U.S. patent application number 14/805776 was filed with the patent office on 2016-01-28 for methods for recovering natural gas using nitrogen rejection units.
The applicant listed for this patent is Martin Kibili, Joseph Naumovitz. Invention is credited to Martin Kibili, Joseph Naumovitz.
Application Number | 20160024900 14/805776 |
Document ID | / |
Family ID | 55166333 |
Filed Date | 2016-01-28 |
United States Patent
Application |
20160024900 |
Kind Code |
A1 |
Naumovitz; Joseph ; et
al. |
January 28, 2016 |
METHODS FOR RECOVERING NATURAL GAS USING NITROGEN REJECTION
UNITS
Abstract
A method and system for enhanced oil recovery by performing the
steps of feeding a mixture of nitrogen from a primary nitrogen
supply and an optional supplemental nitrogen supply into an oil
field; separating recovered oil from a gas mixture comprising
nitrogen, natural gas and C2+ hydrocarbons; feeding the gas mixture
to a nitrogen rejection unit operating at elevated pressures; and
recovering the nitrogen, natural gas and C2+ hydrocarbons. A method
for the recovery of natural gas is also described herein.
Inventors: |
Naumovitz; Joseph; (Lebanon,
NJ) ; Kibili; Martin; (Kleinaitingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Naumovitz; Joseph
Kibili; Martin |
Lebanon
Kleinaitingen |
NJ |
US
DE |
|
|
Family ID: |
55166333 |
Appl. No.: |
14/805776 |
Filed: |
July 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62028091 |
Jul 23, 2014 |
|
|
|
Current U.S.
Class: |
166/265 ;
62/640 |
Current CPC
Class: |
E21B 43/168 20130101;
F25J 3/0209 20130101; F25J 3/0233 20130101; F25J 2260/42 20130101;
F25J 3/0257 20130101; F25J 2215/62 20130101; F25J 3/0238 20130101;
F25J 2270/02 20130101; F25J 2270/88 20130101; F25J 2200/04
20130101 |
International
Class: |
E21B 43/16 20060101
E21B043/16; F25J 1/00 20060101 F25J001/00; E21B 43/34 20060101
E21B043/34 |
Claims
1. A method for enhanced oil recovery comprising the steps of (a)
feeding nitrogen from a primary nitrogen supply into an oil field;
(b) recovering oil and a gas mixture comprising nitrogen, natural
gas and C2+ hydrocarbons from the oil field; (c) separating the oil
from the gas mixture (d) feeding the gas mixture to a nitrogen
rejection unit; and (d) recovering nitrogen, natural gas and C2+
hydrocarbons.
2. The method as claimed in claim 1 further comprising feeding a
supplemental nitrogen supply into the oil field.
3. The method as claimed in claim 1 wherein the primary nitrogen
supply is from an air separation unit.
4. The method as claimed in claim 2 wherein the supplemental
nitrogen supply is from a supplemental air separation unit.
5. The method as claimed in claim 1 wherein the primary nitrogen
supply is fed to a high pressure compressor.
6. The method as claimed in claim 1 wherein the high pressure
compressor operates at a pressure up to 6700 pounds per square
inch.
7. The method as claimed in claim 1 wherein the oil and the gas
mixture are fed to an oil separation and sour gas removal unit,
thereby separating the recovered oil from the gas mixture.
8. The method as claimed in claim 1 wherein the recovered oil is
fed to a storage system.
9. The method as claimed in claim 1 wherein the nitrogen rejection
unit will separate the nitrogen from the natural gas and C2+
hydrocarbons.
10. The method as claimed in claim 1 wherein the nitrogen rejection
unit is operating at high pressures.
11. The method as claimed in claim 10 wherein the high pressure is
30 bar.
12. The method as claimed in claim 1 wherein the recovered nitrogen
is fed to an intermediate pressure compressor before being fed to
the high pressure compressor.
13. The method as claimed in claim 1 wherein a mixture of nitrogen
and methane is recovered from said nitrogen rejection unit and is
fed to the high pressure compressor.
14. The method as claimed in claim 9 further comprising feeding the
C2+ hydrocarbons along with the nitrogen and methane to the high
pressure compressor.
15. The method as claimed in claim 1 wherein the recovered C2+
hydrocarbons are fed to a recycle or fractioning unit.
16. A method for the recovery of natural gas from an enhanced oil
recovery operation comprising the steps of (a) feeding a primary
nitrogen supply into an oil field; (b) recovering oil and a gas
mixture comprising nitrogen, natural gas and C2+ hydrocarbons from
the oil field; (c) separating the oil from the gas mixture; (d)
feeding the gas mixture to a nitrogen rejection unit operating at
elevated pressures: and (e) separating natural gas from nitrogen
and C2+ hydrocarbons.
17. The method as claimed in claim 16 further comprising feeding a
supplemental nitrogen supply into the oil field.
18. The method as claimed in claim 16 wherein the primary nitrogen
supply is from an air separation unit.
19. The method as claimed in claim 17 wherein the supplemental
nitrogen supply is from a supplemental air separation unit.
20. The method as claimed in claim 16 wherein the primary nitrogen
supply is fed to a high pressure compressor.
21. The method as claimed in claim 16 wherein the high pressure
compressor operates at a pressure up to 6700 pounds per square
inch.
22. The method as claimed in claim 16 wherein the oil and the gas
mixture are fed to an oil separation and sour gas removal unit,
thereby separating the recovered oil from the gas mixture.
23. The method as claimed in claim 16 wherein the recovered oil is
fed to a storage system.
24. The method as claimed in claim 16 wherein the nitrogen
rejection unit will separate the natural gas from the nitrogen and
C2+ hydrocarbons.
25. The method as claimed in claim 16 wherein the nitrogen
rejection unit is operating at elevated pressures.
26. The method as claimed in claim 25 wherein the high pressure is
30 bar.
27. The method as claimed in claim 16 wherein the recovered
nitrogen is fed to an intermediate pressure compressor before being
fed to the high pressure compressor.
28. The method as claimed in claim 16 wherein the natural gas is
recovered from said nitrogen rejection unit and is fed to the high
pressure compressor.
29. The method as claimed in claim 16 wherein the recovered C2+
hydrocarbons are fed to a recycle or fractioning unit.
30. A system for enhanced oil recovery comprising a source of
nitrogen, a supplemental source of nitrogen, and a nitrogen
rejection unit.
31. The system as claimed in claim 30 wherein the source of
nitrogen is a primary air separation unit.
32. The system as claimed in claim 30 wherein the supplemental
source of nitrogen is a supplemental air separation unit.
33. The system as claimed in claim 30 wherein the nitrogen
rejection unit operates at high pressure.
34. The system as claimed in claim 30 wherein the high pressure is
30 bar.
35. The system as claimed in claim 30 wherein the nitrogen
rejection unit separates a gas mixture or nitrogen, natural gas and
C2+ hydrocarbons.
36. The system as claimed in claim 30 further comprising an
intermediate pressure compressor.
37. The system as claimed in claim 30 further comprising a high
pressure compressor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority from U.S.
provisional application Ser. No. 62/028,091, filed on Jul. 23,
2014.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the use of high pressure
nitrogen rejection units along with supplemental air separation
units in enhanced oil recovery operations to improve
performance.
[0003] Nitrogen injection in mature oil fields maintains the field
pressure and assists in increasing oil production. The nitrogen
content of an oil field will increase depending upon its age and
maturity. Nitrogen rejection units (NRUs) are used to separate
nitrogen from natural gas thereby resulting in a saleable natural
gas, The nitrogen that is separated is either vented or
recompressed and fed back into the oil field for use in enhanced
oil recovery operations.
[0004] Conventional NRUs are designed for nitrogen contents of
approximately 20% in the feed gas (see for example, Arthur J.
Kidnay, William R. Parrish, Fundamentals of Natural Gas Processing,
2006). Those NRUs operate at low pressures to provide saleable
natural gas at economic operating conditions. The produced natural
gas and the nitrogen will require significant compression power
downstream of the NRU to feed the natural gas into a pipeline and
the nitrogen back for enhanced oil recovery (FOR) operations,
respectively. Some of the produced natural gas is also used to
provide the required compression power.
[0005] However, mature oil fields may reach a nitrogen
concentration that is greater than 80% nitrogen. This high nitrogen
concentration makes the operation of the originally installed NRUs
uneconomical or almost impossible to produce saleable natural gas.
Oil plant owners may face the choice that it is more economic to
bypass the IRU and recompress the nitrogen rich gas which still
contains up to 20% hydrocarbons for EOR. In this instance the oil
plant is not producing any more natural gas. To provide the
required compression power for the EOR operations, the oil plant
owner would need to actually buy natural gas to drive the
compressors which increases their operation expenses
significantly.
[0006] The present invention overcomes these difficulties by using
a primary source of nitrogen and a supplemental source of nitrogen
to assist in recovering oil and a gas mixture from the oil field.
While the oil is recovered, a nitrogen rejection unit is then used
to separate the gas mixture into component portions which can be
utilized for example as a fuel source for the compressors used in
the nitrogen feeding operation.
SUMMARY OF THE INVENTION
[0007] In a first embodiment of the invention, there is disclosed a
method for enhanced oil recovery comprising the steps of (a)
feeding nitrogen from a primary nitrogen supply into an oil field;
(b) recovering oil and a gas mixture comprising nitrogen, natural
gas and C2+ hydrocarbons from the oil field; separating the oil
from the gas mixture (d) feeding the gas mixture to a nitrogen
rejection unit; and (a) recovering nitrogen, natural gas and C2+
hydrocarbons.
[0008] The method may further comprise feeding a supplemental
nitrogen supply into the oil field.
[0009] The primary nitrogen supply is from an air separation unit
and the supplemental nitrogen supply is from a supplemental air
separation unit. The primary nitrogen supply is fed to a high
pressure compressor which preferably operates at a pressure up to
6700 pounds per square inch,
[0010] The oil and the gas mixture are fed to an oil separation and
sour gas removal unit, thereby separating the recovered oil from
the gas mixture.
[0011] The recovered oil may be addressed in a manner of way but is
typically fed to a storage facility.
[0012] The nitrogen rejection unit will separate the nitrogen from
the natural gas and C2+ hydrocarbons. The nitrogen rejection unit
will typically operate at elevated pressures of about 30 bar.
[0013] The recovered nitrogen is fed to an intermediate pressure
compressor before being fed to the high pressure compressor.
[0014] A mixture of nitrogen and methane is recovered from said
nitrogen rejection unit and is fed to the high pressure
compressor.
[0015] Alternatively, the C2+ hydrocarbons may be fed along with
the nitrogen and methane to the high pressure compressor.
[0016] The recovered C2+ hydrocarbons may be fed to a recycle or
fractioning unit.
[0017] In a second embodiment of the invention, there is disclosed
a method for the recovery of natural gas from an enhanced oil
recovery operation comprising the steps of (a) feeding a primary
nitrogen supply into an oil field; (b) recovering oil and a gas
mixture comprising nitrogen, natural gas and C2+ hydrocarbons from
the oil field; (c) separating the oil from the gas mixture; (d)
feeding the gas mixture to a nitrogen rejection unit operating at
elevated pressures; and (e) separating natural gas from nitrogen
and C2+ hydrocarbons.
[0018] In a third embodiment of the there invention, there is
disclosed a system for enhanced oil recovery comprising a source of
nitrogen, a supplemental source of nitrogen, and a nitrogen
rejection unit.
[0019] The source of nitrogen is a primary air separation unit. The
supplemental source of nitrogen is a supplemental air separation
unit.
[0020] The nitrogen rejection unit operates at high pressure of 30
bar.
[0021] The nitrogen rejection unit separates a gas mixture or
nitrogen, natural gas and C2+ hydrocarbons.
[0022] The system further comprises an intermediate pressure
compressor.
[0023] The system further comprises a high pressure compressor.
[0024] About 50% of the hydrocarbon rich stream recovered can be
used for mixing with the existing fuel gas stream. This
modification of the fuel gas stream enables adjustment of its
energy content and the specific heating value to the specific
compressor requirements for both intermediate and high pressure
compressors. The remainder of the hydrocarbon rich stream is
valuable due to its energy content and relatively high
concentration of C2+ components and may be further purified to
produce a saleable product.
[0025] The advantages achieved by the present invention include a
reduction in overall operating expenses by reducing the amount of
natural gas purchased as well as maintaining the recycle stream
nitrogen pressure. Due to the separation of the nitrogen and
hydrocarbons in the nitrogen rejection unit, the content and flow
of recompressed hydrocarbons for enhanced oil recovery is
significantly reduced. There is also less compression power
required to recompress the nitrogen stream from the nitrogen
rejection unit outlet pressure of approximately 30 bar to the
enhanced oil recovery pressures of approximately 6800 psi compared
to conventional low pressure nitrogen rejection units.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic of the method for nitrogen rejection
according to the invention.
[0027] FIG. 2 is a schematic of a nitrogen rejection unit according
to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] FIG. 1 is a schematic of an enhanced oil recovery operation.
An air separation unit (ASU) of 32 million standard cubic feed per
day (MMSCFD) A provides nitrogen through line 1 to line 4. This
nitrogen is fed through line 4 to a high pressure compressor B
which is capable of compressing the nitrogen to 6700 pounds per
square inch (PSI).
[0029] This high pressure nitrogen stream is fed through line 6 to
the oil field E. A supplemental ASU D operating at 17.8 MMSCFD also
produces nitrogen and fees this supplemental nitrogen into line 6
through line 5. The combined nitrogen streams are at 96% nitrogen
purity and 103 MMSCFD when fed into the oil field E.
[0030] The enhanced oil recovery operations are undertaken at the
oil field formation E and the output from the enhanced oil recovery
operation is an oil and gas mixture which is fed through line 8 to
an oil separation process, sour gas removal and chiller and
deethanizer F. The gas that is recovered from this operation is
primarily a mixture of nitrogen, natural gas and C2+ which is fed
through line 9 to a nitrogen rejection unit (NRU) G operating at
elevated pressures of approximately 30 bar. The nitrogen rejection
unit will produce a 96% purity nitrogen feed at quantities of 53
MMSCFD and feed this through line 10 to an intermediate pressure
compressor unit C.
[0031] The intermediate pressure compressor C receives the original
feed from the existing ASU A through line 3 and an additional feed
from the NRU G through line 10. The intermediate pressure
compressor C will combine these two feed and will pressurize the
nitrogen to 2250 psi. This pressurized combination can be fed
through line 4 to the high pressure compressor B for ultimate entry
into the oil field E.
[0032] The nitrogen rejection unit G operating at elevated
pressures will further produce a stream of natural gas and nitrogen
which is recovered through line 12 at a feed rate of 4.5 MMSCFD as
well as a stream of greater than 85% purity C2+ hydrocarbons at a
feed rate of 4.8 MMSCFD which is recovered through line 11.
[0033] This C2+ hydrocarbon stream is fed through line 11 to line
13 where it will be fed into a C2+ recycle or fractioning unit H.
Alternatively, the C2+ hydrocarbons that are recovered can be fed
through line 14 to the high pressure compressor B. This stream will
be joined by the mixture of natural gas and nitrogen recovered
through line 12 which can also be fed to line 14. The resulting
mixture as fed through line 2 can be used to provide fuel to the
high pressure compressor B and limit the amount of natural gas that
must be purchased for use in feeding the high pressure compressor
B.
[0034] FIG. 2 is a schematic of a plant featuring a nitrogen
rejection unit. Feed stock from a gas plant is fed through line 23
and open valve V1 through the main heat exchanger J and into a
flash separator L. The flash separator will separate out the C2+
hydrocarbons from the feed stock and will return the C2+
hydrocarbons with the assistance of pump O back through the main
heat exchanger J where they are recovered through line 21. The
remainder of the feed stock which consists mainly of methane and
nitrogen is fed from the top of the flash separator through line 24
to the pressurized nitrogen rejection column M which will act to
separate the nitrogen from the natural gas and other components of
the gas plant feed stock.
[0035] The nitrogen from the separation process in the pressurized
nitrogen rejection column is collected from the top of this column
through line 22 and recovered after passing through the main heat
exchanger J.
[0036] Gas for combustion purposes is supplied through line 20 and
also passes through the main heat exchanger J and with the
assistance of pump N is fed to the pressurized nitrogen rejection
column.
[0037] A hydrocarbon heat pump compressor K will act to drive the
reboiler R and condenser P and will pass a cooler hydrocarbon
mixture which is mainly methane from the compressor K through line
26 where it will pass through the main heat exchanger J and pass
cooling to the main heat exchanger J. The slightly warmer
hydrocarbon mixture will continue through line 26 where it will
provide some refrigeration to the reboiler R.
[0038] The bottoms from the pressurized nitrogen rejection column
M, namely a mixture of natural gas and other hydrocarbons is fed
through line 31 to the reboiler R. These hydrocarbons are fed to a
subcooler Q through line 27 and then through open valve V2 and line
28 to a condenser P. The condensed hydrocarbons are returned
through line 32 to the pressurized nitrogen rejection column where
they will provide cooler temperatures to the column internals.
[0039] The warmer hydrocarbons that have been fed to the reboiler R
will exit the reboiler through line 30 and pass through the main
heat exchanger J where they will exchange heat and be fed through
line 30 back to the hydrocarbon heat pump compressor K to provide
some cooling to the compressor before being fed back through the
main heat exchanger J through line 26 and cycled again through the
reboiler R.
[0040] While this invention has been described with respect to
particular embodiments thereof, it is apparent that numerous other
forms and modifications of the invention will be obvious to those
skilled in the art. The appended claims in this invention generally
should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the
invention,
* * * * *