U.S. patent application number 09/923211 was filed with the patent office on 2003-02-06 for gas storage and production system.
Invention is credited to Cavender, Travis Wayne.
Application Number | 20030024700 09/923211 |
Document ID | / |
Family ID | 25448316 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030024700 |
Kind Code |
A1 |
Cavender, Travis Wayne |
February 6, 2003 |
Gas storage and production system
Abstract
A gas storage and production system decreases production of
formation sand and permits high gas flow rates in storing and
producing operations. In a described embodiment, different
flowpaths are used for injecting and withdrawing gas from a
subterranean formation. In another embodiment, a gravel pack is
confined to a set volume, so that it is not expanded when gas flows
at a relatively high rate therethrough.
Inventors: |
Cavender, Travis Wayne;
(Angleton, TX) |
Correspondence
Address: |
KONNEKER SMITH
660 NORTH CENTRAL EXPRESSWAY
SUITE 230
PLANO
TX
75074
|
Family ID: |
25448316 |
Appl. No.: |
09/923211 |
Filed: |
August 6, 2001 |
Current U.S.
Class: |
166/278 ;
405/53 |
Current CPC
Class: |
E21B 43/04 20130101;
E21B 43/30 20130101 |
Class at
Publication: |
166/278 ;
405/53 |
International
Class: |
E21B 043/04 |
Claims
What is claimed is:
1. A gas storage and production system, comprising: a gas storage
formation, wherein gas is stored within pores of formation rock; a
production wellbore extending into the formation for withdrawing
gas from the formation; a storage wellbore extending into the
formation for injecting gas into the formation; and the production
and storage wellbores intersecting at a wellbore junction.
2. The system according to claim 1, wherein gas is only withdrawn
through the production wellbore and gas is only injected through
the storage wellbore.
3. The system according to claim 1, further comprising: a main
wellbore extending from the wellbore junction to the earth's
surface; and a tubular string positioned in the main wellbore, gas
being delivered to the storage wellbore via the tubular string for
injection into the formation, and gas being delivered from the
production wellbore via an annulus formed between the tubular
string and the main wellbore for production to the earth's
surface.
4. The system according to claim 1, further comprising: a main
wellbore extending from the wellbore junction to the earth's
surface; and a tubular string positioned in the main wellbore, gas
being delivered to the storage wellbore via the tubular string for
injection into the formation, and gas being delivered from the
production wellbore via the tubular string for production to the
earth's surface.
5. The system according to claim 4, wherein the gas is alternately
delivered to the storage wellbore via the tubular string and
delivered from the production wellbore via the tubular string.
6. The system according to claim 4, further comprising at least one
valve connected to the tubular string, the valve providing
communication between the tubular string and each of the storage
and production wellbores.
7. The system according to claim 6, wherein the valve alternately
provides communication between the tubular string and each of the
storage and production wellbores.
8. The system according to claim 7, wherein the valve is remotely
controlled.
9. The system according to claim 7, wherein there are at least two
of the valves, the valves being operated in response to a direction
of gas flow in the tubular string.
10. The system according to claim 1, further comprising: a main
wellbore extending from the wellbore junction to the earth's
surface; and a tubular string positioned in the main wellbore, gas
being delivered to the storage wellbore via an annulus formed
between the tubular string and the main wellbore for injection into
the formation, and gas being delivered from the production wellbore
via the tubular string for production to the earth's surface.
11. The system according to claim 1, further comprising: a sand
control screen positioned in the production wellbore; a tubular
string connected to the sand control screen and extending toward
the wellbore junction; gravel positioned about the screen in an
annulus formed between the screen and the wellbore; and a retainer
material positioned in the annulus between the gravel and the
wellbore junction, the retainer material preventing displacement of
the gravel.
12. The system according to claim 11, wherein the retainer material
is a cementitious material.
13. The system according to claim 11, wherein the retainer material
is flowed into the annulus via at least one ported collar
interconnected in the tubular string between the screen and the
wellbore junction.
14. The system according to claim 1, further comprising: a main
wellbore extending from the wellbore junction to the earth's
surface; and injection and production tubular strings positioned in
the main wellbore, gas being delivered to the storage wellbore via
the injection tubular string for injection into the formation, and
gas being delivered from the production wellbore via the production
tubular string for production to the earth's surface.
15. The system according to claim 14, wherein the injection and
production tubular strings are coaxial within the main
wellbore.
16. The system according to claim 14, wherein the injection tubular
string is positioned within the production tubular string in the
main wellbore.
17. A method of gravel packing a wellbore, the method comprising
the steps of: positioning a sand control device in the wellbore;
placing gravel in an annulus formed between the sand control device
and the wellbore; and flowing a retainer material into the annulus,
the retainer material preventing displacement of the gravel in the
annulus.
18. The method according to claim 17, wherein the flowing step
further comprises the step of permitting the retainer material to
set in the annulus, the retainer material when set abutting the
gravel and preventing the gravel from displacing in the
annulus.
19. The method according to claim 18, wherein in the flowing step,
the retainer material is cementitious, so that the retainer
material is hardened when set.
20. The method according to claim 18, wherein in the flowing step,
the retainer material is gelatinous, so that the retainer material
is gelled when set.
21. The method according to claim 17, wherein in the positioning
step, the sand control device is connected to a tubular string in
the wellbore, and wherein in the flowing step, the retainer
material is flowed into the annulus between the tubular string and
the wellbore.
22. The method according to claim 21, wherein the flowing step
further comprises flowing the retainer material into the annulus
via at least one ported collar interconnected in the tubular
string.
23. The method according to claim 17, wherein the flowing step is
performed after the placing step.
24. A gas storage and production system, the system comprising: a
main wellbore extending from the earth's surface to a wellbore
junction; a storage wellbore extending from the main wellbore into
a gas storage formation; and a production wellbore extending from
the main wellbore into the formation, gas being injected from the
main wellbore into the formation via the storage wellbore, and gas
being withdrawn from the formation into the main wellbore via the
production wellbore.
25. The system according to claim 24, wherein at least one of the
storage and production wellbores is an extension of the main
wellbore.
26. The system according to claim 24, further comprising a tubular
string positioned in the main wellbore, the tubular string
alternately delivering gas to the storage wellbore and delivering
gas from the production wellbore to the earth's surface.
27. The system according to claim 26, further comprising a valve
connected to the tubular string, the valve alternately providing
communication between the production wellbore and the tubular
string, and between the storage wellbore and the tubular
string.
28. The system according to claim 26, further comprising first and
second valves connected to the tubular string, the first valve
opening in response to a pressure differential from the tubular
string to the storage wellbore, and the second valve opening in
response to a pressure differential from the production wellbore to
the tubular string.
29. The system according to claim 24, further comprising a sand
control screen positioned in the production wellbore, and gravel
disposed in an annulus formed between the screen and the production
wellbore.
30. The system according to claim 29, further comprising cement in
the annulus abutting the gravel and preventing displacement of the
gravel axially relative to the annulus.
31. The system according to claim 24, further comprising first and
second tubular strings positioned in the main wellbore, the first
tubular string delivering gas to the storage wellbore, and the
second tubular string receiving gas from the production
wellbore.
32. The system according to claim 31, wherein the first and second
tubular strings are concentrically disposed in the main
wellbore.
33. The system according to claim 31, wherein the first tubular
string is within the second tubular string in the main
wellbore.
34. The system according to claim 24, further comprising a tubular
string positioned within the main wellbore, the tubular string
delivering gas to the storage wellbore, and an annulus between the
tubular string and the main wellbore receiving gas from the
production wellbore.
35. The system according to claim 34, wherein gas flows from the
production wellbore to the earth's surface substantially entirely
through the annulus.
Description
BACKGROUND
[0001] The present invention relates generally to gas storage in
subterranean formations and, in an embodiment described herein,
more particularly provides a gas storage and production system.
[0002] Natural gas stored underground is typically stored in
leached out salt dome caverns or in depleted hydrocarbon-bearing
formations. Where depleted formations are utilized, the formations
are generally unconsolidated or poorly consolidated sandstones,
which makes it possible to flow gas into and out of pores of the
formations at high flow rates.
[0003] To prevent production of formation sand when gas is
withdrawn from the formations, gravel packing is typically used. In
a gravel packing operation, gravel (e.g., sand, ceramic or bauxite
proppant, etc.) is placed in an annulus between a sand screen and a
wellbore intersecting a formation. The gravel provides structure
against which the formation sand bridges off, thereby preventing
migration of the formation sand through the gravel, while
permitting gas to flow therethrough.
[0004] In a common method of injecting gas into, and withdrawing
gas from, a storage formation, a single tubing string is used for
both the injecting and withdrawing operations. That is, the same
tubing string is used to store the gas in the formation as is used
to produce the stored gas from the formation. Thus, gas is
alternately flowed from the surface through the tubing string into
the formation, and from the formation through the tubing string to
the surface.
[0005] Unfortunately, several problems are associated with this
method. One problem is that only a single wellbore is available for
both storage and production operations. Another problem is that
when operations shift between storage and production, a flow
reversal is experienced at the gravel pack in the wellbore. This
flow reversal disturbs the gravel and the formation sand bridges
therein, thereby escalating the migration of formation sand through
the gravel.
[0006] Yet another problem with gravel packs in gas storage wells
has to do with the high flow rates generally used in these wells.
Typical gravel packs have an open upper end, and so the gravel is
not fully contained. High gas flow rates through these gravel packs
cause the gravel to move about, "fluffing" the gravel so that it
has more open space between its grains. This makes it easier for
formation sand to migrate through the spaces between the grains of
gravel.
[0007] When formation sand migrates through a gravel pack, it
enters the production flowpath and erodes equipment, plugs passages
and must be separated from the produced gas. Each of these
undermines the profitability of the operation. Therefore, it may be
seen that it would be highly advantageous to provide a gas storage
and production system which addresses some or all of the above
problems.
SUMMARY
[0008] In carrying out the principles of the present invention, in
accordance with an embodiment thereof, a gas storage and production
system is provided which enhances the profitability of subterranean
gas storage by preventing or at least substantially decreasing
migration of formation sand through a gravel pack.
[0009] In one aspect of the invention, a gas storage and production
system is provided. The system includes a gas storage formation, a
production and storage wellbores and a junction between the storage
and production wellbores. The system is of the type wherein gas is
stored within pores of formation rock, such as in a depleted
hydrocarbon-bearing formation.
[0010] The production wellbore extends into the formation for
withdrawing gas from the formation. The storage wellbore also
extends into the same formation for injecting gas into the
formation. In this manner, it is not necessary for a single
wellbore to be used for both injecting and producing the gas.
[0011] In another aspect of the invention, a gas storage and
production system is provided wherein production and storage
wellbores extend from a wellbore junction at a main wellbore. The
main wellbore extends from the earth's surface to the wellbore
junction. The storage and production wellbores each extend from the
wellbore junction into a gas storage formation. Gas is injected
from the main wellbore into the formation via the storage wellbore,
and gas is withdrawn from the formation into the main wellbore via
the production wellbore.
[0012] In yet another aspect of the invention, various means may be
utilized for delivering gas to the storage wellbore for injection
into the formation, and for delivering gas from the production
wellbore to the earth's surface. For example, a single tubular
string may be used to deliver the gas to the storage wellbore, and
the gas may be received from the production wellbore into an
annulus between the tubular string and the main wellbore for
flowing to the earth's surface. As another example, a single
tubular string may be used for alternately delivering gas to the
storage wellbore and receiving gas from the production wellbore. As
yet another example, separate tubular strings may be used for
delivering gas to the storage wellbore and receiving gas from the
production wellbore.
[0013] Also provided is a method of gravel packing a wellbore,
which is particularly useful in high flow rate gas production of
the type typically experienced in gas storage and production
systems. The method includes the steps of positioning a sand
control device in the wellbore, placing gravel in an annulus formed
between the sand control device and the wellbore, and flowing a
retainer material into the annulus. The retainer material prevents
displacement of the gravel in the annulus.
[0014] These and other features, advantages, benefits and objects
of the present invention will become apparent to one of ordinary
skill in the art upon careful consideration of the detailed
description of representative embodiments of the invention
hereinbelow and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic view of a gas storage and production
system embodying principles of the present invention, wherein main
and storage wellbores have been drilled, and the storage wellbore
has been gravel packed;
[0016] FIG. 2 is a schematic view of the system of FIG. 1, wherein
a production wellbore has been drilled and gravel packed;
[0017] FIG. 3 is a schematic view of the system of FIG. 1, wherein
cement has been placed above the storage wellbore gravel pack;
[0018] FIG. 4 is a schematic view of the system of FIG. 1, wherein
a first method of storing and producing the gas has been
implemented;
[0019] FIG. 5 is a schematic view of the system of FIG. 1, wherein
a second method of storing and producing the gas has been
implemented;
[0020] FIG. 6 is a schematic view of the system of FIG. 1, wherein
a third method of storing and producing the gas has been
implemented; and
[0021] FIG. 7 is a schematic view of the system of FIG. 1, wherein
a fourth method of storing and producing the gas has been
implemented.
DETAILED DESCRIPTION
[0022] Representatively illustrated in FIG. 1 is a gas storage and
production system 10 which embodies principles of the present
invention. In the following description of the system 10 and other
apparatus and methods described herein, directional terms, such as
"above", "below", "upper", "lower", etc., are used only for
convenience in referring to the accompanying drawings.
Additionally, it is to be understood that the various embodiments
of the present invention described herein may be utilized in
various orientations, such as inclined, inverted, horizontal,
vertical, etc., and in various configurations, without departing
from the principles of the present invention.
[0023] As depicted in FIG. 1, initial steps of a method used to
practice the system have been performed. A main wellbore 12 has
been drilled, cased and cemented, so that it extends from the
earth's surface into a formation 14 in which it is desired to store
gas. It is not necessary, however, for the main wellbore 12 to
extend into the formation 14.
[0024] A casing string 16 cemented in the main wellbore 12 includes
an orienting latch coupling 18 of the type well known to those
skilled in the art. The latch coupling 18 is positioned below a
desired exit window 20 through the casing 16, so that, when a
whipstock 22 is latched into the coupling 18, a window mill (not
shown) will be directed to mill through the casing at the desired
position and in the desired direction. Note that the window 20 may
be preformed, or at least provided for, in the casing string 16
when installed, for example, by including an item of equipment
known to those skilled in the art as a window bushing or a window
joint in the casing string.
[0025] After the casing string 16 is cemented in the main wellbore
12, a storage wellbore 24 is drilled as an extension of the main
wellbore. Alternatively, the storage wellbore 24 could be drilled
as a lateral or branch wellbore from the main wellbore 12. As shown
in FIG. 1, the storage wellbore 24 is deviated, so that it extends
substantially horizontally in the formation 14. This maximizes the
surface area of the formation 14 exposed to the storage wellbore 24
to increase the flow rate at which gas may be flowed from the
storage wellbore into the formation. However, it is to be clearly
understood that it is not necessary for the storage wellbore 24 to
be horizontal or deviated in the formation 14.
[0026] After the storage wellbore 24 is drilled, a sand control
assembly 26 is installed in the storage wellbore. The sand control
assembly 26 may be conventional and may include a gravel pack
packer 28 (which is preferably set in the casing 16 above the
storage wellbore), a tubular string 30 and a sand control device
32. Of course, if the formation 14 is well consolidated, or there
is otherwise no need for controlling influx of formation sand into
the storage wellbore 24, then the sand control assembly 26 may not
be used.
[0027] The sand control device 32 is representatively illustrated
in FIG. 1 as a tubular screen of the kind well known to those
skilled in the art. The screen 32 may be any type of well screen,
including a wire-wrapped screen, a sintered metal screen, a wire
mesh screen, etc. Other types of sand control devices may also be
used in the system 10, such as slotted or perforated liners, etc.
Therefore, the terms "sand control device" and "sand control
screen" as used herein are to be taken as including any apparatus
or device which excludes particulate matter, but permits liquid or
gas to flow therethrough.
[0028] After the sand control assembly 26 is positioned in the
storage wellbore 24, the wellbore is gravel packed. That is, gravel
34 is placed in an annulus 36 formed between the sand control
assembly 26 and the wellbore 24. Placement of the gravel 34 is
accomplished using techniques well known to those skilled in the
art. For example, a workstring (not shown) may be used to flow a
gravel slurry from the workstring outward through a crossover tool
(not shown) below the packer 28. Of course, other methods of gravel
packing the storage wellbore 24 may be used without departing from
the principles of the present invention.
[0029] After the storage wellbore 24 is gravel packed, a plug 38 is
installed in the packer 28. The plug 38 prevents debris from the
window milling and cementing operations described below from
passing into the sand control assembly 26. Otherwise, this debris
could fully or partially plug the screen 32, thereby preventing or
decreasing the flow of gas therethrough.
[0030] A whipstock 22, or other deflection device, is then
installed in the main wellbore 12. The latch coupling 18 secures
the whipstock 22 longitudinally in the casing 16 and orients the
whipstock so that it faces in the desired direction for milling the
window 20 through the casing. A window mill (not shown) or other
cutting device is then deflected off of the whipstock 22, so that
it cuts the window 20 through the casing 16.
[0031] At this point, or after passing additional cutting tools,
such as one or more drills, through the window 20, an initial
recess 40 is cut into the formation 14 beyond the cemented casing
16. Preferably, a permeability reducing material 42 is then forced
outwardly into the formation 14 surrounding the recess 40. The
material 42 may be, for example, a plastic resin, a polymer, a
cementitious material, a material known as PermaSeal.TM., etc. The
main purpose of using the material 42 is to prevent gas in the
formation 14 surrounding the window 20 from passing through the
window into the casing 16. However, use of the material 42 is not
necessary in keeping with the principles of the present
invention.
[0032] Referring additionally now to FIG. 2, the system 10 is
depicted with further steps having been performed. The recess 40
has been extended outward into the formation 14, for example, by
deflecting one or more drill bits off of the whipstock 22 and
through the window 20, thereby forming a production wellbore 44.
The production wellbore 44 is preferably deviated or substantially
horizontal in the formation 14 to expose a greater surface area of
the formation to the wellbore, but this is not necessary in keeping
with the principles of the invention.
[0033] Another sand control assembly 46 is installed in the
production wellbore 44. A packer 48 of the sand control assembly 46
is set in the casing 16 above the window 20, a sand control screen
50 is installed in the production wellbore 44, and a tubular string
52 extends between the packer and the screen. The sand control
assembly 46 is similar to the sand control assembly 26 described
above, but may differ in some respects.
[0034] In particular, the sand control assembly 46 may include
ported collars 54, 56 of the type used in cementing operations,
interconnected in the tubular string 52 between the packer 48 and
the screen 50. Preferably, the ported collar 54 is positioned
between the window 20 and the screen 50, and the ported collar 56
is positioned between the packer 48 and the window. The use of the
ported collars 54, 56 in the system 10 is described in more detail
below.
[0035] After installing the sand control assembly 46, the
production wellbore 44 is gravel packed using techniques well known
to those skilled in the art. Gravel 58 is placed in an annulus 60
between the sand control assembly 46 and the production wellbore 44
about the screen 50. Preferably, the gravel 58 extends somewhat
beyond the ports in the lower ported collar 54.
[0036] One of the inventive aspects of the system 10 is a manner in
which the gravel 58 is retained in the wellbore 44 about the screen
50. Due to high flow rates of gas from a storage formation into a
screen through a conventional gravel pack, the gravel is typically
made to move about, disturbing any sand bridging that had
previously developed, and permitting increased migration of sand
through the gravel pack.
[0037] One reason the gravel in a conventional gravel pack is able
to move about due to high gas flow rates therethrough is that the
annulus above the gravel pack is typically open. That is, the upper
level of a conventional gravel pack is typically spaced apart from
the packer, leaving the annulus therebetween available for the
gravel to displace into.
[0038] An example of this is shown in the accompanying figures
wherein the storage wellbore 24 is gravel packed. The gravel 34
spaced apart from the packer 28, leaving the annulus 36 open
therebetween. This does not present a problem of sand migration in
the system 10, however, since gas preferably flows outward from the
sand control assembly 26 into the formation 14, and not in the
other direction, which is another significant advantage of the
system.
[0039] For the production wellbore 44, wherein gas flows from the
formation 14 into the sand control assembly 46, the problem of
gravel movement is reduced or eliminated by retaining the gravel 58
in the annulus 60 about the screen 50, so that it cannot displace
upward in the annulus 60.
[0040] Referring additionally now to FIG. 3, the system 10 is
depicted wherein additional steps have been performed.
Specifically, a retainer material 62 has been flowed into the
annulus 60 above the gravel 58. The retainer material 62 is flowed
outward into the annulus 60 through the lower ported collar 54, and
is flowed upward through the annulus, until it extends through the
window 20. During this process, returns are taken from the annulus
60 through the upper ported collar 56.
[0041] Preferably, the retainer material 62 is cement or another
cementitious material. In that case, conventional cementing
techniques may be used to place the cement 62 in the annulus 60
above the gravel 58. For example, a workstring, such as a coiled
tubing string (not shown), may be inserted into the sand control
assembly 46 and used to open the ported collars 54, 56 prior to
pumping the cement through the workstring into the annulus 60.
Withdrawal of the workstring may cause the ported collars 54, 56 to
close.
[0042] Any of the gravel 58 above the ports in the ported collar 54
will be displaced along with the cement 62 as it is flowed into the
annulus 60. This procedure will ensure intimate contact between the
cement 62 and the top of the gravel 58 in the annulus 60. Thus,
when the cement 62 sets or hardens in the annulus 60, it will
prevent the gravel 58 from displacing when gas flows therethrough
at a high rate. Note that the gravel 34 in the storage wellbore 24
could similarly be retained in keeping with the principles of the
invention.
[0043] Of course, materials other than cement may be used for the
retainer material 62. For example, a polymer material maybe flowed
into the annulus 60 above the gravel 58. Such a material may gel
instead of harden when set. A gelatinous material may be used. In
short, any material which may serve to prevent displacement of the
gravel 58 in the annulus 60 can be used for the retainer material
62.
[0044] After the retainer material 62 is permitted to set in the
annulus 60, the packer 48 is retrieved from the main wellbore 12.
Alternatively, the packer 48 could be retrieved before placing the
retainer material 62 in the annulus 60, in which case there would
be no need to include the upper ported collar 56 in the tubular
string 52.
[0045] Referring additionally now to FIG. 4, the system 10 is
depicted wherein further steps have been performed. The sand
control assembly 46 extending inwardly through the window 20 has
been milled away, so that the tubular string 52 terminates at the
window. Any retainer material 62 left in the casing string 16 has
also been removed. The whipstock 22 has been retrieved, for
example, by using a washover tool well known to those skilled in
the art. The plug 38 has been retrieved from the packer 28.
[0046] A tubing string 64 having a seal assembly 66 proximate a
lower end thereof is installed in the main wellbore 12. The seal
assembly 66 is stabbed into the packer 28 or an associated seal
bore extension. The tubing string 64 now provides a conduit for
injecting gas from the earth's surface, into the sand control
assembly 26 in the storage wellbore 24, and outward into the
formation 14. The direction of gas flow is indicated by the arrow
68.
[0047] Another conduit for gas flow is provided by an annulus 70
formed between the tubing string 64 and the wellbore 12. Gas is
received into the annulus 70 from the sand control assembly 46,
which in turn receives the gas from the formation 14. The gas may
be flowed to the earth's surface in the annulus 70, in the
direction indicated by arrows 72.
[0048] Preferably, the directions of gas flow indicated by arrows
68, 72 are not reversed in normal gas storage and production
operations. Thus, the problems of flow reversal are substantially,
if not totally, eliminated. In the storage wellbore 24, gas is
preferably only flowed into the formation 14. In the production
wellbore 44, gas is preferably only flowed out of the formation 14.
Of course, these flow directions could be reversed if conditions
warrant.
[0049] It should also be clearly understood that it is not
necessary for the gas to be injected via the tubing string 64 and
the gas to be produced via the annulus 70. The gas could instead be
injected via the annulus 70 and produced via the tubing string 64.
For example, the tubing string 64 could extend into the production
wellbore 44, where the seal assembly 66 could be stabbed into a
seal bore (not shown) of the tubular string 52.
[0050] Referring additionally now to FIG. 5, the system 10 is
depicted wherein an alternate method of storing and producing the
gas in the formation 14 is used. In this version, the tubing string
64 is installed in the main wellbore 12 and a seal assembly 66 is
stabbed into the packer 28, or a seal bore associated therewith, as
described above for the version depicted in FIG. 4. However,
another tubing string 74 is installed in the main wellbore 12, and
a packer 76 on the tubing string is set in the casing 16 above the
window 20.
[0051] As with the version depicted in FIG. 4, gas is preferably
injected into the formation 14 via the tubing string 64. However,
the gas is produced via an annulus 78 formed between the tubing
strings 64, 74. This method may be more desirable in jurisdictions
where an annulus extending to the earth's surface, such as the
annulus 80 between the tubing string 74 and the wellbore 12, must
be available for well control and monitoring, and cannot be used
for production. Use of the tubing string 74 provides the additional
annulus 78 for production of the gas, leaving the annulus 80
available for well control and monitoring.
[0052] As shown in FIG. 5, the tubing strings 64, 74 are concentric
or coaxial, and the flow of gas is as indicated by the arrows 68,
72. However, it is to be clearly understood that the tubing strings
64, 74 could be otherwise positioned, and the gas flow could be
otherwise directed, in keeping with the principles of the
invention. For example, the tubing strings 64, 74 could be
positioned side-by-side in the main wellbore 12, the gas could be
produced through the interior bore of the tubing string 64, the gas
could be injected through the interior bore of the tubing string
74, etc.
[0053] Referring additionally now to FIG. 6, the system 10 is
depicted wherein another alternate method of producing and storing
gas in the formation 14 is used. As with the previously described
versions, the tubing string 64 is installed in the main wellbore 12
and the seal assembly 66 is stabbed into the packer 28. However, in
this version, the tubing string 64 includes a packer 82, which is
set in the casing 16 above the window 20, and a valve 84, which is
positioned between the packers 28, 82.
[0054] The valve 84 is of the type well known to those skilled in
the art which alternately permits flow through its sidewall and its
internal longitudinal bore. That is, the valve 84 has two
positions-in the first position the valve permits flow through its
sidewall but prevents flow through its internal bore, and in the
second position the valve prevents flow through its sidewall and
permits flow through its internal bore. Such valves are used in
several oilfield operations, including drill stem testing, where
the valves are known as "tester" valves. An example is the Omni.TM.
valve available from Halliburton Energy Services, Inc.
[0055] The valve 84 may be of the type which uses pressure in a
control line 86 to control its operation, as is commonly used in
subsea operations. However, other actuation means may be used, such
as acoustic, electromagnetic, etc., telemetry from a remote
location, pressure or pressure pulses in the tubing string 64 or
annulus 70, etc.
[0056] When the valve 84 is in its first position, gas is produced
from the production wellbore 44, through the sidewall of the valve,
and to the earth's surface via the tubing string 64 above the
valve. Flow between the storage wellbore 24 and the tubing string
64 above the valve 84 is prevented by the valve. Thus, when it is
desired to produce gas from the formation 14, the valve 84 is
operated to its first position.
[0057] When the valve 84 is in its second position, gas is injected
through the tubing string 64, through the internal bore of the
valve, and into the storage wellbore 24. Flow between the
production wellbore 44 and the tubing string 64 is prevented by the
valve 84. Thus, when it is desired to store gas in the formation
14, the valve is operated to its second position.
[0058] An advantage of this method shown in FIG. 6 is that only a
single tubing string 64 is needed to both store and produce gas via
the multiple wellbores 24, 44, while leaving an annulus 88
extending to the earth's surface above the packer 82 available for
well control. No flow reversal occurs in any gravel pack of the
system 10. The valve 84 is merely alternated between its first and
second positions as needed to store or produce the gas.
[0059] Referring additionally now to FIG. 7, the system 10 is
depicted wherein yet another method of storing and producing the
gas is used. This method is similar to the method shown in FIG. 6
except that, instead of the valve 84, two check valves 90, 92 are
used to control flow between the tubing string 64 and each of the
storage and production wellbores 24, 44.
[0060] The check valve 90 prevents flow from the interior of the
tubing string 64 to the production wellbore 44, but permits flow
from the production wellbore to the interior of the tubing string.
The check valve 92 prevents flow from the storage wellbore 24 to
the interior of the tubing string 64, but permits flow from the
interior of the tubing string to the storage wellbore.
[0061] When it is desired to produce gas from the formation 14,
pressure in the tubing string 64 is decreased below that in the
production wellbore 44. This pressure differential opens the check
valve 90 and gas flows from the production wellbore 44, through the
check valve 90, into the tubing string 64, and to the earth's
surface. The pressure in the tubing string 64 is also less than
pressure in the storage wellbore 24, which maintains the check
valve 92 in its closed position.
[0062] When it is desired to inject gas into the formation 14,
pressure in the tubing string 64 is increased above that in the
storage wellbore 24. This pressure differential opens the check
valve 92, and gas flows from the tubing string 64, through the
check valve, and into the storage wellbore 24. The pressure in the
tubing string 64 is also greater than pressure in the production
wellbore 44, which maintains the check valve 90 in its closed
position.
[0063] Biasing devices, such as springs, may be added to the check
valves 90, 92, so that predetermined pressure differentials are
needed to open the valves. This may also ensure more positive
closing of the valves 90, 92 and/or allow greater latitude in the
pressures which may be applied to the tubing string 64 to open or
close the valves as desired.
[0064] The check valves 90, 92 are shown schematically in FIG. 7 as
being separate valves spaced apart in the tubing string 64.
However, these valves go, 92 could be otherwise configured and
positioned in keeping with the principles of the present invention.
For example, the valves 90, 92 could be combined into a single
assembly, the valves could be retrievable by slickline or coiled
tubing, etc.
[0065] Note that the system 10 as depicted in FIG. 7 also has the
advantage of using only a single tubing string 64 to inject and
produce gas in the multiple wellbores 24, 44, while leaving the
annulus 88 available for well control. This storage and production
of gas through the tubing string 64 is accomplished without
requiring flow reversal in any gravel pack of the system 10.
[0066] In the accompanying FIGS. 1-7 depicting several embodiments
of the invention, the production wellbore 44 is shown as
intersecting the main wellbore 12 at a wellbore junction, and the
storage wellbore 24 is shown as being an extension of the main
wellbore. The main wellbore 16 is cased, while the production and
storage wellbores 24, 44 are uncased. The production wellbore 44 is
above the storage wellbore 24. However, it is to be clearly
understood that these examples of embodiments of the invention are
merely used for illustration purposes. The main wellbore 12 could
be uncased at its junction with the production and/or storage
wellbores 24, 44, the storage and/or production wellbores could be
cased, the storage wellbore could be above the production wellbore,
the storage wellbore could intersect the main wellbore at a
wellbore junction, the production wellbore could be an extension of
the main wellbore, etc.
[0067] The junction between the main wellbore 12 and the production
wellbore 44 has been depicted in the drawings and described above
as one in which the tubular string 52 in the production wellbore
extends into the main wellbore and is cemented at least up to the
window 20. However, it is to be understood that other types of
wellbore junctions may be utilized, without departing from the
principles of the present invention. For example, any of the
wellbore junctions known to those skilled in the art as Levels 1-6
may be used, as well as any other type of wellbore junction.
[0068] Thus, a person skilled in the art would, upon a careful
consideration of the above description of representative
embodiments of the invention, readily appreciate that many
modifications, additions, substitutions, deletions, and other
changes may be made to these specific embodiments, and such changes
are contemplated by the principles of the present invention.
Accordingly, the foregoing detailed description is to be clearly
understood as being given by way of illustration and example only,
the spirit and scope of the present invention being limited solely
by the appended claims and their equivalents.
* * * * *