise delivering a
working fluid to
a well with a well service pump system comprising: at least three working
fluid pump
assemblies, each comprising: a working fluid end cylinder having a plunger rod
configured to
reciprocate within the fluid end cylinder; and a hydraulic ram cylinder having
a ram piston
configured to reciprocate within the hydraulic ram cylinder and a piston rod
coupled to the ram
piston and coupled to the plunger rod of the working fluid end cylinder;
wherein the hydraulic
ram cylinder includes a first hydraulic port on a first side of the ram piston
and second hydraulic
port on a second side of the ram piston; one or more sources of hydraulic
fluid configured to
selectively direct pressurized hydraulic fluid to each of the hydraulic ram
cylinders to drive the
respective ram piston in at least one of the first and second directions;
wherein delivering the
working fluid comprises, for each operational one of the working fluid pump
assemblies:
actuating the ram piston of the hydraulic ram cylinder to move the plunger rod
of the working
fluid end cylinder: in a first direction to expel working fluid from the fluid
end cylinder during
a forward stroke of the plunger rod, and in a second direction to draw working
fluid into the
fluid end cylinder during a return stroke of the plunger rod; and determining
how many of the
working fluid pump assemblies are operational; and timing actuation of each of
the operational
ones of the working fluid pump assemblies based on the determined number of
operational
working fluid pump assemblies.
[0028] Some embodiments of the present methods comprise identifying a
change in the
number of the working fluid pump assemblies that are operational; and
adjusting the timing of
actuation of each of the operational ones of the working fluid pump assemblies
based on the
number of operational working fluid pump assemblies.
[0029] In some embodiments of the present methods, the timing of
actuation of each of the
operational ones of the working fluid pump assemblies is set or adjusted based
on the number
of operational working fluid pump assemblies relative to the total number of
working fluid
pump assemblies. In some embodiments of the present methods, the working fluid
pump
assemblies are actuated such that the hydraulic ram cylinder of a first one of
the working fluid
pump assemblies is beginning its forward stroke as the hydraulic ram cylinder
of a second one
of the working fluid pump assemblies is ending its forward stroke. In some
embodiments of
the present methods, the working fluid pump assemblies are actuated such that
the hydraulic
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ram cylinder of a third one of the working fluid pump assemblies is beginning
its forward stroke
when the hydraulic ram cylinder of the first one of the working fluid pump
assemblies is a
fraction of the way through its forward stroke, where the fraction equals 1/(n-
1), and n equals
the number of operational working fluid end cylinders.
[0030] In some embodiments of the present methods, the three or more
working fluid pump
assemblies comprises six or more of the working fluid pump assemblies, the
working fluid
pump assemblies are actuated in two sets each with three or more working fluid
pump
assemblies, and determining and setting comprises: determining how many of the
working
fluid pump assemblies are operational in each set; and timing actuation of
each of the
operational ones of the working fluid pump assemblies in each set based on the
number of
operational working fluid pump assemblies in the respective set, independently
of the timing
of the other set.
[0031] Some embodiments of the present methods comprise detecting a
change in the
number of operational working fluid pump assemblies in each set; and adjusting
the timing
actuation of each of the operational ones of the working fluid pump assemblies
in each set
based on the number of operational working fluid pump assemblies in the
respective set,
independently of the timing of the other set. In some embodiments of the
present methods, if
one of the sets has fewer than a threshold number of operational working fluid
pump
assemblies, treating all operational working fluid pump assemblies as a single
set for purposes
of adjusting the timing of actuation of the operational ones of the working
fluid pump
assemblies. In some embodiments of the present methods, the threshold number
is 2.
[0032] In some embodiments of the present methods, the working fluid
pump assemblies
in each set are actuated such that the hydraulic ram cylinder of a first one
of the operational
working fluid pump assemblies is beginning its forward stroke as the hydraulic
ram cylinder
of a second one of the operational working fluid pump assemblies is ending its
forward stroke.
[0033] In some embodiments of the present methods, the working fluid
pump assemblies
in each set are actuated such that the hydraulic ram cylinder of a third one
of the working fluid
pump assemblies is beginning its forward stroke when the hydraulic ram
cylinder of the first
one of the working fluid pump assemblies is a fraction of the way through its
forward stroke,
where the fraction equals 1/(n-1), and n equals the number of operational
working fluid end
cylinders in the set.
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[0034] In some embodiments of the present methods, the working fluid
pump assemblies
are actuated such that the duration of the forward stroke is twice the
duration of the return
stroke.
[0035] In some embodiments of the present methods, the one or more
sources of hydraulic
fluid comprise a plurality of bi-directional pumps, each fluidly coupled to a
respective one of
the working fluid pump assemblies, and actuating each ram piston comprises:
directing
hydraulic fluid, via a corresponding bi-directional pump: from the second
hydraulic port
directly into the first hydraulic port to actuate the ram piston to drive the
plunger rod in the first
direction; and from the first hydraulic port directly into the second
hydraulic port to actuate the
ram piston to drive the plunger rod in the second direction.
[0036] Some embodiments of the present methods comprise actuating a
motor to drive each
of the bi-directional pumps to direct fluid to the first and second ports. In
some embodiments
of the present methods, the motor comprises an electric motor and/or a
combustion engine.
[0037] In some embodiments of the present methods, at least one of the
hydraulic pumps
comprises a fixed-displacement hydraulic pump.
[0038] The term "coupled" is defined as connected, although not
necessarily directly, and
not necessarily mechanically; two items that are "coupled" may be unitary with
each other.
The terms "a" and "an" are defined as one or more unless this disclosure
explicitly requires
otherwise. The term "substantially" is defined as largely but not necessarily
wholly what is
specified (and includes what is specified; e.g., substantially 90 degrees
includes 90 degrees and
substantially parallel includes parallel), as understood by a person of
ordinary skill in the art.
In any disclosed embodiment, the terms "substantially," "approximately," and
"about" may be
substituted with "within [a percentage] of' what is specified, where the
percentage includes .1,
1, 5, and 10 percent.
[0039] The phrase "and/or" means and or or. To illustrate, A, B, and/or C
includes: A
alone, B alone, C alone, a combination of A and B, a combination of A and C, a
combination
of B and C, or a combination of A, B, and C. In other words, "and/or" operates
as an inclusive
or.
[0040] The terms "comprise" (and any form of comprise, such as
"comprises" and
.. "comprising"), "have" (and any form of have, such as "has" and "having"),
"include" (and any
form of include, such as "includes" and "including"), and "contain" (and any
form of contain,
such as "contains" and "containing") are open-ended linking verbs. As a
result, an apparatus
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that "comprises," "has," "includes," or "contains" one or more elements
possesses those one
or more elements, but is not limited to possessing only those elements.
Likewise, a method
that "comprises," "has," "includes," or "contains" one or more steps possesses
those one or
more steps, but is not limited to possessing only those one or more steps.
[0041] Any embodiment of any of the apparatuses, systems, and methods can
consist of or
consist essentially of¨ rather than comprise/include/contain/have ¨ any of the
described steps,
elements, and/or features. Thus, in any of the claims, the term "consisting
of' or "consisting
essentially of' can be substituted for any of the open-ended linking verbs
recited above, in
order to change the scope of a given claim from what it would otherwise be
using the open-
ended linking verb.
[0042] The feature or features of one embodiment may be applied to other
embodiments,
even though not described or illustrated, unless expressly prohibited by this
disclosure or the
nature of the embodiments.
[0043] Further, a device or system that is configured in a certain way
is configured in at
least that way, but it can also be configured in other ways than those
specifically described.
[0044] Some details associated with the embodiments described above and
others are
described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 depicts a first perspective view of one embodiment of the
present well
service pump systems.
[0046] FIG. 2 depicts a second perspective view of the system of FIG. 1.
[0047] FIGs. 3 and 4 depict perspective views of various components of
the system of
FIG. 1.
[0048] FIGs. 5 and 6 depict first and second perspective views of
working pump
assemblies suitable for use with some embodiments of the system of FIG. 1.
[0049] FIG. 7 depicts a cross-sectional side view of an embodiment of
the working fluid
pump assemblies of FIGs. 5 and 6.
[0050] FIG. 8 depicts a schematic of a closed-loop hydraulic circuit,
suitable for use with
some embodiments of the system of FIG. 1.
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[0051] FIG. 9 depicts a flowchart of a methodology for timing the
actuation of operational
ones of a set of reciprocating pump assemblies, such as the working fluid pump
assemblies
depicted in FIG. 8, based on the number of operational pump assemblies.
[0052] FIG. 10 depicts a flowchart of a methodology for determining and
adjusting the
timing of actuation of operational ones of a set of reciprocating pump
assemblies, such as the
working fluid pump assemblies depicted in FIG. 8, based on the number of
operational pump
assemblies.
[0053] FIG. 11 depicts a flowchart of a methodology for determining
whether to merge
and merging operational ones of a set of reciprocating pump assemblies, such
as the working
fluid pump assemblies depicted in FIG. 8, based on the number of operational
pump
assemblies.
[0054] FIG. 12 depicts an exemplary actuation sequence for three
operational
reciprocating pump assemblies actuated as a single set in accordance with the
present
exemplary methodologies.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0055] The following drawings illustrate by way of example and not
limitation. For the
sake of brevity and clarity, every feature of a given structure is not always
labeled in every
figure in which that structure appears. Identical reference numbers do not
necessarily indicate
an identical structure. Rather, the same reference number may be used to
indicate a similar
feature or a feature with similar functionality, as may non-identical
reference numbers. The
figures are drawn to scale (unless otherwise noted), meaning the sizes of the
depicted elements
are accurate relative to each other for at least the embodiment depicted in
the figures.
[0056] Referring now to the figures, and more particularly, to FIGs. 1
and 2, shown therein
and designated by reference numeral 10 is an embodiment of the present well
service pump
systems for delivering working fluid at high pressure to a well. As shown,
system 10 can be
coupled to and carried by a vehicle 14 (e.g., a truck trailer) for
transportation to and from work
sites. In some embodiments, a system (e.g., 10) can be coupled to a skid frame
that can then
be loaded and offloaded from a vehicle (e.g., 14).
[0057] As shown, system 10 includes a motor 18, which is configured to
drive a plurality
of hydraulic pumps 22 (FIG. 3) to direct fluid as described in further detail
below. Motor 18
can include one or more sources of mechanical energy, such as a diesel engine,
gasoline engine,
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and/or an electric motor. In this embodiment, system 10 includes a pump drive
26, which is
coupled to motor 18 (via driveline 30) and each pump 22. Pump drive 26 is
configured to
transfer mechanical energy from motor 18 to each pump 22 one at a time or two
or more at a
time. As shown, each pump 22 is mounted directly onto pump drive 26.
[0058] System 10 includes a plurality of working pump assemblies 34, each
of which are
coupled to and actuatable by a respective pump 22 to deliver working fluid at
a high pressure
to a well. As shown, system 10 can include any suitable number of working pump
assemblies
34, such as two, three, four, five, six, seven, eight, nine, or ten
assemblies. As shown, each
assembly 34 can be mounted on a transport vehicle (e.g., 14) by one or more
vibration-
dampening mounts 38.
[0059] Referring additionally to FIGs. 5-7, one embodiment of the
present working pump
assemblies 34 is shown. As shown, assembly 34 includes a hydraulic ram
cylinder 42 and a
working fluid end cylinder 46. Working fluid end cylinder 46 includes a
plunger rod 50
disposed within a chamber 54 defined by the fluid end cylinder. Plunger rod 50
is configured
to reciprocate within chamber 54 to draw in working fluid into fluid end
cylinder 46 via an
inlet 58 and expel working fluid under high pressure to the well via an outlet
62. As shown in
FIG. 7, hydraulic ram cylinder 42 has a ram piston rod 66 disposed within a
chamber 70 defined
by the ram cylinder. Ram piston rod 66 is coupled to plunger rod 50 to actuate
the plunger rod
and supply the working fluid under pressure. For example, assembly 34 includes
a coupling
member 74, such as a bracket, coupled between piston rod 66 and plunger rod 50
such that
linear and/or rotational movement of the piston rod causes a matching linear
and/or rotational
movement of the plunger rod. Further, coupling member 74 is configured to
connect piston
rod 66 and plunger rod 50 such that the rods are axially aligned relative to
one another.
[0060] Plunger rod 50 has an outer diameter that is smaller than an
inner diameter of a
cylindrical inner sidewall 78 of working fluid end cylinder 46. As such,
plunger rod 50 is
received in spaced-apart fashion from sidewall 78 so that abrasive fluids may
be pumped
without undue wear on the plunger rod and/or sidewalls. For example, an
annular space
between an outer surface of plunger rod 50 and inner sidewall 78 of working
fluid end cylinder
46 is larger than the largest expected transverse dimension of any particle in
the working fluid
to prevent any single particle in the working fluid from simultaneously
contacting the outer
surface of the plunger and the inner sidewall of the working fluid end
cylinder.
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[0061] In the embodiment shown, plunger rod 50 is sealed within fluid
end cylinder 46 by
an end seal 82 that provides a tight seal around an outer surface of the
plunger rod and assists
with maintaining alignment of the plunger rod relative to the fluid end
cylinder. For example,
end seal 82 comprises a hydraulic seal that can be pressurized via a port
extending through
fluid end cylinder 46. Plunger rod 50 can have a length (measured from end
seal 82 to a distal
end of the plunger rod within chamber 54 of fluid end cylinder 46) that
exceeds 12 inches (e.g.,
exceeds 40 inches and/or is between 50 inches and 60 inches, such as 48
inches). The
maximum length of plunger rod 50 that extends into chamber 54 of fluid end
cylinder 46 is
termed a stroke length of the plunger rod.
[0062] Hydraulic ram cylinder 42 includes a ram piston 86 (FIG. 7) coupled
to ram piston
rod 66 and disposed within hydraulic ram cylinder 42. Contrary to plunger rod
50, ram piston
86 includes an outer diameter that fits closely and in a substantially sealed
relationship with a
cylindrical inner sidewall 90 of hydraulic ram cylinder 42. Ram piston 86 is
configured to be
actuatable to reciprocate within ram cylinder 42 such that the piston, via its
connection to piston
rod 66, can cause plunger rod 50 to move accordingly within fluid end cylinder
46. For
example, ram cylinder 42 comprises a first hydraulic port 94 on a first side
of ram piston 86
and a second hydraulic port 98 on a second side of the piston. Each hydraulic
port 94, 98 is
configured to receive hydraulic fluid from a respective pump 22 to actuate ram
piston 86 such
that the piston (via piston rod 66 and coupling member 74) move plunger rod 50
in a first
direction 102 to expel working fluid from fluid end cylinder 46 during a
forward stroke of the
plunger rod and in a second direction 106 to draw working fluid into the fluid
end cylinder
during a return stroke of the plunger rod. For example, in the depicted
embodiment, when
plunger rod 50 is in the forward stroke, the plunger rod occupies a majority
of the volume of
chamber 54, thereby reducing the volume available for working fluid within the
chamber and
thus forcing the working fluid out of fluid end cylinder 46 via outlet 62.
[0063] Ram piston 86 has a piston surface area 110 upon which hydraulic
fluid in chamber
70 can act to move the ram piston, and thus piston rod 66, in first direction
102 and plunger
rod 50 has a piston surface area 114 upon which working fluid in chamber 54
can act to move
the plunger rod in second direction 106. In this embodiment, piston surface
area 110 of at least
one ram piston 86 is greater than, such as approximately two or more times
greater than, piston
surface area of plunger rod 50.
[0064] Each pump 22 is configured to be driven by motor 18 to supply a
hydraulic fluid
under high pressure to first hydraulic port 94 and second hydraulic port 98 of
a respective ram
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cylinder 42. As shown in FIG. 8, each pump 22 can be fluidly coupled to a
respective working
fluid pump assembly 34 using a closed-loop hydraulic circuit 118. Further,
each pump 22 can
operate bi-directionally to actuate ram piston 86 in both first direction 102
and second direction
106. For example, each pump 22 is coupled to a respective ram cylinder 42 such
that the pump
.. is in fluid communication with each of first hydraulic port 94 and second
hydraulic port 98 of
the ram cylinder to pump hydraulic fluid from the second hydraulic port
directly into the first
hydraulic port to actuate ram piston 86 to drive plunger rod 50 in first
direction 102 (forward
stroke) and from the first hydraulic port directly into the second hydraulic
port to actuate the
ram piston to drive the plunger rod in second direction 106 (return stroke).
By using a closed-
loop hydraulic circuit 118 to actuate ram piston 86, and thereby actuate
plunger rod 50, less
hydraulic fluid is required for actuating assembly 34, as compared to a system
(e.g., 10) having
an open-loop hydraulic circuit.
[0065] At least one pump 22 can comprise a fixed-displacement hydraulic
pump. In some
embodiments, at least one pump (e.g., 22) can comprise a variable-displacement
hydraulic
pump. Each pump 22 direct fluid to ports 94, 98 at a variable flow rate.
[0066] In some embodiments, system 10 may include a hydraulic fluid
reservoir 122
configured to be in fluid communication with each pump 22 to compensate for
leakage and/or
other operational losses of hydraulic fluid in the system.
[0067] As shown, system 10 includes a working fluid end block 126 that
comprises, for
.. each assembly 34, an inlet 58 having an inlet check valve 130 fluidly
coupled to chamber 54
of fluid end cylinder 46 and configured to permit working fluid to be drawn
into the fluid end
cylinder but prevent working fluid from exiting the fluid end cylinder through
the inlet check
valve. In this embodiment, for at least one assembly 34, working fluid
directed to inlet 58 can
flow from an elevated tank and/or through a pump, such that the working fluid
is pressured
when it enters chamber 54 of fluid end cylinder 46 through inlet valve 130,
thereby urging
plunger rod 50 in its return stroke. In operation, inlet check valve 130
prevents working fluid
from exiting chamber 54 through inlet 58, thereby enabling working fluid to be
pressurized in
chamber 54 of fluid end cylinder 46 during the forward stroke of plunger rod
50.
[0068] In this embodiment, end block 126 comprises, for each assembly
34, outlet 62
having an outlet check valve 218 fluidly coupled to chamber 54 of fluid end
cylinder 46 and
configured to permit working fluid to exit the fluid end cylinder while
preventing working fluid
from being drawn into the fluid end cylinder through the outlet check valve.
In operation,
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outlet check valve 134 prevents working fluid that is pressurized downstream
of the outlet
check valve from entering chamber 54 of fluid end cylinder 46 during the
return stroke of
plunger rod 50 of assembly 34 and during the forward stroke of a plunger rod
(e.g., 50) of one
or more of the other working fluid pump assemblies (e.g., 34) of system 10.
[0069] As shown, system 10 comprises a suction manifold 138 fluidly coupled
to each inlet
check valve 130 of end block 126 to distribute working fluid to each of the
inlet check valves
in parallel. System 10 comprises a discharge manifold 142 coupled to each
outlet check valve
134 of end block 126 to collect working fluid from each of the outlet check
valves in parallel.
[0070] System 10 comprises a control system 146 having at least one
processor or
programmable logic controller (PLC) 150 and corresponding memory from which
instructions
can be retrieved and executed, one or more of which is configured to control
the operation of
each pump 22 (e.g., by executing instructions from the corresponding memory).
Control
system 146, and thus processor(s) 150 can be electronically coupled to each
pump 22 via wired
or wireless connection. Processor(s) 150 can be configured to control a
flowrate and/or
direction of hydraulic fluid flowing between each pump and its respective ram
cylinder 42. For
example, processor(s) 150 can be configured to control each pump 22 such that
it directs
hydraulic fluid, at any suitable flowrate, in a first direction from second
hydraulic port 98 to
first hydraulic port 94 and a second direction from the first hydraulic port
to the second
hydraulic port. Processor(s) 150 can be configured to control the frequency
and sequence at
which each pump 22 alternates the direction hydraulic fluid between the first
and second
directions such that system 10, via collective operation of the pumps,
delivers a continuous and
pulseless output flow of working fluid from fluid end cylinders 46 to the
well, as described in
paragraphs [0067]-[0069] and FIG. 16 of U.S. Publication US 2015/0192117,
which is hereby
incorporated by reference in its entirety.
[0071] In this embodiment, the length and rate at which each ram piston 86
completes its
forward and return strokes can be adjusted by one or more parameters of system
10. For
example, with the aid of one or more sensors 154 configured to collect data
indicative of the
position of ram piston 86 relative to ram cylinder 42, the length and rate of
the forward and
return strokes of each ramp piston can be adjusted by control system 146,
which can vary the
pressure and/or the rate at which hydraulic fluid is delivered to and removed
from each ram
cylinder 42. For example, assuming that hydraulic fluid is delivered at a
pressure that is
sufficient to move ram piston 86, the faster the hydraulic fluid is delivered
to first hydraulic
port 94 and/or removed from chamber 70 via second hydraulic port 98 by pump
22, the faster
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the ram piston will complete its forward stroke. Conversely, if it is more
advantageous for the
return stroke to be completed faster (have a shorter duration) than the
forward stroke, pump 22
can be controlled to more quickly deliver hydraulic fluid to second hydraulic
port 98 and/or
remove hydraulic fluid from chamber 70 via first hydraulic port 94.
[0072] The length and rate of the forward and return strokes of each ramp
piston 86 can be
adjusted to increase pump efficiency and/or reduce cyclic fatigue. For
example, to increase
pump efficiency, ram cylinder 42 and/or fluid end cylinder 46 can be elongated
to permit ram
piston 86 and/or plunger rod 50 additional travel within respective chambers
70, 54, thereby
allowing for more working fluid to be drawn into fluid end cylinder's chamber
and for more
working fluid to be expelled from the fluid end chamber into the well for
every stroke, as
compared to shorter ram cylinders and/or fluid end cylinders. Further, the
longer stroke length
can significantly reduce the number of strokes required to pump a given
volume, and thereby
reduce the rate at which plunger rod 50 must cycle, reducing fatigue and
extending fluid end
life. For further example, the return and forward stroke of each ram piston 86
can be controlled
(e.g., by control system 146) to prevent contact between the ram piston and
opposing interior
end walls 158 of ram cylinder 42. That is, when ram piston 86 reciprocates
within ram cylinder
42 during and between the forward and return strokes, the ram piston is, at
all times, spaced a
distance from a first interior end wall 158 of the ram cylinder and a second
interior end wall
158 of the ram cylinder opposite the first end wall.
[0073] Some embodiments of the present methods include delivering a working
fluid to a
well with a well service pump system (e.g., 10) comprising: at least two
working fluid pump
assemblies (e.g., 34), each comprising: a working fluid end cylinder (e.g.,
46) having a plunger
rod (e.g., 50) configured to reciprocate within the fluid end cylinder; and a
hydraulic ram
cylinder (e.g., 42) having a ram piston (e.g., 86) configured to reciprocate
within the hydraulic
.. ram cylinder and a piston rod (e.g., 66) coupled to the ram piston and
coupled to the plunger
rod of the working fluid end cylinder; wherein the hydraulic ram cylinder
includes a first
hydraulic port (e.g., 94) on a first side of the ram piston and a second
hydraulic port (e.g., 98)
on a second side of the ram piston; a plurality of bi-directional pumps (e.g.,
22), each fluidly
coupled to a respective one of the working fluid pump assemblies (e.g., 34);
wherein delivering
the working fluid comprises: actuating the ram piston of the hydraulic ram
cylinder to move
the plunger rod of the working fluid end cylinder: in a first direction (e.g.,
102) to expel
working fluid from the fluid end cylinder during a forward stroke of the
plunger rod, and in a
second direction (e.g., 106) to draw working fluid into the fluid end cylinder
during a return
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stroke of the plunger rod; and directing hydraulic fluid, via the bi-
directional pump: from the
second hydraulic port directly into the first hydraulic port to actuate the
ram piston to drive the
plunger rod in the first direction; and from the first hydraulic port directly
into the second
hydraulic port to actuate the ram piston to drive the plunger rod in the
second direction. Some
embodiments of the present methods additionally include actuating a motor
(e.g., 18) to drive
each of the bi-directional pumps to direct fluid to the first and second
ports. In some
embodiments of the present methods, the motor comprises an electric motor
and/or a
combustion engine. In some embodiments of the present methods, at least one of
the hydraulic
pumps comprises a fixed-displacement hydraulic pump.
[0074] FIG. 9 depicts a flowchart of a methodology 200 for timing the
actuation of
operational ones of a set of reciprocating pump assemblies, such as the
working fluid pump
assemblies described above and depicted in FIG. 8, based on the number of
operational pump
assemblies (i.e., the number of pump assemblies that are operating as
intended, or at least
acceptably, for example within a window of acceptable operational parameters
within which
the overall system exhibits acceptable performance). The methodology can be
implemented
manually or in an automated or semi-automated fashion via a processor or PLC
(e.g., 150). In
the depicted example, a step 204 involves determining how many of the working
fluid pump
assemblies are operational (e.g., and identifying a change in the number of
operational ones of
the pump assemblies). For example, while a set may include three pump
assemblies, one or
more of the pump assemblies may cease to be operational (e.g., due to binding,
corrosion, or
the like) such that the non-operational pump assembly/ies may need to be taken
off line. In
prior control methodologies, this typically would require taking an entire set
of pump
assemblies offline. However, in the present methodologies, the timing of
actuation of the
operational pump assemblies can be set and/or adjusted based on the number of
operational
.. pump assemblies (e.g., relative to the total number of working fluid pump
assemblies, such as
increasing the interval between actuation of respective pumps to account for a
decrease in the
number of operational pumps), such as at a step 208 as shown in FIG. 9. Once
set and/or
adjusted, the operational pump assemblies can begin or continue being
sequentially actuated in
accordance with the determining timing, such as at step 212.
[0075] FIG. 10 depicts a flowchart of a methodology 220 for determining and
adjusting the
timing of actuation of operational ones of a set of reciprocating pump
assemblies, such as the
working fluid pump assemblies depicted in FIG. 8, based on the number of
operational pump
assemblies. In the depicted example, the timing of actuation between
individual pumps is
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selected such that a first one of the working fluid pump assemblies is
beginning its forward
stroke as the hydraulic ram cylinder of a second one of the working fluid pump
assemblies is
ending its forward stroke (e.g., as shown in FIG. 12). This timing can be
accomplished by
beginning the forward stroke of the hydraulic ram cylinder of a third one of
the working fluid
pump assemblies when the hydraulic ram cylinder of the first one of the
working fluid pump
assemblies is a fraction of the way through its forward stroke, where that
fraction equals 1/(n-
1), and n equals the number of operational working fluid end cylinders. Thus,
in a set of three
such working fluid pump assemblies, the third piston begins its forward stroke
when the first
piston is halfway through its forward stroke and the second piston is at the
end of its forward
stroke. Similarly, in a set of four such working fluid pump assemblies, the
third piston begins
its forward stroke when the first piston is one third through its forward
stroke; a fourth piston
is two thirds through its forward stroke, and the second piston is at the end
of its forward stroke.
Thus, the depicted example methodology 220 includes a step 254 that involves
determining a
target interval stroke, and a step 258 of comparing that target interval
stroke to the current
interval stroke. If the two strokes are the same, the methodology proceeds to
step 262 of
maintaining the current stroke interval and may then loop back to step 254. If
the two strokes
are not the same, then the methodology 220 proceeds to step 266 of modifying
the current
stroke interval to the target stroke interval, and may then loop back to step
254.
[0076] In some instances, a system may include a sufficient number of
pump assemblies
for the pump assemblies to be actuated in sets. For example, such a system may
include six or
more of the working fluid pump assemblies that can be actuated in two sets,
each with three or
more pump assemblies. In system configurations with multiple sets of pumps, it
may be
advantageous to time the actuation of pumps in each set independently, for
example in
accordance with the methodologies described above, e.g., two sets of three
pump assemblies
each in which (as long as all pump assemblies are operational) the first pump
assemblies of the
two sets are actuated simultaneously, the second pump assemblies of the two
sets are actuated
simultaneously, and the third pump assemblies of the two sets are actuated
simultaneously. Of
course, given the present control methodologies, the sets may be actuated
differently if one of
the pump assemblies in one of the sets ceases to be operational. Additionally,
independent
actuation of separate may become difficult or impracticable (e.g., due to
increasing variations
in flow pattern) if one of the sets falls below a threshold number of
operational working fluid
pump assemblies.
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[0077] FIG. 11 depicts a flowchart of a methodology 380 for determining
whether to merge
and merging operational ones of a set of reciprocating pump assemblies, such
as the working
fluid pump assemblies depicted in FIG. 8, based on the number of operational
pump
assemblies. In the depicted example, methodology 280 includes a step 284 that
involves
determining the number of operational pump assemblies in each set. At a step
288, the number
of operational fluid pump assemblies is compared to a threshold (e.g., minimum
number of
operational pump assemblies to that will achieve acceptable performance in a
set) to determine
whether the number of operational fluid pump assemblies has fallen below the
threshold. The
threshold number may, for example, be two, three, four, or more operational
pump assemblies.
If not below the threshold, the current sets can be maintained, as shown at
step 292, and may
then loop back to step 284. If below the threshold, the independent sets (or
at least two of the
sets) can be functionally merged at step 296 such that the pump assemblies of
the merged sets
are thereafter actuated as a single set (e.g., 3 operational pump assemblies
in first set + 1
operational pump assembly in second set = 4 operational pump assemblies in
merged set), and
may then loop back to step 284.
[0078] FIG. 12 depicts an exemplary actuation sequence for three
operational reciprocating
pump assemblies actuated as a single set (e.g., one of multiple sets) in
accordance with the
present exemplary methodologies. As shown, at time "A," a first ram cylinder
(e.g., 42),
represented by line 42a, is halfway through its forward stroke and a second
ram cylinder (e.g.,
42), represented by line 42b, begins its forward stroke. At time "B," second
cylinder 42b is
halfway through its forward stroke and a third ram cylinder (e.g., 42),
represented by line 42c
beings its forward stroke. At time "C," first cylinder 42a has returned to top
dead center (TDC)
and is beginning a subsequent forward stroke. In use, the relative position of
ram piston 86 in
each respective ram cylinder (e.g., 42) is maintained during its forward
stroke such that, at any
given point in time at which one or more of the ram pistons are at TDC, one or
more of the
other ram pistons are at bottom dead center (BDC), and the any remaining ram
pistons are half
way in between TDC and BDC. In use, these relative positions result in a
relatively smooth
and pulseless delivery of fluid to discharge manifold 142 and to a well. For
example, in the
positions illustrated in FIG. 8, counting from left to right, the third and
sixth ram cylinders
(e.g., 42) are shown to have caused their respective fluid end cylinders
(e.g., 46) to stop
expelling working fluid into the discharge manifold 238, the first and fourth
ram cylinders (e.g.,
42) are shown to have begun to cause their respective fluid end cylinders
(e.g., 46) to start
expelling working fluid into the discharge manifold, and the second and fifth
ram cylinders
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(e.g., 42) are shown to be causing their respective fluid end cylinders (e.g.,
46) to expel working
fluid into the discharge manifold at a substantially constant rate. To
facilitate these relative
relationships between the pistons, the return stroke must be equal to or less
than one half of the
duration of the forward stroke. For example, when the second and fifth ram
cylinders (e.g.,
42) reach BDC, the first and fourth ram cylinders (e.g., 42) will be halfway
through their
forward stroke, and the third and sixth ram cylinders (e.g., 42) must be at
BDC and ready to
begin their forward stroke. Processor or PLC 150 can be configured to actuate
each assembly
34 (e.g., via adjustment of the source of pressurized working fluid, such that
the duration of the
forward stroke is twice the duration of the return stroke. For example, each
ram piston 86 can
.. be paused momentarily at TDC to enable the re-synchronization of the other
ram pistons (e.g.,
at any suitable frequency, such as, at every stroke). The illustrated
relationship corresponds to
a stroke length of 1/(n-1); specifically, with three pumps: 1/(3-1) = 1/2 such
that each piston
begins its forward stroke when the immediately preceding piston is one-half
through its forward
stroke.
[0079] The above specification and examples provide a complete description
of the
structure and use of illustrative embodiments. Although certain embodiments
have been
described above with a certain degree of particularity, or with reference to
one or more
individual embodiments, those skilled in the art could make numerous
alterations to the
disclosed embodiments without departing from the scope of this invention. As
such, the
.. various illustrative embodiments of the methods and systems are not
intended to be limited to
the particular forms disclosed. Rather, they include all modifications and
alternatives falling
within the scope of the claims, and embodiments other than the one shown may
include some
or all of the features of the depicted embodiment. For example, elements may
be omitted or
combined as a unitary structure, and/or connections may be substituted.
Further, where
appropriate, aspects of any of the examples described above may be combined
with aspects of
any of the other examples described to form further examples having comparable
or different
properties and/or functions, and addressing the same or different problems.
Similarly, it will
be understood that the benefits and advantages described above may relate to
one embodiment
or may relate to several embodiments. For example, embodiments of the present
methods and
systems may be practiced and/or implemented using different structural
configurations,
materials, ionically conductive media, monitoring methods, and/or control
methods.
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[0080] The claims are not intended to include, and should not be
interpreted to include,
means-plus- or step-plus-function limitations, unless such a limitation is
explicitly recited in a
given claim using the phrase(s) "means for" or "step for," respectively.
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