Note: Descriptions are shown in the official language in which they were submitted.
TORSIONAL COUPLING FOR ELECTRIC HYDRAULIC
FRACTURING FLUID PUMPS
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This technology relates to hydraulic fracturing in oil and gas wells.
In particular, this
technology relates to pumping fracturing fluid into an oil or gas well using
pumps powered by
electric motors.
2. Brief Description of Related Art
[0002] Typically, motors are used at a well site to drive equipment. For
example, diesel, gas, or
electric motors might be used to drive pumps, blenders, or hydration units for
carrying out
hydraulic fracturing operations. Such motors are attached to the well site
equipment by
connecting the shaft of the motor to a shaft on the equipment, such as a pump
shaft for a pump,
or a hydraulic motor shaft for a blender or a hydration unit. In order to
compensate for
misalignment between the motor and the equipment driven by the motor, a U-
joint shaft is
typically used. The U-joint shaft allows limited radial, angular, or even
axial misalignment
between the motor and the equipment, while still allowing mechanical
communication between
the shafts of the motor and the equipment to drive the equipment.
[0003] Use of U-joint shafts, however, can be problematic in practice. For
example, U-joint
shafts introduce inefficiencies into the system, losing up to 10% or more of
the energy that
would otherwise be transmitted from the motor shaft to the equipment.
Furthermore, a minimum
of 3 degrees of offset can be required between the motor and the equipment in
order for the U-
joint shaft to function properly. This offset leads to the need for a longer
shaft, which in turn
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..
leads to greater separation between the motor and the equipment. Such
separation can be
problematic in setup where space is limited, for example, where both the motor
and a pump are
mounted to a trailer or truck body.
SUMMARY OF THE INVENTION
[0004] The present technology provides a system for hydraulically fracturing
an underground
formation in an oil or gas well. The system includes a pump for pumping
hydraulic fracturing
fluid into the wellbore at high pressure so that the fluid passes from the
wellbore into the
formation and fractures the formation, the pump having a pump shaft that turns
to activate the
pump. The system further includes an electric motor with a motor shaft
mechanically attached to
the pump to drive the pump, and a torsional coupling connecting the motor
shaft to the pump
shaft. The torsional coupling has a motor component fixedly attached to the
motor shaft of the
electric motor and having motor coupling claws extending outwardly away from
the motor shaft,
and a pump component fixedly attached to .the pump shaft of the pump and
having pump
coupling claws extending outwardly away from the pump shaft. The motor
coupling claws
engage with the pump coupling claws so that when the motor shaft and motor
component rotate,
such rotation causes the pump component and the pump shaft to rotate, thereby
driving the
= pump.
[0005] In some embodiments, the pump component or the motor component can
further include
elastomeric inserts positioned between the pump coupling claws or the motor
coupling claws,
respectively, to provide a buffer therebetween and to absorb movement and
vibration in the
torsional coupling. In addition, the motor coupling claws and the pump
coupling claws can be
spaced to allow radial misalignment, axial misalignment, or angular
misalignment of the motor
component and the pump component while still allowing engagement of the motor
component
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and the pump component to transmit torque. Furthermore, the torsional coupling
can further
comprise a retainer cap attached to the motor component or the pump component
to cover the
interface therebetween and to prevent the ingress of debris or contaminates
between the motor
component and the pump component. The retainer cap can be removable from the
torsional
coupling to allow access to the inside of the coupling.
[0006] In some embodiments, the motor component can have a tapered central
bore for receiving
the motor shaft. In addition, the pump and the motor can be mounted on
separate but aligned
weldments. Alternatively, the pump and the motor can be mounted on a single
common
weldment pump and motor mounted on single weldment for ease of alignment and
stability.
[0007] Another embodiment of the present technology provides a system for
pumping hydraulic
fracturing fluid into a wellbore. The system includes a pump having a pump
shaft, an electric
motor having a motor shaft mechanically attached to the pump to drive the
pump, and a torsional
coupling connecting the motor shaft to the pump shaft. The torsional coupling
includes a motor
component fixedly attached to the motor shaft and having motor coupling claws
extending
outwardly away from the motor shaft, and a pump component fixedly attached to
the pump shaft
and having pump coupling claws extending outwardly away from the pump shaft.
The motor
coupling claws engage with the pump coupling claws so that when the motor
shaft and motor
component rotate, such rotation causes the pump component and the pump shaft
to rotate. In
addition, the motor coupling claws and the pump coupling claws are spaced to
allow radial
misalignment, axial misalignment, or angular misalignment of the motor
component and the
pump component, while still allowing engagement of the motor component and the
pump
component to transmit torque.
=
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[0008] In some embodiments, the pump component or the motor component further
include
elastomeric inserts positioned between the pump coupling claws or the motor
coupling claws,
respectively, to provide a buffer therebetween and to absorb movement and
vibration in the
torsional coupling. In addition, the torsional coupling can further include a
retainer cap attached
to the motor component or the pump component to cover the interface
therebetween and to
prevent the ingress of debris or contaminates between the motor component and
the pump
component. The retainer cap can be removable from the torsional coupling to
allow access to the
inside of the coupling.
[0009] In some embodiments, the motor component can have a tapered central
bore for receiving
the motor shaft. In addition, the pump and the motor can be mounted on
separate but aligned
weldments. Alternatively, the pump and the motor can be mounted on a single
common
weldment
[0010] Yet another embodiment of the present technology provides a system for
conducting
hydraulic fracturing operations in a well. The system includes hydraulic
fracturing equipment,
the hydraulic fracturing equipment selected from the group consisting of a
hydraulic fracturing
pump, a hydraulic motor of a blender, and a hydraulic motor of a hydration
unit, the hydraulic
fracturing equipment having a hydraulic fracturing equipment shaft. The system
further includes
an electric motor with a motor shaft mechanically attached to the hydraulic
fracturing equipment
to drive the hydraulic fracturing equipment, and a torsional coupling
connecting the motor shaft
to the hydraulic fracturing equipment shaft. The torsional coupling includes a
motor component
fixedly attached to the motor shaft of the electric motor and having motor
coupling claws
extending outwardly away from the motor shaft, and a hydraulic fracturing
equipment
component fixedly attached to the hydraulic fracturing equipment shaft of the
hydraulic
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fracturing equipment and having hydraulic fracturing equipment coupling claws
extending
outwardly away from the hydraulic fracturing equipment shaft. The motor
coupling claws
engage with the hydraulic fracturing equipment coupling claws so that when the
motor shaft and
motor component rotate, such rotation causes the hydraulic fracturing
equipment component and
the hydraulic fracturing equipment shaft to rotate, thereby driving the
hydraulic fracturing
equipment.
[0011] In some embodiments, the hydraulic fracturing equipment component or
the motor
component can further include elastomeric inserts positioned between the
hydraulic fracturing
equipment coupling claws or the motor coupling claws, respectively, to provide
a buffer
therebetween and to absorb movement and vibration in the torsional coupling.
In addition, the
motor coupling claws and the hydraulic fracturing equipment coupling claws can
be spaced to
allow radial misalignment, axial misalignment, or angular misalignment of the
motor component
and the hydraulic fracturing equipment component while still allowing
engagement of the motor
component and the hydraulic fracturing equipment component to transmit torque.
[0012] In some embodiments, the torsional coupling can further include a
retainer cap attached
to the motor component or the hydraulic fracturing equipment component to
cover the interface
therebetween and to prevent the ingress of debris or contaminates between the
motor component
and the hydraulic fracturing equipment component. In addition, the motor
component can have a
tapered central bore for receiving the motor shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present technology will be better understood on reading the
following detailed
description of nonlimiting embodiments thereof, and on examining the
accompanying drawing,
in which:
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[0014] Fig. 1 is a schematic plan view of equipment used in a hydraulic
fracturing operation,
according to an embodiment of the present technology;
[0015] Fig. 2A is a side view of a torsional coupling according to the present
technology with
the components of the coupling radially misaligned;
[0016] Fig. 2B is a side view of a torsional coupling according to the present
technology with the
components of the coupling angularly misaligned;
[0017] Fig. 2C is a side view of a torsional coupling according to the present
technology with the
components of the coupling axially misaligned;
[0018] Fig. 3 is a perspective view of the torsional coupling with the
components separated;
[0019] Fig. 4 is an end view of the torsional coupling according to an
embodiment of the present
technology;
[0020] Fig. 5 is a side cross-sectional view of the torsional coupling of Fig.
4 taken along the
line 5-5 in Fig. 4;
[0021] Fig. 6 is a side cross-sectional view of the torsional coupling
according to an alternate
embodiment of the present technology;
[0022] Fig. 7A is a side view of a motor according to an embodiment of the
present technology
with a part of the torsional coupling mounted to the motor shaft;
[0023] Fig. 7B is a side cross-sectional view of the part of the torsional
coupling shown in Fig.
7A, taken along line 7B-7B;
[0024] Fig. 8 is a perspective view of a motor and torsional coupling
according to an
embodiment of the present technology;
[0025] Fig. 9 is a side view of a motor and pump mounted to a single weldment;
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=
[0026] Fig. 10 is a schematic plan view of equipment used in a hydraulic
fracturing operation,
according to an alternate embodiment of the present technology;
[0027] Fig. 11 is a left side view of equipment used to pump fracturing fluid
into a well and
mounted on a trailer, according to an embodiment of the present technology;
and
[0028] Fig. 12 is a right side view of the equipment and trailer shown in Fig.
3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] The foregoing aspects, features, and advantages of the present
technology will be further
appreciated when considered with reference to the following description of
preferred
embodiments and accompanying drawing, wherein like reference numerals
represent like
elements. In describing the preferred embodiments of the technology
illustrated in the appended
drawing, specific terminology will be used for the sake of clarity. However,
the technology is not
intended to be limited to the specific terms used, and it is to be understood
that each specific
term includes equivalents that operate in a similar manner to accomplish a
similar purpose.
[0030] Fig. 1 shows a plan view of equipment used in a hydraulic fracturing
operation.
Specifically, there is shown a plurality of pumps 10 mounted to vehicles 12,
such as trailers (as
shown, for example, in Figs. 3 and 4). In the embodiment shown, the pumps 10
are powered by
electric motors 14, which can also be mounted to the vehicles 12. The pumps 10
are fluidly
connected to the wellhead 16 via the missile 18. As shown, the vehicles 12 can
be positioned
near enough to the missile 18 to connect fracturing fluid lines 20 between the
pumps 10 and the
missile 18. The missile 18 is then connected to the wellhead 16 and configured
to deliver
fracturing fluid provided by the pumps 10 to the wellhead 16. Although the
vehicles 12 are
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shown in Figs. 3 and 4 to be trailers, the vehicles could alternately be
trucks, wherein the pumps
10, motors 14, and other equipment are mounted directly to the truck.
100311 In some embodiments, each electric motor 14 can be an induction motor,
and can be
capable of delivering about 1500 horsepower (HP), 1750 HP, or more. Use of
induction motors,
and in particular three-phase induction motors, allows for increased power
output compared to
other types of electric motors, such as permanent magnet (PM) motors. This is
because three-
phase induction motors have nine poles (3 poles per phase) to boost the power
factor of the
motors. Conversely, PM motors are synchronous machines that are accordingly
limited in speed
and torque. This means that for a PM motor to match the power output of a
three-phase
induction motor, the PM motor must rotate very fast, which can lead to
overheating and other
problems.
[0032] Each pump 10 can optionally be rated for about 2250 horsepower (HP) or
more. In
addition, the components of the system, including the pumps 10 and the
electric motors 14, can
be capable of operating during prolonged putriping operations, and in
temperature in a range of
about 0 degrees C or less to about 55 degrees C or more. In addition, each
electric motor 14 can
be equipped with a variable frequency drive (VFD) 15, and an A/C console, that
controls the
speed of the electric motor 14, and hence the speed of the pump 10.
[0033] The VFDs 15 of the present technology can be discrete to each vehicle
12 and/or pump
10. Such a feature is advantageous because it allows for independent control
of the pumps 10
and motors 14. Thus, if one pump 10 and/or motor 14 becomes incapacitated, the
remaining
pumps 10 and motors 14 on the vehicle 12 or in the fleet can continue to
function, thereby
adding redundancy and flexibility to the system. In addition, separate control
of each pump 10
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and/or motor 14 makes the system more scalable, because individual pumps 10
and/or motors 14
can be added to or removed from a site without modification to the VFDs 15.
[0034] The electric motors 14 of the present technology can be designed to
withstand an oilfield
environment. Specifically, some pumps 10 cAn have a maximum continuous power
output of
about 1500 HP, 1750 HP, or more, and a maximum continuous torque of about 8750
ft-lb,
11,485 ft-lb, or more. Furthermore, electric motors 14 of the present
technology can include
class H insulation and high temperature ratings, such as about 1100 degrees C
or more. In some
embodiments, the electric motor 14 can include a single shaft extension and
hub for high tension
radial loads, and a high strength 4340 alloy steel drive shaft, although other
suitable materials
can also be used.
[0035] The VFD 15 can be designed to maximize the flexibility, robustness,
serviceability, and
reliability required by oilfield applications, such as hydraulic fracturing.
For example, as far as
hardware is concerned, the VFD 15 can include packaging receiving a high
rating by the
National Electrical Manufacturers Association (such as nema 1 packaging), and
power
semiconductor heat sinks having one or more thermal sensors monitored by a
microprocessor to
prevent semiconductor damage caused by excessive heat. Furthermore, with
respect to control
capabilities, the VFD 15 can provide complete monitoring and protection of
drive internal
operations while communicating with an operator via one or more user
interfaces. For example,
motor diagnostics can be performed frequently (e.g., on the application of
power, or with each
start), to prevent damage to a grounded or- shorted electric motor 14. The
electric motor
diagnostics can be disabled, if desired, when using, for example, a low
impedance or high-speed
electric motor.
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,
[0036] In some embodiments, the pump 10 can optionally be a 2250 HP triplex or
quintuplex
pump. The pump 10 can optionally be equipped with 4.5 inch diameter plungers
that have an
eight (8) inch stroke, although other size plungers can be used, depending on
the preference of
the operator. The pump 10 can further include additional features to increase
its capacity,
durability, and robustness, including, for example, a 6.353 to 1 gear
reduction, autofrettaged steel
or steel alloy fluid end, wing guided slush ,type valves, and rubber spring
loaded packing.
Alternately, pumps having slightly different specifications could be used. For
example, the
pump 10 could be equipped with 4 inch diameter plungers, and/or plungers
having a ten (10)
inch stroke.
[0037] In certain embodiments of the invention, the electric motor 14 can be
connected to the
pump 10 via a torsional coupling 152, of the type illustrated in Figs. 2A ¨
2C. Use of such a
torsional coupling 152 is advantageous compared to use of, for example, a U-
joint drive shaft to
connect the motor 14 to the pump 10, because the torsional coupling 152 is
more efficient. For
example, in a typical system, in which a pump is connected to and powered by a
diesel motor,
the pump may be connected to the diesel motor using a U-joint drive shaft.
Such drive shafts
typically require at least a 3 degree offset, and they may lose up to 10% or
more energy due to
inefficiencies. By replacing the U-joint drive shaft with a torsional coupling
152 in the system of
the present technology, this inefficiency can be reduced to 1% or less. In
addition, the torsional
coupling 152 allows for a shorter driveshaft than the U-joint drive shaft,
thereby requiring a
smaller space. Such space savings is valuable in particular for trailer or
truck mounted systems.
[0038] The torsional coupling 152 of the present technology compensates for
offset between a
motor shaft and a pump shaft by allowing for some misalignment of the coupling
components,
while still maintaining an operative relationship between the components. For
example, as
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shown in Fig. 2A, the pump component 154 of the coupling 152 can be radially
offset from the
motor component 156 of the coupling 152 by a radial distance R, and the two
components 154,
156 may still be engaged so that when the motor component 156 rotates it
causes rotation of the
pump component 154. In fact, in some embodiments, the radial distance R can be
up to 1.8 mm
or more.
[0039] Similarly, as shown in Fig. 2B, the pump component 154 can be angled
relative to the
motor component 156 of the coupling 152 at an angle 0, and the two components
154, 156 may
still be engaged. In some instances, the angle 0 may be up to about 0.33
degrees. In addition, as
shown in Fig. 2C, the pump component 154 can be axially separated from the
motor component
156 by a distance S, and the two components 154, 156 may still be engaged. In
some
embodiments, the components 154, 156 can be axially separated by an axial
distance S of up to
110 mm or more.
100401 Referring now to Fig. 3, there is shown an isometric view of the pump
component 154
and the motor component 156 of the coupling 152. The pump component 154
includes a
protrusion 158 extending perpendicularly outward toward the pump (not shown),
and which has
a bore 160 configured to receive the shaft with an interference fit so that
the pump component
154 transmits torque to the shaft of the pump when the pump component 154
turns. The pump
component 154 also includes pump coupling claws 162 that extend inwardly
toward the motor
component 156 of the coupling 152 when the coupling 152 is made up. The pump
coupling
claws 162 are spaced circumferentially around.the pump component 154. In some
embodiments,
such as that shown in Fig. 3, there can be six pump coupling claws 162, but
any appropriate
number can be used.
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[0041] In addition to the above, the pump component 154 of the coupling 152
can include
elastomeric inserts 164 surrounding at least a portion of the pump coupling
claws 162 to provide
a buffer between the pump coupling claws 162 of the pump component 154 and
corresponding
claws on the motor component 156. Such a buffer is advantageous to increase
the ability of the
coupling 152 to withstand shocks and vibrations associated with the use of
heavy duty equipment
such as hydraulic fracturing pumps. It is advantageous, when making up the
coupling 152, to
ensure that the components 154, 156 of the coupling are not mounted too far
away from each
other in and axial direction, so that the elastomeric inserts can transmit
torque over the entire
width of the inserts.
[0042] Also shown in Fig. 3 is an isometric view of the motor component 156
according to an
embodiment of the present technology. The motor component 156 includes a
protrusion 166
extending perpendicularly outward toward the motor (not shown), and which has
a bore 168.
The bore 168 engages the shaft of the motor with an interference fit, so that
the motor component
156 receives torque from the shaft of the motor. In some embodiments, the
shaft may be tapered,
as described in greater detail below. This taper helps, among other things, to
properly set the
depth of the motor shaft relative to the motor component 156 when making up
the coupling 152.
The interference fit of the pump shaft and the motor shaft into the pump and
motor components
154, 156 of the coupling 152 can be achieved by heating the pump and motor
components 154,
156 to, for example, about 250 degrees Fahrenheit, and installing the
components on their
respective shafts while hot. Thereafter, as the pump and motor components 154,
156 cool, the
inner diameters of the bores 160, 168 in the pump and motor components 154,
156 decrease,
thereby creating an interference fit between the pump and motor components
154, 156 and the
pump and motor shafts, respectively.
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[0043] The motor component 156 also includes motor coupling claws 170 that
extend inwardly
toward the pump component 154 of the coupling 152 when the coupling 152 is
made up. The
motor coupling claws 170 are spaced circumferentially around the motor
component 156 so as to
correspond to voids between the pump coupling claws 162 and elastomeric
inserts 164 when the
coupling 152 is made up. In some embodiments, a retainer cap 172 can be
included to cover the
interface between the pump component 154 and the motor component 156, to
protect, for
example, the coupling 152 from the ingress of foreign objects or debris. The
retainer cap 172
can be integral to the pump component 154 or it can be a separate piece that
is fastened to the
pump component 154.
[0044] Thus, when the coupling 152 is made up, the motor shaft, which is
inserted into the bore
168 of the motor component 156, can turn and transmit torque to the motor
component 156 of
the coupling 152. As the motor component 156 of the coupling 152 turns, the
motor coupling
teeth 170 transmit torque to the pump coupling teeth 162 through the
elastomeric inserts 164.
Such torque transmission in turn causes the pump component 154 of the coupling
152 to turn,
which transmits torque to the pump shaft engaged with the bore 160 of the pump
component
154. The transmission of torque through the coupling 152 occurs even if the
motor component
156 and the pump component 154 are radially offset, positioned at an angle to
one another, or
separated by an axial distance, as shown in Figs. 2A-2C.
[0045] Referring now to Fig. 4, there is shown an end view of the coupling 152
looking from
the pump side of the coupling 152 toward the motor. In particular, there is
shown the pump
component 154 of the coupling 152, including the protrusion 158 and the bore
160 for receiving
the pump shaft. In the embodiment of Fig. 4, the retainer cap 172 is a
separate piece from the
pump component 154, and is attached to the pump component 154 with fasteners
174. In this
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=
embodiment shown, the fasteners 174 are shown to be bolts, but any appropriate
fasteners could
be used. Provision of a removable retainer cap 172 can be advantageous because
it allows easier
access to the interior components of the coupling 152 for servicing or repair.
For example, if an
operator desires to replace the elastomeric inserts 164 within the coupling
152, it need only
remove the retainer cap 172, after which it can easily replace the elastomeric
inserts 164.
[0046] Fig. 5 shows a cross-sectional view of the coupling 152 of Fig. 3,
taken along line 5-5.
As shown in Fig. 5, the bore 168 in the prOtrusion 166 of the motor component
156 of the
coupling 152 can be tapered from a smaller diameter at an inward side 176 of
the motor
component 156 (toward the pump component 154) to a larger diameter at an
outward side 178 of
the motor component (toward the motor). The tapered diameter of the bore 168
corresponds to a
similarly tapered end of the motor shaft, and helps with torque transmission
and depth setting of
the motor shaft relative to the coupling 152 when the coupling 152 is made up.
[0047] Fig. 6 shows a cross-sectional view of the coupling 152 according to an
alternate
embodiment of the present technology, and including the motor shaft 180 and
pump shaft 182.
In addition, in the view shown in Fig. 6, there is shown the elastomeric
inserts 164 in the
coupling. Furthermore, the embodiment shown in Fig. 6 differs from that shown
in Fig. 5 in that
the retainer cap 172 is integral to the pump component 154 (as opposed to
being a separate piece,
as depicted in Figs. 4 and 5).
[0048] Fig. 7A shows the motor component 156 of the coupling 152 attached to a
motor 14. As
can be seen, the motor shaft 180 extends outwardly from the motor 14 and into
engagement with
the motor component 156. Fig. 7B shows how the end of the motor shaft 180 is
tapered so that it
fits within the tapered bore 168 of the motor component 156. With the motor
shaft 180 thus
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engaged with the motor component 156, the motor shaft 180 transmits torque to
the motor
component 156 as the shaft 180 turns, thereby turning the motor component 156
as well.
[0049] Referring now to Fig. 8, there is shown a motor 14 according to an
embodiment of the
present invention, and a coupling 152. There is also shown a protective cage
184 surrounding
the coupling 152. The protective cage provides the advantage of protecting the
coupling 152
from damage. In addition, the protective cage 184 can have a removable panel
185, or can
otherwise be removable, to allow access to the coupling for repair and
maintenance.
[0050] The coupling 152 of the present technology can be built out of any
suitable materials,
including composite materials, and is designed to allow for high torsional
forces. For example,
the torque capacity of the coupling could be up to about 450,000 lb-in. In
addition, when the
motor, pump, and associated coupling 152 are mounted to a trailer, truck,
skid, or other
equipment, various sized shim plates can be used to allow for more precise
positioning of the
equipment, thereby leading to appropriate alignment of the shafts and coupling
components.
Support brackets may also be provided to fix the motor and the pump in place
relative to the
trailer, truck, skid, or other equipment, thereby helping to maintain such
alignment.
[0051] Furthermore, the pump and motor mounting may be separate weldments, or,
as shown in
Fig. 9, they may alternatively be a combined single weldment 187. If they are
a single weldment
187, the mounting faces can be machined, leveled, and planar to each other to
increase the
accuracy of alignment. Attaching the motor 14 and pump 10 to a single weldment
187 can be
advantageous because it can improve alignment of the components, which can
lead to reduced
torsional stresses in the coupling. Mounting the motor 14 and pump 10 to a
single weldment 187
also helps to ensure that during transport or operation, the motor 14 and pump
10 are moved
together, so that alignment of the coupling halves can be better maintained.
In embodiments
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using separate weldments, the motor 14 can move independently of the pump 10,
thereby
causing a misalignment of the components, and possible damage to the coupling.
In addition, the
separate weldments can have a greater tendency to warp, requiring additional
effort to get the
alignment in the acceptable range.
[0052] Use of the coupling 152 complements the combination of a triplex,
plunger pump, and an
electric motor 14, because such a pump 10 and motor 14 are torsionally
compatible. In other
words, embodiments using this pump 10 and motor 14 are substantially free of
serious torsional
vibration, and vibration levels in the pump input shaft and in the coupling
152 are, as a result,
kept within acceptable levels.
[0053] For example, experiments testing the vibration of the system of the
present technology
have indicated that, in certain embodiments, the motor shaft vibratory stress
can be about 14% of
the allowable limit in the industry. In addition, the coupling maximum
combined order torque
can be about 24% of the allowable industry limit, vibratory torque can be
about 21% of the
allowable industry limit, and power loss can be about 25% of the allowable
industry limit.
Furthermore, the gearbox maximum combined order torque can be about 89% of the
standard
industry recommendations, and vibratory torque can be about 47% of standard
industry
recommendations, while the fracturing pump input shaft combined order
vibratory stress can be
about 68% of the recommended limit.
[0054] The coupling 152 can further be used to connect the motor shaft 180
with other
equipment besides a pump. For example, the coupling 152 can be used to connect
the motor to a
hydraulic drive powering multiple hydraulic motors in a hydration unit, or
associated with
blender equipment. In any of these applications, it is advantageous to provide
a protective cage
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around the coupling 152, and also to provide an easy access panel in the
protective cage to
provide access to the coupling 152.
[0055] In addition to the above, certain embodiments of the present technology
can optionally
include a skid (not shown) for supporting some or all of the above-described
equipment. For
example, the skid can support the electric motor 14 and the pump 10. In
addition, the skid can
support the VFD 15. Structurally, the skid can be constructed of heavy-duty
longitudinal beams
and cross-members made of an appropriate material, such as, for example,
steel. The skid can
further include heavy-duty lifting lugs, or eyes, that can optionally be of
sufficient strength to
allow the skid to be lifted at a single lift point., It is to be understood,
however, that a skid is not
necessary for use and operation of the technology, and the mounting of the
equipment directly to
a vehicle 12 without a skid can be advantageous because it enables quick
transport of the
equipment from place to place, and increased mobility of the pumping system.
[0056] Referring back to Fig. 1, also included in the equipment is a plurality
of electric
generators 22 that are connected to, and provide power to, the electric motors
14 on the vehicles
12. To accomplish this, the electric generators 22 can be connected to the
electric motors 14 by
power lines (not shown). The electric generators 22 can be connected to the
electric motors 14
via power distribution panels (not shown). In certain embodiments, the
electric generators 22
can be powered by natural gas. For example, the generators can be powered by
liquefied natural
gas. The liquefied natural gas can be converted into a gaseous form in a
vaporizer prior to use in
the generators. The use of natural gas to power the electric generators 22 can
be advantageous
because above ground natural gas vessels 24 can already be placed on site in a
field that
produces gas in sufficient quantities. Thus, a portion of this natural gas can
be used to power the
electric generators 22, thereby reducing or eliminating the need to import
fuel from offsite. If
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desired by an operator, the electric generators 22 can optionally be natural
gas turbine generators,
such as those shown in Fig. 10. The generators can run on any appropriate type
of fuel,
including liquefied natural gas (LNG).
[0057] Fig. 1 also shows equipment for transporting and combining the
components of the
hydraulic fracturing fluid used in the system of the present technology. In
many wells, the
fracturing fluid contains a mixture of water, sand or other proppant, acid,
and other chemicals.
Examples of fracturing fluid components include acid, anti-bacterial agents,
clay stabilizers,
corrosion inhibitors, friction reducers, gelling agents, iron control agents,
pH adjusting agents,
scale inhibitors, and surfactants. Historically, diesel has at times been used
as a substitute for
water in cold environments, or where a formation to be fractured is water
sensitive, such as, for
example, clay. The use of diesel, however, has been phased out over time
because of price, and
the development of newer, better technologies.
[0058] In Fig. 1, there are specifically shown sand transporting vehicles 26,
an acid transporting
vehicle 28, vehicles for transporting other chemicals 30, and a vehicle
carrying a hydration unit
32. Also shown are fracturing fluid blenders 34, which can be configured to
mix and blend the
components of the hydraulic fracturing fluid, and to supply the hydraulic
fracturing fluid to the
pumps 10. In the case of liquid components, such as water, acids, and at least
some chemicals,
the components can be supplied to the blenders 34 via fluid lines (not shown)
from the respective
component vehicles, or from the hydration unit 32. In the case of solid
components, such as
sand, the component can be delivered to the blender 34 by a conveyor belt 38.
The water can be
supplied to the hydration unit 32 from, for example, water tanks 36 onsite.
Alternately, the water
can be provided by water trucks. Furthermore, water can be provided directly
from the water
tanks 36 or water trucks to the blender 34, without first passing through the
hydration unit 32.
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[0059] In certain embodiments of the technology, the hydration units 32 and
blenders 34 can be
powered by electric motors. For example, the blenders 34 can be powered by
more than one
motor, including motors having 600 horsepower or more, and motors having 1150
horsepower or
more. The hydration units 32 can be powered by electric motors of 600
horsepower or more. In
addition, in some embodiments, the hydration units 32 can each have up to five
(5) chemical
additive pumps, and a 200 bbl steel hydration tank.
[0060] Pump control and data monitoring equipment 40 can be mounted on a
control vehicle 42,
and connected to the pumps 10, electric motors 14, blenders 34, and other
downhole sensors and
tools (not shown) to provide information to an operator, and to allow the
operator to control
different parameters of the fracturing operation. For example, the pump
control and data
monitoring equipment 40 can include an A/C console that controls the VFD 15,
and thus the
speed of the electric motor 14 and the pump 10. Other pump control and data
monitoring
equipment can include pump throttles, a pump VFD fault indicator with a reset,
a general fault
indicator with a reset, a main estop, a programmable logic controller for
local control, and a
graphics panel. The graphics panel can include, for example, a touchscreen
interface.
[0061] Referring now to Fig. 10, there is shown an alternate embodiment of the
present
technology. Specifically, there is shown a plurality of pumps 110 which, in
this embodiment, are
mounted to pump trailers 112. As shown, the pumps 110 can optionally be loaded
two to a
trailer 112, thereby minimizing the number of trailers needed to place the
requisite number of
pumps at a site. The ability to load two pumps 110 on one trailer 112 is
possible because of the
relatively light weight of the electric powered pumps 110 compared to other
known pumps, such
as diesel pumps. In the embodiment shown, the pumps 110 are powered by
electric motors 114,
which can also be mounted to the pump trailers 112. Furthermore, each electric
motor 114 can
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be equipped with a VFD 115, and an A/C console, that controls the speed of the
motor 114, and
hence the speed of the pumps 110.
[0062] The VFDs 115 shown in Fig. 10 can be discrete to each pump trailer 112
and/or pump
110. Such a feature is advantageous because it allows for independent control
of the pumps 110
and motors 114. Thus, if one pump 110 and/or motor 114 becomes incapacitated,
the remaining
pumps 110 and motors 114 on the pump trailers 112 or in the fleet can continue
to function,
thereby adding redundancy and flexibility to the system. In addition, separate
control of each
pump 110 and/or motor 114 makes the system more scalable, because individual
pumps 110
and/or motors 114 can be added to or removed from a site without modification
to the VFDs 115.
[0063] In addition to the above, and still referring to Fig. 10, the system
can optionally include a
skid (not shown) for supporting some or all of the above-described equipment.
For example, the
skid can support the electric motors 114 and the pumps 110. In addition, the
skid can support the
VFD 115. Structurally, the skid can be constructed of heavy-duty longitudinal
beams and cross-
members made of an appropriate material, such as, for example, steel. The skid
can further
include heavy-duty lifting lugs, or eyes, that can optionally be of sufficient
strength to allow the
skid to be lifted at a single lift point. It is to be understood that a skid
is not necessary for use
and operation of the technology and the mounting of the equipment directly to
a trailer 112 may
be advantageous because if enables quick transport of the equipment from place
to place, and
increased mobility of the pumping system, as discussed above.
[0064] The pumps 110 are fluidly connected to a wellhead 116 via a missile
118. As shown, the
pump trailers 112 can be positioned near enough to the missile 118 to connect
fracturing fluid
lines 120 between the pumps 110 and the missile 118. The missile 118 is then
connected to the
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wellhead 116 and configured to deliver fracturing fluid provided by the pumps
110 to the
= wellhead 116.
[0065] This embodiment also includes a plurality of turbine generators 122
that are connected to,
and provide power to, the electric motors 114 on the pump trailers 112. To
accomplish this, the
turbine generators 122 can be connected to the electric motors 114 by power
lines (not shown).
The turbine generators 122 can be connected to the electric motors 114 via
power distribution
panels (not shown). In certain embodiments, the turbine generators 122 can be
powered by
natural gas, similar to the electric generators 22 discussed above in
reference to the embodiment
of Fig. 1. Also included are control units 144 for the turbine generators 122.
The control units
144 can be connected to the turbine generators 122 in such a way that each
turbine generator 122
is separately controlled. This provides redundancy and flexibility to the
system, so that if one
turbine generator 122 is taken off line (e.g., for repair or maintenance), the
other turbine
generators 122 can continue to function.
[0066] The embodiment of Fig. 10 can include other equipment similar to that
discussed above.
For example, Fig. 10 shows sand transporting vehicles 126, acid transporting
vehicles 128, other
chemical transporting vehicles 130, hydration unit 132, blenders 134, water
tanks 136, conveyor
belts 138, and pump control and data monitoring equipment 140 mounted on a
control vehicle
142. The function and specifications of each of these is similar to
corresponding elements shown
in Fig. 1.
[0067] Use of pumps 10, 110 powered by electric motors 14, 114 and natural gas
powered
electric generators 22 (or turbine generators 122) to pump fracturing fluid
into a well is
advantageous over known systems for many different reasons. For example, the
equipment (e.g.
pumps, electric motors, and generators) is lighter than the diesel pumps
commonly used in the
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industry. The lighter weight of the equipment allows loading of the equipment
directly onto a
truck body or trailer. Where the equipment is attached to a skid, as described
above, the skid
itself can be lifted on the truck body, along with all the equipment attached
to the skid.
Furthermore, and as shown in Figs. 11 and 12, trailers 112 can be used to
transport the pumps
110 and electric motors 114, with two or more pumps 110 carried on a single
trailer 112. Thus,
the same number of pumps 110 can be transported on fewer trailers 112. Known
diesel pumps,
in contrast, cannot be transported directly on a truck body or two on a
trailer, but must be
transported individually on trailers because of the great weight of the pumps.
[0068] The ability to transfer the equipment of the present technology
directly on a truck body or
two to a trailer increases efficiency and lowers cost. In addition, by
eliminating or reducing the
number of trailers to carry the equipment, the equipment can be delivered to
sites having a
restricted amount of space, and can be carried to and away from worksites with
less damage to
the surrounding environment. Another reason that the electric powered pump
system of the
present technology is advantageous is that it runs on natural gas. Thus, the
fuel is lower cost, the
components of the system require less maintenance, and emissions are lower, so
that potentially
negative impacts on the environment are reduced.
[0069] More detailed side views of the trailers 112, having various system
components mounted
thereon, are shown in Figs. 11 and 12, which show left and right side views of
a trailer 112,
respectively. As can be seen, the trailer 112 can be configured to carry pumps
110, electric
motors 114 and a VFD 115. Thus configured, the motors 114 and pumps 110 can be
operated
and controlled while mounted to the trailers 112. This provides advantages
such as increased
mobility of the system. For example, if the equipment needs to be moved to a
different site, or to
a repair facility, the trailer can simply be towed to the new site or facility
without the need to first
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load the equipment onto a trailer or truck, which can be a difficult and
hazardous endeavor. This
is a clear benefit over other systems, wherein, motors and pumps are attached
to skids that are
delivered to a site and placed on the ground.
[0070] In order to provide a system wherein the pumps 110, motors 114, and
VFDs 115 remain
trailer mounted, certain improvements can be made to the trailers 112. For
example, a third axle
146 can be added to increase the load capacity of the trailer and add
stability. Additional
supports and cross members 148 can be added to support the motors' torque. In
addition, the
neck 149 of the trailer can be modified by adding an outer rib 150 to further
strengthen the neck
149. The trailer can also include specially designed mounts 152 for the VFD
115 that allow the
trailer to move independently of the VFD 115, as well as specially designed
cable trays for
running cables on the trailer 112. Although the VFD 115 is shown attached to
the trailer in the
embodiment of Figs. 11 and 12, it could alternately be located elsewhere on
the site, and not
mounted to the trailer 112.
[0071] In practice, a hydraulic fracturing operation can be carried out
according to the following
process. First, the water, sand, and other components are blended to form a
fracturing fluid,
which is pumped down the well by the electric-powered pumps. Typically, the
well is designed
so that the fracturing fluid can exit the wellbore at a desired location and
pass into the
surrounding formation. For example, in some embodiments the wellbore can have
perforations
that allow the fluid to pass from the wellbore into the formation. In other
embodiments, the
wellbore can include an openable sleeve, or the well can be open hole. The
fracturing fluid can
be pumped into the wellbore at a high enough pressure that the fracturing
fluid cracks the
formation, and enters into the cracks. Once inside the cracks, the sand, or
other proppants in the
mixture, wedges in the cracks, and holds the cracks open.
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[0072] Using the pump control and data monitoring equipment 40, 140 the
operator can monitor,
gauge, and manipulate parameters of the operation, such as pressures, and
volumes of fluids and
proppants entering and exiting the well. For example, the operator can
increase or decrease the
ratio of sand to water as the fracturing process progresses and circumstances
change.
[0073] This process of injecting fracturing fluid into the wellbore can be
carried out
continuously, or repeated multiple times in stages, until the fracturing of
the formation is
optimized. Optionally, the wellbore can be temporarily plugged between each
stage to maintain
pressure, and increase fracturing in the formation. Generally, the proppant is
inserted into the
cracks formed in the formation by the fracturing, and left in place in the
formation to prop open
the cracks and allow oil or gas to flow into the wellbore.
[0074] While the technology has been shown or described in only some of its
forms, it should be
apparent to those skilled in the art that it is not so limited, but is
susceptible to various changes
without departing from the scope of the technology. Furthermore, it is to be
understood that the
above disclosed embodiments are merely illustrative of the principles and
applications of the
present technology. Accordingly, numerous modifications can be made to the
illustrative
embodiments and other arrangements can be devised without departing from the
spirit and scope
of the present technology as defined by the appended claims.
=
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