U.S. patent application number 09/886176 was filed with the patent office on 2002-12-26 for sub-sea membrane separation system with temperature control.
Invention is credited to Hampton, John R., Underdown, David R..
Application Number | 20020195251 09/886176 |
Document ID | / |
Family ID | 25388537 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020195251 |
Kind Code |
A1 |
Underdown, David R. ; et
al. |
December 26, 2002 |
SUB-SEA MEMBRANE SEPARATION SYSTEM WITH TEMPERATURE CONTROL
Abstract
A system and method for recovery of hydrocarbon gas and liquids
from a sub-sea environment utilizing a sub-sea membrane separation
system. The system includes a production string located in a
sub-sea wellbore for removing hydrocarbons and contaminants from a
sub-sea formation. At least one membrane separator for separating
contaminants from hydrocarbons removed from the sub-sea formation
is located underwater between the production string and a
hydrocarbon collection tank such that a predetermined temperature
of the hydrocarbons is obtained by the location of the membrane. In
another embodiment, a tube is connected to a sub-sea production
string for removing hydrocarbons and contaminants from a sub-sea
wellbore. At least one membrane separator for separating
contaminants from hydrocarbons in the tube is positioned between
the production string and a hydrocarbon collection tank wherein the
temperature of the hydrocarbons and contaminants is controlled by
the location of the membrane.
Inventors: |
Underdown, David R.;
(Conroe, TX) ; Hampton, John R.; (Houston,
TX) |
Correspondence
Address: |
CHEVRON TEXACO CORPORATION
2613 CAMINO RAMON
LAW DEPARTMENT- INTELLECTUAL PROPERTY UNIT
SAN RAMON
CA
94583
US
|
Family ID: |
25388537 |
Appl. No.: |
09/886176 |
Filed: |
June 20, 2001 |
Current U.S.
Class: |
166/367 ;
166/267 |
Current CPC
Class: |
B01D 63/06 20130101;
E21B 43/017 20130101; B01D 61/10 20130101; B01D 53/22 20130101;
E21B 43/01 20130101; B01D 61/00 20130101; E21B 43/36 20130101; B01D
61/12 20130101; B01D 61/20 20130101; B01D 61/22 20130101 |
Class at
Publication: |
166/367 ;
166/267 |
International
Class: |
E21B 043/34 |
Claims
1. An underwater membrane separation system with temperature
control, the system comprising: a production string located in a
sub-sea wellbore for removing hydrocarbons and contaminants from a
sub-sea formation; and at least one membrane separator for
separating contaminants from hydrocarbons removed from the sub-sea
formation, the membrane separator located underwater between the
production string and a hydrocarbon collection tank, wherein the
temperature of the hydrocarbons and contaminants is controlled to a
predetermined temperature by the location of the membrane.
2. The system of claim 1, wherein the membrane separator is in a
tube.
3. The system of claim 2, wherein the tube is insulated.
4. The system of claim 1, wherein the membrane separator is located
on a sea floor.
5. The system of claim 1, wherein the hydrocarbons and contaminants
pass through a heat-exchange element before entering the membrane
separator.
6. The system of claim 1, wherein the hydrocarbons and contaminants
pass through a liquid/gas separator before entering the membrane
separator.
7. The system of claim 1, wherein the hydrocarbons and contaminants
pass through a cyclone separator before entering the membrane
separator.
8. The system of claim 6, wherein the temperature of the
hydrocarbons and contaminants is lowered to separate at least one
liquid from a gaseous mixture.
9. The system of claim 8, wherein the temperature of the gaseous
mixture is changed following separation of the liquid from the
gas.
10. The system of claim 1, wherein a plurality of membrane
separators are positioned between the production string and the
hydrocarbon collection tank.
11. The system of claim 1, wherein the membrane separator is
located so that the temperature of the hydrocarbons and
contaminants is between about 25.degree. C. and about 100.degree.
C. when entering the membrane separator.
12. The system of claim 2, wherein at least two tubes are connected
to the wellhead for delivering the produced hydrocarbons and
contaminants to the hydrocarbon collection tank.
13. The system of claim 12, wherein a flow of produced hydrocarbons
and contaminants exiting the membrane separator is diverted to one
of the tubes while the membrane separator in another of the tubes
is being serviced.
14. The system of claim 1, further comprising an intelligent
automated system which monitors the flow of hydrocarbons and
contaminants.
15. The system of claim 14, wherein the intelligent automated
system monitors the temperature of the hydrocarbons and
contaminants.
16. The system of claim 14, wherein the intelligent automated
system monitors the pressure of the hydrocarbons and
contaminants.
17. The system of claim 14, wherein the intelligent automated
system controls the opening and closing of a valve.
18. The system of claim 1, wherein at least one contaminant is
removed from the hydrocarbons by the membrane separator and
injected into a disposal formation.
19. The system of claim 1, wherein at least one production string
is connected to a central gathering station, which is connected to
the hydrocarbon collection tank by at least one tube.
20. The system of claim 19, wherein at least two tubes are
connected to the cental gathering station for delivering the
produced hydrocarbons and contaminants to the hydrocarbon
collection tank.
21. The system of claim 20, wherein a flow of produced hydrocarbons
and contaminants exiting the membrane separator is diverted to one
of the tubes while the membrane separator in another of the tubes
is being serviced.
22. An underwater membrane separation method with temperature
control, the method comprising: connecting a tube to a sub-sea
production string for removing hydrocarbons and contaminants from a
sub-sea wellbore; and positioning at least one membrane separator
for separating contaminants from hydrocarbons in the tube between
the production string and a hydrocarbon collection tank wherein the
temperature of the hydrocarbons and contaminants is controlled by
the location of the membrane.
23. The method of claim 22, further comprising the step of
positioning the membrane separator in the tube before the tube is
connected to the sub-sea production string.
24. The method of claim 22, further comprising the step of
positioning the membrane separator in the tube after the tube is
connected to the sub-sea production string.
25. The method of claim 22, further comprising the step of
connecting the production string to a well head on the sea
floor.
26. The method of claim 22, wherein the tube is insulated.
27. The method of claim 22, wherein the membrane separator is
located on the sea floor.
28. The method of claim 22, further comprising the step of passing
the hydrocarbons and contaminants through a heat-exchange element
before entering the membrane separator.
29. The method of claim 22, further comprising the step of passing
the hydrocarbons and contaminants through a liquid/gas separator
before entering the membrane separator.
30. The method of claim 22, further comprising the step of passing
the hydrocarbons and contaminants through a cyclone separator
before entering the membrane separator.
31. The method of claim 22, further comprising the step of
positioning a plurality of membrane separators are positioned
between the sub-sea production string and the hydrocarbon
collection tank.
32. The method of claim 22, wherein the membrane separator so that
the temperature of the hydrocarbons and contaminants is between
about 25 .degree. C. and about 100.degree. C. when entering the
membrane separator.
33. The method of claim 22, wherein at least two tubes are
connected to the sub-sea production string for delivering the
produced hydrocarbons and contaminants to the hydrocarbon
collection tank.
34. The method of claim 33, further comprising the step of
diverting a flow of produced hydrocarbons and contaminants exiting
the membrane separator to one of the tubes while the membrane
separator in another of the tubes is being serviced.
35. The method of claim 22, further comprising the step of
positioning an intelligent automated system in the tube to monitor
the flow of hydrocarbons and contaminants.
36. The method of claim 22, further comprising the step of removing
at least one contaminant from the hydrocarbons and contaminants by
the membrane separator and injecting into a disposal formation.
37. The method of claim 22, further comprising at least one well
head connected to the sub-sea wellbore, the at least one sub-sea
wellbore connected to a central gathering station.
38. The method of claim 37, wherein the central gathering station
is connected to the hydrocarbon collection tank by at least one
tube.
39. The method of claim 38, further comprising the step of
connecting at least two tubes to the central gathering station for
delivering the produced hydrocarbons and contaminants to the
hydrocarbon collection tank.
40. The method of claim 39, further comprising the step of
diverting a flow of produced hydrocarbons and contaminants exiting
the membrane separator to one of the tubes while the membrane
separator in another of the tubes is being serviced.
41. The method of claim 22, further comprising the step of lowering
the temperature of the hydrocarbons and contaminants to separate at
least one liquid from a gaseous mixture.
42. The method of claim 41, further comprising the step of changing
the temperature of the gaseous mixture is changed following
separation of the liquid from the gas.
43. A method of controlling a temperature of a production stream of
hydrocarbons and contaminants to prevent degradation of a
preferentially selective material, the method comprising the steps
of positioning the preferentially selective material underwater at
a location selected to achieve a predetermined temperature of the
hydrocarbons and contaminants contacting the preferentially
selective material.
Description
[0001] The present invention relates generally to recovery of
hydrocarbon gas and liquids from a sub-sea wellbore, and, more
particularly, the invention relates to technology for separation of
contaminants from hydrocarbon gases and liquids utilizing a sub-sea
membrane separation system with temperature control.
BACKGROUND OF THE INVENTION AND BRIEF DESCRIPTION OF THE RELATED
ART
[0002] Hydrocarbon gases and liquids are recovered from underground
wellbores by drilling a wellbore into a hydrocarbon gas or liquid
formation and withdrawing the materials under reservoir pressure or
by artificial lifting. The fluids withdrawn from the reservoir
consist of a combination of hydrocarbon liquids and gases, water,
sediments, and other contaminants. The water fraction is commonly
referred to as produced water. This fraction, although small at the
early stages of oil extraction from most fields, grows over the
years and could constitute the majority (up to about 90%) of the
fluid that is withdrawn from the reservoir.
[0003] The current recovery technology involves removing the
hydrocarbon and any contaminants including water and sediments
which are present from the wellbore, and separating the
contaminants from the hydrocarbon above ground or on the ocean
surface. This method of separation is costly. Disposal of the
removed contaminants may also present environmental problems. The
contaminants which may be produced include carbon dioxide,
nitrogen, water vapor, hydrogen sulfide, helium, other trace gases,
water, water soluble organics, normally occurring radioactive
material and others.
[0004] Membrane technologies have been developed which separate
materials by allowing the selective passage of specific materials
through the membrane. One example of a membrane separation system
for separating oil and water downhole is described in Price, U.S.
Pat. No. 4,296,810. It is desirable to place these membrane
materials downhole or on the sea floor to remove the contaminants
at the sea floor level and avoid the cost-intensive process of
lifting, separating, and disposing of the contaminants. However,
the location of these membrane materials downhole or on the sea
floor results in a number of potential difficulties including
exposure of the membranes to high temperatures and harsh
conditions, which are not suitable for many membrane materials.
[0005] A membrane's permeability and selectivity for hydrocarbon
gases and liquids are material properties of the membrane itself,
and thus these properties are ideally constant with feed pressure,
flow rate and other process conditions. However, permeability and
selectivity are both temperature-dependent. Accordingly, it is
desirable to be able to control the temperature of the hydrocarbons
and contaminants before the hydrocarbons and contaminants enter the
membrane separator.
[0006] It would be desirable to provide an underwater membrane
separation system in which the membrane separator is located
underwater, such that the temperature of the hydrocarbons and
contaminants is controlled to a predetermined temperature by the
location of the membrane.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a system for separating
contaminants from hydrocarbons removed from a sub-sea formation. In
order to prevent the degradation of the membrane material in the
separation system, due to temperature, the present invention
provides one or more membrane separators positioned between the
production string and the hydrocarbon collection tank in a sub-sea
environment wherein the temperature of the hydrocarbons and
contaminants is controlled to a predetermined temperature by the
location of the membrane.
[0008] According to one aspect of the present invention, an
underwater membrane separation system with temperature control
includes a production string located in a sub-sea wellbore for
removing hydrocarbons and contaminants from a sub-sea formation,
and at least one membrane separator for separating contaminants
from hydrocarbons removed from the sub-sea formation, the membrane
separator located underwater between the producing string and a
hydrocarbon collection tank, wherein the temperature of the
hydrocarbons and contaminants is controlled to a predetermined
temperature by the location of the membrane.
[0009] According to another aspect of the invention, an underwater
membrane separation method with temperature control includes
connecting a tube to a sub-sea production string for removing
hydrocarbons and contaminants from a sub-sea wellbore, and
positioning at least one membrane separator for separating
contaminants from hydrocarbons in a tube between the production
string and a hydrocarbon collection tank wherein the temperature of
the hydrocarbons and contaminants is controlled by the location of
the membrane.
[0010] According to a further aspect of the invention, a method of
controlling a temperature of a production stream of hydrocarbons
and contaminants to prevent degradation of a preferentially
selective material includes positioning the preferentially
selective material underwater at a location selected to achieve a
predetermined temperature of the hydrocarbons and contaminants
contacting the preferentially selective material.
[0011] The present invention provides a system and method for
separation of hydrocarbons and contaminants utilizing an underwater
membrane separator with temperature control where, by location of
the membrane separator, the temperature of the hydrocarbons and
contaminants is controlled to a predetermined range optimizing
performance of the membrane separator. The system and method also
provide reduced downtime and improved efficiency of the membrane
separation system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described in greater detail with
reference to the preferred embodiments illustrated in the
accompanying drawings, in which like elements bear like reference
numerals, and wherein:
[0013] FIG. 1 is a schematic side cross-sectional view of a sea
floor membrane separation system with temperature control for
separating hydrocarbons and contaminants according to the present
invention;
[0014] FIG. 2 is a perspective view of a membrane separator for
separating contaminants from hydrocarbons for use in the system of
FIG. 1;
[0015] FIG. 3 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing the membrane separator within a tube
according to the present invention;
[0016] FIG. 4 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing a tube insulated with an insulating
layer according to the present invention;
[0017] FIG. 5 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing a heat exchange element according to
the present invention;
[0018] FIG. 6 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing a heat exchange element and a
gas/liquid separator according to the present invention;
[0019] FIG. 7 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing a plurality of membrane separators
according to the present invention;
[0020] FIG. 8 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing an intelligent automated system in the
production string according to the present invention;
[0021] FIG. 9 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control showing a heat exchange element, a gas/liquid
separator, and an intelligent automated system according to the
present invention;
[0022] FIG. 10 is a schematic side cross-sectional view of another
embodiment of a sea floor membrane separation system with
temperature control with a reinjection system according to the
present invention;
[0023] FIG. 11 is a perspective view of another embodiment of a sea
floor membrane separation system with temperature control showing
at least two tubes connected to a wellhead according to the present
invention;
[0024] FIG. 12 is a perspective view of a sea floor membrane
separation with temperature control located on the sea floor with a
central gathering station according to the present invention;
and
[0025] FIG. 13 is a schematic diagram of an underwater membrane
separation method with temperature control according to the present
invention; and
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The method and system according to the present invention
provide for the separation of contaminants from hydrocarbon gases
and liquids in a sub-sea environment. Membrane separation systems
are used for separating contaminants from hydrocarbon gases and
liquids. Once the contaminants are removed from the hydrocarbon
stream, the contaminants may be disposed of by injection into an
underground disposal formation, removed to the surface for
disposal, or released into the ocean. The release of contaminants
into the ocean would only be performed when the release meets
applicable local and environmental standards.
[0027] Some of the contaminants which may be removed are gases
including carbon dioxide, nitrogen, water vapor, hydrogen sulfide,
helium, and other trace gases, and liquids including water, and
other liquids. In addition, heavy hydrocarbons may be separated
from hydrocarbon gases. The hydrocarbon from which the contaminants
are separated according to the present invention may be oil,
methane, ethane, propane, or others.
[0028] The present technology for membrane separation primarily
uses preferentially selective materials for the separation of
contaminates from the hydrocarbons. Preferentially selective
materials are defined as materials which are permeable to a first
fluid and substantially impermeable to a second fluid. Generally,
the preferentially selective materials are durable, resistant to
high temperatures, and resistant to exposure to liquids. The
materials may also be coated to help prevent fouling and improve
durability. Examples of suitable membrane materials for removal of
contaminants from a hydrocarbon gas stream include cellulose
acetate, polysulfones, polyimides, cellulose triacetate (CTA),
carbon molecular sieve membranes, ceramic and other inorganic
membranes, composites comprising any of the above membrane
materials with another polymer, composite polymer and molecular
sieve membranes including polymer zeolite composite membranes,
polytrimethylsilene (PTMSP), and rubbery polymers.
[0029] However, the preferred membrane materials are often subject
to degradation at temperatures greater than 100.degree. C. With the
recent advances in geophysical exploration methods, oil and gas
wells are being drilled deeper into the earth's crust. With the
deeper wells also come higher temperatures for the hydrocarbons
produced from the reservoirs. In an offshore gas well, the
temperature of the gaseous mixture of hydrocarbons and contaminants
can be in excess of 150.degree. C. as the mixture exits the
wellbore on the sea floor. Thus, the temperature of the hydrocarbon
and contaminant mixture needs to be cooled before the mixture
enters the membrane separator.
[0030] The selection of the membrane material for a gas and/or
liquid separator is made on the basis of the produced hydrocarbons
and contaminants. Once the hydrocarbon and contaminant mixture is
identified, the material for the membrane separator is selected.
The polymer membranes which are used today are selected based on
the heat resistance, solvent resistance, and the mechanical
strength of the porous separation membrane, as well as other
factors dictated by the operating conditions for selective
permeation. At the present time, most of the polymer membrane
separators have a preferred operating temperature of between about
25.degree. C. to about 100.degree. C. Accordingly, it is highly
desirable to control the temperature of the flow of hydrocarbons
and contaminants before the mixture enters the membrane
separator.
[0031] In addition, the permeability of gases through rubbery
membranes depends upon both the gas solubility in the membrane and
the diffusivity of the gas through the membrane. Diffusivity
increases while solubility decreases with temperature. In general,
these competing effects result in a net increase in permeability
with increasing temperature. The exception occurs at very low
temperatures where the increased solubility can dominate and the
permeability increases with decreasing temperature.
[0032] For two or more gases, the permeability of each gas will,
per rule, increase with temperature. The selectivity will change
with the ratio of the individual permeability. This effect can
result in increasing or decreasing selectivity with temperature,
and may even result in maximum, or minimum selectivity. As a rule,
however, selectivity will decrease with increasing temperature.
[0033] Furthermore, for glassy polymers, the mechanisms of
solubility and diffusion are somewhat different. However, the same
overall trends have been observed, with selectivity usually
decreasing and permeability increasing with temperature. The
examples listed reflect present membrane material technology. It
can be appreciated, however, other temperatures may be preferred in
the future depending on technological advances.
[0034] FIG. 1 illustrates an underwater membrane separation system
10 with temperature control for separation of hydrocarbons and
contaminants. The underwater membrane separation system 10 includes
a production string 12 located in a sub-sea wellbore 14 for
removing hydrocarbons and contaminants from a sub-sea formation 16.
The membrane separator 18 is located underwater 20 between the
production string 12 and a hydrocarbon collection tank 22. The
temperature of the hydrocarbons and contaminants is controlled to a
predetermined temperature by the location of the membrane separator
18.
[0035] FIG. 2 illustrates an example of a membrane element 30
formed of a preferentially selective material for permeating
contaminants. The membrane element 30 is a tubular element having a
central bore 32 through which the produced hydrocarbons and
contaminants pass in the direction indicated by the arrows A. The
contaminants permeate out through the preferentially selective
material as indicated by the arrows B, and the hydrocarbons
continue out of the top of the membrane element as indicated by the
arrows C. One or more membrane elements 30 may be stacked within a
perforated tube to form a membrane separator 18 or may be
interconnected to form a membrane separator 18 in the form of a
self-supporting tube. It can be appreciated, however, that other
types of configurations of the separation cartridge can be used. It
is common knowledge to those skilled in the art that hollow fibers,
spiral wound sheets and other materials are also effective in
effecting a reasonable or acceptable separation.
[0036] Each one of the stacked membrane elements 30 may be designed
to permeate one or more of the contaminants which are present in
the well. For example, one membrane element 30 may be designed for
removal of carbon dioxide, a second for removal of hydrogen
sulfide, and a third for removal of heavy hydrocarbons. The
membrane elements 30 or the membrane separators 18 may be stacked
in different arrangements to remove contaminants from the flow of
hydrocarbons in different orders. For example, the bottom membrane
elements may be those that remove water and heavy hydrocarbons
which may damage some of the gas removal membrane materials. The
top membrane elements may be those that remove carbon dioxide and
hydrogen sulfide.
[0037] As shown in FIG. 1, the mixture of hydrocarbon and
contaminants enters the sub-sea wellbore 14 from the sub-sea
formation 16 and flows through the production string 12 to a
wellhead 50 located on a sea floor 44. After exiting the production
string 12, the hydrocarbons and contaminants will enter a flow line
or tube 24 which is connected to a hydrocarbon collection tank 22.
The collection tank 22 will be preferably located at or near the
water surface. However, it can be appreciated that the collection
tank can be located on a tanker, platform or a piece of land. As
the mixture passes through an inner tube of the membrane separator
18, one or more components of the mixture permeate out of the inner
tubes through the selective membrane and enters a contaminant
collection zone. The membrane separator 18 is permeable to a first
fluid and substantially impermeable to a second fluid.
[0038] In the present invention, the mixture of hydrocarbons and
contaminants will enter the production string 12 from the sub-sea
wellbore 14 and flow into at least one tube 24 on the sea floor 44.
Typically, the water temperature on the sea floor 44 is between
0.degree. C. and 10.degree. C. As a result of the water
temperature, the mixture of hydrocarbons and contaminants will
experience a natural cooling process as the mixture flows through
the tube 24 to the membrane separator 18. The temperature change of
the hydrocarbons and contaminants is dependent on the location of
the membrane separator 18 and other factors, such as the size of
the tube 24, the heat-transfer properties of the tube 24, and the
composition of the produced hydrocarbons. In one of the
embodiments, the membrane separator 18 is located at a position
where the hydrocarbons and contaminants achieve a predetermined
temperature range.
[0039] As the mixture of hydrocarbon and contaminants pass through
the membrane separator 18, one or more contaminants permeate out of
the membrane separator through the preferentially selective
material and enter the contaminant collection zone. The
hydrocarbons plus any remaining contaminants which were not removed
continue out the top of the membrane separator 18. The hydrocarbons
with the reduced contaminants are passed to the surface or to
another membrane separation system. Once the contaminants are
removed from the hydrocarbon stream, the contaminants may be
disposed of by injection into an underground disposal formation,
removed to the surface for disposal, or released into the
ocean.
[0040] FIG. 3 illustrates a further embodiment of the invention in
which the membrane separator 18 is placed within a tube 24. The
tube 24 is connected to a production string 12 on the sea floor 44
and to a hydrocarbon collection tank 22. The tube 24 can be made of
any material that will convey the hydrocarbons and contaminants to
the hydrocarbon collection tank 22, including flexible tubing for
ease of replacing the membrane unit and handling of the sub-sea
conditions. The location of the membrane separator 18 between the
sea floor 44 and the hydrocarbon collection tank 22 results in the
mixture of hydrocarbons and contaminants, achieving a predetermined
temperature for separation of the hydrocarbons from the
contaminants.
[0041] The tubing 24 in one subordiment is a plurality of tubes
having a common center. In one of the tubes the hydrocarbons plus
any remaining contaminants are conveyed to the hydrocarbon
collection tank, and in a separate tube the contaminants are
conveyed to the surface. It can be appreciated, however, that the
tube 24 can be a single tube for only one hydrocarbon and
contaminants or a series of tubes.
[0042] In another embodiment, as shown in FIG. 4, the tube 24 is
insulated with an insulating layer 40. The insulating layer 40 can
be made of any number of materials with the length and type of the
insulation depending on the location of the membrane separator 18
and the sub-sea environment. There are several commercially
available insulation materials 30 for use in sub-sea transport of
hydrocarbons. These include non-jacketed and pipe-in-pipe
insulation. A non-jacketed insulation is coated directly on the
exterior of a pipe. Pipe-in-pipe configurations include an
insulation medium in the annulus between the inner pipe (carrier)
and the outer pipe (jacket). Conventional pipe-in-pipe technology
uses two steel pipes fabricated together to form an annulus that is
insulated by some means which may include polyurethane foam (PUF),
insulating micro-spheres, or a vacuum. The insulating layer 40 and
the location of the membrane separator 18 will achieve a
predetermined temperature for the hydrocarbons and
contaminants.
[0043] In another embodiment shown in FIG. 5, the hydrocarbon and
contaminates passes through a heat-exchange element 60 before
entering into the membrane separator 18. The heat-exchange element
60 may use water from the sea floor to cool the hydrocarbon and
contaminants to the predetermined temperature. In addition to a
heat-exchange element 60, a filter, a guard bed, a liquid/gas
separator, a cyclone separator or an inverse selection membrane may
be installed in the production string 12 and/or tube 24 before the
membrane separator 18. As in the previous embodiments, a
heat-exchange element 60 in combination with the natural cooling
effect of the sea water temperature will result in the cooling of
the mixture of hydrocarbons and contaminants to a desired
temperature as the mixture enters the membrane separator 18.
[0044] According to a further embodiment as shown in FIG. 6, the
hydrocarbons and contaminants enter the production string 12 and
flow into a heat-exchange element 60 located on the sea floor 44.
The mixture of hydrocarbons and contaminants are cooled in the
heat-exchange element 60 and then enter a gas/liquid separator 66.
The gas/liquid separator 66 may be any of the various known
separators, including a centrifugal or a hydrocyclone separator, a
multi-stage structure including both dynamic and static separating
elements, or a gas and liquid membrane separator wherein the
separator removes at least one contaminant from the hydrocarbon and
contaminant mixture. The remaining hydrocarbon and contaminants
then pass back through the heat-exchange element 60 once again
where the temperature of the hydrocarbon and contaminants is
changed to a predetermined temperature before the mixture flows
into the membrane separator 18, where at least one contaminant is
removed.
[0045] In another embodiment illustrated in FIG. 7, a plurality of
membrane separators are positioned between the production string 12
and the hydrocarbon collection tank 22. In one embodiment the
membrane separators are positioned in series. Alternatively, (not
shown) the membrane separators are positioned in parallel. The
location of the plurality of membrane separators 18 will remove at
least one desired contaminant in combination with achieving a
predetermined temperature for separation of the hydrocarbons from
the contaminants.
[0046] In addition, the membrane separators can remove only gases
and/or may be interspaced with liquid separation membranes for the
removal of liquids. Liquid separation membranes generally function
to remove a mixture of liquids and gases from a hydrocarbon stream
and are termed liquid separation membranes based on their primary
purpose of removing liquid based or condensed contaminants from a
hydrocarbon gas stream. The removal of liquids from a gaseous
mixture can greatly prolong the life of the gas separation
membranes. In addition, the overall efficiency of the well is
improved by reducing the amount of down time for replacement of
damaged membranes.
[0047] The membrane separator 18 is located so that the temperature
of the mixture of hydrocarbons and contaminants is between about
25.degree. C. and about 100.degree. C. when entering the membrane
separator 18. This temperature is achieved by placement of the
membrane separator 18 on the sea floor 44 at a location wherein an
optimum temperature of the hydrocarbons and contaminants is
achieved before the mixture enters the membrane separator. It can
also be appreciated, that in addition to the location of the
membrane separator, the optimum temperature can also be achieved
through use of a heat-exchange element 60, or a combination of
insulation 30, heat-exchange element 60, location of the membrane
separator 18, or other device which affects the temperature of the
hydrocarbons and contaminants before entering the membrane
separator.
[0048] In another embodiment, as shown in FIG. 8, an intelligent
automated system 80 is placed in the production string 12 or in the
tube 24 to monitor the flow of hydrocarbons and contaminants. The
intelligent automated system 80 monitors and controls the flow of
the hydrocarbons and contaminants before the mixture passes through
the membrane separator 18, or any of the pretreatment devices
including heat-exchange element 60, filter, guard bed, liquid/gas
separator, cyclone separator or inverse membrane. The intelligent
automated system has a sensor which monitors the pressure,
temperature and flow of the hydrocarbons and contaminants in the
wellbore or tube. If the intelligent automated system senses that
the temperature of the hydrocarbons and contaminants is too high,
the intelligent automated system 80 controls a valve to the
heat-exchanger element 60 to allow more water into the heat
exchanger to decrease the temperature of the hydrocarbons and
contaminants. It can be appreciated that the intelligent automated
system may control a series of valves or controls for adjusting the
pressure, temperature flow of the hydrocarbons and
contaminants.
[0049] In FIG. 9, an intelligent automated system 80 is shown with
a heat exchanger 60, liquid gas separator 66, and a membrane
separator 18. The intelligent automated system 80 monitors the
pressure and temperature of the hydrocarbons and contaminants.
Accordingly, the pressure of the hydrocarbons and contaminants can
be measured across a membrane separator or within the entire
system, and if conditions require, the temperature of the
hydrocarbons and contaminants can be increased or decreased through
the heat exchanger 60, liquid/gas separator 66 or other device.
[0050] In an alternative embodiment, as shown in FIG. 10, at least
one contaminant is removed from the hydrocarbons and contaminants
by the membrane separator 18 and reinjected into a disposal
formation 84 below the sea floor by pumping the contaminant through
a disposal flow line 86. The location of the membrane separator 18,
as in the previous embodiments, will result in the hydrocarbons and
contaminants entering the membrane separator 18 at a predetermined
temperature and enhancing the separation of the hydrocarbons from
the contaminants.
[0051] In another embodiment, as shown in FIG. 11, at least two
tubes 24 are connected to the well head 50 for delivering the
produced hydrocarbons and contaminants to the hydrocarbon
collection tank 22. In each of the tubes 24, at least one membrane
separator 18 is placed for removing at least one contaminant from
the flow of hydrocarbons and contaminants. The membrane separators
are fitted with a valve which diverts the flow of hydrocarbons and
contaminants to one of at least two tubes 24 while the membrane
separator 18 in another of the tubes 24 is serviced.
[0052] In a further embodiment as illustrated in FIG. 12, at least
one production string is connected to a central gathering station
100 located on the sea floor 44. The central gathering station 100
can be connected to a series of production strings 12 or well heads
50. The central gathering station 100 is connected to the
hydrocarbon collection tank 22 by at least one tube 24.
Alternatively, as shown in FIG. 12, at least two tubes 24 are
connected to the central gathering station 100 for delivering the
produced hydrocarbons and contaminants to the hydrocarbon
collection tank 22. The membrane separators 18 are also connected
to one another by a tube 92. The membrane separators 18 are also
fitted with a valve for diverting the flow of hydrocarbons and
contaminants to one of the tubes 24 while the membrane separator 18
in another of the tubes is serviced. Once again as shown in the
previous embodiments, the location of the membrane separator 18
achieves a predetermined temperature for optimizing the separation
of hydrocarbons and contaminants.
[0053] In FIG. 13, an underwater membrane separation method with
temperature control 200 is shown. The method includes the steps of
connecting a tube to a sub-sea production string for removing
hydrocarbons and contaminants from a sub-sea wellbore 210, and
positioning at least one membrane separator for separating
contaminants from hydrocarbons in the tube between the production
string and a hydrocarbon collection tank wherein the temperature of
the hydrocarbons and contaminants is controlled by the location of
the membrane 220.
[0054] In operation of the membrane separators 18, when the
membranes become fouled, an increase in the amount of contaminants
produced will be observed indicating that the membrane should be
replaced. In addition to replacement of membranes when they have
become fouled, it may be desirable to replace the membrane
separation system for alterations, modifications, or updates when
the production of the well changes or when new oil recovery methods
and technology become available.
[0055] The operation of the present invention has been illustrated
and described with respect to a sub-sea environment, however, it
should be understood that the invention may be employed in any body
of water including lakes, seas and oceans.
[0056] The number, type, and configuration of the membranes may
vary depending on a particular well. The separation system may be
specifically designed for each individual well or a production zone
based on the hydrocarbon and contaminants produced by the well or
reservoir. It should be understood that due to the nature of
membranes, the separation process is imperfect with some of the
hydrocarbon passing through the membranes with the contaminants and
some of the contaminants remaining in the production string.
However, the imperfect membrane separation system can be used to
greatly reduce the above ground or water separation required.
[0057] The present invention may be combined with existing down
hole technologies from mechanical physical separation systems, such
as cyclones or centrifugal separation systems. The invention may be
also used for partial removal of the contaminants to reduce the
burden on surface removal facilities with the remaining
contaminants removed by conventional surface technologies. Some
types of separated contaminants such as carbon dioxide can be
injected into the productive horizon to maintain pressurization of
the reservoir.
[0058] FIGS. 1-6 and 8-12, each illustrates a singular tubular
membrane for purposes of illustration. However, the membrane
separation systems and methods, may include multiple membranes
arranged in series or parallel.
[0059] The invention has been described in detail with a reference
to the preferred embodiments thereof, it will be apparent to one
skilled in the art that various changes and modifications can be
made and equivalence employed, without departing from the present
invention.
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