U.S. patent application number 14/048501 was filed with the patent office on 2014-04-24 for direct steam generation of boiler blowdown.
This patent application is currently assigned to Conocophillips Company. The applicant listed for this patent is Conocophillips Company. Invention is credited to Michelle R. FIEDLER, Edward G. LATIMER.
Application Number | 20140110109 14/048501 |
Document ID | / |
Family ID | 50484288 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140110109 |
Kind Code |
A1 |
LATIMER; Edward G. ; et
al. |
April 24, 2014 |
DIRECT STEAM GENERATION OF BOILER BLOWDOWN
Abstract
Systems and methods generate steam from produced water by
passing the produced water through first and second steam
generators coupled together. The first steam generator produces wet
steam in which a liquid effluent with impurities of the produced
water passes to the second steam generator. The second steam
generator combusts fuel and oxidant in direct contact with the
liquid effluent. The first and second steam generators limit
fouling and waste while providing a combined steam output that may
include combustion products from only the second steam
generator.
Inventors: |
LATIMER; Edward G.;
(Bartlesville, OK) ; FIEDLER; Michelle R.;
(Bartlesville, OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Conocophillips Company |
Houston |
TX |
US |
|
|
Assignee: |
Conocophillips Company
Houston
TX
|
Family ID: |
50484288 |
Appl. No.: |
14/048501 |
Filed: |
October 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61717676 |
Oct 24, 2012 |
|
|
|
Current U.S.
Class: |
166/267 ; 122/1B;
122/31.1; 122/379; 166/272.3; 166/57 |
Current CPC
Class: |
F22B 37/56 20130101;
F22B 29/06 20130101; Y02E 20/344 20130101; E21B 43/2406 20130101;
E21B 43/164 20130101; F22B 1/18 20130101; Y02E 20/34 20130101 |
Class at
Publication: |
166/267 ;
166/272.3; 166/57; 122/1.B; 122/31.1; 122/379 |
International
Class: |
F22B 1/18 20060101
F22B001/18; F22B 37/56 20060101 F22B037/56; F22B 29/06 20060101
F22B029/06; E21B 43/24 20060101 E21B043/24; E21B 43/16 20060101
E21B043/16 |
Claims
1. A method of generating steam, comprising: injecting water into
an initial steam generator to produce steam and a liquid effluent
containing a remainder of the water with impurities; and injecting
the liquid effluent into a direct steam generator to vaporize at
least part of the liquid effluent upon contact with combustion
products such that a resulting gas phase including additional steam
and carbon dioxide is output separate from a non-gas phase waste
stream.
2. The method of claim 1, wherein the liquid effluent vaporizes in
the direct steam generator leaving the waste stream formed of solid
particles.
3. The method of claim 1, wherein the waste stream includes liquid
brine formed by incomplete vaporization of the liquid effluent
supplied in excess of a saturation amount for the direct steam
generator.
4. The method of claim 1, wherein the impurities include
combustible compounds combusted by excess oxidant supplied to the
direct steam generator.
5. The method of claim 1, wherein the steam from both the initial
and direct steam generators is injected into a well for a steam
assisted gravity drainage operation.
6. The method of claim 1, wherein the steam from the direct steam
generator is superheated.
7. The method of claim 1, wherein the steam from both the initial
and direct steam generators is injected into a well and the steam
from the direct steam generator is superheated to a temperature
that prevents condensation prior to injection into the well.
8. The method of claim 1, wherein the steam from the initial steam
generator and the gas phase from the direct steam generator are
combined into a mixture that is injected into a well and includes
steam with less than 5 percent carbon dioxide by weight.
9. The method of claim 1, wherein the steam from the initial steam
generator and the gas phase from the direct steam generator are
combined into a mixture that is injected into a well and includes
steam with between 2 and 4 percent carbon dioxide by weight.
10. The method of claim 1, wherein the initial steam generator
includes a once through steam generator that produces a steam
quality between 70 percent and 85 percent with the remainder of the
water going to the liquid effluent.
11. A system for generating steam, comprising: an initial steam
generator coupled to receive water and having a first output for
steam and a second output for liquid effluent containing a
remainder of the water with impurities; and a direct steam
generator coupled to receive the liquid effluent for at least
partial vaporization upon contact with combustion products and
having a third output for a resulting gas phase including
additional steam and carbon dioxide and a fourth output for a
non-gas phase waste stream.
12. The system of claim 11, wherein the direct steam generator
vaporizes the liquid effluent leaving the waste stream formed of
solid particles.
13. The system of claim 11, wherein the direct steam generator
produces the waste stream of liquid brine formed by incomplete
vaporization of the liquid effluent.
14. The system of claim 11, wherein the impurities include
combustible compounds combusted by excess oxidant supplied to the
direct steam generator.
15. The system of claim 11, further comprising a well for a steam
assisted gravity drainage operation that is coupled to both the
initial and direct steam generators for steam injection.
16. The system of claim 11, wherein the direct steam generator
produces the steam that is superheated.
17. The system of claim 11, further comprising a well coupled to
the first and third outputs such that a mixture injected into the
well includes steam with less than 5 percent carbon dioxide by
weight.
18. The system of claim 11, further comprising a well coupled to
the first and third outputs such that a mixture injected into the
well includes steam with 2 to 4 percent carbon dioxide by
weight.
19. The system of claim 11, wherein the initial steam generator
includes a once through steam generator that produces a steam
quality between 70 percent and 85 percent with the remainder of the
water going to the liquid effluent.
20. A method of generating steam, comprising: recovering production
fluid from a reservoir; separating the production fluid into an oil
stream and a water stream; generating steam from the water stream
by partial vaporization of the water stream while isolated from
fluid communication with combustion products and then further
vaporization of the water stream while in fluid communication with
combustion products; and injecting the steam into the reservoir for
a steam assisted gravity drainage operation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional application which
claims benefit under 35 USC .sctn.119(e) to U.S. Provisional
Application Ser. No. 61/717,676 filed Oct. 24, 2012, entitled
"DIRECT STEAM GENERATION OF BOILER BLOWDOWN," which is incorporated
herein in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] None
FIELD OF THE INVENTION
[0003] Embodiments of the invention relate to methods and systems
of handling blowdown from initial steam generation with additional
direct steam generation.
BACKGROUND OF THE INVENTION
[0004] Enhanced oil recovery processes employ thermal methods to
improve recovery of heavy oils from subsurface reservoirs. For
example, injection of steam into heavy oil bearing formations heats
the oil in the reservoir, which reduces the viscosity of the oil
and allows the oil to flow to a collection well. A mixture of the
oil and produced water that flows to the collection well is
recovered to the surface where the oil is separated from the
water.
[0005] For economic and environmental reasons, these operations
recycle the water used in the steam injection by treating the
produced water and directing treated feedwater to a steam generator
or boiler. Several treatment processes remove constituents which
form harmful deposits in the boiler or steam generator but without
even further costs do not remove all dissolved solids. Blowdown in
steam generation thus includes impurities and can include about a
quarter of the feedwater input for a once-through type steam
generator.
[0006] The blowdown presents a problem regardless of application
requiring the steam. The impurities can limit reuse as feedwater
without further expensive treatment or inefficient concentrating of
the impurities. If not reused, the blowdown represents a
significant and unacceptable water portion for disposal.
[0007] Therefore, a need exists for systems and methods to limit
production of undesirable waste streams during steam
generation.
SUMMARY OF THE INVENTION
[0008] In one embodiment, a method of generating steam includes
injecting water into an initial steam generator to produce steam
and a liquid effluent containing a remainder of the water with
impurities. Injecting the liquid effluent into a direct steam
generator vaporizes at least part of the liquid effluent upon
contact with combustion products. A resulting gas phase including
additional steam and carbon dioxide outputs from the direct steam
generator separate from a non-gas phase waste stream.
[0009] For one embodiment, a system for generating steam includes
an initial steam generator coupled to receive water and having a
first output for steam and a second output for liquid effluent
containing a remainder of the water with impurities. A direct steam
generator couples to receive the liquid effluent for at least
partial vaporization upon contact with combustion products. The
direct steam generator includes a third output for a resulting gas
phase including additional steam and carbon dioxide and a fourth
output for a non-gas phase waste stream.
[0010] A method of generating steam includes recovering production
fluid from a reservoir and separating the production fluid into an
oil stream and a water stream. Generating steam from the water
stream includes partial vaporization of the water stream while
isolated from fluid communication with combustion products and then
further vaporization of the water stream while in fluid
communication with combustion products. The method further includes
injecting the steam into the reservoir for a steam assisted gravity
drainage operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete understanding of the present invention and
benefits thereof may be acquired by referring to the follow
description taken in conjunction with the accompanying
drawings.
[0012] FIG. 1 depicts a schematic of a system including initial and
direct steam generators coupled together for a heavy oil extraction
process, according to one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Embodiments of the invention relate to systems and methods
of generating steam from produced water by passing the produced
water through first and second steam generators coupled together.
The first steam generator produces wet steam in which a liquid
effluent with impurities of the produced water passes to the second
steam generator. The second steam generator combusts fuel and
oxidant in direct contact with the liquid effluent. The first and
second steam generators limit fouling and waste while providing a
combined steam output that may include combustion products from
only the second steam generator.
[0014] FIG. 1 depicts a production well 100, a separator 102, a
treatment facility 108, an initial steam generator 112, a direct
steam generator 118 and an injection well 114 used in conjunction
with heavy oil or bitumen extraction from a reservoir. During the
extraction, steam injected into the reservoir through the injection
well 114 increases the mobility of the sought after oil within the
reservoir. In an exemplary embodiment, the injection well 114 and
the production well 100 from a well pair for a steam assisted
gravity drainage (SAGD) operation.
[0015] In operation, a liquid mixture of oil and water recovered
through the production well 100 enters the separator 102, which
outputs an oil stream 104 divided from a water stream 106. The
water stream 106 passes through the treatment facility 108 that
removes contaminants in the water stream 106 to a level acceptable
for the initial steam generator 112. The treatment facility 108 may
include de-oiling, such as by addition of a de-oiling polymer, warm
lime softening, filtering and/or weak acid cation exchanging.
[0016] Treated water 110 then exits the treatment facility and
passes to the initial steam generator 112. In some embodiments, one
or more once through steam generators (OTSG) provide the initial
steam generator 112 such that water quality needed by the initial
steam generator 112 is reduced compared to conventional drum
boilers employing more expensive pretreatment schemes. The initial
steam generator 112 further may produce a steam quality between 70
percent and 85 percent with such steam exiting through a first
output to the injection well 114.
[0017] A remainder of the treated water 110 thus not converted into
the steam goes to a liquid effluent 116 exiting the initial steam
generator 112 through a second output coupled to the direct steam
generator 118. The liquid effluent 116 furthermore contains
impurities that were not removed by the treatment facility 108. The
impurities in the liquid effluent 116 may make the liquid effluent
116 unsuitable for recycle through the initial steam generator
112.
[0018] The liquid effluent 116 however contains enough water
content to make disposal undesirable. Replacement of the water not
being recycled presents a problem in many areas with limited makeup
water availability. In addition, limitations on volumes sent to
waste disposal wells make additional concentrating of the liquid
effluent 116 desirable.
[0019] The direct steam generator 118 enables producing additional
steam from the liquid effluent 116 since not restrained by as
stringent requirements on water quality as the initial steam
generator 112. While the direct steam generator 118 may accept even
untreated water, use in combination with the initial steam
generator 112 may enable keeping carbon dioxide concentration
injected into the reservoir below a certain threshold if desired to
control carbon dioxide concentration based on potential for the
carbon dioxide to impact recovery. The direct steam generator 118
may also provide solutions for handling the liquid effluent 116
from the initial steam generator 112 preexisting at some
facilities.
[0020] One example of the direct steam generator 118 utilizes
oxy-combustion by burning fuel, such as natural gas 120, and an
oxidant, such as oxygen 122, in a pressurized chamber with the
liquid effluent 116 injected into the chamber for chamber cooling
upon vaporization into the steam. Unlike generating the steam in
the initial steam generator 112 where water vaporization may occur
while isolated from fluid communication with combustion products,
water vaporization occurs while in fluid communication with
combustion products using the direct steam generator 118. Products
of the direct steam generator 118 include the steam, both from the
combustion of the natural gas and the vaporization of the injected
liquid effluent 116, and carbon dioxide from the combustion of the
natural gas.
[0021] A resulting gas phase that exits the direct steam generator
118 through a third output contains about 80 to 95 weight percent
steam along with carbonaceous combustion products, such as carbon
dioxide. In some embodiments, the steam exiting the initial steam
generator 112 through the first output combines with the gas phase
exiting the direct steam generator 118 through the third output to
form a gas mixture prior to being conveyed into the injection well
114. The gas mixture that is introduced into the injection well 114
may therefore include steam with less than 5 percent carbon dioxide
by weight or between 2 and 4 percent carbon dioxide by weight.
[0022] For some embodiments, the direct steam generator 118
superheats the steam exiting through the third output. This
superheating prevents condensation of the gas mixture prior to
introduction into the injection well 114. While not desired, the
condensation may otherwise occur since the steam from the initial
steam generator 112 may cool as conveyed from a central processing
facility to a wellpad.
[0023] With respect to impurities in the effluent stream 116 from
the initial steam generator 112, the impurities may include one or
more of NaCl, Ca, Mg, Na, K, Fe.sup.+3, Mn.sup.+2, Ba.sup.+2,
Sr.sup.+2, SO.sub.4, Cl, F, NO.sub.3, HCO.sub.3, CO.sub.3,
PO.sub.4, SiO.sub.2 and combustible compounds, such as tar, gas,
oil, dioxins, nitrogen and organometallic compounds. Inside the
direct steam generator 118, the combustible compounds combust and
form part of the combustion products. Excess oxygen 122 supplied to
the direct steam generator 118 may ensure that the combustible
compounds are burned.
[0024] Some of the impurities, such as Na+ and Cl-, form solid
particles (i.e., NaCl crystals) if the direct steam generator 118
is operated for complete vaporization of all the water inside the
direct steam generator 118. A variety of different phase separation
techniques can remove the solid particles from the gas phase
exiting the direct steam generator 118. For example, the direct
steam generator 118 may utilize a cyclone or filters to separate
the solid particles into a non-gas phase waste stream 124 the exits
the direct steam generator 118 through a fourth output.
[0025] The non-gas phase waste stream 124 may contain the solid
particles with no liquid or substantially no liquid. All water may
thus get recycled in some embodiments. The solid particles enable
disposal of waste in a landfill.
[0026] For some embodiments, a brine or slurry forms the non-gas
phase waste stream 124 due to incomplete vaporization of the liquid
effluent 116 supplied in excess of a saturation amount for the
direct steam generator 118. Vaporization energy generated by the
combustion of the natural gas 120 and the oxygen 122 determines the
saturation amount. The impurities from the effluent stream 116
thereby concentrate in the non-gas phase waste stream 124, which
may have sufficient low water content to be acceptable for
injection into a disposal well. Further treatment of the non-gas
phase waste stream 124 may also remove the impurities as solid
waste and produce water suitable for recycle to the initial steam
generator 112 or the direct steam generator 118.
[0027] In some embodiments, the non-gas phase waste stream 124 as
shown enables rejection and disposal of all the impurities
remaining after steam generation without any recycle thereof. Past
configurations require recycling a portion of aqueous blowdown
streams to meet regulatory requirements resulting in some of the
impurities being added back into feed streams for the steam
generators. These impurities that get recycled contribute to making
quality of the blowdown streams worse due to gradual buildup and
also to increasing fouling of the steam generators that thereby
need more frequent expensive cleaning cycles, which hinder
production.
[0028] The preferred embodiments of the invention have been
disclosed and illustrated. However, the invention is intended to be
as broad as defined in the claims below. Those skilled in the art
may be able to study the preferred embodiments and identify other
ways to practice the invention that are not exactly as described
herein. It is the intent of the inventors that variations and
equivalents of the invention are within the scope of the claims
below and the description, abstract and drawings are not to be used
to limit the scope of the invention.
* * * * *