U.S. patent application number 14/169690 was filed with the patent office on 2014-05-29 for frac water heating system and method for hydraulically fracturing a well.
The applicant listed for this patent is Ronald L. Chandler. Invention is credited to Ronald L. Chandler.
Application Number | 20140144393 14/169690 |
Document ID | / |
Family ID | 50772260 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140144393 |
Kind Code |
A1 |
Chandler; Ronald L. |
May 29, 2014 |
FRAC WATER HEATING SYSTEM AND METHOD FOR HYDRAULICALLY FRACTURING A
WELL
Abstract
The present invention overcomes many of the disadvantages of
prior art mobile oil field heat exchange systems by providing an
improved frac water heating system. The present invention is a
self-contained unit which is easily transported to remote
locations. In one embodiment, the present invention includes a
single-pass tubular coil heat exchanger contained within a
closed-bottom firebox having a forced-air combustion and cooling
system. In another embodiment, the present invention includes
multiple, single-pass heat exchanger units arranged in a vertically
stacked configuration. The rig also includes integral fuel tanks,
hydraulic and pneumatic systems for operating the rig at remote
operations in all weather environments. In a preferred embodiment,
the improved frac water heating system is used to heat water
on-the-fly (i.e., directly from the supply source to the well head)
to complete hydraulic fracturing operations. The present invention
also includes systems for regulating and adjusting the fuel/air
mixture within the firebox to maximize the combustion efficiency.
The system includes a novel hood opening mechanism attached to the
exhaust stack of the firebox.
Inventors: |
Chandler; Ronald L.;
(Wichita Falls, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chandler; Ronald L. |
Wichita Falls |
TX |
US |
|
|
Family ID: |
50772260 |
Appl. No.: |
14/169690 |
Filed: |
January 31, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13897883 |
May 20, 2013 |
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14169690 |
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12352505 |
Jan 12, 2009 |
8534235 |
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13897883 |
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61078734 |
Jul 7, 2008 |
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Current U.S.
Class: |
122/14.2 ;
122/17.2; 122/18.4 |
Current CPC
Class: |
F24H 1/43 20130101; F24H
9/2035 20130101; F24H 1/06 20130101; F24H 1/08 20130101; F24H 1/40
20130101; F28D 7/08 20130101; F28F 9/26 20130101; E21B 43/26
20130101; F28D 7/02 20130101; F28D 7/0066 20130101 |
Class at
Publication: |
122/14.2 ;
122/17.2; 122/18.4 |
International
Class: |
F24H 1/06 20060101
F24H001/06; F24H 1/00 20060101 F24H001/00; F24H 9/20 20060101
F24H009/20; F24H 1/08 20060101 F24H001/08 |
Claims
1. A portable system for heating treatment fluids at a remote work
site, comprising: a closed-bottom firebox having an exhaust stack
configured near the top of said firebox; a heat exchanger device
contained within said firebox, said heat exchanger device
comprising an upper portion oriented about a first axis and a lower
portion oriented about a second axis, said lower portion comprising
a helical tubular coil oriented about a horizontal axis so as to
define a chamber for receiving a substantially horizontal
combustion flow, said chamber being substantially enclosed by said
helical tubular coil on all but one opened side; a fluid supply
system including a fluid supply pump in fluid communication with an
inlet of said heat exchanger device; three or more burner
assemblies configured in said firebox, each of said burner
assemblies comprising a nozzle that projects an atomized fuel-air
spray into said chamber though said opened side, which when
combusted results in a substantially horizontal combustion flow
into said chamber, a primary air system for supplying a first
pressurized air flow to each of said burner assemblies, wherein
said primary air system comprises a blower pump fluidly connected
to a primary air inlet of each of said plurality of burner
assemblies, said blower pump comprising a positive displacement
rotary blower; and a secondary air system for supplying a second
pressurized air flow to said firebox, wherein said helical tubular
coil includes a plurality of traversing lateral tubes which
substantially enclose said chamber on side opposing said opened
side, wherein at least one of said traversing lateral tubes is
configured directly in line with said substantially horizontal
combustion flow; and wherein said second pressurized air flow
increases the convective heat transfer of thermal energy from said
combustion flow to said treatment fluid as said fluid is pumped
through said heat exchanger by said supply pump.
2. The system of claim 1, wherein said heat exchanger device has a
single inlet and a single outlet, wherein said inlet is configured
substantially near the top of the heat exchanger and said outlet is
configured substantially near the bottom of the heat exchanger to
minimize back pressure on said fluid supply pump.
3. The system of claim 2, wherein said three or more burner
assemblies each comprise a gas-fired burner assembly and said upper
portion of said heat exchanger device comprises a plurality of
stacked horizontal rows of tubing faked down in a series of
reversing loops oriented about a vertical axis.
4. The system of claim 1, wherein said heat exchanger device
comprises a plurality of single-pass heat exchanger units arranged
in a vertically stacked configuration, wherein each of said
plurality of heat exchanger units includes a separate inlet in
fluid communication with said fluid supply pump, and a separate
outlet in fluid communication with a common outlet conduit.
5. The system of claim 4, wherein said plurality of heat exchanger
units comprises a first heat exchanger unit configured in said
lower portion and a second heat exchanger unit configured in said
upper portion, said second heat exchanger unit comprises a
plurality of stacked horizontal rows of tubing faked down in a
series of reversing loops oriented about a vertical axis.
6. The system of claim 4, wherein each of said three or more burner
assemblies comprise a gas-fired burner assembly.
7. The system of claim 4, wherein each of said three or more burner
assemblies comprise an oil-fired burner assembly.
8. The system of claim 4, wherein said secondary air system
comprises a plurality of centrifugal fan mechanisms aligned in a
parallel configuration and having a common driveshaft, wherein each
of said plurality of centrifugal fan mechanisms includes a housing
in fluid communication with ductwork that is fluidly connected to a
plurality of vents in said firebox.
9. The system of claim 8, wherein said blower pump is rotatively
coupled to said driveshaft.
10. The system of claim 9, wherein the blower pump and said
plurality of centrifugal fan mechanisms are powered by a motor
attached to said driveshaft.
11. The system of claim 10, wherein said motor is hydraulically
powered.
12. The system of claim 4, wherein said plurality of burner
assemblies comprises a first and second set of burner assemblies,
wherein each set comprises more than one burner assembly; said
primary air system comprises a first primary blower system which
includes a first blower pump fluidly connected to a primary air
inlet of each of said first set of burner assemblies, and a second
primary blower system which includes a second blower pump fluidly
connected to a primary air inlet of each of said second set of
burner assemblies; said secondary air system comprises a first
secondary blower system which includes a first plurality of
centrifugal fan mechanisms aligned in a parallel configuration and
having a common first driveshaft, wherein each of said first
plurality of centrifugal fan mechanisms includes a housing in fluid
communication with a first ductwork that is fluidly connected to a
first plurality of vents in said firebox, and a second secondary
blower system which includes a second plurality of centrifugal fan
mechanisms aligned in a parallel configuration and having a common
second driveshaft, wherein each of said second plurality of
centrifugal fan mechanisms includes a housing in fluid
communication with a second ductwork that is fluidly connected to a
second plurality of vents in said firebox; wherein said first
blower pump is rotatively coupled to said first driveshaft and said
second blower pump is rotatively coupled to said second
driveshaft.
13. The system of claim 12, wherein said first blower pump and said
first plurality of centrifugal fan mechanisms are powered by first
motor rotatively coupled to said first driveshaft; and said second
blower pump and said second plurality of centrifugal fan mechanisms
are powered by second motor rotatively coupled to said second
driveshaft.
14. A system of claim 4, further comprising a fuel supply system,
which includes a fuel pressure control motor valve that controls
the volume of pressurized fuel supplied to each set of burner
assemblies.
15. The system of claim 14, wherein said fuel pressure control
motor valve is pneumatically actuated.
16. The system of claim 14, further comprising a temperature
controller mechanism, which controls the temperature of the
treatment fluid exiting said heat exchanger outlet conduit by
adjusting a control signal to said fuel pressure control motor
valve to increase or decrease the volume of pressurized fuel
supplied to each set of burner assemblies.
17. The system of claim 16, wherein said temperature controller
mechanism automatically adjusts said control signal in response to
a comparison between the temperature of the treatment fluid exiting
said heat exchanger outlet conduit and a set point temperature
setting on said temperature controller mechanism.
18. The system of claim 17, wherein said temperature controller
mechanism senses the temperature of said treatment fluid at said
heat exchanger outlet conduit, compares said temperature to a
set-point temperature, and adjusts said control signal to said fuel
pressure control motor valve to increase or decrease the volume of
pressurized fuel supplied to each set of burner assemblies so that
said temperature will equal said set-point temperature.
19. The system of claim 1, wherein said firebox includes at least
one vent and passageway, which supplies ambient air from the upper
exterior of the firebox to the front of the burner assemblies.
20. The system of claim 4, further including a hood door assembly,
which comprises a first door, which is pivotally mounted to one
side of said exhaust stack; and a second door, which is pivotally
mounted to an opposing side of said exhaust stack.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part application of
U.S. application Ser. No. 13/897,883 filed May 20, 2013, which is a
divisional application of U.S. application Ser. No. 12/352,505 (now
U.S. Pat. No. 8,534,235) filed Jan. 12, 2009, which claims the
benefit of and priority to a U.S. Provisional Patent Application
No. 61/078,734 filed Jul. 7, 2008, the technical disclosure of
which is hereby incorporated herein by reference.
[0002] This application is related to the following copending US
Patent Applications, which are incorporated by reference herein in
their entirety:
[0003] U.S. patent application Ser. No. 14/______, (Attorney Docket
No. DCHAN.0101DIV-CIP2), "Frac Water Heating System and Method for
Hydraulically Fracturing a Well," filed Jan. 31, 2014.
[0004] U.S. patent application Ser. No. 14/______, (Attorney Docket
No. DCHAN.0101DIV-CIP3), "Frac Water Heating System and Method for
Hydraulically Fracturing a Well," filed Jan. 31, 2014.
BACKGROUND OF THE INVENTION
[0005] 1. Technical Field
[0006] The present invention relates to apparatus and methods for
heating a water or petroleum based fluid for injection into an oil
or gas well or into a pipeline system.
[0007] 2. Description of the Related Art
[0008] It is common in the oil and gas industry to treat oil and
gas wells and pipelines with heated fluids such as water and oil.
For example, one such application commonly known as a hydraulic
fracturing job or "frac" job, involves injecting large quantities
of a heated aqueous solution into a subterranean formation to
hydraulically fracture it. Such frac jobs are typically used to
initiate production in low-permeability reservoirs and/or
re-stimulate production in older producing wells. Water is
typically heated to a specific temperature range to prevent
expansion or contraction of the downhole well casing. The heated
water is typically combined with a mixture of chemical additives
(e.g., friction reducer polymers which reduce the viscosity of the
water and improve its flowability so that it's easier to pump down
the well), proppants (e.g., a special grade of light sand), and a
cross-linked guar gel that helps to carry the sand down into the
well. This fracking fluid is then injected into a well hole at a
high flow rate and pressure to break up the formation, increasing
the permeability of the rock and helping the gas or oil flow toward
the surface. As the fracking solution cracks the rock formation, it
deposits the sand. As the fractures try to close, the sand keeps
them propped open. Frac jobs are typically performed once when a
well is newly drilled, and again after a couple of years when the
production flow rate begins to decline
[0009] Another application, commonly referred to as a "hot oil
treatment", involves treating tubulars of an oil and gas well or
pipeline by flushing them with a heated solution to remove build up
of paraffin along the tubulars that precipitate from the oil stream
that is normally pumped therethrough.
[0010] Frac jobs and hot oil treatments are typically performed at
the remote well sites and usually require less than a week to
complete. Consequently, the construction of a permanent heating
facility at the well site is not cost effective. Instead, portable
heat exchangers, which are capable of transport to remote well
sites via improved and unimproved roads, are commonly used.
[0011] In the past, such portable heat exchangers have typically
employed gas-fired heat sources using a liquefied petroleum gas
(LPG) such as propane to heat treatment fluids at remote well
sites. Such gas-fired heater units typically include a tubular coil
heat exchanger configured above one or more ambient aspirated
open-flame gas burners in an open-ended firebox housing. The
tubular coil heat exchanger typically comprises a fluid inlet in
communication with a plurality of interconnected tubes, which in
turn communicate with a fluid outlet. The plurality of tubes is
typically arranged in a stacked configuration of planar rows,
wherein each tube in a row is aligned in parallel with the other
tubes. The outlet of each tube is connected in series to the inlet
of an adjacent tube in the row by means of a curved tube or return
bend. Similarly, each planar row is connected to the adjacent rows
above and below by connecting the outlet of the outermost tube in
one row with the inlet of the outermost tube in another row by
means of a curved tube or return bend.
[0012] The one or more gas burners are typically positioned below
the tubular coil heat exchanger so as to project a vertical flame
up and through the heat exchanger. The gas burners are supplied
with gas fuel from a nearby gas storage tank (e.g., a propane
tank). Ambient air is also supplied to the burners via the
opened-ended bottom of the firebox housing. The hot flue gasses
generated from the burning of the LPG rise up and through the
tubular coil heat exchanger within the firebox housing and exhaust
via a vent at the top of the firebox housing.
[0013] While such conventional gas-fired heat sources are adequate
for performing many oil field servicing tasks, they exhibit a
number of inherent drawbacks. These inherent limitations
significantly impact their effectiveness in performing certain
heating operations at remote oil field work sites. For example,
frac jobs typically require the production of massive volumes of
heated water. While conventional gas-fired heat sources are
certainly capable of heating fluids such as water, they are poorly
suited to heating in a timely manner large volumes of continuously
flowing water in many commonly occurring climactic and atmospheric
conditions. Moreover, the logistics involved in conducting such
heating operations at remote work sites negatively impacts the cost
efficiencies of such a system.
[0014] For example, LPG (e.g., propane gas) has a relatively low
energy content and density when compared to other fuel options. For
example, diesel fuel when properly combusted typically releases
about 138,700 British thermal units (BTU) per US gallon, while
propane typically releases only about 91,600 BTU per liquid gallon,
or over 33% less. Thus, conventional gas-fired heating units often
lack sufficient heating capacity to produce sufficient quantities
of heated water rapidly enough for the required operation to be
completed. Consequently, in order to provide sufficient quantities
of heated water on a timely basis for a typical frac job, the
treatment water must often be preheated and stockpiled in numerous
frac water holding tanks These holding tanks range in size up to
500 bbl. (i.e., approximately 21,000 gallons). It is not unusual
for a typical frac job to require 10 or even 20 frac water holding
tanks at the remote work site. The preheated water is typically
overheated so as to allow for cooling while waiting to be injected
into the well. Oftentimes, the preheated treatment water must be
reheated just prior to injection into the well head. Needless to
say, the logistics involved with providing additional holding tanks
at the remote work site and the additional costs incurred in
overheating or reheating the supply water negatively impacts the
efficiency of the overall operation.
[0015] While the technique of overheating and stockpiling supply
water can ameliorate some the shortcomings in the heating capacity
of conventional gas-fired heat sources, in certain circumstances
(e.g., severely cold weather or high altitude) it is inadequate.
This is due to a number of reasons. First, the temperature change
requirement for the system is simply greater in colder weather.
That is, in colder weather the intake water supplied to the
gas-fired heating unit is colder while the required injection
temperature remains essentially the same. Thus, it takes longer for
the conventional gas-fired heating unit to preheat the supply
water. The problem is further compounded by the fact that the
stockpiled preheated water cools more rapidly in colder weather.
Moreover, at higher altitudes there is less oxygen in the ambient
atmosphere for combustion in a conventional, naturally aspirated
gas burner. Thus, at higher altitudes the heating capacity of
conventional gas-fired heat sources is further reduced.
[0016] In addition, propane gas requires large and heavy
high-pressure fuel tanks for its transport to remote sites. The
size of such high-pressure fuel tanks is, of course, limited by the
size of existing roads. Thus, a typical frac job may require the
transport of multiple large high-pressure fuel tanks to a remote
site to ensure an adequate supply of fuel to complete the
operation.
[0017] Furthermore, there are several safety concerns which must be
taken into consideration when using conventional gas-fired heat
sources. As mentioned previously, current gas-fired heat exchangers
typically use a naturally aspirated, open flame burner (i.e., a
burner which is open to the ambient atmosphere). The fire boxes of
such heat exchanger are typically elevated above the ground and
opened on the bottom. The gas-fired burners are typically
positioned near the open bottom of the firebox and directly below
the heat exchange tubing. Theses conventional gas-fired burners
draw ambient air as necessary to assist in the combustion of the
propane gas. While simple and efficient in providing air for
combustion, open flame burners present a number of safety concerns.
An open flame at the well site poses a substantial risk of
explosion and uncontrolled fire, which can destroy the investment
in the rig and injure or even cost the lives of the well operators.
Moreover, open flame burners are particularly susceptible to
erratic burning or complete blow-out in gusty wind conditions.
Current U.S. government safety regulations provide that the open
flame heating of the treatment fluids cannot take place within the
immediate vicinity of the well.
[0018] While safety concerns are of overriding importance,
compliance with the no open-flame regulations requires additional
time and expense to conduct heated fluid well treatments. Thus,
there has been a long felt need for safer and more efficient
apparatus and methods of heating treatment fluid for injecting into
the tubulars of oil and gas wells and pipelines without using an
open flame heat source in the vicinity of the treatment
location.
SUMMARY OF THE INVENTION
[0019] The present invention overcomes many of the disadvantages of
prior art mobile oil field heat exchange systems by providing a
self-contained, frac-water heating system that is capable of safely
and continuously heating large quantities of treatment fluids at
remote locations in severely cold weather or at high altitude. In
one embodiment, the present invention is disposed on a trailer rig
and includes a closed-bottom firebox having a forced-air combustion
and cooling system. The rig also includes integral fuel tanks,
hydraulic and pneumatic systems for operating the rig at remote
operations in all-weather environments. In a preferred embodiment,
the frac-water heating system is used to heat treatment fluid
on-the-fly (i.e., directly from the supply source to the well head)
to complete hydraulic fracturing operations.
[0020] The present invention comprises a closed firebox that
includes a novel heat exchanger comprised of one or more
single-pass tubular coils configured in a highly oscillating or
serpentine manner and oriented along multiple axes so as to
maximize its exposure to the heat generated by the burner
assemblies. The design of the heat exchanger includes a horizontal
tunnel configured within a bottom portion. The burner assemblies
are configured and oriented in relation to the tunnel so that their
flames are initially generated in a horizontal fashion into the
tunnel within the heat exchanger. In one embodiment, the burner
assemblies comprise oil-fired burner assemblies which combust fuel
oil. In another embodiment, the burner assemblies comprise
gas-fired burner assemblies, which combust a liquefied petroleum
gas (LPG) such as propane.
[0021] The present invention further includes a novel forced-air
combustion and cooling system. The forced-air system is comprised
of a primary air system and a secondary air system. The primary air
system provides pressurized air directly to the burner assemblies
to maximize atomization and combustion of the fuel. The secondary
air system provides pressurized air to strategic positions within
the firebox to assist in controlling the cooling of the firebox and
to maximize the combustion of the fuel/air mixture. In addition,
vents and vent passageways are formed in the wall of the firebox
and supply supplemental ambient air to front of the burner
assemblies. The vents allow the system to be operated more safely
by allowing burner access doors to be configured in a "down" or
"closed" position during operations, which significantly reduces
the operational noise created by burner assemblies when operating.
Moreover, with the burner access doors configured in the "down"
position, the danger inherent in a blowback event of the burner
assemblies is greatly reduced. The primary and secondary air
systems are powered by hydraulic pumps integral to the overall
system. The present invention also includes systems for regulating
and adjusting the fuel/air mixture within the firebox to maximize
the combustion efficiency.
[0022] The improved system of the present invention also includes
several subsystems for maximizing the safety and efficiency of the
heat exchanger system. The system includes a novel hood mechanism
attached to the exhaust stack of the firebox. In addition, the
system includes a novel intake air muffler/silencer system, which
signifi-cantly reduces the noise generated by the intake of such
large quantities of ambient air.
[0023] The system also includes novel methods for heating large
volumes of treatment fluids, such as water, in a continuously
flowing fashion so that heating operations can be performed
"on-the-fly", i.e., without the use of preheated stockpiles of
treatment fluid. For example, water at ambient temperature
conditions can be drawn into the device of the present invention
and heated so that sufficient volumes of continuously flowing
heated treatment fluid may be supplied directly to the well head
for conducting hydraulic fracturing operations on the well. The
system also includes novel methods for controlling the heating of
the treatment fluid as it passes through the system. The system
further includes novel methods for controlling the temperature
change and volume flow of treatment fluid as it passes through the
system. The novel methods include using two or more frac water
heating systems in a parallel configuration to increase the
continuous flowrate of treatment fluid to the well head.
Alternatively, the novel methods include using two or more frac
water heating systems in a tandem configuration to increase the
differential in temperature of the treatment fluid from the ambient
source to the wellhead.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A more complete understanding of the method and apparatus of
the present invention may be had by reference to the following
detailed description when taken in conjunction with the
accompanying drawings, wherein:
[0025] FIG. 1A is a perspective view of an embodiment of the Frac
Water Heating System of the present invention;
[0026] FIG. 1B is a perspective view of an alternate embodiment of
the Frac Water Heating System of the present invention;
[0027] FIG. 2A is a left side elevation view of the embodiment of
the Frac Water Heating System of the present invention shown in
FIG. 1A;
[0028] FIG. 2B is a right side elevation view of the embodiment of
the Frac Water Heating System of the present invention shown in
FIG. 1A;
[0029] FIG. 2C is a close-up view of the mechanism for opening and
closing the opposing hood doors of the embodiments of the Frac
Water Heating System of the present invention shown in FIGS. 1A and
1B;
[0030] FIG. 2D is a left side elevation view of the alternate
embodiment of the Frac Water Heating System of the present
invention shown in FIG. 1B;
[0031] FIG. 2E is a right side elevation view of the alternate
embodiment of the Frac Water Heating System of the present
invention shown in FIG. 1B;
[0032] FIG. 3A is an overhead plan view of the embodiment of the
Frac Water Heating System of the present invention shown in FIG.
1A;
[0033] FIG. 3B is an overhead plan view of the alternate embodiment
of the Frac Water Heating System of the present invention shown in
FIG. 1B;
[0034] FIG. 4A is a front perspective view of an embodiment of the
heat exchanger of the Frac Water Heating System of the present
invention;
[0035] FIG. 4B is a back perspective view of the embodiment of the
heat exchanger shown in FIG. 4A;
[0036] FIG. 4C is a front perspective view of an alternate
embodiment of the heat exchanger of the Frac Water Heating System
of the present invention;
[0037] FIG. 4D is a front perspective, exploded view of the
embodiment of the heat exchanger shown in FIG. 4C;
[0038] FIG. 4E is a cross-sectional view of the embodiments of the
heat exchanger shown in FIGS. 4A-4D installed in the embodiments of
the Frac Water Heating System of the present invention;
[0039] FIG. 5 is perspective view of a portion of the primary and
secondary air systems of the Frac Water Heating System of the
present invention;
[0040] FIG. 6 is cut-away cross-sectional view of a portion of the
secondary blower section of the secondary air system of the Frac
Water Heating System of the present invention;
[0041] FIG. 7A is a schematic depiction of the hydraulic, fuel, and
air supply systems of the embodiment of the Oil-Fired Frac Water
Heating System of the present invention;
[0042] FIG. 7B is a schematic depiction of the hydraulic, fuel, and
air supply systems of the embodiment of the Gas-Fired Frac Water
Heating System of the present invention;
[0043] FIG. 8A is an overhead view of a schematic depiction of the
hydraulic, fuel, and air supply systems of the embodiment of the
Oil-Fired Frac Water Heating System of the present invention shown
in FIG. 7A;
[0044] FIG. 8B is an overhead view of a schematic depiction of the
hydraulic, fuel, and air supply systems of the embodiment of the
Gas-Fired Frac Water Heating System of the present invention shown
in FIG. 7B
[0045] FIG. 9A is a schematic diagram of a preferred embodiment of
the method of the present invention;
[0046] FIG. 9B is a schematic diagram of an alternative embodiment
of the method of the present invention; and
[0047] FIG. 9C is a schematic diagram of another alternative
embodiment of the method of the present invention.
[0048] Where used in the various figures of the drawing, the same
numerals designate the same or similar parts. Furthermore, when the
terms "top," "bottom," "first," "second," "upper," "lower,"
"height," "width," "length," "end," "side," "horizontal,"
"vertical," and similar terms are used herein, it should be
understood that these terms have reference only to the structure
shown in the drawing and are utilized only to facilitate describing
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0049] With reference to the Figures, and in particular to FIGS. 1A
and 2A-C, a first embodiment of the improved frac water heating
system 100 of the present invention is shown. The first embodiment
100 shown in the referenced Figures can be configured with either
an oil-fired or a gas-fired heating system. As depicted, the first
embodiment of the frac water heating system 100 is configured on a
drop deck trailer 14 and suitable for transport to remote oil field
sites. The system 100 includes a fuel storage and supply system, a
firebox 40 containing a single heat exchanger 50, primary 70 and
secondary 80 air supply systems connected to the firebox 40, and an
auxiliary power plant 30 for driving an accessory gearbox 32. The
accessory gearbox 32, in turn, drives multiple hydraulic pumps,
which power a main fluid pump 94 and the air supply systems. The
main fluid pump 94 is used to draw treatment fluid, such as water,
from a fluid source and supply it to the intake 51 of the heat
exchanger 50. The hydraulic pressure generated by the main fluid
pump 94 effectively pumps the treatment fluid through the heat
exchanger 50 where it is heated. As the treatment fluid proceeds
through a single pass of the heat exchanger 50 it increases in
temperature until it reaches an outlet 52 of the heat exchanger 50
where it is directed via tubular conduits or hose to the well head
for injection into the formation. The system 100 also includes a
control quadrant 10 and control levers 12 for operating and
monitoring the system 100.
[0050] With reference to the Figures, and in particular to FIGS. 1B
and 2C-E, a second alternative embodiment of the improved frac
water heating system 1008 of the present invention is shown. The
second embodiment 100A shown in the referenced Figures can be
configured with either an oil-fired or a gas-fired heating system.
As depicted, the second embodiment of the frac water heating system
100A is configured on a drop deck trailer 14 and suitable for
transport to remote oil field sites. The system 100A includes a
fuel storage and supply system, a firebox 40 containing a heat
exchanger device 50A having two or more single-pass heat exchanger
units arranged in a stacked configuration, primary 70 and secondary
80 air supply systems connected to the firebox 40, and an auxiliary
power plant 30 for driving an accessory gearbox 32. The accessory
gearbox 32, in turn, drives multiple hydraulic pumps, which power a
main fluid pump 94 and the air supply systems. The main fluid pump
94 is used to draw treatment fluid, such as water, from a fluid
source and supply it to the multiple inlets 51A-C of the a heat
exchanger device 50A having two or more single-pass heat exchanger
units arranged in a stacked configuration. The hydraulic pressure
generated by the main fluid pump 94 effectively pumps the treatment
fluid through the heat exchanger device 50A where it is heated. As
the treatment fluid proceeds through a single pass of its
respective heat exchanger unit, its temperature increases until it
reaches the outlet 52A-C of its respective heat exchanger unit 56A,
53A, 53B where it is collected and directed via tubular conduits or
hose to the well head for injection into the formation. The system
100A also includes a control quadrant 10 and control levers 12 for
operating and monitoring the system 100A.
[0051] As shown in the embodiments depicted in the FIGS. 1A and 1B,
the entire frac water heating system of the present invention may
be configured on a single drop deck trailer 14 having multiple
wheels 16 and connected to a separate towing vehicle 2. It is
understood that alternate embodiments of the system of the present
invention may be skid mounted or configured integral to a single
vehicle. In addition, the subject invention may also be configured
so that one or more of the various components of the system (e.g.,
fuel tank 20, firebox 40, and auxiliary power plant 30) are
configured on separate trailers, vehicles or skids for transport to
the remote work site.
[0052] With reference again to the Figures, and in particular to
FIGS. 2A-2E and 3A-B, the first and second embodiments of the
improved frac water heating system 100, 100A of the present
invention include several common components. The components of the
embodiments of the improved frac water heating system 100, 100A of
the present invention will now be described in greater detail. As
depicted in the Figures, each of the embodiments the present
invention 100, 100A is disposed on a single trailer rig 14 and
includes a firebox 40 containing a heat exchanger device, primary
70 and secondary 80 air supply systems connected to the firebox 40,
a fuel system for storing and supplying fuel to multiple burner
assemblies 60 configured in the firebox 40, and an auxiliary power
plant 30, which powers multiple hydraulic systems and assorted
auxiliary systems. The firebox 40 may also include one or more
vents 40b and passageway 40c which supplies ambient air from the
upper exterior of the firebox 40 to the front of the burner
assemblies 60. The vent 40b and passageway 40c enable the burner
assemblies 60 to operate with the access door 40a configured in a
"closed" position, which significantly reduces the operational
noise created by burner assemblies 60 when operating. Moreover,
with the burner access doors 40a configured in the "down" position
(shown in FIG. 1A), the danger inherent in a blowback event of the
burner assemblies 60 is greatly reduced.
Auxiliary Power Plant & Hydraulic System
[0053] As depicted in the Figures, the auxiliary power plant 30 is
configured near the front end of the trailer 14. The auxiliary
power plant 30 provides power for driving an accessory gearbox 32
and assorted auxiliary systems (e.g., electric, pneumatic). In one
embodiment, the auxiliary power plant 30 comprises a diesel engine,
which includes an electric alternator and air compressor.
Alternatively, the electric alternator and air compressor may be
powered by the accessory gearbox 32. The electric alternator
provides electrical power to the system 100 and the pneumatic
compressor provides pneumatic pressure for controlling the system
100.
[0054] The auxiliary power plant 30 provides the primary motive
force for driving the accessory gearbox 32. The accessory gearbox
32, in turn, drives multiple hydraulic pumps that power the
hydraulic systems of the present invention. Each hydraulic pump is
used to power an independent hydraulic circuit. For example, in the
depicted embodiment, the accessory gearbox 32 powers three
hydraulic circuit systems. The first hydraulic circuit includes a
first hydraulic pump 33 that supplies pressurized hydraulic fluid
via supply/return line 33a to a first hydraulic motor 36, which
powers the first air blower system. The second hydraulic circuit
includes a second hydraulic pump 34 that supplies pressurized
hydraulic fluid via supply/return line 34a to the second hydraulic
motor 37, which powers the second air blower system. The third
hydraulic circuit includes a third hydraulic motor 35 that supplies
pressurized hydraulic fluid via supply/return line 35a to a third
hydraulic motor 38, which powers the main fluid pump 94. The three
hydraulic systems are supplied by a hydraulic reservoir 31
positioned near the accessory gearbox 32. In a preferred
embodiment, the three hydraulic pumps 33, 34, 35 each comprise a
mechanically-driven, variable-displacement, hydraulic pump; while
the three hydraulic motors 36, 37, 38 each comprise fixed
displacement hydraulic motors. The hydraulic pumps 33, 34, 35 are
rated at 5000 psi, but typically operated at approximately
2500-3000 psi.
Treatment Fluid Supply System
[0055] The main fluid pump 94 is used to draw treatment fluid, such
as water, from a fluid source and supply it to the inlet of the
heat exchanger device. The main fluid pump 94 is typically integral
to the system and has sufficient power to both draw the treatment
fluid from a source and to pump the treatment fluid through the
heat exchanger device and on to the well head for subsequent
injection into the formation. In one embodiment, the main fluid
pump 94 comprises a hydraulically-powered centrifugal fluid pump
that is capable of supplying treatment fluid to the heat exchanger
device at a pressure of about 150 psi. The volume of treatment
fluid pumped through the heat exchanger device will vary with the
pump speed and the configuration of the heat exchanger device. In a
preferred embodiment, the main fluid pump 94 is capable of pumping
a maximum of 252 gpm of treatment fluid through the heat exchanger
device.
[0056] As shown in the Figures, the fluid supply system may include
an intake manifold 90 for connecting one or more supply hose (not
shown) to the system's respective intake. The intake manifold 90
may include one or more spigots 91 for receiving supply hose in
fluid communication with the fluid source. Each inlet spigot 91 may
further include a valve mechanism 92, which selectively controls
the fluid flow through its respective inlet spigot 91. Tubular
intake conduits 93a, 93b fluidly connect the inlet of the main
fluid pump 94 with the intake manifold 90. Inlet conduit 93c
fluidly connects the outlet of the main fluid pump 94 with the
inlet of the heat exchanger device. For example, as shown in FIG.
2A, inlet conduit 93c of the first embodiment of the improved frac
water heating system 100 fluidly connects the outlet of the main
fluid pump 94 to the single inlet 51 of the heat exchanger 50. In
contrast, while conduit 93c of the second embodiment of the
improved frac water heating system 100A (see FIG. 2B) includes an
inlet that is fluidly connected to the outlet of the main fluid
pump 94, it further includes multiple outlets which divide the
fluid flow amongst the plurality of inlets 51A-C of the plurality
of single-pass heat exchanger units. As will be explained in
greater detail infra, by dividing the fluid flow amongst multiple
inlets the flow capacity of a heat exchanger device is greatly
enhanced while reducing internal pressures on the system.
[0057] The hydraulic pressure generated by the main fluid pump 94
effectively pumps the treatment fluid through the heat exchanger
device where it is heated. As the treatment fluid proceeds through
a single pass of the heat exchanger device it increases in
temperature until it reaches an outlet of the heat exchanger device
where it is directed via tubular outlet conduit 95 and supply hose
(not shown) to the well head for injection into the formation.
[0058] For example, as shown in FIG. 2B, in the first embodiment of
the improved frac water heating system 100 the single outlet 52 of
the heat exchanger 50 is fluidly connected to outlet conduit 95. In
contrast, as shown in FIGS. 2E and 3B, in the second embodiment of
the improved frac water heating system 100A the multiple outlets
52A-C of the plurality of single-pass heat exchanger units that are
fluidly connected to a common outlet conduit 95.
[0059] As shown in the Figures, the fluid supply system may further
include an outlet manifold 96 having one or more spigots 97 for
connecting with supply hose. Each outlet spigot 97 may further
include a valve mechanism 98, which selectively controls the fluid
flow through its respective outlet spigot 97.
Fuel Supply & Control Systems
[0060] As shown in the Figures and schematically depicted in FIGS.
7A and 8A, in one embodiment the fuel system includes a fuel tank
20, which is configured near the rear or back end of the trailer
14. The fuel tank 20 is typically unpressurized and used to store
the liquid fuel used by the multiple burner assemblies 60
configured in the firebox 40. In the depicted embodiment 100, the
fuel tank 20 is unpressurized and can hold up to 60 bbl. of diesel
fuel. The fuel system also includes an unpressurized fuel line 21,
which supplies fuel from the fuel tank 20 to the intake of a fuel
pump 22. The fuel pump 22 boosts the fuel pressure and directs it
to the multiple burner assemblies 60 by means of a pressurized fuel
line 26. In one embodiment, the fuel pump 22 boosts the fuel
pressure to approximately 50-100 psi, preferably 60 psi.
[0061] The liquid fuel system also includes a pressure relief valve
24 in fluid communication with the pressurized fuel line 26. The
pressure relief valve 24 permits fuel to vent back into the fuel
tank by means of fuel line 25 when the fuel pressure in the
pressurized fuel line 26 exceeds a certain pressure.
[0062] The fuel system further includes a fuel pressure control
motor valve 27, which regulates the flow of fuel from the
pressurized fuel line 26. The pressurized fuel line 26 fluidly
connects the outlet of the fuel pump 22 with the inlet of a fuel
pressure control motor valve 27. The fuel pressure control motor
valve 27 controls the amount of fuel supplied to the multiple
burner assemblies 60 via pressurized metered fuel lines 28. As
depicted in the drawings, the metered fuel lines 28 may be
configured so as to supply pressurized fuel to sets of burner
assemblies, which are comprised of more than one burner assembly
60. The fuel pressure control motor valve 27 may be electrically,
pneumatically or hydraulically actuated. In a preferred embodiment,
the fuel pressure control motor valve 27 comprises a
pneumatically-actuated flow control valve.
[0063] The temperature of the treatment fluid exiting the heat
exchanger outlet 52 is a function of three variables: the
volumetric flow rate of the treatment fluid through the heat
exchanger 50; the flow rate of the pressurized secondary air; and
the heat generated by the multiple burner assemblies 60 configured
in the heat exchanger 50. The flow rate of the secondary air is
typically held constant during all operations while the volumetric
flow rate of the treatment fluid is typically constant for a given
operation. Thus, the temperature of the treatment fluid exiting the
heat exchanger outlet 52 is controlled by regulating the volume of
fuel supplied to the multiple burner assemblies 60.
[0064] An adjustable temperature controller mechanism 68 is used to
send a control signal, which causes the fuel pressure control motor
valve 27 to open or close, thereby increasing or decreasing the
volume of fuel supplied to the multiple burner assemblies 60 via
pressurized metered fuel lines 28. The control signal may comprise
an electrical, wireless, pneumatic, or hydraulic signal. For
example, in one embodiment, the adjustable temperature controller
mechanism 68 comprises a simple manual rotary or slider rheostat
device, which controls an electric signal that controls the
actuation of the fuel pressure control motor valve 27. In another
embodiment, the adjustable temperature controller mechanism 68
comprises a simple manual rotary valve, which controls a pneumatic
pressure signal that controls the actuation of the fuel pressure
control motor valve 27.
[0065] The temperature controller mechanism 68 may further includes
a thermostat mechanism, which continually monitors the temperature
of the treatment fluid exiting the heat exchanger outlet 52 and
automatically adjusts the control signal to the fuel pressure
control motor valve 27 to open or close as necessary to maintain a
set point temperature.
[0066] Thus, the fuel pressure supplied to the multiple burner
assemblies 60 is initially generated by the fuel pump 22 and
regulated by the fuel pressure control motor valve 27. For example,
in the previously noted embodiment, the fuel pump 22 boosts the
fuel pressure to approximately 50-100 psi, preferably 60 psi. The
fuel pressure is limited to a maximum pressure of 100 psi by the
pressure relief valve 24, which permits fuel to vent back into the
fuel tank by means of fuel line 25 when the fuel pressure in the
pressurized fuel line 26 exceeds 100 psi. The fuel pressure control
motor valve 27 regulates the maximum fuel pressure supplied to the
multiple burner assemblies 60 via pressurized metered fuel lines 28
to approximately 60 psi.
[0067] Recent increases in the price of diesel and other liquid
fuels concurrent with relative decreases in the price of liquefied
petroleum gas (LPG) and natural gas have made the use of gas-fired
burner assemblies an economically attractive alternative. As shown
in the Figures and schematically depicted in FIGS. 7B and 8B, in an
alternate embodiment the fuel system includes a fuel tank 20A,
which is configured near the rear or back end of the trailer 14.
The fuel tank 20A is typically pressurized and insulated, and used
to store the gas fuel used by the multiple gas-fired burner
assemblies 60 configured in the firebox 40. In the one embodiment,
the fuel tank 20A is pressurized and can hold up to 83 bbl. (3,500
gallons) of LPG fuel. Alternatively, it is understood that fuel
tank 20A may comprise a remote LPG or natural gas pipeline, which
is fluidly connected to the system. The fuel system also includes a
pressurized fuel line 21A, which supplies gas fuel from the fuel
tank supply 20A to a gas regulator mechanism 22A. The gas regulator
mechanism 22A controls the downstream gas fuel pressure in the
pressurized fuel line 26A, which directs the gas fuel to the
multiple burner assemblies 60.
[0068] The gas fuel system may also include a gas fuel pressure
control motor valve 27A, which regulates the flow of gas fuel from
the pressurized fuel line 26A. The pressurized fuel line 26A
fluidly connects the outlet of the gas regulator mechanism 22A with
the inlet of a gas fuel pressure control motor valve 27A. The fuel
pressure control motor valve 27A controls the amount of gas fuel
supplied to the multiple gas burner assemblies 60 via pressurized
metered fuel lines 28A. As depicted in the drawings, the metered
fuel lines 28A may be configured so as to supply pressurized fuel
to sets of burner assemblies, which are comprised of more than one
burner assembly 60. The fuel pressure control motor valve 27A may
be electrically, pneumatically or hydraulically actuated. In a
preferred embodiment, the gas fuel pressure control motor valve 27A
comprises a pneumatically-actuated flow control valve.
[0069] The temperature of the treatment fluid exiting the heat
exchanger outlet(s) is a function of three variables: the
volumetric flow rate of the treatment fluid through the heat
exchanger device; the flow rate of the pressurized secondary air;
and the heat generated by the multiple burner assemblies 60
configured in the heat exchanger device. The flow rate of the
secondary air is typically held constant during all operations
while the volumetric flow rate of the treatment fluid is typically
constant for a given operation. Thus, the temperature of the
treatment fluid exiting the heat exchanger outlet(s) is controlled
by regulating the volume of fuel supplied to the multiple gas-fired
burner assemblies 60.
[0070] An adjustable temperature controller mechanism 68 may be
used to send a control signal, which causes the fuel pressure
control motor valve 27A to open or close, thereby increasing or
decreasing the volume of fuel supplied to the multiple gas-fired
burner assemblies 60 via pressurized metered fuel lines 28A. The
control signal may comprise an electrical, wireless, pneumatic, or
hydraulic signal. For example, in one embodiment, the adjustable
temperature controller mechanism 68 comprises a simple manual
rotary or slider rheostat device, which controls an electric signal
that controls the actuation of the fuel pressure control motor
valve 27A. In another embodiment, the adjustable temperature
controller mechanism 68 comprises a simple manual rotary valve,
which controls a pneumatic pressure signal that controls the
actuation of the fuel pressure control motor valve 27A.
[0071] The temperature controller mechanism 68 may further includes
a thermostat mechanism, which continually monitors the temperature
of the treatment fluid exiting the heat exchanger outlet(s) and
automatically adjust the control signal to the fuel pressure
control motor valve 27A to open or close as necessary to maintain a
set point temperature.
[0072] Thus, the gas fuel pressure supplied to the multiple burner
assemblies 60 is initially regulated by the gas regulator mechanism
22A and controlled by the fuel pressure control motor valve 27A.
The fuel pressure control motor valve 27A regulates the maximum
fuel pressure supplied to the multiple gas-fired burner assemblies
60 via pressurized metered fuel lines 28A.
Firebox
[0073] As depicted in the Figures, the firebox 40 is configured
near the center of the trailer 14. The firebox 40 is a
closed-bottomed box having one or more exhaust stacks 42 configured
near the top. In a preferred embodiment, the outer shell of the
firebox 40 is constructed substantially of 3/16'' carbon steel. The
firebox 40 houses a single heat exchanger device (e.g., 50 or 50A)
and a plurality of burner assemblies 60 for heating a treatment
fluid during a single pass through the heat exchanger device. The
closed-bottom design of the firebox 40 ensures the plurality of
burner assemblies 60 are less susceptible to changes in ambient
conditions, such as wind direction or gustiness. The interior walls
and bottom of the firebox 40 are lined with an insulating
refractory material. The refractive lining 48 is configured between
the interior walls and bottom of the firebox 40 and the heat
exchanger device. In one embodiment, the refractive lining 48
comprises one or more layers of fiber-type insulation coated with a
cementious refractive compound.
[0074] In a preferred embodiment, the firebox 40 further includes
at least one vent 40b and passageway 40c, which supplies ambient
air from the upper exterior of the firebox 40 to the front of the
burner assemblies 60. The vent 40b and passageway 40c enable the
burner assemblies to operate with the access door 40a configured in
a "closed" position, which significantly reduces the operational
noise created by burner assemblies 60 when operating. Moreover,
with the burner access doors 40a configured in the "down" position,
the danger inherent in a blowback event of the burner assemblies is
greatly reduced.
Exhaust Stacks
[0075] As previously noted, one or more exhaust stacks 42 are
configured near the top the firebox 40 providing an exhaust for
flue gases to exit the firebox 40. In the depicted embodiments, the
firebox 40 further includes a tapered hood assembly 41, which
incorporates the one or more exhaust stacks 42. The tapered hood
assembly 41 is removable so as to allow access to the heat
exchanger device (e.g., 50 or 50A) for servicing. Each exhaust
stack 42 also includes a hood door assembly 44, which is opened
when the system 100 is operating. As depicted in FIG. 2C, each hood
door assembly 44 includes two doors 44a, 44b which are pivotally
mounted to opposing sides of a respective exhaust stack 42.
Hood Door Opening Mechanism
[0076] With reference to FIGS. 2B and 2E, each hood door assembly
44 may further include a novel mechanism 46 for opening and closing
the opposing hood doors. As shown in greater detail in FIG. 2C, the
mechanism 46 comprises a series of bell crank mechanisms, which
cause the hood doors to open or close when actuated. The embodiment
in FIG. 2C depicts the hood door assembly 44 on the left side in an
opened position and the hood door assembly 44 on the right side in
a closed position. Each mechanism 46 comprises a piston 46a having
one end attached to the firebox 40 and a second end attached to a
first bell crank 46b. The first bell crank is pivotally attached to
the side of the firebox 40. When actuated, the piston 46a causes
the first bell crank 46b to rotate about its pivot point p.sub.1.
The first bell crank 46b also includes a pivotally attached push
rod linkage 46c that connects the first bell crank 46b to a second
bell crank 46d, which is fixably attached to the side edge of one
of the hood doors 44a. The second bell crank 46d is configured so
that its pivot point p.sub.2 is co-aligned with that of its
respective hood door. The second bell crank 46d also includes a
pivotally attached push rod linkage 46e that connects the second
bell crank 46d to a third bell crank 46f, which is also fixably
attached to the side edge of the other of the hood doors 44b. The
third bell crank 46f is also configured so that its pivot point
p.sub.3 is co-aligned with that of its respective hood door.
Actuating the piston 46a causes the extension or retraction of a
piston rod r.sub.p, which causes each of the three bell cranks to
rotate simultaneously about their respective pivot points. This, in
turn, causes the hood doors 44a, 44b to pivot open or closed as
desired. In a preferred embodiment, the piston 46a is a
pneumatically actuated piston.
Burner Assemblies
[0077] The firebox 40 also includes a plurality of burner
assemblies 60, which are configured in the lower side of the
firebox 40. As will be subsequently described in greater detail,
each of the burner assemblies 60 are connected to a fuel system and
a pressurized air supply. For example, FIGS. 7A and 8A
schematically depicts a first embodiment, which features oil-fired
burner assemblies 60 connected to a fuel oil supply system. Liquid
fuel is supplied to each burner assembly 60 via the metered
pressurized fuel line 28. Similarly, pressurized air for combustion
is supplied to each burner assembly 60 via a primary air conduit
78c. The pressurized air and fuel are combined in the burner
assembly 60 and directed through an atomizer nozzle 64, which
projects an atomized air-fuel spray into the firebox 40 where it is
combusted. Each burner assembly 60 is configured in the lower side
of firebox 40 so as to initially generate a substantially
horizontal combustion flow within the firebox 40. Each burner
assembly 60 includes self-contained controls for adjusting the
fuel-air mixture and an ignition mechanism for initially igniting
the fuel-air mixture. In a preferred embodiment, the burner
assembly 60 comprises a 780-Series self-proportioning, oil-fired
burner manufactured by the Hauck Manufacturing Company of Lebanon,
Pa.
[0078] Similarly, FIGS. 7B and 8B schematically depicts a second
embodiment, which features gas-fired burner assemblies 60 connected
to a gas fuel supply system. Flammable gas fuel (e.g., LPG or
natural gas) is supplied to each gas-fired burner assembly 60 via
the metered pressurized gas fuel line 28A. Similarly, pressurized
air for combustion is supplied to each gas-fired burner assembly 60
via a primary air conduit 78c. The pressurized air and fuel are
combined in the burner assembly 60 and directed through a mixer
nozzle 64A, which projects an air-gas fuel spray into the firebox
40 where it is combusted. Each gas-fired burner assembly 60 is
configured in the lower side of firebox 40 so as to initially
generate a substantially horizontal combustion flow within the
firebox 40. Each gas-fired burner assembly 60 includes
self-contained controls for adjusting the gas fuel-air mixture and
an ignition mechanism for initially igniting the gas fuel-air
mixture. In a preferred embodiment, the gas-fired burner assembly
60 comprises a 781-Series (with a converter plate kit) gas-fired
burner manufactured by the Hauck Manufacturing Company of Lebanon,
Pa.
Heat Exchanger
[0079] The heat exchanger device contained within the firebox 40 is
comprised of a tubular coil which is configured in a highly
oscillating or serpentine manner and oriented along multiple axes
so as to maximize its exposure to the heat generated by the
multiple burner assemblies 60. The heat exchanger device of the
present invention may comprise either a single continuous unit or
multiple single-pass heat exchanger units arranged in a vertically
stacked configuration. In addition, heat exchanger device of the
present invention may further comprise a single continuous unit
having valve mechanisms that allow it to be configured as either a
single continuous unit or as multiple single-pass heat exchanger
units.
Single Continuous Heat Exchanger Unit
[0080] With reference now to FIGS. 4A-4B, an embodiment of the
single continuous heat exchanger 50 of the present invention is
depicted. The heat exchanger 50 is comprised of a tubular coil
which is configured in a highly oscillating and serpentine manner
and oriented along two axes so as to maximize its exposure to the
heat generated by the burner assemblies 60. The heat exchanger coil
50 includes a single inlet 51 configured at or near the top of the
heat exchanger coil 50 and a single outlet 52 configured at or near
the bottom of the heat exchanger coil 50. Such a configuration
greatly improves the efficiency of the system 100 by minimizing the
back pressure exerted on the main fluid pump 94 by the treatment
fluid and providing a gravity assist to the flow of treatment fluid
through the heat exchanger 50. As the treatment fluid proceeds
through a single pass through of the heat exchanger coil 50 it
increases in temperature until it reaches the outlet 52 where it is
directed, via an outlet conduit 95 and supply hose (not shown), to
the well head for injection into the formation.
[0081] The depicted embodiment of heat exchanger 50 includes an
upper portion 53 configured in stacked horizontal rows of tubing
faked down in a series of reversing loops oriented about a vertical
axis; and a lower portion 56 configured in a helical coil oriented
about a horizontal axis. The upper portion 53 is fluidly connected
to the lower portion 56 forming the single heat exchanger 50. In
one embodiment, the upper 53 and lower 56 portions of the tubular
coil of the heat exchanger 50 comprise approximately 1,300 ft. of
3'' seamless steel pipe with weld fittings.
[0082] Each row of the upper portion 53 of the heat exchanger 50 is
constructed of a plurality of tubes 54 aligned in parallel with
each other. The outlet of each tube 54 is connected in series with
the inlet of an adjacent tube 54 by means of an approximate
180.degree. curved tube or return bend 55. Similarly, each planar
row is connected in series to the adjacent rows above and below by
connecting the outlet of the outermost tube in one row with the
inlet of the outermost tube in another row by means of a return
bend 55a. In a preferred embodiment, each planar row is laterally
offset from the planar row above and below it so that the tubes 54
in one row are centered on the space between two adjacent tubes 54
in the rows above and below it.
[0083] Each return bend 55 may further include an alignment bolt 47
extending from the approximate exterior inflection point of the
return bend 56. The multiple alignment bolts 47 correspond to holes
formed in an alignment plate 98, which is fixably attached to the
upper portion 53 of the heat exchanger 50 by means of mechanical
fasteners 45, such as threaded nut fasteners. The alignment plate
98 maintains the alignment of the stacked planar rows of the upper
portion 53 of the heat exchanger 50 so that the adjacent rows do
not touch and space is maintained between all adjacent tubes 54,
thereby enabling the flow of heated air through the upper portion
53 of the heat exchanger 50 during operation.
[0084] The upper portion 53 is fluidly connected in series to the
lower portion 56 of the heat exchanger 50. As shown in FIGS. 4A-4B,
the lower portion 56 transitions to an angled rectangular helical
coil configuration, which is oriented about a horizontal plane and
defines a five-sided cavity/chamber or tunnel 65. As will be
described infra, the tunnel 65 serves as an effective combustion
chamber for the multiple burner assemblies 60. The lower portion 53
of the heat exchanger 50 comprises a tubular coil constructed a
plurality of adjacently aligned upper 57a and lower 57b lateral
tubes, which are vertically spaced and connected in series by means
of quarter-bend (i.e., approximately 90.degree. bend) tubes 58 and
riser tubes 59. The outlet of each lateral tube 57 is fluidly
connected in series with the inlet of the next vertically spaced
lateral tube 57 by means of a quarter-bend tube 58 followed by a
riser tube 59 followed by another quarter-bend tube 58. As shown in
FIG. 4A, the outlet of the last lateral tube 57 in the tubular coil
forming the lower portion 53 is fluidly connected to the outlet 52
of the heat exchanger 50.
[0085] Multiple Single-Pass Heat Exchanger Units in Vertically
Stacked Configuration
[0086] With reference now to FIGS. 4C-4D, an embodiment of a
multiple single-pass heat exchanger 50A of the present invention is
depicted. The heat exchanger 50A is comprised of a tubular coil
which is also configured in a highly oscillating and serpentine
manner and oriented along two axes so as to maximize its exposure
to the heat generated by the burner assemblies 60. However, while
having a similar overall design to the previously described single
continuous heat exchanger 50, the tubular coil of the multiple
single-pass heat exchanger 50A is divided into a plurality of
separate single-pass heat exchanger units. Each single-pass heat
exchanger unit includes a single inlet, which is fluidly connected
to a common intake conduit 93c, and a single outlet, which is
fluidly connected to a common outlet conduit 95.
[0087] While such a configuration can be accomplished by inserting
4-way valves at selected intervals along the tubular lengths of the
previously described single continuous heat exchanger 50, the
alternate embodiment of the heat exchanger 50A is preferably
comprised of two or more separate heat exchanger units arranged in
a stacked configuration. For example, as shown in FIGS. 4C-4D, in a
preferred embodiment the multiple single-pass heat exchanger 50A of
the present invention is comprised of three separate heat exchanger
units 56A, 53A, 53B arranged in a vertically stacked
configuration.
[0088] Each of the heat exchanger units 56A, 53A, 53B includes a
single inlet and a single outlet. For example, the lower heat
exchange unit 56A includes a single inlet 51A' and a single outlet
52A', while the upper heat exchanger unit 53A similarly includes a
single inlet 51 C' and a single outlet 52C'. Likewise an
intermediate heat exchanger unit 53B configured between the lower
56A and upper 53A heat exchanger units also includes a single inlet
51 B' and a single outlet 52B' outlet. While each of the heat
exchanger units has a separate inlet, all of the inlets 51A', 51B',
51C' are preferably fluidly connected to the common intake conduit
93c. Similarly, while each of the heat exchanger units has a
separate outlet, all of the outlets 52A', 52B', 52C' are preferably
fluidly connected to the common outlet conduit 95. As the treatment
fluid proceeds through a single pass of its respective heat
exchanger unit 56A, 53A, 53B its temperature increases until it
reaches its respective outlet 52A', 52B', 52C' where the separate
outlet flows are combined and directed, via an outlet conduit 95
and supply hose (not shown), to the well head for injection into
the formation.
[0089] By dividing the intake stream of treatment fluid into a
plurality of inlets the overall flow rate of the treatment fluid
through the alternate heat exchanger 50A is significantly increased
and the internal operating pressures are greatly lessened.
[0090] The depicted embodiment of heat exchanger 50A includes an
upper portion 53 configured in stacked horizontal rows of tubing
faked down in a series of reversing loops oriented about a vertical
axis; and a lower portion 56 configured in a helical coil oriented
about a horizontal axis. The alternate heat exchanger 50A is
divided into two or more separate heat exchanger units. For
example, in the embodiment depicted, the helical coil of the lower
portion comprises a single heat exchanger unit 56A, while the upper
portion is divided into two separate heat exchanger units 53A, 53B,
each having a separate inlet and outlet for receiving treatment
fluid.
[0091] With the exception of the multiple inlets and outlets, the
construction of the alternate heat exchanger 50A is very similar to
that of the previously described single pass heat exchanger 50.
Thus, each row of the upper portion 53 of the heat exchanger 50A is
constructed of a plurality of tubes 54 aligned in parallel with
each other. The outlet of each tube 54 is connected in series with
the inlet of an adjacent tube 54 by means of an approximate
180.degree. curved tube or return bend 55. Similarly, each planar
row is connected in series to the adjacent rows above and below by
connecting the outlet of the outermost tube in one row with the
inlet of the outermost tube in another row by means of a return
bend 55a. In a preferred embodiment, each planar row is laterally
offset from the planar row above and below it so that the tubes 54
in one row are centered on the space between two adjacent tubes 54
in the rows above and below it.
[0092] Each return bend 55 may further include an alignment bolt 47
extending from the approximate exterior inflection point of the
return bend 56. The multiple alignment bolts 47 correspond to holes
formed in an alignment plate 98, which is fixably attached to the
upper portion 53 of the heat exchanger 50 by means of mechanical
fasteners 45, such as threaded nut fasteners. The alignment plate
98 maintains the alignment of the stacked planar rows of the upper
portion 53 of the heat exchanger 50 so that the adjacent rows do
not touch and space is maintained between all adjacent tubes 54,
thereby enabling the flow of heated air through the upper portion
53 of the heat exchanger 50 during operation.
[0093] The lower heat exchanger unit 56A is constructed in the same
manner as the lower portion of the previously described heat
exchanger 50. Thus, as similarly shown in FIGS. 4A-4B, the lower
heat exchanger unit 56A also transitions to an angled rectangular
helical coil configuration, which is oriented about a horizontal
plane and defines a five-sided cavity/chamber or tunnel 65. The
tunnel 65 serves as an effective combustion chamber for the
multiple burner assemblies 60. The lower heat exchanger unit 56A of
the heat exchanger 50A comprises a tubular coil comprising a
plurality of adjacently aligned upper 57a and lower 57b lateral
tubes, which are vertically spaced and connected in series by means
of quarter-bend (i.e., approximately 90.degree. bend) tubes 58 and
riser tubes 59. The outlet of each lateral tube 57 is fluidly
connected in series with the inlet of the next vertically spaced
lateral tube 57 by means of a quarter-bend tube 58 followed by a
riser tube 59 followed by another quarter-bend tube 58. As shown in
FIGS. 2E and 4C, the outlet 52A' of the last lateral tube 57 in the
tubular coil forming lower heat exchanger unit 56A is fluidly
connected to the outlet conduit 95.
[0094] Operation of Heat Exchanger Within Firebox
[0095] With reference now to FIG. 4E, a cross-sectional view is
shown that depicts either of the embodiments of the heat exchanger
device of the present invention (i.e., 50 shown in FIGS. 4A-4B, or
50A shown in FIGS. 4C-4D) installed in the firebox 40 of the
present invention is shown. The firebox 40 includes a refractive
lining 48 configured between the interior walls and bottom of the
firebox 40 and the tubular coil of the heat exchanger 50. In a
preferred embodiment, the firebox 40 may further include at least
one vent 40b and passageway 40c, which supplies ambient air from
the upper exterior of the firebox 40 to the front of the burner
assemblies 60. The passageway 40c is typically configured between
the exterior wall of the firebox housing 40 and the refractive
lining 48. The vent 40b and passageway 40c enable the burner
assemblies 60 to operate with the access door 40a configured in a
"closed" position, which significantly reduces the operational
noise created by burner assemblies 60 when operating. Moreover,
with the burner access doors 40a configured in the "down" position,
the danger inherent in a blowback event of the burner assemblies 60
is greatly reduced.
[0096] As previously described, the single pass heat exchanger
device 50 comprises a tubular coil which is configured in a highly
oscillating and serpentine manner and oriented along two axes so as
to maximize its exposure to the heat generated by the burner
assemblies 60. The upper portion 53 configured in tightly stacked
horizontal rows of tubing faked down in a series of reversing loops
oriented about a vertical axis; and a lower portion 56 configured
in a helical coil oriented about a horizontal axis. The upper
portion 53 is fluidly connected to the lower portion 56 forming the
single heat exchanger 50. The attached alignment plate 98 maintains
the alignment of the stacked planar rows of the upper portion 53 of
the heat exchanger 50 so that the adjacent rows do not touch and
space is maintained between all adjacent tubes 54, thereby enabling
the flow of heated exhaust or flue gases 88 through the upper
portion 53 of the heat exchanger 50 during operation. The lower
portion 56 of the heat exchanger 50 transitions to an angled
rectangular helical coil configuration, which is oriented about a
horizontal plane and defines a five-sided cavity/chamber or tunnel
65.
[0097] Likewise, the multiple single-pass heat exchanger 50A has a
very similar cross-section but is divided into multiple, vertically
stacked heat exchanger units, which each have a separate inlet and
outlet. The depicted embodiment of heat exchanger 50A includes an
upper portion 53 divided into two separate heat exchanger units
53A, 53B, each having a separate inlet and outlet for receiving
treatment fluid; and a lower portion 56 configured in a helical
coil heat exchanger unit 56A oriented about a horizontal axis. The
two separate heat exchanger units 53A, 53B are each configured in
stacked horizontal rows of tubing faked down in a series of
reversing loops oriented about a vertical axis. The lower heat
exchanger unit 56A is constructed in the same manner as the lower
portion of the previously described heat exchanger 50, with the
exception of having a separate inlet and outlet from the other heat
exchanger units above it. Thus, the lower heat exchanger unit 56A
also comprises an angled rectangular helical coil, which is
oriented about a horizontal plane and defines a five-sided
cavity/chamber or tunnel 65.
[0098] Therefore, with the exception of the multiple inlets and
outlets, the cross-sectional view of both embodiments of heat
exchanger devices is, for purposes of illustration, essentially the
same.
[0099] The tunnel 65 serves as an effective combustion chamber for
the multiple burner assemblies 60 configured in the lower side of
the firebox 40. Each burner assembly 60 is connected to the fuel
system and a pressurized air supply. For example, as schematically
depicted in FIGS. 7 and 8, fuel is supplied from the fuel tank 20
to each burner assembly 60 pressurized fuel line 26,26A, fuel
pressure control motor valve 27, 27A and the metered pressurized
fuel line 28, 28A. Similarly, pressurized air for combustion is
supplied to a primary air inlet 62 configured on each burner
assembly 60 via a primary air conduit 78c. With reference again to
FIG. 4E, the primary air and fuel are combined in the burner
assembly 60 and directed through an atomizer nozzle 64, which
projects an atomized air-fuel spray F.sub.A into the firebox 40
where it is combusted in the previously described cavity/chamber or
tunnel 65 formed in the heat exchanger device 50, 50A. It is
further noted that each burner assembly 60 is oriented so as to
initially generate a substantially horizontal combustion flow 69
within the firebox 40. Each burner assembly 60 includes
self-contained controls 66 for adjusting the fuel-air mixture and
an ignition mechanism for initially igniting the fuel-air
mixture.
[0100] The firebox 40 depicted in FIGS. 4E, 7 and 8 further
includes ductwork 85a, 85b, which supply pressurized secondary air
to the interior of firebox 40. The pressurized secondary air
assists in directing and regulating the flow of heated flue gases
88 through the heat exchanger 50 during operation. The ductwork
85a, 85b supplies pressurized secondary air to vents 86, 87
configured on opposing sides of the firebox 40. The vents 86, 87
are typically configured so that their respective airflows F.sub.B,
F.sub.C are generally directed into the cavity/chamber or tunnel 65
formed in the heat exchanger 50. The secondary airflows F.sub.B,
F.sub.C, which are projected from their respective vents 86, 87,
assist in regulating and directing the flow of heated flue gases 88
through the heat exchanger 50 during operation.
[0101] For example, a first or front vent 86 is configured under
the burner assemblies 60 and projects a first flow of secondary
pressurized air F.sub.B into the open front portion of the
cavity/chamber or tunnel 65 formed in the heat exchanger 50. In one
embodiment, the first vent 86 comprises an individual nozzle vent
configured under each burner assembly 60. The first flow of
secondary pressurized air F.sub.B provides a thermal air barrier
that partially insulates the lateral tubes 57b on the bottom of the
heat exchanger 50 from the substantially horizontal combustion
flame 69 generated by the burner assembly 60. In addition, the
first flow of secondary pressurized air F.sub.B absorbs the heat
produced by the substantially horizontal combustion flow 69
generating a flow of heated flue gases 88, which exhausts up
through the heat exchanger 50 during operation. In a preferred
embodiment, the first vent 86 is angled at a slightly upward angle,
so that the first flow of secondary pressurized air F.sub.B
combines with the atomized air-fuel spray F.sub.A to effectively
supercharge the resulting combustion flow 69 with additional
air.
[0102] The second or rear vent 87 is configured on the opposing
wall or side from the first vent 86 and burner assemblies 60, and
projects a second flow of secondary pressurized air F.sub.C into
the rear portion of the cavity/chamber or tunnel 65 formed in the
heat exchanger device (e.g., 50 or 50A). As depicted in Figures,
the rear portion of the cavity/chamber or tunnel 65 formed in the
heat exchanger device (e.g., 50 or 50A) is obscured by the lateral
tubes 57c traversing the tunnel 65. Thus, the second or rear vent
87 is configured so as to project the second flow of secondary
pressurized air F.sub.C through gaps existing between adjacent
lateral tubes 57. The injection of the second flow of secondary
pressurized air F.sub.C provides a thermal air barrier that
partially insulates the lateral tubes 57c traversing the back of
the heat exchanger device (e.g., 50 or 50A). In addition, the
second flow of secondary pressurized air F.sub.C also absorbs the
heat produced by the substantially horizontal combustion flow 69
generating a flow of heated flue gases 88, which exhausts up
through the heat exchanger device (e.g., 50 or 50A) during
operation. In one embodiment, the second vent 87 may also be angled
at a slightly upward angle.
Air Supply System
[0103] With reference again to the Figures, and in particular to
FIGS. 5 and 6 the air supply system of the present invention will
be described in greater detail. The air supply system of the
present invention is a forced-air or pressurized system which is
not susceptible to changes in ambient conditions, such as wind
direction or gustiness. The air supply system of the present
invention is comprised of primary and secondary air systems. The
primary air system supplies large volumes of pressurized air to the
multiple burner assemblies 60 configured in the side of the firebox
40. The primary air system includes a high-pressure pump which
compresses ambient air and directs it to the primary air inlet 62
of each burner assembly 60 where it is where it is thoroughly
combined with the fuel. The secondary air system supplies large
volumes of pressurized air to strategic locations within the
firebox 40 to control and regulate the heating of the heat
exchanger device (e.g., 50 or 50A) and firebox 40. The secondary
air system includes a secondary air blower mechanism, which draws
in large volumes of ambient air. The secondary air is then directed
via ductwork to the previously described vents 86, 87 configured on
opposing sides of the firebox 40. The secondary air assists in
maximizing the combustion of the fuel/air mixture while directing
and regulating the flow of heated flue gases 88 through the heat
exchanger device (e.g., 50 or 50A) during operation. By controlling
and regulating the heating of the heat exchanger device (e.g., 50
or 50A) and firebox 40 during operation, the frac water heating
system of the present invention can continuously heat large volumes
of treatment fluid safely.
[0104] In the embodiments of the present invention depicted in the
Figures, the air supply system is comprised of matched sets of
primary and secondary blower systems disposed on opposing sides
(i.e., the front and rear) of the firebox 40 in a mirror-image
configuration. Each set includes a primary blower system 70 and a
secondary blower system 80, which are powered by a single motor
mechanism. For example, the first or front of blower system set is
powered by motor 36 while the second or rear blower system set is
powered by motor 37. The single motor mechanism 36, 37 are
preferably hydraulically powered. For example, in the depicted
embodiment, the motors 36, 37 are powered by hydraulic pumps 33,
34, respectively, which are driven by the accessory pump drive gear
box 32. As noted previously, in a preferred embodiment, the
hydraulic pumps 33, 34 comprise mechanically-driven hydraulic pumps
which are rated at 5000 psi, but typically operate at approximately
2500-3000 psi.
[0105] As shown in FIG. 5, which depicts in greater detail the
second or rear blower system of the present invention, each primary
air blower system 70 includes a high- pressure blower pump 74
having an intake which draws ambient air through an intake filter
72 and intake conduit 73. In a preferred embodiment, each
high-pressure blower pump 74 is a positive displacement rotary
blower. Each high-pressure blower pump 74 is powered by its
respective motor mechanism 36, 37 through a rotary driveshaft 84.
The high-pressure blower pump 74 compresses the air and directs it
via primary air conduits 78a, 78b, 78c to the primary air inlet 62
of each oil-fired burner assembly 60. The primary air conduits 78a,
78b, 78c may further include a primary air silencer 76, which
muffles the noise generated by the suction of ambient air into the
primary air system 70. In one embodiment, the primary air conduits
78a, 78b, 78c also include a pressure relief "pop-off" valve, which
limits the primary air pressure to approximately 5 psi.
[0106] Each secondary air system 80 includes one or more secondary
air blowers 81, which are also powered by the respective motor
mechanism (e.g., 37) through a common rotary driveshaft 84. As
shown in the FIG. 6, in one embodiment the one or more secondary
air blowers 81 each comprise a conventional centrifugal or
squirrel-cage fan mechanism 82 contained in a protective housing
83. As depicted, the one or more fan mechanisms 82 are aligned in a
parallel configuration along and coupled to a common rotary
driveshaft 84 so that when the driveshaft 84 rotates, each fan
mechanism 82 also rotates within its housing 83. It is further
noted that the co-alignment of the rotary shaft 84 with the fan
mechanisms 82 of the secondary air system 80 and the high-pressure
blower pump 74 of the primary air blower system 70 enables both air
supply systems to be simultaneously powered by the same motor
37.
[0107] The protective housing 83 of each secondary air blower 81
includes an opening, which allows the fan mechanism 82 to draw
ambient air into its housing 83 where it is directed to the
ductwork of the secondary air system. The output of pressurized air
from the secondary air blowers 81 is combined in a first ductwork
85, which then divides into secondary ductwork 85a, 85b, which
supply pressurized secondary air to vents 86, 87 configured on
opposing sides of the firebox 40. In the depicted embodiment,
secondary air is pressurized to approximately 2.5-3 psi. As
previously noted, the vents 86, 87 are typically configured so that
their respective airflows F.sub.B, F.sub.C are generally directed
into the cavity/chamber or tunnel 65 formed in the heat exchanger
50. The secondary airflows F.sub.B, F.sub.C, which are projected
from their respective vents 86, 87, assist in regulating,
directing, and enhancing the convective flow of heated flue gases
88 through the heat exchanger 50 during operation.
[0108] As shown in the embodiment depicted in FIG. 5, the first or
front vents 86 preferably comprise oblong circular vents positioned
below the nozzles 64 of the burner assemblies 60. The depicted
oblong circular vents 86 extend away from the firebox 40 wall and
project one secondary air stream F.sub.B up towards the fuel/air
mixture spray F.sub.A generated by the burner fuel nozzle 64. The
second or rear vent 87 is configured on the opposing wall of the
firebox 40. As noted previously, the configuration of the second
oblong circular vents 87 provides a layer of cooling air F.sub.C
between the main burner fire and the bottom of the firebox.
Moreover, the angular set of the secondary vents 86, 87 causes
their respective opposing secondary air flows F.sub.B, F.sub.C to
collide in the tunnel 65 formed in the heat exchanger device (e.g.,
50 or 50A), thereby affecting the flow of heated exhaust or flue
gases 88 up and through the upper portion 53 of the heat exchanger
device during operation.
[0109] The integrated temperature controller mechanism 68 in
conjunction with forced- air supply system and refractive
insulation lining 48 in the firebox 40 enable the frac water
heating system of the present invention to safely heat water
continuously. Operation time is limited only by fuel supply. For
example, the depicted first embodiment of the present invention
100, which is configured with six (6) burner assemblies, typically
consumes 150-165 gallons of fuel per hour. The burner fuel tank 20
on the unit holds about 2500 gallons and is therefore sized for
15-16.5 hours of continuous operation. The auxiliary powerplant 30
has its own fuel tank that holds approximately 150 gallons of fuel
that allow it to operate up to 18 hours depending on operating
conditions. In the field, operators may have additional fuel
delivered every 12 hours or so to allow the system 100 to continue
operations on large heating jobs.
Method of Operation
[0110] The previously disclosed embodiments of frac water heating
system of the present invention includes novel methods for heating
large volumes of treatment fluid in a continuously flowing fashion
so that on-site heating operations can be performed "on-the-fly",
i.e., without the use of preheated stockpiles of treatment fluid.
For example, the embodiments of the system of the present invention
depicted in the Figures, is capable of heating sufficient
quantities of continuously flowing water to conduct "on-the-fly"
hydraulic fracturing operations at remote well sites. The frac
water heating system of the present invention also includes novel
methods for controlling the heating of the treatment fluid as it
passes through the system. The frac water heating system of the
present invention further includes novel methods for controlling
the temperature change and volume flow of treatment fluid as it
passes through the system.
[0111] Operation of System Having Single Pass Heat Exchanger
Device
[0112] With reference again to the Figures and in particular FIGS.
7A, 8A and 9, the method of operation of the present invention
featuring a single pass heat exchanger device 50 is depicted. A
treatment fluid, such as water, is drawn from an ambient fluid
source 112 into the system 100. The treatment fluid is then pumped
through a single pass of a tubular coil heat exchanger device 50
contained within firebox 40 where it is heated. As the treatment
fluid proceeds through a single pass of the entire heat exchanger
device 50 it increases in temperature until it reaches the outlet
52 of the heat exchanger device 50 where it is directed via tubular
conduits or hose to the well head for injection into the
formation.
[0113] The main fluid pump 94 is used to control the flow rate of
the treatment fluid through the system 100. For example, a supply
line 114 extending to the fluid source 112 is connected to the
intake manifold 90 so as to put the system 100 in fluid
communication with the fluid source 112. The main fluid pump 94
draws the treatment fluid via conduits 93a, 93b from the fluid
source and supplies it to the inlet(s) 51 of the heat exchanger
device 50. The main fluid pump 94 has sufficient power to both draw
the treatment fluid from the fluid source and pump the treatment
fluid through the heat exchanger device 50 and on to the well head
for injection into the formation. In addition, auxiliary or booster
pumping apparatus may be positioned along the supply line 126 and
the supply line 128 to the well head 116 to assist the flow rate of
the treatment fluid.
[0114] For example, in one embodiment of the frac water heating
system 100 of the present invention that features a single-pass,
continuous heat exchanger 50, the main fluid pump 94 is capable of
supplying treatment fluid to the heat exchanger device 50 at a
pressure of about 150 psi. In a preferred embodiment, the main
fluid pump 94 is also capable of drawing and pumping a maximum of
252 gpm of treatment fluid through the system 100.
[0115] The requisite volumetric flow rate of treatment fluid is
typically dictated by the particular operational requirements
desired at the well head. By adjusting the speed of the main fluid
pump 94, the volumetric flow rate of treatment fluid is controlled.
The main fluid pump 94 is driven by a hydraulic motor 38 powered
via supply line 35a by a hydraulic pump 35 attached to the
accessory pump drive gear box 32. Consequently, the speed of the
main fluid pump 94 is controlled by the operator using a control
lever 12 to increase or decrease the amount of pressurized
hydraulic fluid supplied to hydraulic motor 38. In a preferred
embodiment, control lever 12 comprises an electronic joystick
actuator, which regulates the displacement of the hydraulic pump to
change the speed of its respective hydraulic motor. The hydraulic
pressure depends on the loads placed on the hydraulic motors.
[0116] As the treatment fluid is pumped through the heat exchanger
device 50 contained within the firebox 40, the fluid is heated by
the transfer of thermal energy generated by the combustion of a
fuel/air mixture in the firebox 40. As previously detailed,
pressurized primary air and a liquid or gaseous fuel are combined
in the multiple burner assemblies 60, which each project an
atomized air-fuel spray F.sub.A into the firebox 40 where it is
combusted. The burner assemblies 60 are configured near the bottom
of the firebox 40 and oriented so as to initially generate a
substantially horizontal combustion flow 69 within the firebox 40.
Pressurized secondary air assists in directing and controlling the
thermal energy generated by the substantially horizontal combustion
flow 69 to exhaust in a convective flow up and through the upper
portion 53 of the heat exchanger device 50.
[0117] The tubular coil heat exchanger device 50 is designed to
maximize the heat transfer of the thermal energy within the
confines of the firebox 40. The heat exchanger 50 is, therefore,
comprised of a tubular coil which is configured in a two
interconnected portions, which are oriented along two distinct axes
so as to maximize exposure to the heat generated by the burner
assemblies. The ambient or cool treatment fluid enters the heat
exchanger 50 through the inlet 51 configured at or near the top of
the heat exchanger coil 50. As the fluid flows through the upper
portion 53 of the heat exchanger 50 thermal energy is transferred
by the convective flow of the hot flue gases 88 over and between
the stacked horizontal rows of interconnected adjacent tubes faked
down in a series of reversing loops oriented about a vertical axis.
As the fluid continues through the lower portion 56 of the heat
exchanger 50 it flows through a helical coil oriented about a
horizontal axis, thermal energy is transferred by the both the
convective flow of the hot flue gases 88 and the radiant heat
emanating from the substantially horizontal combustion flow 69
within the cavity/chamber or tunnel 65.
[0118] The convective flow of flue gases 88 through heat exchanger
50 is substantially enhanced by the secondary air system, which
continually supplies large volumes of pressurized air to
strategically configured vents 86, 87 on opposing sides of the
firebox 40. The secondary air flow is essentially a forced air
system which uses air as its heat transfer medium to extract
thermal energy from the substantially horizontal combustion flow
69. The vents 86, 87 are positioned near the bottom of the
closed-bottom firebox 40 and configured so that their respective
airflows F.sub.B, F.sub.C are generally directed into the
cavity/chamber or tunnel 65 formed in the heat exchanger device
50.
[0119] The treatment fluid continues to absorb thermal energy as it
flows through the lower portion 56 of the heat exchanger 50 until
it reaches the outlet 52 of the heat exchanger 50 where it is
directed via tubular 95 and supply line to the well head for
injection into the formation.
[0120] As the heated treatment fluid exits the outlet 52 of the
single continuous heat exchanger 50 its temperature is monitored.
The temperature of the treatment fluid exiting the heat exchanger
outlet 52 is a function of three variables: the volumetric flow
rate of the treatment fluid through the heat exchanger 50; the flow
rate of the pressurized secondary air; and the heat generated by
the multiple burner assemblies 60 configured in the heat exchanger
50. The flow rate of the secondary air is typically held constant
during all operations while the volumetric flow rate of the
treatment fluid is typically constant for a given operation. Thus,
the temperature of the treatment fluid exiting the heat exchanger
outlet 52 is controlled by regulating the volume of fuel supplied
to the multiple burner assemblies 60.
[0121] In one embodiment, the operator monitors the temperature of
the heated treatment fluid as it exits the outlet 52 of the heat
exchanger 50. The operator then adjusts the temperature controller
mechanism 68 sending a control signal to the fuel pressure control
motor valve 27 to increase or decrease the volume of fuel supplied
to the multiple burner assemblies 60 via pressurized metered fuel
lines 28. The control signal may comprise an electrical, wireless,
pneumatic, or hydraulic signal. For example, in the depicted
embodiment, the adjustable temperature controller mechanism 68
comprises a simple manual rotary valve, which controls the
pneumatic pressure supplied to the fuel pressure control motor
valve 27.
[0122] In another embodiment, the temperature controller mechanism
68 is an automated thermostat mechanism that continually monitors
the temperature of the treatment fluid exiting the heat exchanger
outlet 52. An operator inputs a desired temperature reading (i.e.,
set point temperature). The temperature controller mechanism 68
compares the actual temperature of the treatment fluid exiting the
heat exchanger outlet 52 with the set point temperature and
automatically adjusts the control signal supplied to the fuel
pressure control motor valve 27. For example, if the temperature of
the treatment fluid exiting the heat exchanger outlet 52 is less
than the set point temperature, the temperature controller
mechanism 68 adjusts the control signal supplied to the fuel
pressure control motor valve 27 to increase the volume of fuel
supplied to the multiple burner assemblies 60 via pressurized
metered fuel lines 28 in order to maintain a set point temperature.
Conversely, if the temperature of the treatment fluid exiting the
heat exchanger outlet 52 is higher than the set point temperature,
the temperature controller mechanism 68 adjusts the control signal
supplied to the fuel pressure control motor valve 27 to decrease
the volume of fuel supplied to the multiple burner assemblies 60
via pressurized metered fuel lines 28 in order to maintain a set
point temperature.
[0123] The temperature of the treatment fluid is also typically
monitored at the inlet 51 of the heat exchanger 50. The temperature
spread between the inlet 51 and outlet 52 of the heat exchanger 50,
when combined with the volumetric flow rate of treatment fluid, is
indicative of the heating capacity of the system. Field testing has
determined that the depicted embodiment of the oil-fired heat
exchanger system 100 of the present invention is capable of heating
ambient water from 70.degree. F. to 210.degree. F. at a maximum
volumetric flow rate of 252 gpm. Moreover, field reports further
indicate that the system 100 is capable of heating water from
40.degree. F. to 210.degree. F. in ambient atmospheric temperatures
below 25.degree. F. at a slightly reduced volumetric flow rate
(e.g., 200-250 gpm).
[0124] The single continuous heat exchanger 50 excels in heating
the treatment fluid to an exceptional degree. However, its flow
rate is limited by the generated internal pressures. For example,
an embodiment of a single continuous heat exchanger 50 is typically
operated at a treatment fluid flow rate of about 4.5 barrels (189
gallons) per minute with an outlet temperature of 205.degree. F.
and an internal pressure of approximately 180-200 psi. The
superheated water is then typically mixed with cooler water, either
in intermediate holding tanks or injected into a flowing stream of
cool, ambient temperature water to produce a resulting stream of
warm treatment fluid at a target or goal temperature for actual
injection into the well head. While the outlet temperature can be
adjusted somewhat (e.g., water boils at 212.degree. F.), the flow
rate is limited by the maximum operating internal pressures of the
system. Moreover, the mixing process of the superheated water and
the cooler, ambient temperature water must be constantly monitored
to ensure that the treatment fluid reaching the well head remains
at the target or goal temperature.
[0125] Operation of System Having Multiple, Single-Pass Heat
Exchangers Device
[0126] With reference again to the Figures and in particular FIGS.
7B, 8B and 9, the method of operation of the present invention
featuring a multiple, single-pass heat exchanger device 50A is
depicted. A treatment fluid, such as water, is drawn from an
ambient fluid source 112 into the system 100A. The flow of the
treatment fluid is then divided amongst a plurality of inlets 51
A-C of the plurality of single-pass heat exchanger units 56A, 53A,
53B. The divided flows of treatment fluid are each then pumped
through a single pass of its respective tubular coil heat exchanger
units 56A, 53A, 53B contained within firebox 40 where it is heated.
As the divided flows of treatment fluid proceed through a single
pass of its respective heat exchanger unit it increases in
temperature until it reaches its respective outlet 52A-C of the
heat exchanger device units 56A, 53A, 53B where the separate flows
are recombined into single conduit 95 and directed via tubular
conduits or hoses to the well head for injection into the
formation.
[0127] The main fluid pump 94 is used to control the flow rate of
the treatment fluid through the system 100A. For example, a supply
line 114 extending to the fluid source 112 is connected to the
intake manifold 90 so as to put the system 100A in fluid
communication with the fluid source 112. The main fluid pump 94
draws the treatment fluid via conduits 93a, 93b from the fluid
source and supplies it to the plurality of inlets 51A-C of the
plurality of single-pass heat exchanger units 56A, 53A, 53B. The
main fluid pump 94 has sufficient power to both draw the treatment
fluid from the fluid source and pump the treatment fluid through
the heat exchanger device 50A and on to the well head for injection
into the formation. In addition, auxiliary or booster pumping
apparatus may be positioned along the supply line 114 and the
supply line 120 to the well head 116 to assist the flow rate of the
treatment fluid.
[0128] For example, in an embodiment of the alternate frac water
heating system 100A of the present invention having a multiple,
single-pass heat exchanger device 50A, the main fluid pump 94 is
capable of pumping treatment fluid through the heat exchanger
device 50A at a significantly higher flow rate. However, because
the flow of treatment fluid is divided the internal pressures are
greatly decreased. For example, in one embodiment the main fluid
pump 94 is capable of drawing and pumping a maximum of 12.5
barrels/minute (525 gpm) of treatment fluid through the system 100A
at an inlet pressure of 90-100 psi. The requisite volumetric flow
rate of treatment fluid is typically dictated by the particular
operational requirements desired at the well head. By adjusting the
speed of the main fluid pump 94, the volumetric flow rate of
treatment fluid is controlled. The main fluid pump 94 is driven by
a hydraulic motor 38 powered via supply line 35a by a hydraulic
pump 35 attached to the accessory pump drive gear box 32.
Consequently, the speed of the main fluid pump 94 is controlled by
the operator using a control lever 12 to increase or decrease the
amount of pressurized hydraulic fluid supplied to hydraulic motor
38. In a preferred embodiment, control lever 12 comprises an
electronic joystick actuator, which regulates the displacement of
the hydraulic pump to change the speed of its respective hydraulic
motor. The hydraulic pressure depends on the loads placed on the
hydraulic motors.
[0129] As the treatment fluid is pumped through the multiple heat
exchanger units (e.g., 56A, 53A, 53B) of the alternate heat
exchanger device 50A contained within the firebox 40, the fluid is
heated by the transfer of thermal energy generated by the
combustion of a fuel/air mixture in the firebox 40. As previously
detailed, pressurized primary air and a liquid or gaseous fuel are
combined in the multiple burner assemblies, which each project an
atomized air-fuel spray F.sub.A into the firebox 40 where it is
combusted. The burner assemblies 60 are configured near the bottom
of the firebox 40 and oriented so as to initially generate a
substantially horizontal combustion flow 69 within the firebox 40.
Pressurized secondary air assists in directing and controlling the
thermal energy generated by the substantially horizontal combustion
flow 69 to exhaust in a convective flow up and through the upper
portion 53 of the heat exchanger device 50.
[0130] The multiple heat exchanger units (e.g., 56A, 53A, 53B) of
the alternate tubular coil heat exchanger device 50A are designed
to maximize the heat transfer of the thermal energy within the
confines of the firebox 40. The heat exchanger 50A is, therefore,
comprised of multiple tubular coils which are oriented along two
distinct axes so as to maximize exposure to the heat generated by
the burner assemblies. The ambient or cool treatment fluid enters
the alternate heat exchanger 50A through one of the multiple inlets
51A-C of the plurality of heat exchanger units. As the treatment
fluid flows through a single pass of its respective heat exchanger
unit thermal energy is transferred by the convective flow of the
hot flue gases 88 and the radiant heat emanating from the
substantially horizontal combustion flow 69 within the
cavity/chamber or tunnel 65.
[0131] The convective flow of flue gases 88 through heat exchanger
50 is substantially enhanced by the secondary air system, which
continually supplies large volumes of pressurized air to
strategically configured vents 86, 87 on opposing sides of the
firebox 40. The secondary air flow is essentially a forced air
system which uses air as its heat transfer medium to extract
thermal energy from the substantially horizontal combustion flow
69. The vents 86, 87 are positioned near the bottom of the
closed-bottom firebox 40 and configured so that their respective
airflows F.sub.B, F.sub.C are generally directed into the
cavity/chamber or tunnel 65 formed in the heat exchanger device
50A.
[0132] The treatment fluid continues to absorb thermal energy as it
flows through its respective heat exchanger unit until it reaches
the outlet 52A-C of its respective heat exchanger unit 56A, 53A,
53B where it is collected and directed via tubular conduits or hose
to the well head for injection into the formation. As the heated
treatment fluid exits the outlet 52A-C of its respective heat
exchanger unit 56A, 53A, 53B its temperature is monitored. The
temperature of the treatment fluid exiting each heat exchanger unit
56A, 53A, 53B is a function of four variables: the size or length
of the heat exchanger unit, the volumetric flow rate of the
treatment fluid through the heat exchanger unit; the flow rate of
the pressurized secondary air; and the heat generated by the
multiple burner assemblies 60 configured in the heat exchanger
device 50A. Preferably, the respective heat exchanger units 56A,
53A, 53B are designed so that the temperature increase of the
treatment fluid through the heat exchanger device 50A is balanced
and consistent. The flow rate of the secondary air is typically
held constant during all operations while the volumetric flow rate
of the treatment fluid is typically constant for a given operation.
Thus, the temperature of the treatment fluid exiting the heat
exchanger outlets 52A-C is typically controlled by regulating the
volume of fuel supplied to the multiple burner assemblies 60.
[0133] In one embodiment, the operator monitors the temperature of
the heated treatment fluid as it exits the outlets 52A-C of the
heat exchanger device 50A. The operator then adjusts the
temperature controller mechanism 68 sending a control signal to the
fuel pressure control motor valve 27 to increase or decrease the
volume of fuel supplied to the multiple burner assemblies 60 via
pressurized metered fuel lines 28. The control signal may comprise
an electrical, wireless, pneumatic, or hydraulic signal. For
example, in the depicted embodiment, the adjustable temperature
controller mechanism 68 comprises a simple manual rotary valve,
which controls the pneumatic pressure supplied to the fuel pressure
control motor valve 27.
[0134] In another embodiment, the temperature controller mechanism
68 is an automated thermostat mechanism that continually monitors
the temperature of the treatment fluid exiting the heat exchanger
outlets 52A-C. An operator inputs a desired temperature reading
(i.e., set point temperature). The temperature controller mechanism
68 compares the actual temperature of the treatment fluid exiting
the heat exchanger units' outlets 52A-C with the set point
temperature and automatically adjusts the control signal supplied
to the fuel pressure control motor valve 27. For example, if the
temperature of the treatment fluid exiting the heat exchanger
outlet 52 is less than the set point temperature, the temperature
controller mechanism 68 adjusts the control signal supplied to the
fuel pressure control motor valve 27 to increase the volume of fuel
supplied to the multiple burner assemblies 60 via pressurized
metered fuel lines 28 in order to maintain a set point temperature.
Conversely, if the temperature of the treatment fluid exiting the
heat exchanger outlet 52 is higher than the set point temperature,
the temperature controller mechanism 68 adjusts the control signal
supplied to the fuel pressure control motor valve 27 to decrease
the volume of fuel supplied to the multiple burner assemblies 60
via pressurized metered fuel lines 28 in order to maintain a set
point temperature.
[0135] The temperature of the treatment fluid is also typically
monitored at the inlets 51A-C or the intake conduit 93c of the heat
exchanger device 50A. The temperature spread between the respective
inlets 51 A-C and outlets 52 A-C of the heat exchanger device 50A,
when combined with the volumetric flow rate of treatment fluid, is
indicative of the heating capacity of the system. While the
temperature spread of the alternate heat exchanger device 50A is
markedly less than that of a similarly sized single pass continuous
heat exchanger device 50 due to the increase volumetric flow rate
of the treatment fluid and decreased exposure time within the
firebox 40, the heating capacity is very similar. Field testing has
determined that an embodiment of the heat exchanger system 100A of
the present invention is capable of increasing the temperature of
treatment fluid (i.e., AT) 60 degrees Fahrenheit at a high
volumetric flow rate. For example, initial field tests indicate
that the system 100A is capable of heating water from 40.degree. F.
to 100.degree. F. in ambient atmospheric temperatures of 29.degree.
F. at a volumetric flow rate of 12.5 barrels/minute (525 gpm).
Method of Use for Supplying Heated Treatment Fluid to a Well
Head
[0136] The two disclosed embodiments of heat exchanger devices each
exhibit pronounced, yet different, strengths in supplying heated
treatment fluid to a well head for injection into a formation. For
example, the single continuous heat exchanger device 50 excels at
heating the treatment fluid to an exceptional degree, but its flow
rate, while exceptional when compared to conventional frac water
heaters, is limited somewhat by the generated internal pressures.
In contrast, while the multiple, single-pass heat exchanger device
50A is not able to heat treatment fluid to the same degree as the
other heat exchanger device 50, its flow rate capacity is enhanced
greatly. Thus, different methods of use may be employed depending
upon which of the two disclosed embodiments of heat exchanger
devices is used in a frac water heating system.
[0137] For example, an embodiment of a frac water heating system
100 having a single continuous heat exchanger 50 is typically
operated at a treatment fluid flow rate of about 4.5 barrel (189
gallons) per minute with an outlet temperature of 205.degree. F.
and an internal pressure of approximately 180-200 psi. Since the
target or goal temperature of the treatment fluid actually injected
into the well head is usually much lower, the superheated water is
typically mixed with cooler water, either in holding tanks or
injected into a flowing stream of cool, ambient temperature water,
to produce a resulting stream of warm treatment fluid at a target
or goal temperature for actual injection into the well head. Thus,
the flow rate or volume of water heated to the target or goal
temperature is increased by effectively diluting the superheated
water with cooler water. While effective in producing large
quantities of heated treatment, such methods often require
additional mixing manifolds, holding and surge tanks, as well as
complicated fluid supply lines and systems between the frac water
heating system and the well head. Moreover, the high outlet
temperature and internal pressures that the frac water heating
system 100 generates in accordance with the method requires
constant vigilance to ensure that the system operates in a safe
manner.
[0138] Alternatively, methods for using a frac water heating system
100A having a multiple, single-pass heat exchanger device 50A are
even more straightforward. For example, with reference to FIGS. 9A
and 9B, two methods of use 110, 150 are depicted which illustrate a
greatly simplified and more efficient system. A source of treatment
fluid water source 112 can be a reservoir, lake or other source of
water. An embodiment of the frac water heating system 100A of the
present invention having multiple, single- pass heat exchanger
device 50A is used to heat treatment fluid for use in frac
operations in an oil well. In general, such frac operations can be
seen in U.S. Pat. No. 4,137,182, hereby incorporated herein by
reference.
[0139] The prepared fracking fluid (i.e., water plus selected
chemical (optional) and proppant) to be injected into an oil well
116 as part of a hydraulic fracturing operation typically includes
a treatment fluid (e.g., water) heated to a target temperature by
the frac water heating system 100A. A pumping apparatus 117, which
can include a truck and trailer, pumps the prepared fracking fluid
into the well 116.
[0140] As shown in FIG. 9A, treatment fluid (i.e., water) from a
source 112 flows in flowline 114 to the intake manifold 90 of the
frac water heating system 100A where it proceeds to be heated in
accordance with the process of the present invention discussed
previously. Upon heating to the target or goal temperature, the
heated water is directed via outlet conduit 95 and manifold 96 to
flow line 120, which transfers the warmed water between the frac
water heating system 100A and the mixing tanks or downhole tanks
146. The mixing tanks 146 can be used to mix any selected chemical
and/or proppants with the heated treatment fluid that has been
discharged from the frac water heating systems100A creating a
prepared fracking fluid that is ready for use in hydraulic
fracturing operations in the well 116. Flow lines 122, 124 and 126
illustrate the transfer of the prepared fracking fluid from mixing
tanks or downhole tanks 146 to pumping apparatus 117 and then into
the well 116 for use in fracking operations.
[0141] To achieve greater flow rates of heated water, multiple frac
water heating systems 100A can also be used in combination with one
another. For example, as shown in FIG. 9B, two or more frac water
heating systems 100A are preferably arranged in a parallel
configuration to heat the water from a common source, all of which
is done on a continuous flow basis. The multiple frac water heating
systems typically draw the treatment fluid from a common source
112. For example, in the depicted embodiment, treatment fluid
(i.e., water) from a source 112 flows in flowline 114, which is
divided into flowlines 114A and 1148. Flowline 114A is fluidly
connected to the intake manifold 90 of a first frac water heating
system 100A-1, where it proceeds to be heated in accordance with
the process of the present invention discussed previously.
Likewise, flowline 1148 is fluidly connected to the intake manifold
90 of a second frac water heating system 100A-2, where it proceeds
to be heated in accordance with the process of the present
invention discussed previously.
[0142] Upon heating to the target or goal temperature, the heated
water from the first frac water heating system 100A-1 is directed
via its outlet conduit 95 and manifold 96 to flow line 120A, which
transfers the warmed water produced by the first frac water heating
system 100A-1 to a common flowline 121, which flows into the mixing
tanks or downhole tanks 146. Similarly, upon heating to the target
or goal temperature, the heated water from the second frac water
heating system 100A-2 is directed via its outlet conduit 95 and
manifold 96 to flow line 1208, which transfers the warmed water
from the second frac water heating system 100A-2 to the common
flowline 121 that flows into the mixing tanks or downhole tanks
146. From that point on, the two processes 110, 150 are essentially
the same. The common flowline 121 transfers the combined flows of
heated treatment fluid discharged by the multiple frac water
heating systems to the mixing or downhole tanks 146.
[0143] The mixing tanks 146 can be used to mix any selected
chemical and/or proppants with the heated treatment fluid from the
multiple frac water heating systems to create a prepared fracking
fluid that is ready for use in hydraulic fracturing operations in
the well 116. Flow lines 122, 124 and 126 illustrate the transfer
of the prepared fracking fluid from mixing tanks or downhole tanks
146 to pumping apparatus 117 and then into the well 116 for use in
fracking operations. The moving stream of uniformly heated water
can also be piped to surge tank(s) which can be used as a safety
buffer between the water flow and the pumping operations, in the
case of a mechanical breakdown or operational problems.
[0144] Alternatively, the multiple frac water heating systems may
each acquire its treatment fluid from a different source or
independently from the same source. Similarly, the multiple frac
water heating systems may each transfer its warm treatment fluid to
the mixing tanks or downhole tanks 146 via a flowline that is
separate and distinct from the flowline used in common by the
others.
[0145] To achieve greater or higher temperature differentials (AT)
of the treatment fluid from the source to the well head, multiple
frac water heating systems 100A can also be used in tandem with one
another. For example, as shown in FIG. 9C, two or more frac water
heating systems 100A are preferably arranged in a tandem or series
configuration to heat the treatment fluid from a common source, all
of which is done on a continuous flow basis. For example, in the
depicted embodiment of the method 160, treatment fluid (e.g.,
water) from a source 112 flows in flowline 114 to the intake
manifold 90 of a first (A) frac water heating system 100A-1, where
it proceeds to be heated in accordance with the process of the
present invention discussed previously. Upon heating to a first
temperature, the heated water from the first frac water heating
system 100A-1 is directed via its outlet conduit 95 and manifold 96
to flow line 120, which transfers the warmed water produced by the
first frac water heating system 100A-1 to the intake manifold 90 of
a second (B) frac water heating system 100A-2, where it proceeds to
be heated a second time to the second temperature (i.e., target or
goal temperature) in accordance with the process of the present
invention discussed previously. Upon heating to the second
temperature, the super heated treatment fluid from the second frac
water heating system 100A-2 is directed via its outlet conduit 95
and manifold 96 to flow line 140, which transfers the super heated
water to the mixing tanks or downhole tanks 146. From that point
on, the process 160 is essentially the same as the previously
disclosed processes 110, 150.
[0146] The mixing tanks 146 can be used to mix any selected
chemical and/or proppants with the heated treatment fluid from the
multiple frac water heating systems to create a prepared fracking
fluid that is ready for use in hydraulic fracturing operations in
the well 116. Flow lines 122, 124 and 126 illustrate the transfer
of the prepared fracking fluid from mixing tanks or downhole tanks
146 to pumping apparatus 117 and then into the well 116 for use in
fracking operations. The moving stream of uniformly heated water
can also be piped to surge tank(s) which can be used as a safety
buffer between the water flow and the pumping operations, in the
case of a mechanical breakdown or operational problems.
[0147] It is, of course, understood that a first grouping of frac
water heating systems 100A arranged in a tandem configuration can
be further configured in-parallel with a second grouping of frac
water heating systems 100A, also arranged in a tandem
configuration, in order to increase both the flow rate and the AT
of the treatment fluid.
[0148] While the methods illustrated in FIGS. 9A-9C preferably
depict the frac water heating system 100A as having a multiple,
single-pass heat exchanger device 50A, it is understood that
depending upon the actual operating conditions, a frac water
heating system 100 having a single continuous heat exchanger device
50 may also be used in accordance with the operating principles of
the disclosed methods.
[0149] It will now be evident to those skilled in the art that
there has been described herein an improved heat exchanger system
for heating large, continuously flowing volumes of treatment fluids
at remote locations. Although the invention hereof has been
described by way of a preferred embodiment, it will be evident that
other adaptations and modifications can be employed without
departing from the spirit and scope thereof. For example, instead
of the treatment fluid being water, it could be a petroleum based
liquid such as oil for hot oil well treatments. The terms and
expressions employed herein have been used as terms of description
and not of limitation; and thus, there is no intent of excluding
equivalents, but on the contrary it is intended to cover any and
all equivalents that may be employed without departing from the
spirit and scope of the invention.
* * * * *