Note: Descriptions are shown in the official language in which they were submitted.
=
COLD WEATHER PACKAGE FOR OIL FIELD HYDRAULICS
BACKGROUND OF THE INVENTION
1. Field of Invention
[0002] The present disclosure relates to hydraulic fracturing of subterranean
formations. In
particular, the present disclosure relates to an electrical hydraulic
fracturing system having heaters
for heating hydraulic fluid.
2. Description of Prior Art
[0003] Hydraulic fracturing is a technique used to stimulate production from
some hydrocarbon
producing wells. The technique usually involves injecting fluid into a
wellbore at a pressure
sufficient to generate fissures in the formation surrounding the wellbore.
Typically the
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pressurized fluid is injected into a portion of the wellbore that is pressure
isolated from the
remaining length of the wellbore so that fracturing is limited to a designated
portion of the
formation. The fracturing fluid slurry, whose primary component is usually
water, includes
proppant (such as sand or ceramic) that migrate into the fractures with the
fracturing fluid slurry
and remain to prop open the fractures after pressure is no longer applied to
the wellbore. A
primary fluid for the slurry other than water, such as nitrogen, carbon
dioxide, foam, diesel, or
other fluids is sometimes used as the primary component instead of water.
Typically hydraulic
fracturing fleets include a data van unit, blender unit, hydration unit,
chemical additive unit,
hydraulic fracturing pump unit, sand equipment, wireline, and other equipment.
[0004] Traditionally, the fracturing fluid slurry has been pressurized on
surface by high pressure
pumps powered by diesel engines. To produce the pressures required for
hydraulic fracturing,
the pumps and associated engines have substantial volume and mass. Heavy duty
trailers, skids,
or trucks are required for transporting the large and heavy pumps and engines
to sites where
wellbores are being fractured. Each hydraulic fracturing pump is usually
composed of a power
end and a fluid end. The hydraulic fracturing pump also generally contains
seats, valves, a
spring, and keepers internally. These parts allow the hydraulic fracturing
pump to draw in low
pressure fluid slurry (approximately 100 psi) and discharge the same fluid
slurry at high
pressures (over 10,000 psi). Recently electrical motors controlled by variable
frequency drives
have been introduced to replace the diesel engines and transmission, which
greatly reduces the
noise, emissions, and vibrations generated by the equipment during operation,
as well as its size
footprint.
100051 On each separate unit, a closed circuit hydraulic fluid system is often
used for operating
auxiliary portions of each type of equipment. These auxiliary components may
include dry or
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liquid chemical pumps, augers, cooling fans, fluid pumps, valves, actuators,
greasers, mechanical
lubrication, mechanical cooling, mixing paddles, landing gear, and other
needed or desired
components. This hydraulic fluid system is typically separate and independent
of the main
hydraulic fracturing fluid slurry that is being pumped into the wellbore. At
times a separate
heating system is deployed to heat the actual hydraulic fracturing fluid
slurry that enters the
wellbore. The hydraulic fluid system can thicken when ambient temperatures
drop below the
gelling temperature of the hydraulic fluid. Typically waste heat from diesel
powered equipment
is used for warming hydraulic fluid to above its gelling temperature. For
diesel powered
equipment, this typically allows the equipment to operate at temperatures down
to -20 C.
However, because electrically powered fracturing systems generate an
insignificant amount of
heat, hydraulic fluid in these systems is subject to gelling when exposed to
low enough
temperatures. These temperatures for an electric powered fracturing system
typically begin to
gel at much higher temperatures of approximate 5 C.
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SUMMARY OF THE INVENTION
100061 Disclosed herein is an example of a hydraulic fracturing system for
fracturing a
subterranean formation, and which includes at least one hydraulic fracturing
pump fluidly
connected to the well and powered by at least one electric motor, and
configured to pump fluid
slurry into the wellbore at high pressure so that the fluid slurry passes from
the wellbore into the
formation, and fractures the formation. The system also includes a variable
frequency drive
connected to the electric motor to control the speed of the motor, wherein the
variable frequency
drive frequently performs electric motor diagnostics to prevent damage to the
at least one electric
motor, and a working fluid system having a working fluid, and a heater that is
in thermal contact
with the working fluid. Other electric motors on the equipment that do not
require variable or
adjustable speed (which generally operate in an on or off setting, or at a set
speed), may be
operated with the use of a soft starter. The working fluid can be lube oil,
hydraulic fluid, or other
fluid. In one embodiment, the heater includes a tank having working fluid and
a heating element
in the tank in thermal contact with the working fluid. The heating element can
be an elongate
heating element, or a heating coil, or a thermal blanket that could be wrapped
around the
working fluid tank. The system can further include a turbine generator, a
transformer having a
high voltage input in electrical communication with an electrical output of
the turbine generator
and a low voltage output, wherein the low voltage output is at an electrical
potential that is less
than that of the high voltage input, and a step down transformer having an
input that is in
electrical communication with the low voltage output of the transformer. The
step down
transformer can have an output that is in electrical communication with the
heater. In an
example, more than one transformer may be used to create multiple voltages
needed for the
system such as 13,800 V three phase, 600 V three phase, 600 V single phase,
240 V single phase,
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and others as required. In an example, the pumps are moveable to different
locations on mobile
platforms.
100071 Also described herein is another example of a hydraulic fracturing
system for fracturing a
subterranean formation and that includes a pump having a discharge in
communication with a
wellbore that intersects the formation, an electric motor coupled to and that
drives the pump, a
variable frequency drive connected to the electric motor that controls a speed
of the motor and
performs electric motor diagnostics, and a working fluid system made up of a
piping circuit
having working fluid, and a heater that is in thermal contact with the working
fluid. The
working fluid can be lube oil or hydraulic fluid, which is circulated using an
electric lube pump
through the hydraulic fluid closed circuit for each piece of equipment. In one
embodiment, on
each separate unit, a closed circuit hydraulic fluid system can be used for
operating auxiliary
portions of each type of equipment. These auxiliary components may include dry
or liquid
chemical pumps, augers, cooling fans, fluid pumps, valves, actuators,
greasers, mechanical
lubrication, mechanical cooling, mixing paddles, landing gear, conveyer belt,
vacuum, and other
needed or desired components. This hydraulic fluid system can be separate and
independent of
the main hydraulic fracturing fluid slurry that is being pumped into the
wellbore. At times a
separate heating system is deployed to heat the actual hydraulic fracturing
fluid slurry that enters
the wellbore. The hydraulic fracturing system can optionally include a turbine
generator that
generates electricity for use in energizing the motor. In an example, the pump
is a first pump and
the motor is a first motor, the system further including a trailer, a second
pump, and a second
motor coupled to the second pump and for driving the second pump, and wherein
the first and
second pumps and motors are mounted on the trailer. In another embodiment, a
single motor
with drive shafts on both sides may connect to the first and second pumps,
wherein each pump
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could be uncoupled from the motor as required. The hydraulic fracturing system
can further
include a first transformer for stepping down a voltage of electricity from an
electrical source to
a voltage that is useable by the pump's electrical motor, and a second
transformer that steps
down a voltage of the electricity useable by the pump's electrical motor to a
voltage that is
usable by the heater.
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BRIEF DESCRIPTION OF DRAWINGS
[0008] Some of the features and benefits of the present invention having been
stated, others will
become apparent as the description proceeds when taken in conjunction with the
accompanying
drawings, in which:
[0009] FIG. 1 is a schematic of an example of a hydraulic fracturing system.
[0010] FIGS. 2-4 are schematics of examples of step down transformers and
hydraulic fluid
heaters for use with the hydraulic fracturing system of FIG. 1.
[0011] FIG. 5A is a perspective view of an example of a tank with a heating
element for
warming hydraulic fluid for use with the hydraulic fracturing system of FIG.
I.
[0012] FIG. 5B is a side view of an alternate embodiment of a heating element
for use with the
tank of FIG. 5A.
[0013] While the invention will be described in connection with the preferred
embodiments, it
will be understood that it is not intended to limit the invention to that
embodiment. On the
contrary, it is intended to cover all alternatives, modifications, and
equivalents, as may be
included within the spirit and scope of the invention as defined by the
appended claims.
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DETAILED DESCRIPTION OF INVENTION
[0014] The method and system of the present disclosure will now be described
more fully
hereinafter with reference to the accompanying drawings in which embodiments
are shown. The
method and system of the present disclosure may be in many different forms and
should not be
construed as limited to the illustrated embodiments set forth herein; rather,
these embodiments
are provided so that this disclosure will be thorough and complete, and will
fully convey its
scope to those skilled in the art. Like numbers refer to like elements
throughout. In an
embodiment, usage of the term "about" includes +/- 5% of the cited magnitude.
In an
embodiment, usage of the term "substantially" includes +/- 5% of the cited
magnitude.
[0015] It is to be further understood that the scope of the present disclosure
is not limited to the
exact details of construction, operation, exact materials, or embodiments
shown and described, as
modifications and equivalents will be apparent to one skilled in the art. In
the drawings and
specification, there have been disclosed illustrative embodiments and,
although specific terms
are employed, they are used in a generic and descriptive sense only and not
for the purpose of
limitation.
[0016] Figure 1 is a schematic example of a hydraulic fracturing system 10
that is used for
pressurizing a wellbore 12 to create fractures 14 in a subterranean formation
16 that surrounds
the wellbore 12. Included with the system 10 is a hydration unit 18 that
receives fluid from a
fluid source 20 via line 22, and also selectively receives additives from an
additive source 24 via
line 26. Additive source 24 can be separate from the hydration unit 18 as a
stand-alone unit, or
can be included as part of the same unit as the hydration unit 18. The fluid,
which in one
example is water, is mixed inside of the hydration unit 18 with the additives.
In an embodiment,
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the fluid and additives are mixed over a period of time to allow for uniform
distribution of the
additives within the fluid. In the example of Figure 1, the fluid and additive
mixture is
transferred to a blender unit 28 via line 30. A proppant source 32 contains
proppant, which is
delivered to the blender unit 28 as represented by line 34, where line 34 can
be a conveyer.
Inside the blender unit 28, the proppant and fluid/additive mixture are
combined to form a
fracturing slurry, which is then transferred to a fracturing pump system 36
via line 38; thus fluid
in line 38 includes the discharge of blender unit 28, which is the suction (or
boost) for the
fracturing pump system 36. Blender unit 28 can have an onboard chemical
additive system, such
as with chemical pumps and augers. Optionally, additive source 24 can provide
chemicals to
blender unit 28; or a separate and standalone chemical additive system (not
shown) can be
provided for delivering chemicals to the blender unit 28. In an example, the
pressure of the
slurry in line 38 ranges from around 80 psi to around 100 psi. The pressure of
the slurry can be
increased up to around 15,000 psi by pump system 36. A motor 39, which
connects to pump
system 36 via connection 40, drives pump system 36 so that it can pressurize
the slurry. After
being discharged from pump system 36, slurry is injected into a wellhead
assembly 41; discharge
piping 42 connects discharge of pump system 36 with wellhead assembly 41 and
provides a
conduit for the slurry between the pump system 36 and the wellhead assembly
41. In an
alternative, hoses or other connections can be used to provide a conduit for
the slurry between
the pump system 36 and the wellhead assembly 41. Optionally, any type of fluid
can be
pressurized by the fracturing pump system 36 to form injection fracturing
fluid that is then
pumped into the wellbore 12 for fracturing the formation 14, and is not
limited to fluids having
chemicals or proppant. Examples exist wherein the system 10 includes multiple
pumps 36, and
multiple motors 39 for driving the multiple pumps 36. Examples also exist
wherein the system
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includes the ability to pump down equipment, instrumentation, or other
retrievable items
through the slurry into the wellbore.
[0017] An example of a turbine 44 is provided in the example of Figure 1 and
which receives a
combustible fuel from a fuel source 46 via a feed line 48. In one example, the
combustible fuel
is natural gas, and the fuel source 46 can be a container of natural gas or a
well (not shown)
proximate the turbine 44. Combustion of the fuel in the turbine 44 in turn
powers a generator 50
that produces electricity. Shaft 52 connects generator 50 to turbine 44. The
combination of the
turbine 44, generator 50, and shaft 52 define a turbine generator 53. In
another example, gearing
can also be used to connect the turbine 44 and generator 50. An example of a
micro-grid 54 is
further illustrated in Figure 1, and which distributes electricity generated
by the turbine generator
53. Included with the micro-grid 54 is a transformer 56 for stepping down
voltage of the
electricity generated by the generator 50 to a voltage more compatible for use
by electrical
powered devices in the hydraulic fracturing system 10. In another example, the
power generated
by the turbine generator and the power utilized by the electrical powered
devices in the hydraulic
fracturing system 10 are of the same voltage, such as 4160 V so that main
power transformers
are not needed. In one embodiment, multiple 3500 kVA dry cast coil
transformers are utilized.
Electricity generated in generator 50 is conveyed to transformer 56 via line
58. In one example,
transformer 56 steps the voltage down from 13.8 kV to around 600 V. Other
stepped down
voltages can include 4,160 V, 480 V, or other voltages. The output or low
voltage side of the
transformer 56 connects to a power bus 60, lines 62, 64, 66, 68, 70, and 72
connect to power bus
60 and deliver electricity to electrically powered end users in the system 10.
More specifically,
line 62 connects fluid source 20 to bus 60, line 64 connects additive source
24 to bus 60, line 66
connects hydration unit 18 to bus 60, line 68 connects proppant source 32 to
bus 60, line 70
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connects blender unit 28 to bus 60, and line 72 connects motor 39 to bus 60.
In an example,
additive source 24 contains ten or more chemical pumps for supplementing the
existing chemical
pumps on the hydration unit 18 and blender unit 28. Chemicals from the
additive source 24 can
be delivered via lines 26 to either the hydration unit 18 and/or the blender
unit 28. In one
embodiment, the elements of the system 10 are mobile and can be readily
transported to a
wellsite adjacent the wellbore 12, such as on trailers or other platforms
equipped with wheels or
tracks.
[0018] Figure 2 shows in a schematic form a portion of the system 10 of Figure
1 having the
electric motor 39. In one embodiment, this is for the hydraulic fracturing
pump unit. Included
with this example is a step down transformer 80 with a high voltage side HV in
communication
with line 72 via line 82. Voltage is stepped down or reduced across
transformer 80 to a low
voltage side LV; which is shown in electrical communication with a load box 84
via line 86. In
one example, the high voltage side HV of transformer 80 is at around 600 V,
and the stepped
down (or low voltage side LV) is at around 240 V. Load box 84, which operates
similar to a
breaker box, provides tie ins for devices that operate at the stepped down
voltage. Line 88
provides communication between motor 39 and a heater system 90, which is
illustrated adjacent
to motor 39 and is for heating lube oil that is used within pump 36 and other
auxiliaries as
needed (not shown). Heater system 90 includes a tank 91 in which oil can
collect, and flow lines
92, 94 for directing lube oil between the tank 91 and a lube oil system 95
schematically shown
with pump 36. An example of a heating element 96 is shown disposed within tank
91 which
receives current via line 88 from load box 84. Electrical current flowing
through the element 96
is converted into thermal energy, which is transferred to the lube oil and for
heating the lube oil
in the heater system 90. The heater system 90 may be selectivity energized
manually and/or
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include a thermal switch (not shown) to automatically turn the heating element
96 on and off at
desired hydraulic fluid temperatures. Ground lines 100, 102, 106 provide
connection between a
ground side respectively of the heater system 96, low voltage side of
transformer 80, pump 36,
and high voltage side of transformer 80 to ground G. Further illustrated in
Figure 2 is an
example of a variable frequency drive of ("VFD") 107 and an A/C console (not
shown), that
control the speed of the electric motor 39, and hence the speed of the pump
36.
[0019] Figure 3 is a schematic example of a transformer 108 which steps down
voltage of
electricity within line 64 (which is on the low voltage or stepped down side
of transformer 56 of
Figure 1). Line 64 connects to transformer via line 110. Line 112, which
connects to a low
voltage side LV of transformer 108, conducts electricity at the stepped down
voltage to a load
box 114, which can provide a source point for use by components (not shown) in
or associated
with the hydration unit 18 that operate on electricity at the stepped down
voltage. Branching
from line 112 is line 116 which conducts electricity at the stepped down
voltage to a load box
118. Load box 118 defines an energy source point of energy for use by
components (not shown)
associated with the additive source 24 that operate on electricity at the
stepped down voltage. In
one example, load boxes 114 and 118 are replaced by a single load box. A
hydraulic fluid
heating system 122, which is attached to the hydration unit 18, and which
includes a tank 123 in
which hydraulic fluid used in operating components within hydration unit 18 is
heated. An
element 124 disposed within tank 123 operates similar to element 96 of Figure
2. In another
embodiment, element 124 is a heating blanket that wrapped around tank 123.
Hydraulic fluid is
transmitted to and from tank 123 through flow lines 126, 128, which connect to
a hydraulically
powered device 129 in hydration unit 18. Hydraulically powered device 129 is a
schematic
representation of any equipment or devices in or associated with hydration
unit 18 that are
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operated by hydraulic fluid. Thus hydraulic fluid heating system 122 warms
hydraulic fluid used
by hydraulically powered device 129 and prevents thickening of the hydraulic
fluid. Line 120
provides electrical communication between element 124 so that it can be
selectively energized to
warm the hydraulic fluid. The selectivity can be manually operated and/or
include a thermal
switch to automatically turn the heating element 124 on and off at desired
hydraulic fluid
temperatures. In one embodiment, a secondary power source (not shown) such as
an external
generator, grid power, battery bank, or other power source at the same voltage
as load box 84 can
be connected directly into the as load box 84 to power the heating element
without the entire
microgrid being energized. This allows heating of the hydraulic fluid prior to
starting the entire
hydraulic fracturing fleet system.
[0020] Electrical connection between load box 118 and additive source 24 is
shown provided by
line 132. Also included with additive source 24 is a hydraulic fluid heating
system 134 which
includes a tank 135 for containing hydraulic fluid, and an element 136 within
tank 135 for
heating hydraulic fluid that is within tank 135. Flow lines 138, 140 provide
connectivity
between tank 135 and a hydraulically powered device 141 shown disposed in or
coupled with
additive source 24. Similar to hydraulically powered device 129, hydraulically
powered device
141 schematically represents hydraulically operated devices in or coupled with
additive source
24. Line 132 provides electrical communication to heating element 136 from
load box 118.
Similar to hydraulic fluid heating system 122, hydraulic fluid heating system
134 heats hydraulic
fluid used by hydraulically powered device 141 so that the hydraulic fluid
properties remain at
designated operational values. As determined manually and/or include a thermal
switch to
automatically turn the heating element on and off at desired hydraulic fluid
temperatures.
Ground lines 143, 146, 148, 152 provide connection to ground G respectively
from, hydraulic
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fluid heating system 34, additive source 24, low voltage side LV of
transformer 108, a hydraulic
heating fluid system 122, hydration unit 18, and the high voltage HV side of
transformer 108. In
one embodiment, a secondary power source (not shown) such as an external
generator, grid
power, battery bank, or other power source at substantially the same voltage
as load box 118 and
load box 114 can be connected directly into the as load box 118 and load box
114 to power the
heating element without the entire microgrid being energized. This allows
heating of the
hydraulic fluid prior to starting the entire hydraulic fracturing fleet
system.
100211 Figure 4 illustrates a schematic example of a transformer 154 to
provide electricity at a
stepped down voltage to blender unit 28. In one embodiment, transformer 154
and transformer
108 (Figure 3) are replaced by a single transformer. In this example, a high
voltage side HV of
transformer 154 connects to line 70 via line 156. Voltage of electricity
received by transformer
154 is stepped down and delivered to a low voltage side LV of transformer 154.
A load box 158
is in communication with the low voltage side LV of transformer 154 via line
160. Electricity at
load box 158 is communicated through line 162 to blender unit 28. Line 162
selectively
energizes an element 166 shown as part of hydraulic fluid heating system 168.
Selectivity
energizing element 166 can be manually operated and/or include a thermal
switch to
automatically turn the heating element 166 on and off at desired hydraulic
fluid temperatures.
System 168 includes a tank 169 in which element 166 is disposed, and which
receives hydraulic
fluid from blender unit 28 via flow lines 170 and returns hydraulic fluid via
flow line 172. Flow
lines 170, 172 connect to a hydraulically powered device 173 that is part of
the hydration unit.
Examples of hydraulically powered units that are powered by hydraulic fluid
include chemical
pumps, tub paddles (mixers), cooling fans, fluid pumps, valve actuators, and
auger motors.
Ground lines 174, 176, 180 provide connectivity through ground G from the
heating system 168,
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low voltage side LV of transformer 154, and high voltage side HV of
transformer 154. In one
embodiment, a secondary power source (not shown) such as an external
generator, grid power,
battery bank, or other power source at the same voltage as load box 158 can be
connected
directly into the load box 158 to power the heating element 166 without the
entire microgrid
being energized. This allows heating of the hydraulic fluid prior to starting
the entire hydraulic
fracturing fleet system.
100221 Figure 5A shows in perspective one example of a fluid heating system
181 and which
includes a tank 182 having a housing 184 in which fluid F is contained. The
fluid F can be
hydraulic fluid or lube oil. The heating system 181 of Figure 5A also includes
an elongate
heating element 186 shown projecting through a side wall of housing 184. Heat
element 186 is
strategically disposed so that the portion projecting into tank 182 is
submerged in fluid F. Line
188 provides electrical current to the element 186 and which may be from the
stepped down
voltage of one of the transformers 80 (Figure 2), 108 (Figure 3), or 154
(Figure 4). In this
example, the housing 184 can be connected to ground G thereby eliminating the
need for a
ground line. Fluid heating system 181 of Figure 5A provides an example
embodiment to the
heating systems of Figures 2-4. Figure 59 illustrates an alternate example of
the element 186A
and which is shown made up of a number of coils 190 that are generally
coaxially arranged.
Opposing ends of the coils 190 have contact leads 192, 194 attached for
providing electrical
connectivity through which an electrical circuit can be conducted and that in
turn causes element
186A to generate thermal energy that can be used in heating the hydraulic
fluid or lube oil
discussed above.
100231 The present invention described herein, therefore, is well adapted to
carry out the objects
and attain the ends and advantages mentioned, as well as others inherent
therein. While a
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presently preferred embodiment of the invention has been given for purposes of
disclosure,
numerous changes exist in the details of procedures for accomplishing the
desired results. For
example, heating the fluids as described above can be accomplished by other
means, such as heat
exchangers that have fluids flowing through tubes. Moreover, electricity for
energizing a heater
can be from a source other than a turbine generator, but instead can be from a
utility, solar,
battery, to name but a few. These and other similar modifications will readily
suggest
themselves to those skilled in the art, and are intended to be encompassed
within the spirit of the
present invention disclosed herein and the scope of the appended claims.
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