U.S. patent application number 14/854823 was filed with the patent office on 2016-03-17 for produced water steam generation process using produced water boiler with gas turbine.
The applicant listed for this patent is Husky Oil Operations Limited. Invention is credited to Rodger Francesco Bernar, Bertrand Francois Mathias Burg, Lei Jia.
Application Number | 20160076345 14/854823 |
Document ID | / |
Family ID | 55454257 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160076345 |
Kind Code |
A1 |
Bernar; Rodger Francesco ;
et al. |
March 17, 2016 |
PRODUCED WATER STEAM GENERATION PROCESS USING PRODUCED WATER BOILER
WITH GAS TURBINE
Abstract
A method and system for producing steam for use in heavy
hydrocarbon recovery operations. Water, containing impurities,
produced from the well is separated from hydrocarbons and other
materials, and subsequently directly passed to a produced water
boiler with online pigging. The boiler is indirectly heated by
means of a hot flue gas, such as a gas turbine exhaust, which
produces electricity (for powering a central processing facility,
or alternatively a burner to heat the boiler) and exhaust heat for
heating the boiler.
Inventors: |
Bernar; Rodger Francesco;
(Calgary, CA) ; Burg; Bertrand Francois Mathias;
(Calgary, CA) ; Jia; Lei; (Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Husky Oil Operations Limited |
Calgary |
|
CA |
|
|
Family ID: |
55454257 |
Appl. No.: |
14/854823 |
Filed: |
September 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62050894 |
Sep 16, 2014 |
|
|
|
Current U.S.
Class: |
166/303 ;
166/57 |
Current CPC
Class: |
E21B 36/025
20130101 |
International
Class: |
E21B 43/24 20060101
E21B043/24 |
Claims
1. A method for generating steam for use in a thermal hydrocarbon
recovery operation, the operation comprising at least one
hydrocarbon recovery well, the method comprising the steps of:
producing produced materials from the at least one hydrocarbon
recovery well; treating the produced materials to separate water
from the produced materials; feeding the water into steam
generation means; providing a heat source; providing heat exchange
means between the heat source and the steam generation means;
transferring heat from the heat source to the steam generation
means via the heat exchange means; allowing the heat to increase
the temperature of the steam generation means; and heating at least
a portion of the water in the steam generation means to or above
the water's boiling point to generate steam.
2. The method of claim 1 further comprising the step of treating
the produced materials to separate gas and/or solids and/or
hydrocarbon from the produced materials.
3. The method of claim 2, wherein the gas is separated, further
comprising the step of treating the gas by using gas treating
means.
4. The method of claim 3 wherein treating the gas comprises
reducing sulphur content of the gas.
5. The method of claim 2, wherein the hydrocarbon is separated,
further comprising the step of diluting the hydrocarbon with a
diluent for transport of the hydrocarbon.
6. The method of claim 1 further comprising the step of injecting
the steam into the at least one hydrocarbon recovery well.
7. The method of claim 2, wherein the gas is separated, further
comprising the steps of feeding the gas to the heat source and
using the gas to at least partially fuel the heat source.
8. The method of claim 1 further comprising the step of injecting
the steam into the at least one hydrocarbon recovery well.
9. The method of claim 1 wherein the heat source is waste heat from
a machine.
10. The method of claim 9 wherein the machine is an electricity
generator.
11. The method of claim 1 wherein the steam generation means are a
produced water boiler.
12. The method of claim 1 further comprising the step of cleaning
build-up from the steam generation means via mechanical cleaning
means.
13. The method of claim 10 wherein gas is separated from the
produced materials, the electricity generator is a gas turbine
unit, and the gas is used to at least partially fuel the gas
turbine unit, the waste heat comprising heated exhaust produced by
the gas turbine unit.
14. The method of claim 12 wherein the mechanical cleaning means
comprise on-line pigging.
15. The method of claim 2, wherein the hydrocarbon is separated,
further comprising the step of partially upgrading the
hydrocarbon.
16. A steam generation system for use in thermal hydrocarbon
recovery operations wherein the operations comprise at least one
hydrocarbon recovery well, the system comprising: produced
materials treatment means configured to separate water from
produced materials produced from the at least one hydrocarbon
recovery well; feeding means for feeding the water to steam
generation means; a heat source; and heat exchange means between
the heat source and the steam generation means for transferring
heat from the heat source to the steam generation means, allowing
heat to increase the temperature of the steam generation means and
heating at least a portion of the water in the steam generation
means to or above the water's boiling point to generate steam from
the water.
17. The system of claim 16 wherein the produced materials treatment
means are configured to separate gas and/or solids and/or
hydrocarbon from the produced materials.
18. The system of claim 17 wherein the produced materials treatment
means are configured to separate the gas from the produced
materials, further comprising gas treating means for treating the
gas.
19. The system of claim 18 wherein the gas treating means are for
reducing sulphur content of the gas.
20. The system of claim 17 wherein the produced materials treatment
means are configured to separate the hydrocarbon from the produced
materials, further comprising a diluent source for diluting the
hydrocarbon with a diluent for transport of the hydrocarbon.
21. The system of claim 16 further comprising steam injection means
for injecting the steam into the at least one hydrocarbon recovery
well.
22. The system of claim 16 wherein the heat source is waste heat
from a machine.
23. The system of claim 22 wherein the machine is an electricity
generator.
24. The system of claim 16 wherein the steam generation means are a
produced water boiler.
25. The system of claim 16 further comprising mechanical cleaning
means for cleaning build-up inside the steam generation means.
26. The system of claim 23 wherein the produced materials treatment
means are configured to separate the gas from the produced
materials, the electricity generator is a gas turbine unit, and the
gas is used to at least partially fuel the gas turbine unit, the
waste heat comprising heated exhaust produced by the gas turbine
unit.
27. The system of claim 25 wherein the mechanical cleaning means
comprise on-line pigging.
28. The system of claim 17 wherein the produced materials treatment
means are configured to separate the hydrocarbon from the produced
materials, further comprising partial upgrading means for partially
upgrading the hydrocarbon.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of and priority to U.S.
Provisional Patent Application Serial No. 62/050,894, filed Sep.
16, 2014, entitled "Produced Water Steam Generation Process Using
Produced Water Boiler with Gas Turbine," the contents of which are
incorporated herein in its entirety for all purposes.
FIELD OF THE INVENTION
[0002] The invention relates to thermal recovery methods and
systems for heavy hydrocarbon deposits, and specifically to such
methods and systems requiring steam injection to mobilize the
deposits.
BACKGROUND
[0003] In the field of subsurface hydrocarbon production, it is
known to employ various stimulation procedures and techniques to
enhance production. For example, in the case of heavy oil and
bitumen housed in subsurface reservoirs, conventional drive
mechanisms may be inadequate to enable production to surface, and
it is well known to therefore inject steam or steam-solvent
mixtures to make the heavy hydrocarbon more amenable to movement
within the reservoir permeability pathways, by heating the
hydrocarbon and/or mixing it with lighter hydrocarbons or hot
water.
[0004] In steam-assisted gravity drainage ("SAGD") and cyclic steam
stimulation ("CSS") hydrocarbon recovery operations, steam is
generated at surface by steam generation units and injected
downhole into a well, where it is subsequently introduced into an
underground hydrocarbon formation in which the well lies, after
which the steam warms bitumen and oil within the formation.
Thus-warmed hydrocarbon within the formation is mobilized and moves
or is drawn toward the well, where it is then collected and
produced to surface. The steam, when contacting cooler subterranean
bitumen and oil, typically condenses to water, releasing latent
heat of condensation and thereby effectively transferring heat to
the oil/bitumen.
[0005] Due to the foregoing condensation of injected steam to
water, and also by reason that underground formations typically
contain amounts of water in the form of brine or the like, water is
typically produced to surface with the recovered hydrocarbon and
the brine. Because proximate surface sources of water for producing
steam for injection downhole are often in very short supply, or
their use prevented or limited due to governmental restrictions, it
is very desirable to use produced water to generate steam. Not only
is such water (although contaminated) available at site, but by
generating steam from produced water the disposal costs of such
contaminated produced water is reduced.
[0006] Typically, water that is produced to surface with the
collected hydrocarbon arrives in the form of free water, suspended
water, water-in-oil emulsions and/or oil-in-water reverse
emulsions. The produced water must go through a series of
processing steps to be useful as conventional boiler feedwater,
such as de-oiling and softening, or evaporation. Typical de-oiler
systems include a free water knock out ("FWKO") vessel, followed by
a skim tank, induced gas floatation and finally an oil removal
filter. The de-oiler system is conventionally used at surface to
separate the recovered hydrocarbons from the produced water, and
the produced water is thereafter recycled to the steam generation
unit for re-use in converting same to steam for injection downhole;
typically, however, the produced water contains significant
impurities in the form of inorganic compounds, such as silica,
calcium and magnesium ions, which must be addressed before the
de-oiled produced water can be introduced to steam generation units
as feedstock.
[0007] Conventional drum boilers operating at circa 2% blowdown
cannot typically be used to generate steam from the produced water
without using evaporators to generate high purity feedwater due to
the concentration of dissolved salts and impurities such as
calcium, silica, organics and the like that cause precipitation and
thereby scaling within boiler tubes during the boiling of the
water, which thereby very quickly renders the boiler ineffective in
transferring heat to the water to generate steam and can also
rupture boiler tubes due to the generation of hot spots.
[0008] Alternatively, special types of steam generators are
commonly used, namely so-called "once-through steam generators"
("OTSG" or "OTSGs"), which can better handle higher amounts of
impurities in the produced water feed stream and generate steam
ranging from 65% to 90% steam quality (65-90 parts steam vapor,
10-35 parts liquid water containing the impurities). Operating at
this steam quality greatly reduces the tendency of the dissolved
salts to precipitate and scale the tubes. Nevertheless, produced
water pre-conditioning steps are still necessary, such as the
conventional warm lime softening ("WLS") or hot lime softening
("HLS") process, which injects lime to reduce water hardness and
alkalinity and precipitates silica and carbonate ions out of the
water, and in conjunction with a weak acid cation or strong acid
cation ion exchange ("WACS" or "SACS") process, removes the calcium
and magnesium scale generating ions to acceptable concentrations,
thereby reducing build-up of scale in the OTSG. The major bulk
chemicals used in these processes are lime (Ca(OH)2), magnesium
oxide (MgO), soda ash (Na2CO3), caustic (NaOH), and hydrochloric
acid (HCl). Minor amounts of coagulant and polymer are used to aid
in solid separation.
[0009] It is known and generally acknowledged that conventional
steam generation technologies suffer from numerous disadvantages.
For example, OTSGs still require boiler feedwater pretreatment,
require large volumes of feedwater since much of the feed is
rejected downhole as blowdown to manage impurities, and can suffer
large amounts of downtime to clean boiler tubes (pigging). However,
alternative drum boilers require the use of evaporation technology,
which adds significant capital expense and requires high energy
consumption.
[0010] Indirect fired steam generators have been introduced as a
possible alternative to such conventional technologies. Indirect
boiling can be used with more contaminated feed water, thus
reducing some equipment line-up complexity and capital cost. For
example, United States Patent Application Publication No. US
2014/0165928 to Larkin et al. teaches a steam generation system in
which solid particulate such as sand is first heated by heat
exchange with hot fluids, and then the heated particulate is
contacted with the water to be vaporized. As a further example,
Hipvap Technologies of Alberta, Canada, is pilot testing an
indirect fired steam generation system which uses a
forced-circulation heat exchanger process to recirculate a hot oil
fluid in a closed loop to generate steam from produced water.
[0011] However, indirect boiling technologies currently under
consideration are often complex and likely relatively expensive to
implement as they may contain double the heat transfer surface area
than what is required to generate steam alone. It would therefore
be desirable to have access to a steam generation system that is
relatively simple and inexpensive, while still possessing the
advantages of indirect boiling in terms of equipment line-up
simplification, moderated, constant and homogeneous heat flux on
the tube walls and reduced operating costs.
BRIEF SUMMARY
[0012] The present invention therefore seeks to provide a system
for generating steam from produced water with a value-added and
simplified line-up that avoids heat transfer surface area
duplication and minimizes the need for boiler feedwater
treating.
[0013] According to a first aspect of the present invention there
is provided a steam generation system for use in thermal
hydrocarbon recovery operations, the system comprising a produced
water boiler for generating steam, the boiler tubes heated
indirectly by means of flue gas, such as a gas turbine exhaust. The
gas turbine produces electricity which can be used for powering
submersible pumps, and/ or the central processing facility ("CPF")
of the hydrocarbon recovery operation, and/or for powering an
electric heater on the surface or subsurface, while exhaust heat
from the turbine is used to heat the produced water boiler. The
heat supplied by the gas turbine vaporizes a portion of the
produced water in the produced water boiler, thus providing steam
for injection downhole to enable subsequent hydrocarbon
production.
[0014] In some exemplary embodiments of the present invention,
mechanical cleaning means, such as but not limited to online
"pigging", is applied to clean build-up from the produced water
boiler tube interior.
[0015] A detailed description of exemplary embodiments of the
present invention is given in the following. It is to be
understood, however, that the invention is not to be construed as
being limited to these embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In the accompanying drawings, which illustrate exemplary
embodiments of the present invention:
[0017] FIG 1A is a simplified schematic view of a conventional
prior art process for recycling produced water for steam
generation;
[0018] FIG. 1B is a simplified schematic view of a conventional
prior art process for recycling produced water for steam
generation;
[0019] FIG. 2 is a simplified schematic view of a novel produced
water recycling process line-up according to the present invention;
and
[0020] FIG. 3 is a schematic view of a first exemplary embodiment
of a system and process in accordance with the present invention,
wherein electricity produced by the gas turbine is used for
powering the central processing facility or electric heaters or
submersible pumps, etc.
[0021] Exemplary embodiments of the present invention will now be
described with reference to the accompanying drawings.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0022] As mentioned above, conventional produced water steam
generation systems involve a number of subsystems to separate and
purify the produced water to a state that is acceptable as
feedwater for the steam generation equipment. As is shown in FIG.
1A, the subsystems of a conventional prior art system for
processing water produced from a wellhead 1 include a gas/oil/free
water/solids separation stage 2, a produced water removal stage 3,
a produced water treatment impurity removal stage 4 and steam
generation 5. The oil/produced water separation stage 2 is designed
to remove most of the oil from the water, the oil then being stored
or pipelined elsewhere for processing, while the produced
water--still somewhat contaminated with minor amounts of oil--must
undergo additional processing in the oil removal stage 3 (in which
further removed oil is recovered and processed). The produced water
treatment impurity removal stage 4, as discussed above, removes
various impurities from the de-oiled water that create heat
transfer tube surface scaling and fouling to prepare it for
introduction to the steam generation stage 5, in which steam is
produced for downhole injection at the wellhead 1 (with waste water
or blowdown being rejected from the system for impurities buildup
management and disposed of as necessary).
[0023] FIG. 1B provides further details regarding a conventional
prior art OTSG system for recycling produced water to generate
steam. Again, material from the reservoir (along with condensed
water from previously injected steam) is produced at the wellhead
1, and a water-oil mixture is sent to the FWKO unit 6 to separate
the oil and produced water (this is the oil/water separation stage
2 shown in FIG. 1A). The de-oiled produced water is then sent to
one or more skim tanks 7, and then to an induced gas flotation
("IGF") unit 8, the oil froth being removed and then cleaned water
being sent to the next stage in the process. To remove various
inorganic impurities, the cleaned water stream is pumped to a WLS
unit 9, through a series of afterfilters 10, and then to an ion
exchange unit 11 such as WACS. At this stage the treated water is
of sufficient purity to be fed into an OTSG 12, producing
waste/blowdown and steam for downhole injection.
[0024] The above description is simplified and does not include all
of the equipment or additives that might be required under the
conventional OTSG system, and thus it would be clear to those
skilled in the art that such a system is complex, capital-intensive
and relatively expensive to operate.
[0025] Turning now to FIGS. 2 to 3, exemplary embodiments of the
present invention are illustrated. The exemplary embodiments are
presented for the purpose of illustrating the principles of the
present invention, and are not intended to be limiting in any
way.
[0026] FIG. 2 illustrates, in a simplified schematic view, the
basic stages of produced water processing according to the present
invention. Materials including gas, solids, oil/bitumen and water
are produced at the wellhead 20, and subsequently separated into
various desired components at the separator 22. Gas would normally
be piped to the boiler burners, and may or may not need to be
processed for sulphur removal in a sulphur recovery unit, while
solids are landfilled. The separated oil can be diluted with a
diluent for pipelining if necessary, or it may be subjected to
partial upgrading on-site in a manner known to those skilled in the
art.
[0027] The separated water is then sent to an impurity containing
produced water boiler with on line pigging unit 24, and again
numerous types of produced water boiler technologies may be useful
with the present invention so long as they enable a heat exchange
to heat the water pumped through the impurity containing produced
water boiler with on line pigging 24 to its boiling point. The
impurity containing produced water boiler with on line pigging 24
is heated by means of the hot exhaust of a gas turbine 26, which
turbine 26 can be powered by either fresh gas or a mixture of fresh
gas and produced gas separated by the separator 22, as would be
clear to those skilled in the art. Once the water is heated to
boiling in the impurity containing produced water boiler with on
line pigging 24, steam is generated for downhole injection at the
wellhead 20 and the remaining concentrate can be disposed of as
waste/blowdown in a conventional manner.
[0028] Turning now to FIG. 3, a first embodiment of the present
invention is illustrated. As with FIG. 2, materials produced at the
wellhead 20 are pumped to the separator 22 for separation into the
four main components. FIG. 3 illustrates that separated gas may or
may not be re-used as part of the feedstock for the gas turbine
unit 26. Separated water is pumped into the impurity containing
produced water boiler with on line pigging 24, which in this case
is a heat exchanger.
[0029] The gas turbine unit 26 comprises an upstream compressor 28
coupled to a downstream turbine 30; although not shown in this
simplified illustration, there is a combustion chamber between the
compressor 28 and turbine 30, in a manner well known to those
skilled in the art. The gas is fed into the compressor 28, which
increases the pressure of the gas, and then into the combustion
chamber, and then fuel is fed into the combustion chamber and
ignited, resulting in a high-temperature gas flow that enters the
turbine 30. The heated gas flow expands in the turbine 30,
producing shaft work output. This work output is illustrated as
creating electricity, which would be achieved by the shaft driving
an electricity generator in a conventional manner. In this
embodiment, the created electricity would be used to power the
submersible pumps, the central processing facility or "CPF" of the
hydrocarbon recovery operation, or electric heaters.
[0030] The gas turbine 26 operation described above also produces
exhaust heat. While heat from a turbine can be rejected as waste,
or recovered through a heat recovery steam generator, or through a
once through steam generator lacking on-line pigging and fed with
impurity removed boiler feedwater, in the present case the exhaust
heat is used to heat the untreated produced water boiler 24 that
has online pigging. In a heat exchanger arrangement, the exhaust
heat would indirectly heat the water that is pumped through the
impurity containing produced water boiler with on line pigging 24,
and at least some of the water would be converted to steam as a
result, which can then be used for downhole injection as part of
the thermal hydrocarbon recovery operation. Any water not converted
to steam would be rejected from the impurity containing produced
water boiler with on line pigging 24 as waste or blowdown and can
be disposed of by conventional means. Online pigging or other
conventional cleaning techniques can be used to clean the impurity
containing produced water boiler with on line pigging 24
internals.
[0031] Unlike other prior art indirect boiling systems, which use
energy simply to power steam generation, the use of a turbine
allows for both the production of heat for the impurity containing
produced water boiler with on line pigging and useful electricity
for the hydrocarbon recovery operation.
[0032] As can be readily seen, then, there are numerous advantages
provided by the present invention. In addition to the simplified
equipment line-up, which can in appropriate circumstances eliminate
or reduce the need for de-oiling or water treatment stages such as
the IGF, ORF, warm lime softener, after filters, and ion exchange,
chemical additive requirements can be reduced. In addition to this
potential reduction in capital and operating costs, recovering what
would have been waste heat helps to reduce energy consumption when
compared to indirect fired steam generation systems, and the
turbine-generated electricity can be used to either power the CPF
or even supplement the exhaust heat that is used to boil produced
water in the impurity containing produced water boiler with on line
pigging unit.
[0033] The foregoing is considered as illustrative only of the
principles of the invention. Thus, while certain aspects and
embodiments of the invention have been described, these have been
presented by way of example only and are not intended to limit the
scope of the invention. The scope of the claims should not be
limited by the exemplary embodiments set forth in the foregoing,
but should be given the broadest interpretation consistent with the
specification as a whole.
* * * * *