Note: Descriptions are shown in the official language in which they were submitted.
MOBILE, MODULAR, ELECTRICALLY POWERED SYSTEM
FOR USE IN FRACTURING UNDERGROUND FORMATIONS
USING LIQUID PETROLEUM GAS
BACKGROUND
1.
[0001]
2. Field of Invention
[0002] This invention relates generally to hydraulic stimulation of
underground hydrocarbon-
bearing formations, and more particularly, to the generation and use of
electrical power to deliver
fracturing fluid to a wellbore.
3. Description of the Related Art
[0003] Over the life cycle of a typical hydrocarbon-producing wellbore,
various fluids (along with
additives, proppants, gels, cement, etc...) can be delivered to the wellbore
under pressure and
injected into the wellbore. Surface pumping systems must be able to
accommodate these various
fluids. Such pumping systems are typically mobilized on skids or tractor-
trailers and powered
using diesel motors.
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[0004] Technological advances have greatly improved the ability to identify
and recover
unconventional oil and gas resources. Notably, horizontal drilling and multi-
stage fracturing
have led to the emergence of new opportunities for natural gas production from
shale formations.
For example, more than twenty fractured intervals have been reported in a
single horizontal
wellbore in a tight natural gas formation. However, significant fracturing
operations are required
to recover these resources.
[0005] Currently contemplated natural gas recovery opportunities require
considerable
operational infrastructure, including large investments in fracturing
equipment and related
personnel. Notably, standard fluid pumps require large volumes of diesel fuel
and extensive
equipment maintenance programs. Typically, each fluid pump is housed on a
dedicated truck
and trailer configuration. With average fracturing operations requiring as
many as fifty fluid
pumps, the on-site area, or "footprint", required to accommodate these
fracturing operations is
massive. As a result, the operational infrastructure required to support these
fracturing
operations is extensive. Greater operational efficiencies in the recovery of
natural gas would be
desirable.
[0006] When planning large fracturing operations, one major logistical concern
is the availability
of diesel fuel. The excessive volumes of diesel fuel required necessitates
constant transportation
of diesel tankers to the site, and results in significant carbon dioxide
emissions. Others have
attempted to decrease fuel consumption and emissions by running large pump
engines on "Bi-
Fuel", blending natural gas and diesel fuel together, but with limited
success. Further, attempts
to decrease the number of personnel on-site by implementing remote monitoring
and operational
control have not been successful, as personnel are still required on-site to
transport the
equipment and fuel to and from the location.
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SUMMARY
100071 Various illustrative embodiments of a system and method for hydraulic
stimulation of
underground hydrocarbon-bearing formations are provided herein. In accordance
with an aspect of the
disclosed subject matter, a method of delivering fracturing fluid to a
wellbore is provided. The method
can comprise the steps of: providing a dedicated source of electric power at a
site containing a wellbore to
be fractured; providing one or more electric fracturing modules at the site,
each electric fracturing module
comprising an electric motor and a coupled fluid pump, each electric motor
operatively associated with
the dedicated source of electric power; providing a wellbore treatment fluid
for pressurized delivery to a
wellbore, wherein the wellbore treatment fluid can be continuous with the
fluid pump and with the
wellbore; and operating the fracturing unit using electric power from the
dedicated source to pump the
treatment fluid to the wellbore.
100081 In certain illustrative embodiments, the dedicated source of electrical
power is a turbine generator.
A source of natural gas can be provided, whereby the natural gas drives the
turbine generator in the
production of electrical power. For example, natural gas can be provided by
pipeline, or natural gas
produced on-site. Liquid fuels such as condensate can also be provided to
drive the turbine generator.
[0009] In certain illustrative embodiments, the electric motor can be an AC
permanent magnet motor
and/or a variable speed motor. The electric motor can be capable of operation
in the range of up to 1500
rpms and up to 20,000 ft/lbs of torque. The pump can be a triplex or
quintiplex plunger style fluid pump.
[0010] In certain illustrative embodiments, the method can further comprise
the steps of: providing an
electric blender module continuous and/or operatively associated with the
fluid pump, the blender module
comprising: a fluid source, a fluid additive source, and a centrifugal blender
tub, and supplying electric
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power from the dedicated source to the blender module to effect blending of
the fluid with fluid additives
to generate the treatment fluid.
[0011] In accordance with another aspect of the disclosed subject matter, a
system for use in delivering
pressurized fluid to a wellborn is provided. The system can comprise: a well
site comprising a wellbore
and a dedicated source of electricity; an electrically powered fracturing
module operatively associated
with the dedicated source of electricity, the electrically powered fracturing
module comprising an electric
motor and a fluid pump coupled to the electric motor; a source of treatment
fluid, wherein the treatment
fluid can be continuous with the fluid pump and with the wellborn; and a
control system for regulating the
fracturing module in delivery of treatment fluid from the treatment fluid
source to the wellbore.
[0012] In certain illustrative embodiments, the source of treatment fluid can
comprise an electrically
powered blender module operatively associated with the dedicated source of
electricity. The system can
further comprise a fracturing trailer at the well site for housing one or more
fracturing modules. Each
fracturing module can be adapted for removable mounting on the trailer. The
system can further comprise
a replacement pumping module comprising a pump and an electric motor, the
replacement pumping
module adapted for removable mounting on the trailer. In certain illustrative
embodiments, the
replacement pumping module can be a nitrogen pumping module, or a carbon
dioxide pumping module.
The replacement pumping module can be, for example, a high torque, low rate
motor or a low torque,
high rate motor.
[00131 In accordance with another aspect of the disclosed subject matter, a
fracturing module for use in
delivering pressurized fluid to a wellbore is provided. The fracturing module
can comprise: an AC
permanent magnet motor capable of operation in the range of up to 1500 rpms
and up to 20,000 ft/lbs of
torque; and a plunger-style fluid pump coupled to the motor.
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[00141 In accordance with another aspect of the disclosed subject matter, a
method of blending a
fracturing fluid for delivery to a wellbore to be fractured is provided. A
dedicated source of electric
power can be provided at a site containing a wellbore to be fractured. At
least one electric blender
module can be provided at the site. The electric blender module can include a
fluid source, a fluid
additive source, and a blender tub. Electric power can be supplied from the
dedicated source to the
electric blender module to effect blending of a fluid from the fluid source
with a fluid additive from the
fluid additive source to generate the fracturing fluid. The dedicated source
of electrical power can be a
turbine generator. A source of natural gas can be provided, wherein the
natural gas is used to drive the
turbine generator in the production of electrical power. The fluid from the
fluid source can be blended
with the fluid additive from the fluid additive source in the blender tub. The
electric blender module can
also include at least one electric motor that is operatively associated with
the dedicated source of electric
power and that effects blending of the fluid from the fluid source with the
fluid additive from the fluid
additive source.
[00151 In certain illustrative embodiments, the electric blender module can
include a first electric motor
and a second electric motor, each of which is operatively associated with the
dedicated source of electric
power. The first electric motor can effect delivery of the fluid from the
fluid source to the blending tub.
The second electric motor can effect blending of the fluid from the fluid
source with the fluid additive
from the fluid additive source in the blending tub. In certain illustrative
embodiments, an optional third
electric motor may also be present, that can also be operatively associated
with the dedicated source of
electric power. The third electric motor can effect delivery of the fluid
additive from the fluid additive
source to the blending tub.
[00161 In certain illustrative embodiments, the electric blender module can
include a first blender unit
and a second blender unit, each disposed adjacent to the other on the blender
module and each capable of
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independent operation, or collectively capable of cooperative operation, as
desired. The first blender unit
and the second blender unit can each include a fluid source, a fluid additive
source, and a blender tub.
The first blender unit and the second blender unit can each have at least one
electric motor that is
operatively associated with the dedicated source of electric power and that
effects blending of the fluid
from the fluid source with the fluid additive from the fluid additive source.
Alternatively, the first
blender unit and the second blender unit can each have a first electric motor
and a second electric motor,
both operatively associated with the dedicated source of electric power,
wherein the first electric motor
effects delivery of the fluid from the fluid source to the blending tub and
the second electric motor effects
blending of the fluid from the fluid source with the fluid additive from the
fluid additive source in the
blending tub. in certain illustrative embodiments, the first blender unit and
the second blender unit can
each also have a third electric motor operatively associated with the
dedicated source of electric power,
wherein the third electric motor effects delivery of the fluid additive from
the fluid additive source to the
blending tub.
100171 In accordance with another aspect of the disclosed subject matter, an
electric blender module for
use in delivering a blended fracturing fluid to a wellbore is provided. The
electric blender module can
include a first electrically driven blender unit and a first inlet manifold
coupled to the first electrically
driven blender unit and capable of delivering an unblended fracturing fluid
thereto. A first outlet
manifold can be coupled to the first electrically driven blender unit and can
be capable of delivering the
blended fracturing Fluid away therefrom. A second electrically driven blender
unit can be provided_ A
second inlet manifold can be coupled to the second electrically driven blender
unit and capable of
delivering the unblended fracturing fluid thereto. A second outlet manifold
can be coupled to the second
electrically driven blender unit and can be capable of delivering the blended
fracturing fluid away
therefrom. An inlet crossing line can be coupled to both the first inlet
manifold and the second inlet
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manifold and can be capable of delivering the unblended fracturing fluid
therebetween. An outlet crossing
line can be coupled to both the first outlet manifold and the second outlet
manifold and can be capable of
delivering the blended fracturing fluid therebetween. A skid can be provided
for housing the first
electrically driven blender unit, the first inlet manifold, the second
electrically driven blender unit, and the
second inlet manifold.
[0017a] In one aspect, there is provided a system for hydraulically fracturing
underground formations,
comprising: one or more transportable electric turbine generator; an electric
motor electrically connected
to the one or more turbine generator; one or more fracturing fluid pump,
wherein the one or more
fracturing fluid pump is configured to receive one or more conduit to deliver
a fracturing fluid comprising
liquefied petroleum gas, liquid N2, N2/CO2 binary fluid, or a combination
thereof into a wellbore; a
blender system configured to provide the fracturing fluid to one or more
fracturing fluid pump, the
blender system comprising a first inlet electric motor, a second inlet
electric motor, a first discharge
electric motor, a second discharge electric motor, wherein one or more of the
motors is connected to the
turbine generator.
10017b1 In another aspect, there is provided a method of delivering
pressurized fluid to a wellbore to be
fractured, comprising: providing one or more transportable electric turbine
generator; providing an
electric motor electrically connected to the one or more turbine generator;
providing one or more
fracturing fluid pump configured to receive one or more conduit to deliver a
fracturing fluid comprising
liquefied petroleum gas, liquid N2, N2/CO2 binary fluid, or a combination
thereof into a wellbore;
providing a blender system configured to provide the fracturing fluid to one
or more fracturing fluid
pump, the blender system comprising a first inlet electric motor, a second
inlet electric motor, a first
discharge electric motor, a second discharge electric motor, wherein one or
more of the motors is
connected to the turbine generator.
[0018] Other aspects and features of the present invention will become
apparent to those of ordinary skill
in the art upon review of the following detailed description in conjunction
with the accompanying figures.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0019] A better understanding of the presently disclosed subject matter can be
obtained when the
following detailed description is considered in conjunction with the following
drawings, wherein:
[0020] Figure 1 is a schematic plan view of a traditional fracturing site;
100211 Figure 2 is a schematic plan view of a fracturing site in accordance
with certain illustrative
embodiments described herein;
100221 Figure 3 is a schematic perspective view of a fracturing trailer in
accordance with certain
illustrative embodiments described herein;
[0023] Figure 4A is a schematic perspective view of a fracturing module in
accordance with certain
illustrative embodiments described herein;
[0024] Figure 48 is a schematic perspective view of a fracturing module with
maintenance personnel in
accordance with certain illustrative embodiments described herein;
100251 Figure 5A is a schematic side view of a blender module in accordance
with certain illustrative
embodiments described herein;
[0026] Figure 5B is an end view of the blender module shown in Figure 4A;
[0027] Figure 5C is a schematic top view of a blender module in accordance
with certain illustrative
embodiments described herein;
[0028] Figure 5D is a schematic side view of the blender module shown in
Figure 5C;
100291 Figure 5E is a schematic perspective view of the blender module shown
in Figure 5C;
[0030] Figure 6 is a schematic top view of an inlet manifold for a blender
module in accordance with
certain illustrative embodiments described herein; and
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100311 Figure 7 is a schematic top view of an outlet manifold for a blender
module in accordance with
certain illustrative embodiments described herein.
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DETAILED DESCRIPTION
100321 The presently disclosed subject matter generally relates to an
electrically powered fracturing
system and a system and method for providing on-site electrical power and
delivering fracturing fluid to a
wellbore at a fracturing operation.
100331 In a conventional fracturing operation, a "slurry" of fluids and
additives is injected into a
hydrocarbon bearing rock formation at a wellbore to propagate fracturing. Low
pressure fluids are mixed
with chemicals, sand, and, if necessary, acid, and then transferred at medium
pressure and high rate to
vertical and/or deviated portions of the wellbore via multiple high pressure,
plunger style pumps driven
by diesel fueled prime movers. The majority of the fluids injected will be
flowed back through the
wellbore and recovered, while the sand will remain in the newly created
fracture, thus "propping" it open
and providing a permeable membrane for hydrocarbon fluids and gases to flow
through so they may be
recovered.
100341 According to the illustrative embodiments described herein, natural gas
(either supplied to the site
or produced on-site) can be used to drive a dedicated source of electrical
power, such as a turbine
generator, for hydrocarbon-producing wellbore completions. A scalable,
electrically powered fracturing
fleet is provided to deliver pressurized treatment fluid, such as fracturing
fluid, to a wellbore in a
fracturing operation, obviating the need for a constant supply of diesel fuel
to the site and reducing the
site footprint and infrastructure required for the fracturing operation, when
compared with conventional
operations. The treatment fluid provided for pressurized delivery to the
wellbore can be continuous with
the wellbore and with one or more components of the fracturing fleet, in
certain illustrative embodiments.
In these embodiments, continuous generally means that downhole hydrodynamics
are dependent upon
constant flow (rate and pressure) of the delivered fluids, and that there
should not be any interruption in
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fluid flow during delivery to the wellbore if the fracture is to propagate as
desired. However, it should not
bc interpreted to mean that operations of the fracturing fleet cannot
generally be stopped and started, as
would be understood by one of ordinary skill in the art. In certain
illustrative embodiments, the treatment
fluid can comprise a water-based fracturing fluid. In other illustrative
embodiments, the treatment fluid
can comprise a waterless liquefied petroleum gas (LPG) fracturing fluid, the
use of which conserves water
and can reduce formation damage caused by introducing water to the wellbore.
In certain illustrative
embodiments, the liquefied petroleum gas can comprise one or more gases from
the group consisting of
propane, butane, propylene and butylene. In other illustrative embodiments,
the treatment fluid can
suitably comprise, consist of, or consist essentially of: linear gelled water
including but not limited to
guar, hydroxypropyl guar ("HPG") and/or carboxymethylhydroxypropyl guar
("CMHPG"), gelled water
including but not limited to guar/borate, HPG/borate, guar/zirconium,
HPG/zireonium and/or
CMHPG/zirconium, gelled oil, slick water, slick oil, poly emulsion,
foam/emulsion including but not
limited to N2 foam, viscoelastic, and/or CO, emulsion, liquid CO2, N2, binary
fluid (CO2/1\12) and/or acid.
[00351 With reference- to Figure 1, a site plan for a traditional fracturing
operation on an onshore site is
shown. Multiple trailers 5 arc provided, each having at least one diesel tank
mounted or otherwise
disposed thereon. Each trailer 5 is attached to a truck 6 to permit refueling
of the diesel tanks as required.
Trucks 6 and trailers 5 are located within region A on the fracturing site.
Each truck 6 requires a
dedicated operator. One or more prime movers are fueled by the diesel and are
used to power the
fracturing operation. One or more separate chemical handling skids 7 are
provided for housing of
blending tanks and related equipment.
[0036] With reference to Figure 2, an illustrative embodiment of a site plan
for an electrically powered
fracturing operation on an onshore site is shown. The fracturing operation
includes one or more trailers
10, each housing one or more fracturing modules 20 (see Figure 3). Trailers 10
arc located in region 13
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on the fracturing site. One or more natural gas-powered turbine generators 30
are located in region C on
the site, which is located a remote distance D from region B where the
trailers 10 and fracturing modules
20 are located, for safety reasons. Turbine generators 30 replace the diesel
prime movers utilized in the
site plan of Figure 1. Turbine generators 30 provide a dedicated source of
electric power on-site. There is
preferably a physical separation between the natural gas-based power
generation in region C and the
fracturing operation and wellborc located in region B. The natural gas-based
power generation can
require greater safety precautions than the fracturing operation and wellhead.
Accordingly, security
measures can be taken in region C to limit access to this more hazardous
location, while maintaining
separate safety standards in region B where the majority of site personnel are
typically located. Further,
the natural gas powered supply of electricity can be monitored and regulated
remotely such that, if
desired, no personnel are required to be within region C during operation.
[00371 Notably, the setup of Figure 2 requires significantly less
infrastructure than the setup shown in
Figure 1, while providing comparable pumping capacity. Fewer trailers 10 are
present in region B of
Figure 2 than the trucks 6 and trailers 5 in region A of Figure 1, due to the
lack of need for a constant
diesel fuel supply. Further, each trailer 10 in Figure 2 does not need a
dedicated truck 6 and operator as
in Figure 1. Fewer chemical handling skids 7 are required in region B of
Figure 2 than in region A of
Figure I. as the skids 7 in Figure 2 can be electrically powered. Also, by
removing diesel prime movers,
all associated machinery necessary for power transfer can be eliminated, such
as the transmission, torque
converter, clutch, drive shaft, hydraulic system, etc ...., and the need for
cooling systems, including
circulating pumps and fluids, is significantly reduced. In
an illustrative embodiment, the physical
footprint of the on-site area in region B of Figure 2 is about 80% less than
the footprint for the
conventional system in region A of Figure I .
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10038] With reference to the illustrative embodiments of Figure 3, trailer 10
for housing one or more
fracturing modules 20 is shown. Trailer 10 can also bc a skid, in certain
illustrative embodiments, Each
fracturing module 20 can include an electric motor 21 and a fluid pump 22
coupled thereto. During
fracturing, fracturing module 20 is operatively associated with turbine
generator 30 to receive electric
power therefrom. In certain illustrative embodiments, a plurality of electric
motors 21 and pumps 22 can
be transported on a single trailer 10. In the illustrative embodiments of
Figure 3, four electric motors 21
and pumps 22 are transported on a single trailer 10. Each electric motor 21 is
paired to a pump 22 as a
single fracturing module 20. Each fracturing module 20 can be removably
mounted to trailer 10 to
facilitate ease of replacement as necessary. Fracturing modules 20 utilize
electric power from turbine
generator 30 to pump the fracturing fluid directly to the wellbore.
[0039] Electrical Power Generation
100401 The use of a turbine to directly drive a pump has been previously
explored. In such systems, a
transmission is used to regulate turbine power to the pump to allow for speed
and torque control. In the
present operation, natural gas is instead used to drive a dedicated power
source in the production of
electricity_ In illustrative embodiments, the dedicated power source is an on-
site turbine generator. The
need for a transmission is eliminated, and generated electricity can be used
to power the fracturing
modules, blenders, and other on-site operations as necessary.
[0041] Grid power may be accessible on-site in certain fracturing operations,
but the use of a dedicated
power source is preferred. During startup of a fracturing operation, massive
amounts of power are
required such that the use of grid power would be impractical. Natural gas
powered generators are more
suitable for this application based on the likely availability of natural gas
on-site and the capacity of
natural gas generators for producing large amounts of power. Notably, the
potential for very large
instantaneous adjustments in power drawn from the grid during a fracturing
operation could jeopardize
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the stability and reliability of the grid power system. Accordingly, a site-
generated and dedicated source
of electricity provides a more feasible solution in powering an electric
fracturing system. In addition, a
dedicated on-site operation can be used to provide power to operate other
local equipment, including
coiled tubing systems, service rigs, etc...
100421 In an illustrative embodiment, a single natural gas powered turbine
generator 30, as housed in a
restricted area C of Figure 2, can generate sufficient power (for example 31
MW at 13,800 volts AC
power) to supply several electric motors 21 and pumps 22, avoiding the current
need to deliver and
operate each fluid pump from a separate diesel-powered truck. A turbine
suitable for this purpose is a
TM2500+ turbine generator sold by General Electric. Other generation packages
could be supplied by
Pratt & Whitney or Kawasaki for example. Multiple options are available for
turbine power generation,
depending on the amount of electricity required. In an illustrative
embodiment, liquid fuels such as
condensate can also be provided to drive turbine generator 30 instead of, or
in addition to, natural gas.
Condensate is less expensive than diesel fuels, thus reducing operational
costs.
100431 Fracturing Module
[0044] With reference to Figures 4A and 4B, an illustrative embodiment of
fracturing module 20 is
provided. Fracturing module 20 can include an electric motor 21 coupled to one
or more electric pumps
22, in certain illustrative embodiments. A suitable pump is a quintiplex or
triplex plunger style pump, for
example, the SWGS-2500 Well Service Pump sold by Gardner Denver, Inc.
[0045] Electric motor 21 is operatively associated with turbine generator 30,
in certain embodiments.
Typically, each fracturing module 20 will be associated with a drive housing
for controlling electric motor
21 and pumps 22, as well as an electrical transformer and drive unit 50 (see
Figure 3) to step down the
voltage of the power from turbine generator 30 to a voltage appropriate for
electric motor 21. The
electrical transformer and drive unit 50 can be provided as an independent
unit for association with
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fracturing module 20, or can be permanently fixed to the trailer 10, in
various embodiments. If
permanently fixed, then transformer and drive unit 50 can be scalable to allow
addition or subtraction of
pumps 22 or other components to accommodate any operational requirements.
[0046] Each pump 22 and electric motor 21 are modular in nature so as to
simplify removal and
replacement from fracturing module 20 for maintenance purposes. Removal of a
single fracturing module
20 from trailer 10 is also simplified. For example, any fracturing module 20
can be unplugged and
unpinned from trailer 10 and removed, and another fracturing module 20 can be
installed in its place in a
matter of minutes.
[00471 In the illustrative embodiment of Figure 3, trailer 10 can house four
fracturing modules 20, along
with a transformer and drive unit 50. In this particular configuration, each
single trailer 10 provides more
pumping capacity than four of the traditional diesel powered fracturing
trailers 5 of Figure 1, as parasitic
losses are minimal in the electric fracturing system compared to the parasitic
losses typical of diesel
fueled systems. For example, a conventional diesel powered fluid pump is rated
for 2250 hp. However,
due to parasitic losses in the transmission, torque converter and cooling
systems, diesel fueled systems
typically only provide 1800 hp to the pumps. In contrast, the present system
can deliver a true 2500 hp
directly to each pump 22 because pump 22 is directly coupled to electric motor
21. Further, the nominal
weight of a conventional fluid pump is up to 120,000 lbs. In the present
operation, each fracturing
module 20 weighs approximately 28,000 lbs., thus allowing for placement of
four pumps 22 in the same
physical dimension (size and weight) as the spacing needed for a single pump
in conventional diesel
systems, as well as allowing for up to 10,000 hp total to the pumps. In other
embodiments, more or fewer
fracturing modules 20 may be located on trailer 10 as desired or required for
operational purposes.
[0048] In certain illustrative embodiments, fracturing module 20 can include
an electric motor 21 that is
an AC permanent magnet motor capable of operation in the range of up to 1500
rpms and up to 20,000
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ftilbs of' torque. Fracturing module 20 can also include a pump 22 that is a
plunger-style fluid pump
coupled to electric motor 21. In certain illustrative embodiments, fracturing
module 20 can have
dimensions of approximately 136" width x 108" length x 100" height. These
dimensions would allow
fracturing module 20 to be easily portable and fit with a ISO intcrmodal
container for shipping purposes
without the need for disassembly. Standard sized ISO container lengths are
typically 20' , 40' or 53'. In
certain illustrative embodiments, fracturing module 20 can have dimensions of
no greater than 136" width
x 108" length x 100" height. These dimensions for fracturing module 20 would
also allow crew
members to easily fit within the confines of fracturing module 20 to make
repairs, as illustrated in Figure
4b. In certain illustrative embodiments, fracturing module 20 can have a width
of no greater than 102" to
fall within shipping configurations and road restrictions. In a specific
embodiment, fracturing module 20
is capable of operating at 2500 hp while still having the above specified
dimensions and meeting the
above mentioned specifications for rpms and ft/lbs of torque.
100491 Electric Motor
100501 With reference to the illustrative embodiments of Figures 2 and 3, a
medium low voltage AC
permanent magnet electric motor 21 receives electric power from turbine
generator 30, and is coupled
directly to pump 22. In order to ensure suitability for use in fracturing,
electric motor 21 should be
capable of operation up to 1,500 rpm with a torque of up to 20,000 ft/lbs, in
certain illustrative
embodiments. A motor suitable for this purpose is sold under the trademark
TeraTorq(R) and is available
from Comprehensive Power, Inc. of Marlborough, Massachusetts. A compact motor
of sufficient torque
will allow the number of fracturing modules 20 placed on each trailer 10 to be
maximized.
100511 Blender
100521 For greater efficiency, conventional diesel powered blenders and
chemical addition units can be
replaced with electrically powered blender units. In certain illustrative
embodiments as described herein,
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the electrically powered blender units can be modular in nature for housing on
trailer 10 in place of
fracturing module 20, or housed independently for association with each
trailer 10. An electric blending
operation permits greater accuracy and control of fracturing fluid additives.
Further, the centrifugal
blender tubs typically used with blending trailers to blend fluids with
proppant, sand, chemicals, acid,
etc... prior to delivery to the wellbore are a common source of maintenance
costs in traditional fracturing
operations.
[0053] With reference to Figures 5A-5E and Figures 6-7, illustrative
embodiments of a blender module
40 and components thereof are provided. Blender module 40 can be operatively
associated with turbine
generator 30 and capable of providing fractioning fluid to pump 22 for
delivery to the wellbore. In certain
embodiments, blender module 40 can include at least one fluid additive source
44, at least one fluid
source 48, and at least one centrifugal blender tub 46. Electric power can be
supplied from turbine
generator 30 to blender module 40 to effect blending of a fluid from fluid
source 48 with a fluid additive
from fluid additive source 44 to generate the fracturing fluid. In certain
embodiments, the fluid from fluid
source 48 can be, for example, water, oils or methanol blends, and the fluid
additive from fluid additive
source 44 can be, for example, friction reducers, gellents, gellent breakers
or biocides.
[0054] In certain illustrative embodiments, blender module 40 can have a dual
configuration, with a first
blender unit 47a and a second blender unit 47b positioned adjacent to each
other. This dual configuration
is designed to provide redundancy and to facilitate access for maintenance and
replacement of
components as needed. In
certain embodiments, each blender unit 47a and 47b can have its own
electrically-powered suction and tub motors disposed thereon, and optionally,
other electrically-powered
motors can be utilized for chemical additional and/or other ancillary
operational functions, as discussed
further herein.
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10055] For example, in certain illustrative embodiments, first blender unit
47a can have a plurality of
electric motors including a first electric motor 43a and a second electric
motor 41a that are used to drive
various components of blender module 40. Electric motors 41a and 43a can be
powered by turbine
generator 30. Fluid can be pumped into blender module 40 through an inlet
manifold 48a by First electric
motor 43a and added to tub 46a. Thus, first electric motor 43a acts as a
suction motor. Second electric
motor 41a can drive the centrifugal blending process in tub 46a. Second
electric motor 41a can also drive
the delivery of blended fluid out of blender module 40 and to the wellbore via
an outlet manifold 49a.
Thus, second electric motor 41a acts as a tub motor and a discharge motor.
In certain illustrative
embodiments, a third electric motor 42a can also be provided. Third electric
motor 42a can also be
powered by turbine generator 30, and can power delivery of fluid additives to
blender 46a. For example,
proppant from a hopper 44a can be delivered to a blender tub 46a, for example,
a centrifugal blender tub,
by an auger 45a, which is powered by third electric motor 42a.
100561 Similarly, in certain illustrative embodiments, second blender unit 47b
can have a plurality of
electric motors including a first electric motor 43b and a second electric
motor 41b that are used to drive
various components of blender module 40. Electric motors 41b and 43b can be
powered by turbine
generator 30. Fluid can be pumped into blender module 40 through an inlet
manifold 48b by first electric
motor 43b and added to tub 46b. Thus, second electric motor 43a acts as a
suction motor. Second
electric motor 41b can drive the centrifugal blending process in tub 46b.
Second electric motor 41b can
also drive the delivery of blended fluid out of blender module 40 and to the
wellbore via an outlet
manifold 49b. Thus, second electric motor 41b acts as a tub motor and a
discharge motor. In certain
illustrative embodiments, a third electric motor 42b can also be provided.
Third electric motor 42b can
also be powered by turbine generator 30, and can power delivery of fluid
additives to blender 46b. For
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example, proppant from a hopper 44b can be delivered to a blender tub 46b, for
example, a centrifugal
blender tub, by an auger 45b, which is powered by third electric motor 42b.
100571 Blender module 40 can also include a control cabin 53 for housing
equipment controls for first
blender unit 47a and second blender unit 47b, and can further include
appropriate drives and coolers as
required.
100581 Conventional blenders powered by a diesel hydraulic system arc
typically housed on a forty-five
foot tractor trailer and are capable of approximately 100 bbl/min. In
contrast, the dual configuration of
blender module 40 having first blender unit 47a and second blender unit 47b
can provide a total output
capability of 240 bbl/min in the same physical footprint as a conventional
blender, without the need for a
separate backup unit in case of failure.
[00591 Redundant system blenders have been tried in the past with limited
success, mostly due to
problems with balancing weights of the trailers while still delivering the
appropriate amount of power.
Typically, two separate engines, each approximately 650 hp, have been mounted
side by side on the nose
of the trailer. In order to run all of the necessary systems, each engine must
drive a mixing tub via a
transmission, drop box and extended drive shaft. A large hydraulic system is
also fitted to each engine to
run all auxiliary systems such as chemical additions and suction pumps.
Parasitic power losses are very
large and the hosing and wiring is complex.
100601 In contrast, the electric powered blender module 40 described in
certain illustrative embodiments
herein can relieve the parasitic power tosses of conventional systems by
direct driving each piece of
critical equipment with a dedicated electric motor. Further, the electric
powered blender module 40
described in certain illustrative embodiments herein allows for plumbing
routes that are unavailable in
conventional applications. For example, in certain illustrative embodiments,
the fluid source can be an
inlet manifold 48 that can have one or more inlet crossing lines 50 (see
Figure 7) that connect the section
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of inlet manifold 48 dedicated to delivering fluid to first blender unit 47a
with the section of inlet
manifold 48 dedicated to delivering fluid to second blender unit 47b.
Similarly, in certain illustrative
embodiments, outlet manifold 49 can have one or more outlet crossing lines 51
(see Figure 6) that connect
the section of outlet manifold 49 dedicated to delivering fluid from first
blender unit 47a with the section
of outlet manifold 49 dedicated to delivering fluid from second blender unit
47b. Crossing lines 50 and
51 allow flow to be routed or diverted between first blender unit 47a and
second blender unit 47b. Thus,
blender module 40 can mix from either side, or both sides, and/or discharge to
either side, or both sides, if
necessary. As a result, the attainable rates for the electric powered blender
module 40 are much larger
that of a conventional blender. In certain illustrative embodiments, each side
(i.e., first blender unit 47a
and second blender unit 47b) of blender module 40 is capable of approximately
120 bbl/min. Also, each
side (i.e., first blender unit 47a and second blender unit 47b) can move
approximately 15 tlmin of sand, at
least in part because the length of auger 45 is shorter (approximately 6') as
compared to conventional
units (approximately 12')
100611 In certain illustrative embodiments, blender module 40 can be scaled
down or "downsized" to a
single, compact module comparable in size and dimensions to fracturing module
20 described herein. For
smaller fracturing or treatment jobs requiring fewer than four fracturing
modules 20, a downsized blender
module 40 can replace one of the fracturing modules 20 on trailer 10, thus
reducing operational costs and
improving transportability of the system.
100621 Control System
100631 A control system can be provided for regulating various equipment and
systems within the electric
powered fractioning operation. For example, in certain illustrative
embodiments, the control system can
regulate fracturing module 20 in delivery of treatment fluid from blender
module 30 to pumps 22 for
delivery to the wellbore. Controls for the electric-powered operation
described herein are a significant
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improvement over that of conventional diesel powered systems. Because electric
motors are controlled
by variable frequency drives, absolute control of all equipment on location
can be maintained from one
central point. When the system operator sets a maximum pressure for the
treatment, the control software
and variable frequency drives calculate a maximum current available to the
motors. Variable frequency
drives essentially "tell" the motors what they are allowed to do.
100641 Electric motors controlled via variable frequency drive arc far safer
and easier to control than
conventional diesel powered equipment. For example, conventional fleets with
diesel powered pumps
utilize an electronically controlled transmission and engine on the unit.
There can be up to fourteen
different parameters that need to be monitored and controlled for proper
operation. These signals are
typically sent via hardwired cable to an operator console controlled by the
pump driver. The signals are
converted from digital to analog so the inputs can be made via switches and
control knobs. The inputs are
then converted from analog back to digital and sent back to the unit. The
control module on the unit then
tells the engine or transmission to perform the required task and the signal
is converted to a mechanical
operation. This process takes time.
100651 Accidental over-pressures are quite common in these conventional
operations, as the signal must
travel to the console, back to the unit and then perform a mechanical
function. Over-pressures can occur
in milliseconds due to the nature of the operations. These are usually due to
human error, and can be as
simple as a single operator failing to react to a command. They aye often due
to a valve being closed,
which accidentally creates a "deadhead" situation.
100661 For example, in January of 2011, a large scale fractioning operation
was taking place in the Horn
River Basin of north-eastern British Columbia, Canada. A leak occurred in one
of the lines and a
shutdown order was given. The master valve on the wellhead was then closed
remotely. Unfortunately,
multiple pumps were still rolling and a system over-pressure ensued. Treating
iron rated for 10,000 psi
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was taken to well over 15,000 psi. A line attached to the well also separated,
causing it to whip around.
The incident caused a shutdown interruption to the entire operation for over a
week while investigation
and damage assessment were performed.
[00671 Thc control system provided according to the present illustrative
embodiments, being electrically
powered, virtually eliminates these types of scenarios from occurring. A
maximum pressure value set at
the beginning of the operation is the maximum amount of power that can be sent
to electric motor 21 for
pump 22. By extrapolating a maximum current value from this input, electric
motor 21 does not have the
available power to exceed its operating pressure. Also, because there are
virtually no mechanical systems
between pump 22 and electric motor 21, there is far less "moment of inertia"
of gears and clutches to deal
with. A near instantaneous stop of electric motor 21 results in a near
instantaneous stop of pump 22.
[00681 An electrically powered and controlled system as described herein
greatly increases the case in
which all equipment can be synced or slaved to each other. This means a change
at one single point will
be carried out by all pieces of equipment, unlike with diesel equipment. For
example, in conventional
diesel powered operations, the blender typically supplies all the necessary
fluids to the entire system. In
order to perform a rate change to the operation, the blender must change rate
prior to the pumps changing
rates. This can often result in accidental overflow of the blender tubs and/or
cavitation of the pumps due
to the time lag of each piece of equipment being given manual commands.
[0069] In contrast, the present operation utilizes a single point control that
is not linked solely to blender
operations, in certain illustrative embodiments. All operation parameters can
be input prior to beginning
the fractioning. If a rate change is required, the system will increase the
rate of the entire system with a
single command. This means that if pumps 22 are told to increase rate, then
blender module 40 along
with the chemical units and even ancillary equipment like sand belts will
increase rates to compensate
automatically.
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100701 Suitable controls and computer monitoring for the entire fracturing
operation can take place at a
single central location, which facilitates adherence to pre-set safety
parameters. For example, a control
center 40 is indicated in Figure 2 from which operations can be managed via
communications link 41.
Examples of operations that can be controlled and monitored remotely from
control center 40 via
communications link 41 can be the power generation function in Area B, or the
delivery of treatment fluid
from blender module 40 to pumps 22 for delivery to the wellbore.
100711 Comparison Example
[0072] Table 1, shown below, compares and contrasts the operational costs and
manpower requirements
for a conventional diesel powered operation (such as shown in Figure 1) with
those of a electric powered
operation (such as shown in Figure 2).
100731 Table 1
100741 Comparison of Conventional Diesel Powered Operation
vs. Electric Powered Operation
Diesel Powered Operation Electric Powered Operation
Total fuel cost (diesel) - Total fuel cost (natural gas) -
about $80,000 per day about $2,300 per day
Service interval for diesel engines - Service interval for electric motor -
about every 200-300 hours about every 50,000 hours
Dedicated crew size - Dedicated crew size -
about 40 people about 10 people
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100751 In Table 1, the "Diesel Powered Operation" utilizes at least 24 pumps
and 2 blenders, and requires
at least 54,000 hp to execute the fracturing program on that location. Each
pump burns approximately
300-400 liters per hour of operation, and the blender units burn a comparable
amount of diesel fuel.
Because of the fuel consumption and fuel capacity of this conventional unit,
it requires refueling during
operation, which is extremely dangerous and presents a fire hazard. Further,
each piece of conventional
equipment needs a dedicated tractor to move it and a driver/operator to run
it. The crew size required to
operate and maintain a conventional operation such as the one in Figure 1
represents a direct cost for the
site operator.
[0076] In contrast, the electric powered operation as described herein
utilizes a turbine that only
consumes about 6mm scf of natural gas per 24 hours. At current market rates
(approximately $2.50 per
mmbtu), this equates to a reduction in direct cost to the site operator of
over $77,000 per day compared to
the diesel powered operation. Also, the service interval on electric motors is
about 50,000 hours, which
allows the majority of reliability and maintainability costs to disappear.
Further, the need for multiple
drivers/operators is reduced significantly, and electric powered operation
means that a single operator can
run the entire system from a central location. Crew size can be reduced by
around 75%, as only about 10
people are needed on the same location to accomplish the same tasks as
conventional operations, with the
people including off-site personnel maintenance personnel. Further, crew size
does not change with
the amount of equipment used. Thus, the electric powered operation is
significantly more economical.
[00771 Modular Design and Alternate Embodiments
[00781 As discussed above, the modular nature of the electric powered
fracturing operation described
herein provides significant operational advantages and efficiencies over
traditional fracturing systems.
Each fracturing module 20 sits on trailer 10 which houses the necessary mounts
and manifold systems for
low pressure suctions and high pressure discharges. Each fracturing module 20
can be removed from
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service and replaced without shutting down or compromising the fractioning
spread. For instance, pump
22 can be isolated from trailer 10, removed and replaced by a new pump 22 in
just a few minutes. If
fracturing module 20 requires service, it can be isolated from the fluid
lines, unplugged, un-pinned and
removed by a forklift. Another fracturing module 20 can be then re-inserted in
the same fashion, realizing
a drastic time savings. In addition, the removed fracturing module 20 can be
repaired or serviced in the
field. In contrast, if one of the pumps in a conventional diesel powered
system goes down or requires
service, the tractor/trailer combination needs to be disconnected from the
manifold system and driven out
of the location. A replacement unit must then be backed into the line and
reconnected. Maneuvering
these units in these tight confines is difficult and dangerous.
[00791 The presently described electric powered fracturing operation can be
easily adapted to
accommodate additional types of pumping capabilities as needed. For example, a
replacement pumping
module can be provided that is adapted for removable mounting on trailer 10.
Replacement pumping
module can be utilized for pumping liquid nitrogen, carbon dioxide, or other
chemicals or fluids as
needed, to increase the versatility of the system and broaden operational
range and capacity. In a
conventional system, if a nitrogen pump is required, a separate unit
truck/trailer unit must be brought to
the site and tied into the fractioning spread. In
contrast, the presently described operation allows for a
replacement nitrogen module with generally the same dimensions as fractioning
module 20, so that the
replacement module can fit into the same slot on the trailer as fractioning
module 20 would. Trailer 10
can contain all the necessary electrical power distributions as required for a
nitrogen pump module so no
modifications are required. The same concept would apply to carbon dioxide
pump modules or any other
pieces of equipment that would be required. Instead of another truck/trailer,
a specialized replacement
module can instead be utilized.
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100801 Natural gas is considered to be the cleanest, most efficient fuel
source available. By designing and
constructing "fit for purpose equipment" that is powered by natural gas, it is
expected that the fracturing
footprint, manpower, and maintenance requirements can each be reduced by over
60% when compared
with traditional diesel-powered operations.
100811 In addition, the presently described electric powered fracturing
operation resolves or mitigates
environmental impacts of traditional diesel-powered operations. For example,
the presently described
natural gas powered operation can provide a significant reduction in carbon
dioxide emissions as
compared to diesel-powered operations. In an illustrative embodiment, a
fractioning site utilizing the
presently described natural gas powered operation would have a carbon dioxide
emissions level of about
2200 kg/hr, depending upon the quality of the fuel gas, which represents an
approximately 200%
reduction from carbon dioxide emissions of diesel-powered operations.
Also, in an illustrative
embodiment, the presently described natural gas powered operation would
produces no greater than about
80 decibels of sound with a silencer package utilized on turbine 30, which
meets OSHA requirements for
noise emissions. By comparison, a conventional diesel-powered fractioning pump
running at full rpm
emits about 105 decibels of sound. When multiple diesel-powered fractioning
pumps are running
simultaneously, noise is a significant hazard associated with conventional
operations.
[0082] In certain illustrative embodiments, the electric-powered fractioning
operation described herein
can also be utilized for offshore oil and gas applications, for example,
fracturing of a wellbore at an
offshore site. Conventional offshore operations already possess the capacity
to generate electric power
on-site. These vessels are typically diesel over electric, which means that
the diesel powerplant on the
vessel generates electricity to meet all power requirements including
propulsion. Conversion of offshore
pumping services to run from an electrical power supply will allow transported
diesel fuel to be used in
power generation rather than to drive the fracturing operation, thus reducing
diesel fuel consumption. The
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electric power generated from the offshore vessel's power plant (which is not
needed during station
keeping) can be utilized to power one or more fracturing modules 10. This is
far cleaner, safer and more
efficient than using diesel powered equipment. Fracturing modules 10 are also
smaller and lighter than
the equipment typically used on the deck of offshore vessels, thus removing
some of the current ballast
issues and allowing more equipment or raw materials to be transported by the
offshore vessels.
[0083] In a deck layout for a conventional offshore stimulation vessel, skid
based, diesel powered
pumping equipment and storage facilities on the deck of the vessel create
ballast issues. Too much heavy
equipment on the deck of the vessel causes the vessel to have higher center of
gravity. Also, fuel lines
must be run to each piece of equipment greatly increasing the risk of fuel
spills. In illustrative
embodiments of a deck layout for an offshore vessel utilizing electric-powered
fractioning operations as
described herein, the physical footprint of the equipment layout is reduced
significantly when compared
to the conventional layout. More free space is available on deck, and the
weight of equipment is
dramatically decreased, thus eliminating most of the ballast issues. A vessel
already designed as diesel-
electric can be utilized. When the vessel is on station at a platform and in
station keeping mode, the vast
majority of the power that the ship's engines are generating can be run up to
the deck to power modules.
The storage facilities on the vessel can be placed below deck, further
lowering the center of gravity, while
additional equipment, for instance, a 3-phase separator, or coiled tubing
unit, can be provided on deck,
which is difficult in existing diesel-powered vessels. These benefits, coupled
with the electronic control
system, give a far greater advantage over conventional vessels.
100841 While the present description has specifically contemplated a
fracturing system, the system can be
used to power pumps for other purposes, or to power other oilfield equipment.
For example, high rate and
pressure pumping equipment, hydraulic fracturing equipment, well stimulation
pumping equipment
and/or well servicing equipment could also be powered using the present
system. In addition, the system
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can be adapted for use in other art fields requiring high torque or high rate
pumping operations, such as
pipeline cleaning or &watering mines.
10085] It is to be understood that the subject matter herein is not limited to
the exact details of
construction, operation, exact materials, or illustrative embodiments shown
and described, as
modifications and equivalents will be apparent to one skilled in the art.
Accordingly, the subject matter is
therefore to be limited only by the scope of the appended claims.
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