U.S. patent number RE39,077 [Application Number 10/300,265] was granted by the patent office on 2006-04-25 for acid gas disposal.
This patent grant is currently assigned to Master Corporation. Invention is credited to Frank H. Eaton.
United States Patent |
RE39,077 |
Eaton |
April 25, 2006 |
Acid gas disposal
Abstract
Acid gas is liquified by compression and cooling, mixed with
water under pressure and flowed into a disposal well.
Inventors: |
Eaton; Frank H. (Odessa,
TX) |
Assignee: |
Master Corporation (Odessa,
TX)
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Family
ID: |
26740672 |
Appl.
No.: |
10/300,265 |
Filed: |
November 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60061043 |
Oct 4, 1997 |
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Reissue of: |
09159986 |
Sep 24, 1998 |
06149344 |
Nov 21, 2000 |
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Current U.S.
Class: |
405/129.28;
166/271; 405/129.35; 588/250 |
Current CPC
Class: |
B01D
53/002 (20130101); B09B 1/00 (20130101); E21B
41/0057 (20130101) |
Current International
Class: |
B09B
1/00 (20060101) |
Field of
Search: |
;405/129.28,129.35
;588/250 ;166/305.1,271,402 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
HL. Longworth, SPE, G.C. Dunn, and M. Semchuch; Underground
Disposal of .quadrature. .quadrature. Acid Gas in Alberta, Canada:
Regulatory Concerns and Case Histories; Apr. 28, .quadrature.
.quadrature. 1996. .quadrature. .quadrature. cited by examiner
.
E. Wichert, Gascan Resources Ltd., and T. Royan, Tartan Engineering
Corp. .quadrature. .quadrature. Ltd.; Sulfur Disposal by Acid Gas
Injection; Apr. 28, 1996. cited by examiner .
Duncan, Grant and Hartford, Catherine A., Operation of Acid Gase
Injection/Disposal Wells; World Oil, Oct. 1998, pp. 69-75. cited by
other .
Clark, M.A.; Svrcek, W.Y; Monnery, W.D; Jamaluddin, A.K.M; Bennion,
D.B.; Thomas, F.B.; Wicher, E.; Reed, A.D; and Johnson, D.J.;
Designing an Optimized Injection Strategy for Acid Gas Disposal
Without Dehydration; 77.sup.th Annual GPA Convention, Mar. 16-18,
1998, Dallas, TX. cited by other .
Ho, K.T., McMullen, J. Boyle, P., Rojek, O., Forgo, M., Beatty, T.
Longworth, H.L.; Subsurface Acid Gas Disposal Scheme in
Wayne-Rosedale, Alberta; International Conference on Health, Safety
and Environment, Jun. 9-12, 1996, New Orleans, LA; reprinted by
Society of Petroleum Engineers, Inc., No. SPE 35848, pp. 691-704.
cited by other .
Marathon Oil Company Indian Basin Gas Plant Acid Gas Compressor
Injection Study AFE 456195; Holloman Corporation; Mar. 27, 1996.
cited by other.
|
Primary Examiner: Kreck; John
Attorney, Agent or Firm: Storm & Hemingway LLP Perdue;
Mark O.
Parent Case Text
PATENT SPECIFICATIONS
Applicant filed a Provisional Application on this subject matter on
Oct. 4, 1997, Ser. No. 60/061,043. Specific reference is made to
that document.
Claims
I claim as my invention:
1. The method of disposing of acid gas removed from hydrocarbon
products comprising the steps of: a) compressing the acid gas to a
pressure wherein the acid gas will form a dense fluid, b) forming a
dense fluid by cooling the compressed acid gas, c) mixing the acid
gas as a dense fluid with sufficient water to form a stable mixture
at injection pressure, and d) injecting said stable mixture at
injection pressure into a disposal well.
2. The method as defined in claim 1 wherein said compression
pressure is at least 650 psi.
3. The method as defined in claim 1 wherein said water is alkaline
.[.and has a pH of at least 7.5.]. .
4. The method as defined in claim 1 wherein a minimum pressure of
step .[.a).]. .Iadd.c) .Iaddend.is P.sub.mix
=284+21.55.times.CO.sub.2% wherein P.sub.mix is said minimum
pressure in psi and CO.sub.2% is the percentage of carbon dioxide
in the acid gas.
5. The method as defined in claim 4 wherein the compressed acid gas
is cooled to a temperature of below 130.degree. F.
6. The method as defined in claim 1 wherein sufficient water is a
minimum of R.sub.H.sub.2.sub.O=0.25+0.10345.times.CO.sub.2% wherein
R.sub.H.sub.2.sub.O is the minimum ratio by volume of water having
at least a pH of 7.5 to the dense fluid acid gas.
7. The method as defined in claim 6 wherein the mixed acid gas and
water has a temperature of below 110.degree. F.
8. The method as defined in claim 1 further comprising: e) mixing
the acid gas and water in a confluent line, and f) maintaining the
pressure in the confluent line to the compression pressure by g)
limiting the flow from the confluent line by a pressure control
valve.
9. The method as defined in claim 8 wherein h) determining that the
mixture found is stable by less than a significant amount of any
component of the acid gas flashing into the gas phase down stream
from the control valve.
10. The method as defined in claim 9 wherein determining that the
amount of any component of acid gas flashed is more than a
significant amount by formation of hydrates adhering on surfaces of
the disposal well.
11. The method as defined in claim 9 wherein determining that the
amount of any component of acid gas flashed is more than a
significant amount by formation of gas pockets down stream of the
control valve as determined by rapid increase of pressure down
stream of the control valve.
12. The method as defined in claim 9 wherein less than a
significant amount of any component of acid gas is flashed is
determined when less the 5 percent of said mixture is flashed.
13. The method as defined in claim 9 wherein less than a
significant amount of any component of acid gas is flashed is
determined by process simulation.
14. The method as defined in clam 9 wherein less than a significant
amount of any component of acid gas is flashed is determined by
manual process calculations.
.Iadd.15. The method according to claim 1 wherein sufficient water
is an amount of water such that no more than about 5% of the mixed
acid gas as a dense fluid and water vaporizes during said injecting
step. .Iaddend.
.Iadd.16. The method of claim 1 wherein the compressed acid gas is
cooled to a temperature between its freezing point and about
130.degree. F. .Iaddend.
.Iadd.17. The method of claim 1 wherein the mixed acid gas and
water has a temperature between its freezing point and about
110.degree. F. .Iaddend.
.Iadd.18. A method of disposing of an acid gas comprising the steps
of: forming a dense fluid of an acid gas; mixing the dense fluid
acid gas with water to form a stable mixture of acid gas and water
having a ratio of water to acid gas of about .Iaddend.
R.sub.H2O=0.25+0.10345.times.CO.sub.2% wherein R.sub.H2O is the
volume of water to one volume of acid gas and CO.sub.2% is the
percentage of CO.sub.2 on a mole basis in the acid gas; and
injecting the mixture under pressure into a disposal well.
.Iadd.19. The method according to claim 18 wherein water in an
amount less than about twice the ratio
R.sub.H2O=0.25+0.10345.times.CO.sub.2% is mixed with acid gas.
.Iaddend.
.Iadd.20. The method according to claim 18 wherein water in an
amount less than about three times the ratio
R.sub.H2O=0.25+0.10345.times.CO.sub.2% is mixed with acid gas.
.Iaddend.
.Iadd.21. The method according to claim 18 wherein the pressure in
said injecting step is at least about
P.sub.mix=284+21.55.times.CO.sub.2% and wherein P.sub.mix is the
pressure in psi and CO.sub.2% is the percentage of carbon dioxide
on a mole basis in the acid gas. .Iaddend.
.Iadd.22. The method according to claim 18 wherein the pressure in
said injecting step is sufficient to prevent more than about 5% of
the mixture from flashing. .Iaddend.
.Iadd.23. The method according to claim 18 wherein the dense fluid
acid gas is formed by compressing and cooling an acid gas.
.Iaddend.
.Iadd.24. The method according to claim 23 wherein the acid gas is
compressed to pressure of at least about 650 psi. .Iaddend.
.Iadd.25. The method according to claim 24 wherein the compressed
acid gas is cooled to a temperature between its freezing point and
about 130.degree. F. .Iaddend.
.Iadd.26. A method of disposing of an acid gas comprising the steps
of: mixing an acid gas with water to form a stable mixture that is
substantially not a solution of absorbed acid gas in water;
injecting the mixture under pressure into a disposal well.
.Iaddend.
.Iadd.27. The method according to claim 26 wherein the acid gas is
a dense fluid. .Iaddend.
.Iadd.28. The method according to claim 27 wherein the pressure in
said injecting step is at least about
P.sub.mix=284+21.55.times.CO.sub.2% and wherein P.sub.mix is the
pressure in psi and CO.sub.2% is the percentage of carbon dioxide
on a mole basis in the acid gas. .Iaddend.
.Iadd.29. The method according to claim 27 wherein the pressure in
said injecting step is sufficient to prevent more than about 5% of
the mixture from flashing. .Iaddend.
.Iadd.30. The method according to claim 27 wherein water in an
amount less than about three times a ratio of
R.sub.H2O=0.25+0.10345.times.CO.sub.2%, wherein R.sub.H2O is the
volume of water to one volume of dense fluid acid gas and CO.sub.2%
is the percentage of CO.sub.2 on a mole basis in the acid gas, is
mixed with acid gas. .Iaddend.
.Iadd.31. A method of disposing of an acid gas comprising the steps
of: forming a dense fluid of an acid gas; mixing the dense fluid
acid gas with an amount of water to form a stable mixture of acid
gas and water; and injecting the mixture under pressure into a
disposal well. .Iaddend.
.Iadd.32. The method according to claim 31 wherein the pressure in
said injecting step is sufficient to prevent more than about 5% of
the mixture from flashing. .Iaddend.
.Iadd.33. The method according to claim 31 wherein water in a
volume amount of less than about eleven times the volume of acid
gas is mixed. .Iaddend.
.Iadd.34. The method according to claim 31 wherein water in a
volume amount of less than about thirty-three times the volume of
acid gas is mixed. .Iaddend.
.Iadd.35. The method according to claim 31 wherein water in an
amount sufficient to prevent the formation of hydrates in the
disposal well is mixed with acid gas. .Iaddend.
.Iadd.36. The method according to claim 35 wherein the formation of
hydrates is determined by an increase in injection pressure of
about 5-10 psi per hour. .Iaddend.
.Iadd.37. A method of disposing of a dense fluid acid gas
comprising the steps of: mixing the dense fluid acid gas with water
to form a stable mixture; and injecting the mixture under pressure
into a disposal well such that less than about 5% of the mixture
vaporizes during injection. .Iaddend.
.Iadd.38. The method of disposing of acid gas removed from
hydrocarbon products comprising the steps of: a. compressing the
acid gas to a pressure wherein the acid gas will form a dense
fluid, b. forming a dense fluid by cooling the compressed acid gas,
c. mixing the acid gas as a dense fluid with sufficient liquid
water to form a stable mixture at injection pressure, and d.
injecting said stable mixture at injection pressure into a disposal
well. .Iaddend.
Description
.Iadd.Notice: More than one reissue application has been filed for
the reissue of U.S. Pat. No. 6,149,344. The reissue applications
are application numbers 10/300,265 (the present application), and
10/937,789, all of which are divisional reissues of U.S. Pat. No.
6,149,344. .Iaddend.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to disposal of acid gases. Acid gas as used
herein is defined as a gaseous mixture of varying concentrations of
carbon dioxide (CO.sub.2) and hydrogen sulfide (H.sub.2S) resulting
from treating processes employed to remove these contaminants from
sour hydrocarbon streams such as produced natural gas. These
mixtures often are water saturated and contain small amounts of
hydrocarbons, treating solvents, absorbants, and other matter.
(2) Description of the Related Art
Before this invention, BEARD in U.S. Pat. No. 5,340,382 disclosed
the process of absorbing acid gas at about 400 psi into produced
water by a static mixing unit and then pumping the solution into a
disposal well. The BEARD process uses about 160 barrels water for
about 1,000 cu. ft. of acid gas. If the acid gas were liquified,
this would be a ratio (by volume) of approximately 424 H.sub.2O:1
dense fluid acid gas.
In Canada (where the acid gases have high hydrogen sulfide content)
acid gas is dehydrated, compressed, and injected into disposal
wells. Reports of such are found in the Oil & Gas Journal of
Apr. 18, 1997 by Edward Wichert and Tom Royan; the 1996 paper given
by H. L. Longworth, G. C. Dunn and M. Semchuck at the gas and
technology conference held in Calgary, Alberta from the 28th of
April until May 1, 1996; the paper of Wichert and Royan given at
the same meeting in 1996.
Sulfur recovery plants are another method of dealing with acid gas.
This process utilizes catalyst beds to convert over 99% of the
H.sub.2S to elemental sulfur. The process off gas is incinerated
resulting in release of associated carbon and sulfur dioxides as
emissions to the atmosphere.
SUMMARY OF THE INVENTION
This invention disposes of the acid gases by forming the acid gas
into a dense aqueous fluid by compression followed by cooling. Then
the dense fluid is mixed at high pressure (circa 650 to 2,000 psi)
with water.
Occasionally herein the forming of the acid gas into a dense fluid
will be referred to as liquefying, and the acid gas as a dense
fluid may be referred to as liquid gas or aqueous gas. The term
"liquified" or "aqueous" is used in this application to include
dense compressed gases which might not technically be a liquid.
Also, the alkaline water may be referred to as brackish water or
salt water disposal (SWD) water. Although alkaline water is
preferred, water with pH below 7.0 may be used as necessary.
A pressure regulated valve controls the pressure of the liquified
gas and the water to a suitable pressure until they are mixed.
Thereafter the pressure regulated valve releases the mixture into a
disposal well.
OBJECTS OF THIS INVENTION
An object of this invention is to dispose of acid gas.
Another object of this invention is to dispose of the acid gas
along with the disposing of unwanted alkaline water and other
undesirable liquids.
Further objects are to achieve the above with equipment that is
sturdy, compact, durable, simple, safe, efficient, versatile,
ecologically compatible, energy conserving, and reliable, yet
inexpensive and easy to manufacture, install, operate, and
maintain.
Other objects are to achieve the above with a method that is rapid,
versatile, ecologically compatible, energy conserving, efficient,
and inexpensive, and does not require highly skilled people to
install, operate, and maintain.
The specific nature of the invention, as well as other objects,
uses, and advantages thereof, will clearly appear from the
following description and from the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawing is a flow diagram of the process involved.
CATALOGUE OF ELEMENTS
As an aid to correlating the terms to the exemplary drawing(s), the
following catalog of elements is provided. 10 source of acid gas 12
source of water 14 compressor 16 cooler 18 pump 20 Tee connection
22 check valve 24 check valve 25 confluent line 26 pressure control
valve 28 disposal well 30 strata 32 injection tube 34 injection
pressure gage 36 confluent pressure gage
DESCRIPTION OF THE PREFERRED EMBODIMENT
According to this invention there will be a source 10 of acid gas
resulting from a source such as the treating system for a sour
natural gas stream. Usually a source of alkaline water 12 resulting
from the production of petroleum products is available. In the
event that there is insufficient alkaline water to be disposed of,
the source 12 alkaline water might be a well drilled to a strata
producing alkaline water. Although fresh water is operable, greater
alkalinity, found in brackish water, results in a more neutral
solution.
The acid gas from the source 10 is compressed by compressor 14.
After the gas is compressed it is cooled by cooler 16. Those
skilled in the art will understand that although the compressor 14
and cooler 16 are each shown as single elements, the compression
will normally be in stages with cooling after each stage. Also,
those skilled in the art are familiar with compressors, coolers,
etc. to compress acid gas to pressures necessary for operation,
i.e. approximately 650 to 2000 psi.
It is important not to produce bulk aqueous acid gas before the
final compression stage. Cooler 16 sufficiently cools the acid gas
until it condenses to a dense fluid.
The water is pumped by pump 18 to a high pressure.
The acid gas dense fluid and the high pressure water are combined
by Tee connection 20. Although the connection 20 is described as a
Tee, it will be understood that the connection of the two flows
could be in the form of a Y or a 45.degree. connection. Confluent
line 25 receives the mixture from Tee 20. Check valve 22 between
the acid gas cooler 16 and the Tee 20 prevents the flow of water
from the pump 18 into the cooler 16. Likewise check valve 24
prevents the flow of acid gas dense fluid toward the pump 18.
Confluent pressure gage 36 indicates the pressure in the confluent
line 25. There is no minimum length for the confluent line 25
except for physical structural limitations.
Pressure valve 26 controls the pressure in confluent line 25 at a
suitably high pressure to prevent vaporization of the acid gas
dense fluid. Normally according to the design of the particular
unit, the pressure control valve will control the pressure at the
Tee connection to a range of approximately 650-2000 psi. With a
high percentage (e.g. 83%) of H.sub.2S the pressure may be as low
as 650 psi and with a high percentage of CO.sub.2 (e.g. 75%) the
pressure may be as high as 1900 psi. The increase in minimum
pressure also will approximate a linear relationship to the
percentage of CO.sub.2.
The pressure control valve 26 discharges the mixture into an
injection tube 32 which extends into the disposal well 28. The
injection tube 32 normally has a well head assembly (not shown in
drawings) to control the flow. The well head assembly could include
both manual and automatic valves. The mixture of acid gas dense
fluid and water is injected into the disposal well into a suitable
strata 30 deep within the earth.
The size of the compressor will be determined by the amount of acid
gas requiring disposal. This amount will generally be known at the
time the equipment is assembled. The cooler likewise will be
sufficient to cool the compressed gases to a liquid or dense fluid
state. The minimum water requirement will depend upon the amount of
acid gas to be disposed and also the composition of the acid
gas.
Basically hydrogen sulfide is more soluble in water than carbon
dioxide. As one example, if the gas for disposal is about 83%
hydrogen sulfide and 17% carbon dioxide the disposal process will
require approximately two units of water for one unit of aqueous
acid gas. The percentages of hydrogen sulfide and carbon dioxide
are by mole percent. The unit of water and acid gas dense fluid is
by volume.
As another example, if aqueous acid gas has about 50% hydrogen
sulfide and about 50% carbon dioxide, a 5.1 ratio of water to dense
fluid is satisfactory.
As another example, if the aqueous mixture is about 25% hydrogen
sulfide and about 75% carbon dioxide an 8:1 water to dense fluid
ratio is required. Basically and approximately the minimum volume
of water for one volume of acid gas dense fluid will be a linear
relationship.
The minimum water and pressure for the normal range of operation
may be estimated as follows.
R.sub.H.sub.2.sub.O=0.25+0.10345.times.CO.sub.2%
P.sub.mix=284+21.55.times.CO.sub.2% Where R.sub.H.sub.2.sub.O is
the minimum ratio by volume of water having at least a pH of 7.5 to
the dense fluid acid gas. (i.e. R.sub.H.sub.2.sub.O:1AG where AG is
unit volume of acid gas). P.sub.mix is the minimum pressure in the
confluent line in psi. CO.sub.2% is the percent of CO.sub.2 in a
mixture of acid gas on a mole basis.
The above formulas are for temperatures in the range of 60.degree.
to 140.degree. F. in the confluent line 25.
The upper temperature limit of acid gas dense fluid at check valve
22 and the mix in the confluent line 25 is approximately
140.degree. F. The preferred temperature of the acid gas at the
check valve 22 is below 130.degree. F., and of the mix in the
confluent line 25 is below 110.degree. F.
The lower operation limit of temperatures is freezing of the fluid
involved.
The above ratios of water to acid gas dense fluid are approximately
the minimal amount of water required. If lesser water is used,
difficulties may be expressed. If there is an excess of alkaline
water to be disposed of in excess of the minimum requirements there
is no problem in mixing the additional water into the Tee 20. Those
with ordinary skill will know how to proportion the desired volume
of water to the volume of acid gas dense fluid. If other compatible
and suitable liquids require disposal, they too may be pumped into
the confluent line 25.
The pressures are also approximately the minimal pressures to form
a dense fluid at temperatures below 120.degree. F. at the check
valve 22. The maximum pressures are limited only by the higher cost
of higher pressures.
There must be sufficient water to form a stable mixture at the
injection pressure. By injection pressure it is meant that pressure
at the well head, which is at the top of the disposal well 28.
Injection pressure gage 34 in the injection tube 32 down stream
from the control valve 26 indicates the injection pressure.
If less than 5% of the mixture of alkaline water and aqueous acid
gas vaporizes at this point, normally satisfactory operation will
be maintained. If no greater amount of gas than 5% is formed within
the flow of the mixture, the gas will normally be in the form of
small bubbles. These bubbles will be carried by the flow of fluid
into the disposal well 28. As the mixture descends into the
disposal well 28 there will be a pressure increase which will force
the vapor back into a liquid or dense fluid phase.
If there is insufficient water to form a stable mixture such that
more than 5% gas vaporizes; a gas pocket will often form within the
injection tube 32 at about the top of the disposal well. This gas
pocket will cause an increase in pressure and the operation will
become unstable at that time.
The pressure in the injection tube at the pressure gage 34 will be
responsive to different events. Obviously the pressure gage 34 will
increase with an increased volume of liquids being pumped. For
example, if pump 18 were to pump twice as much water, the hydraulic
flow in the injection tube would result in a higher pressure at
pressure gage 34. Also, as the disposal well is operated, different
solids, for example, chemical precipitates or the like will begin
to collect in the strata 30 which will reduce its porosity
surrounding the disposal well 28. This build-up is to be expected
and will result in a slow increase in injection pressure. Such an
increase in pressure might normally be no more than 1 psi per
day.
Also, under certain condition hydrates will form and adhere to the
well surfaces, particularly the inside bore of the injection tube
32. If hydrates form they would be an indication that there was
insufficient water being mixed with the aqueous acid gas. This
would result in a pressure increase in the range of 5 or 10 pounds
per square inch per hour until no flow could be achieved.
The preferred operation includes that manual process calculations
or a computer process simulation be conducted with a complete
analysis of the acid gas and water to be used. When this simulation
is completed, the appropriate process pressures and temperatures
can be determined for optimum performance. Such computer
simulations can be made with HYSYS software available from
Hyprotech, Inc., located in Houston, Tex. for example.
With these different operating criteria the operator can adjust the
ratio of water to acid gas dense fluid to obtain stable and
satisfactory operating conditions. Normally the unstable conditions
will result from an insufficient amount of water for the amount of
aqueous acid gas being injected.
From the above it may be seen that it is desirable to always have
water flowing into the disposal well even if there is no acid gas
being liquified and disposed of at the time.
It is desirable that the confluent line 25 be of a material which
resists corrosion from the acid gas and alkaline water mixture. The
suitable grades of stainless steel for this purpose are well known
in the art and in certain cases it is necessary to solution treat
and/or coat the stainless steel before it is put into service.
Those skilled in the art will know of the materials of construction
for the confluent line.
The embodiment shown and described above is only exemplary. I do
not claim to have invented all the parts, elements or steps
described. Various modifications can be made in the construction,
material, arrangement, and operation, and still be within the scope
of my invention.
The restrictive description and drawings of the specific examples
above do not point out what an infringement of this patent would
be, but are to enable one skilled in the art to make and use the
invention. The limits of the invention and the bounds of the patent
protection are measured by and defined in the following claims.
* * * * *