Note: Descriptions are shown in the official language in which they were submitted.
1 1 B6531 ICR 6362
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STEAM GENERATION F ROM
LOW QU~LITY ~'EEDW~TER
Background of the Invention
1. Field oE the Invention
The presen-t invention relates generally to appara-
-tus and rnethods for producing steam, and more particularly,
but not by way of limitation, to apparatus and methods
for produciny steam Erom low quality feedwater including
oily saline water produced from an underground oil and
gas production zone.
2. Description of the Prior Art
One manner oE stimulating the production of hydro-
carbons fr~msubsurface formations is to inject steam intothe subsurface formation. An oil production operation
based on such steam injec-tion normally requires a source
of high ~uali-ty feedwater for ~te.lm genera-tion and also
requires a means for disposing of oily saline produced
water which is recoverecl from the formation along with
the hydrocarbons.
In some areas, however, a reliable supply of high
quality feedwater is not readily available, and it is,
therefore, desirable to recycle oily saline produced water
25~ and u-tllize the same to generate steam to be injected back
nto~the underground formation.
Several prior ar-t systems have provided means Eor
generating steam from low quality feedwater or o-therwise
rela-te~to some part of the s-team production sys-tem of -the
30 ~ present~invent~ion~as described below.
U. S.~Patent No. 2,947,68~ to Cain discloses a pro-
ce;s~s~and system for genera-ting hot processed water from
feedwater~havlng scale forming salts therein~ As illu-
strated in~the;figure o-~ the Cain disclosure, that refer-
~ènce~discloses a process~wherein low quali-ty feedwater 14
s~charged to a~heating -tower 10 first contacting hot flue
gas from a~superheater, then ho-t gases from a burner 16,
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precip:ita-ti.ng out sludcJe at 17. The heatecl water is aci-
dified ancl purnpecl by pump 2l -to heating vessel 20 by out-
let 24. Steam from heati.ng vesse:l. 20 exits by outle-t 26
and is prehea-ted by an exchanger 31 in superheater 29 prior
to pressuring up by compressor 33 and superheating in
exchanger 34 in superheater 29. The superheated steam pro-
duced thereby flows from line 25 to heater 20 to form more
steam, exiting by line 26, by a gas liquid contact with the
wa-ter in heater 20. This process differs substantially
from the present invention in that it produces hot water
rather than steam.
British Pa-tent No. 669,923 di.scloses a system for
making dis-tilled water from low quality water such as sea
water. Sea water enters pre-heater 4 by inlet 3 and is
heated by ~ay of a gas liquid interface by superheated
steam entering by inlets 5. Sludge from scaling minerals
is disposed of by outlet 6. The heated brine then passes
throuyh a distilla-tion process and a portion of the steam
generated during -that distillation process is superhea-ted
in superheater 21 and recycled to the preheater 4 by the
: outlets 5.
U. S~ Patent No. 3,410,796 -to IIull and an article
entitled "The Thermosludge Wa-ter Treating and Steam Gener-
:~ ation Process" from the December, 1967 of -the Journal of
Petroleum ~'ec.hnoloyy at pages 1537-1540 thereof, describe
a process generally referred to as the "thermosludge"
: : process. Re.ferring to the Hull patent, low quality feed-
:water~enters the system by line 12 and scaling elements
are removed as sludge:from water feed tank 10 which is
3~0 ~hea-ted by recycled steam from line 40. Hot feedwater ha~-
ing~much of; the mineral con-tent -thereof removed passes
: by line 14 t~ stripper 24, and is -treated with sulfite
: : and;amine on ~-the way. Steam is generated by line 26, from
stripper 24, which conducts -the produced steam to the poin-t
: 35~ of use thereof. Blowdown from the stripper 24 and steam
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drum 30 passes by outlet 34 through a low pressure separa-
-tor 33 which drops out more sludge of precipitated minerals
by means of line 42, and which passes the steam content of
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the blowdown to -the water feed tanl~ 10 by line ~0. The
s-tripper 2~ ancl steam drum 30 are heated by a thermosiphon
system wherein water passes by :Line 32 to a s~eam chest
where a heat exchanger ~ transmits heat to the steam from
a mol-ten salt circuit. Al-though the systern illustrated
in -the Hull reference cloes produce steam as opposed to
merely producing water, its manner of doing so is such
that the heat exchanger -tubes within the heaters are in
contact with hard water and scaling is a problem as is
disc]osed in column 6, lines ~8-56 of the ~ull patent.
U. S. Patent No. 2,756,208 to Axelrad et al. dis-
closes a process for producing hot water utilizing high
pressure steam from a conventional boiler to contact water
and hea-t the same.-
Another prior art process generally known as the
"vapor therm process" is described in ERDA publication
No. 10 entitled "Enhanced Recovery of Oil and Gas" at
pages 55-57 thereof, and is also described in Report Num-
ber 72 of -the "Firs-t International Conference on the F'uture
of Heavy Crude and Tar Sands", entitlecl "The Vapor Therm
Process for Recovery of Viscous Crude Oil" by F.~. Young,
Jr. and R.W. Krajicek. The vapor therm process includes
a high pressure air compressor, a high pressure combustion
chamber, a water chamber, a water injection and blowdown
; 25 drum and related pumps and :instrumen-tation. The high
pressure combustion gas is con-tacted with low quality
feedwater to generate steam. The mixture of steam and
combustion gases is -then injected in-to the wells to per-
;form the flood~ing operation. Blowdown water including
precipitated mineral solids is withdrawn from the contac-
tor.
Another prior ar-t process devel-oped by Esso Resources
and described in Application No. 770866 to -the Energy
Resources Conservation Board, May 1978, includes the gen-
eration of superhea-ted steam in a utility type boiler and
the subsequen-tly blending of the superhea-ted steam with
heated produced brine. Approximately one barrel of high
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quali-ty water is required for each barrel of saline water
to be recycled. The saturated steam generated by the
blending of -the superheated steam with produced brine is
then injected in the subsurface forma-tion.
Summary of the Invention
By the present invention, a low quality feedwater
stream is introduced into a contactor vessel. Superheated
steam is also introduced into the contactor vessel and
contacted with the feedwater to thereby produce saturated
steam in the contactor vessel and -to precipitate minerals
from the feedwater in the contactor vessel. The preci-
pitated minerals are removed from the contactor vessel
by withdrawing a waste wa-ter stream containing said miner-
als from -the contactor vessel.
If saturated s-team is required at a use terminal,
the saturated steam is wi-thdrawn from the con-tactor vessel
and divided into a primary and secondary stream. The
~primary stream is then flowed to -the use terminal, which
may be an injection well in a steam flooding system for
a subsurface bydrocarbon producing formation. The secon-
dary stream is directed -to a steam compressor from which
it is directed to a su~L~erheate~ The superheated
~ secondary stream of steam is then recycled to the con~
tactor vessel.
If superheated steam is required at the use terminal,
the saturated steam is withdrawn from the contactor vessel
and directed to the steam compressor and then to the
30 ~superheater. ~Superheated stéam Erom the superheater is
then divided into a primary stream and a secondary stream.
The primary stream is flowed to the use terminal, which
may be a steam powered~generator. The secondary stream
is recycled -to the contactor vessel.
35 ~ ~ A general objec-t of the present invention is the
provision of apparatus and methods for producing steam.
Another object of the present invention is the pro-
vision of apparatus and methods for producing steam from
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low quality feedwa-ter such as oi]y saline procluced water
or boiler blowdown water.
And another objec-t of the present :invention is -the
provision of improved appara-tus and methods for steam
flooding a subsurface hydrocarbon formation by recycling
oily saline produced water.
Yet another obje-ct of the present lnvention is the
provision of improved appara-tus and methods for generating
power with a steam powered yenera-tion device.
And another object of the present invention is the
provision of apparatus and methods for producing steam
from low quality feedwater while avoiding problems of
scaling of heat exchangers by utilizing a gas-liquid con-
-tact for steam generation.
Yet another object of the present invention is the
provision of apparatus and methods for generating steam
from low quality feedwater, and removing precipitated
minerals from a steam-feedwa-ter contacting vessel.
And another object of the presen-t invention is the
provision of appara-tus and methods for initially starting
a steam genera-tion system which u]tima-tely relies on re-
cycled superhea-ted steam for the generation of saturated
steam produced by the sys-tem.
Numerous other o~jects, fea-tures and advantages of
~; 25 the presen-t invention will be readily apparent to those
skilled in the art upon a reading of the following dis-
closure when taken in conjunction with the accompanying
.
drawlngs.
Brief Description of the Drawings
F~G. 1 is a schematic block diagram of the s-team
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generation sys-tem of the present invention illustrating
the same being utilized to steam flood a subsurface hyclro-
carbon producing formation.
; FIG. 2 is a simplified schematic block diagram of
the steam genera-tion system of the present invention,
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illustratin~j the same being utilized to produce super-
heated s-team for powerincJ a steam powered ~eneratiny sys-
tem.
Detailed Description of the Preferred Embodiments
. . . , _ . . . _ _ . . _ . . . _ _
STEAM INJECTED WELLS
Referrin~ now -to the drawings, and par-ticularly to
FIG. 1, the steam production system of the present inven~
tion is shown and generally designated by the numeral 10.
The steam production system 10 includes a separator-con-
tactor 12, which may generally be referred -to as a contac-
~ 15 tor vessel 12.
; ~ The contactor vessel 12 provides a means for contacting
feedwater and superheated steam to produce sa-turated steam
and waste water. The was-te wa-ter contains mineral solids
precipita-ted from the feedwa-ter.
~ Low quality or hard feedwater is introduced to the
separa-tor vessel~12 by a first conduit 14, which may be
referred to as an inlet condui-t means.
Superheated steam is introduced to the contactor
vessel 12~ by a second conduit 16, which may be referred
to as a recycle~ condui-t means.
A third conduit 18 withdraws satura-ted steam from
-the contactor vessel 12 and carries -the same to a conduit
unction~20 which may generally be referred -to as a divi-
der~means 20 for dividing the saturated steam from third
3~0;~ condult~18~1nto a~primary stream and a secondary stream.
A fourth condui-t~22, which may be referred to as a flow
conduit means, is connected to a~well 24 and the first
stream of saturated steam flows -throu~h conduit 22 to the
we~]1 24 where the same is used for~flooding a subsurface
35 ~ hydrocarbon~producing formation 26.
; A~fifth conduit 28 direc-ts the secondary stream of
satur~ated steam from divider means 20 to a superheater 30.
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Connected within fifth co:nduit 28 is a low compression
ratio steam cor,lpressor 32. Third and fifth conduits 18 &
and 23 may be collectively referred to as an outlet conduit
means for withdrawing saturated s-team frorn vessel 12 and
5 conducting at least a portion of the same to superheater
30.
It will be appreciated by those skilled in the ar-t
that the relative positions of compressor 32 and super-
heater 30 could be reversed. In many situations the most
10 suitable configuration is to install compressor 32 between
two superheaters.
An outlet of the superheater 30 is connected to second
conduit 16 for recycling the superheated second stream of
steam to the contactor vessel 12 where the process repeats
: 15 itself.
A sixth conduit 34, which may be referred to as a
waste conduit, provides a means for removing precipitated
minerals from the contactor vessel 12 by withdrawing a
waste water stream containing said minerals from the con-
20 tactor vessel 12.
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Example
;~: : An example of the basic steam generation system of FIG.
: : 25 1 for producing 25 miLlion BTU's per hour at 500 psig
through flow conduit 22 -to the well 24 is given in the fol-
lowing Table l. :The various f:Luid streams are indicated
by the numbers of the conduits through which -they flow.
Fuel~and power~inputs to superheater 30 and compressor 32
30 ~ are lndicated schematically by energy input streams 31 and
3:3t respectively. ~
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Table :[
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APPROXI~ TE ENERGY AND MATERIAL Bl\L,~NCE ~OR A RE,CYCL~, STEAM GENERATOR
25_ M Btu/ ~r . OU'L'P UT ~T 5 00 Ps -1. a
Rate Total
Temp Pressure I,OOO ~nt:halpy Enthalpy
Stream Description F Psia _ Ib/llr BtUllb r~MBtu!hr
14 C~ld ~eed 50 50023. l 18 O. 4
18 Sat. Vapor467 500144.:L1204.4173.6
22 Sat. Vapor467 50020.81204.4 25.0
28 Sat. Vapor470 515123.31204.3148.5
16 Superheated 800 500 123.31412.1 174.2
34 Sat. Llquid 467 500 2.3 449 1.0*
31 Fuel 2.0**16000 32.1
33 Power (diesel) 225 IIP .1~**18000 2. ()
* 60% ~an be recovered by flashing, to heat feedwat~r.
** at 80% heat efficiency
*** at 0.5 lbs/HP hour.
AUXILIARY EQUIPME,NT
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: Referring agai.n to FIG. 1, the varlous auxiliary
equipment connected to the main power generation system
~; ~: just described will now be described.
The waste water withdrawn from contactor vessel 12
:~ through conduit 34 is directed to a flash drum 36 where
i-t is flashed to approximately atmospheric pressure. Low
~: : pressure steam created in flash drum 36 is directed by
conduit 38 to a junction 40 with inlet 14 for pre-heating
the feedwater inlet stream in conduit 14. .
Water carrying precipitated mineral solids is direc-ted
through a conduit 42 to a settling -tank 44 where the solid
`30 materials are separated from the water. Water from settling
tank :44 may be recycled by a conduit 46 and a recycle pump
: 48 disposed -thereln to the feedwater inlet s-tream in con-
duit 14.
: The feedwater s-tream in conduit 14 is pumped to vessel
12 by a feedwater pump 49.
. One problem which may be encountered with a system
like that shown in FIG. 1 is tha-t superheated steam is
~ required to~produce satu.rated steam and once the system
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is on line, -the superheatecl s-team itselE :is produced from
the saturatecl steam. Therefore, upon initially s-tarting up
the system, there is no saturatecl s-team with which to pro-
duce superheated steam from the normal recycle process.
This problem may be overcome in several ways.
One manner is to utilize air, nitrogen, or some other
suitable gas, the inpu-t of which is represented at condui-t
50, which is pumped by compressor 52 into -the superheater
30 which may be u-tilized to heat the gas. The use of nitro-
gen is preferrable for corrosion pro-tection. The heated
gas is then introduced to the contactor vessel 12 -through
conduit 16 and generates steam within the contactor vessel
12. Subsequently, after sufficient steam is being generated
in the contactor vessel 12 so that adequate amounts thereof
may be recycled to conduit 28 and thro~ superheater 30, the
gas supply may be cut off by closing valve 54 thereby re-
placing the step of heating gas with the desired superheating
of the secondary stream of steam.
Another manner of overcoming the problem of providiny
initial startup steam is to provide a conventional low pres-
sure auxiliary boiler 56 to which a smaller supply of soft
feedwater is p~rovided by conduit 53. 1'he steam generated
in boiler 56 may then be fed to superheater 30 by conduit
60. Again, once sufficient satura-ted steam is being gener-
ated in contactor vessel 12 -to provide adequate amounts of
steam in the recycle line 28, the auxiliary boiler 56 may
be shut down.
With -the system shown in FIG. 1, the primary stream
of produced saturated steam is directed to well 24 by con-
30 duit 22 as previously mentioned. A pressure regulatingmeans 62 wi-thin condui-t 22 regula-tes the pressure of steam
being injected into the well.
A mixture of hydrocarbons and oily saline produced
water is produced from well 24 by production line 64,
35 which may be referred to as a production conduit means.
It is directed by production line 64 to an oil separator
66 from which an oil line 68 carries the liquid hydro-
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carbon and from which an oi:Ly wa-ter line 70 conducts the
oily saline produced water. The oily saline produced water
may be recycled from condui-t 70 to feedwa-ter line 14 by a
produc-tion recycle conduit 72.
STEAM DRIVEN POWER GEI~iERATOR
Referring now to FIG. 2 the main power generation
system of -the present invention is again shown, in a slightly
modified form from that of FIG. 1, being adapted for the
production of superheated steam rather than saturated steam.
In the embodiment of FIG. 2, the outlet conduit 18
directs all of the saturated steam produced by vessel 12
to compressor 32, from which the produced steam flows
through cond~lit 28 to superheater 30.
The recycle conduit 16 includes a dlvider means 74,
which is a junction with a superheated steam flow conduit
76, for dividing the superheated steam from superheater
~ 30 into a primary stream and a secondary stream.
; ~ 20 Flow conduit 76 flows the primary stream of super-
heated produced steam to a power turbine 78, which may be
generally referred to as a use terminal.
Recycle conduit 16 recycles the secondary stream of
superheated produced steam to vessel 12.
2~5~ Turbine 78 drives an~electric generator 80 through a
shaft 82. Low pressure steam exits turbine 78 by conduit
84 to a condensor 86. High quality water discharged from
condensor 86 may ei-ther be recycled to feedwater stream 14
through a discharge recycle conduit 88 or it may be directed
;20 ~to a process zone 90 requiring high quality feedwater.
All~the various auxiliary equipment shown in FIG. 1
may also be used with the modified equipmen-t in FIG. 2.
The ~lvider means 74 and superheated steam flow con-
duit 76 could also be added to the system of FIG. 1 so
; tha~t one system could produce both saturated and super-
` heated steam for use at one or two use -terminals.
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Thus it is seen that the apparatus and me-thods for
producinc3 s-team from low quality feedwater of the present
invention are readily adap-ted to achieve the ends and ad-
vantayes mentioned as well as those inherent therein.
While presently preferred embodiments of the invention
have been illus-tra-ted and described for the purpose of
this disclosure, numerous chancJes in the arrangement and
construction of parts may be made by -those skilled in the
art which changes are encompassed within the scope and
spirit of this invention as defined by the appended claims.
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