U.S. patent application number 15/381374 was filed with the patent office on 2017-06-22 for downhole system.
The applicant listed for this patent is WELLTEC A/S. Invention is credited to Ricardo Reves VASQUES.
Application Number | 20170175485 15/381374 |
Document ID | / |
Family ID | 57758582 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170175485 |
Kind Code |
A1 |
VASQUES; Ricardo Reves |
June 22, 2017 |
DOWNHOLE SYSTEM
Abstract
The present invention relates to a downhole system for
completing a well. The downhole system comprises a downhole well
tubular structure having a wall and being configured to be arranged
in a borehole of the well and a first annular barrier for being
expanded in an annulus between the downhole well tubular structure
and a wall of the borehole. The first annular barrier comprises a
tubular part for mounting as part of the downhole well tubular
structure, the tubular part having a first expansion opening and an
outer face; an expandable metal sleeve surrounding the tubular part
and having an inner face facing the tubular part and an outer face
facing the wall of the borehole; a first connection part and a
second connection part configured to connect a first end and a
second end, respectively, of the expandable metal sleeve with the
tubular part; and an annular space between the inner face of the
expandable metal sleeve and the tubular part, the expandable metal
sleeve being expanded by pressurising the annular space to an
expansion pressure by pressurising the tubular part opposite the
expansion opening. The downhole system further comprises a first
aperture in the wall of the downhole well tubular structure. The
aperture is at least partly plugged with an acid-soluble material.
The present invention further relates to a completion method for
completing a downhole system according to the present
invention.
Inventors: |
VASQUES; Ricardo Reves;
(Allerod, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WELLTEC A/S |
Allerod |
|
DK |
|
|
Family ID: |
57758582 |
Appl. No.: |
15/381374 |
Filed: |
December 16, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 17/00 20130101;
E21B 34/063 20130101; E21B 34/10 20130101; E21B 2200/06 20200501;
E21B 34/16 20130101; E21B 34/06 20130101; E21B 43/25 20130101; E21B
33/127 20130101 |
International
Class: |
E21B 34/06 20060101
E21B034/06; E21B 33/127 20060101 E21B033/127; E21B 17/00 20060101
E21B017/00; E21B 34/10 20060101 E21B034/10; E21B 34/16 20060101
E21B034/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2015 |
EP |
15201248.0 |
Mar 9, 2016 |
EP |
16159369.4 |
Claims
1-20. (canceled)
21. A downhole system for completing a well, comprising: a downhole
well tubular structure having a wall and being configured to be
arranged in a borehole of the well, a first annular barrier for
being expanded in an annulus between the downhole well tubular
structure and a wall of the borehole, the first annular barrier
comprising: a tubular part for mounting as part of the well tubular
structure, the tubular part having a first expansion opening and an
outer face, an expandable metal sleeve surrounding the tubular part
and having an inner face facing the tubular part and an outer face
facing the wall of the borehole, a first connection part and a
second connection part configured to connect a first end and a
second end, respectively, of the expandable metal sleeve with the
tubular part, and an annular space between the inner face of the
expandable metal sleeve and the tubular part, the expandable metal
sleeve being expanded by pressurising the annular space to an
expansion pressure by pressurising the tubular part opposite the
expansion opening, and a first aperture in the wall of the downhole
well tubular structure, wherein the aperture is at least partly
plugged with an acid-soluble material.
22. A downhole system according to claim 21, wherein the downhole
well tubular structure has a first end nearest a top of the well
and a second end, the second end is configured to be closed, and
the second end comprises a second aperture in which a burstable
element is arranged for closing the second end.
23. A downhole system according to claim 21, wherein the first
aperture plugged with a plug of the material is configured to
withstand a first pressure higher than the expansion pressure.
24. A downhole system according to claim 21, wherein the plug has a
body part and a flange, the body part extending into the aperture
and the flange abutting an inner face of the well tubular
structure.
25. A downhole system according to claim 21, wherein the body part
of the plug has a bore.
26. A downhole system according to claim 21, wherein the body part
has a notch.
27. A downhole system according to claim 21, wherein the first
aperture plugged with the material is configured to withstand a
first pressure being higher than the expansion pressure.
28. A downhole system according to claim 21, further comprising a
second annular barrier, the aperture being arranged between the
first annular barrier and the second annular barrier.
29. A downhole system according to claim 21, further comprising a
sliding sleeve arranged opposite the aperture and having a first
initial position uncovering the aperture.
30. A downhole system according to claim 21, further comprising: an
inner well tubular structure arranged inside the downhole well
tubular structure, the inner well tubular structure comprising a
wall, a first inner annular barrier and a second inner annular
barrier, each inner annular barrier comprising: a tubular part for
mounting as part of the inner well tubular structure, the tubular
part having an inner expansion opening, an expandable metal sleeve
surrounding the tubular part and having an inner face facing the
tubular part and an outer face facing the wall of the downhole well
tubular structure, a first connection part and a second connection
part configured to connect a first end and a second end,
respectively, of the expandable metal sleeve with the tubular part,
and an annular space between the inner face of the expandable metal
sleeve and the tubular part, the expandable metal sleeve being
expanded by pressurising the annular space to an inner expansion
pressure by pressurising the tubular part opposite the inner
expansion opening, and a second aperture in the wall of the inner
well tubular structure.
31. A downhole system according to claim 21, wherein a burst disc
is arranged in the second aperture and configured to burst at a
burst pressure higher than the inner expansion pressure.
32. A downhole system according to claim 21, wherein the inner well
tubular structure comprises a sliding sleeve arranged opposite the
second aperture.
33. A downhole system according to claim 21, further comprising a
dart tool having projecting elements for engaging a groove in the
sliding sleeve and an inflatable element.
34. A completion method for completing a downhole system according
to claim 21, comprising: inserting the downhole well tubular
structure into the borehole, pressurising the downhole well tubular
structure to expand the annular barriers, and acidising the
acid-soluble material to clear the first aperture.
35. A completion method according to claim 34, which before
acidising the acid-soluble material further comprises pressurising
the well tubular structure to a pressure above the expansion
pressure to burst a burstable element in a second end of the well
tubular structure below the annular barrier.
36. A completion method according to claim 34, wherein the well
tubular structure comprises a sliding sleeve which is run in hole
in an open position, uncovering the first aperture.
37. A completion method according to 34, which before acidising the
acid-soluble material further comprises inserting an inner well
tubular structure.
38. A completion method according to claim 37, which before
acidising the acid-soluble material and after inserting the inner
well tubular structure further comprises pressurising the inner
well tubular structure to the inner expansion pressure to expand
inner annular barriers connected with the inner well tubular
structure.
39. A completion method according to claim 38, which before
acidising the acid-soluble material and after pressurising the
inner well tubular structure to the inner expansion pressure
further comprises pressurising the inner well tubular structure to
the burst pressure to burst a burst disc.
40. A completion method according to claim 38, which after
pressurising the inner well tubular structure to the burst pressure
to burst the burst disc lets acid through a second aperture into a
second annulus between the inner well tubular structure, the
downhole well tubular structure and the inner annular barriers to
acidise the acid-soluble material.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a downhole system for
completing a well, comprising a downhole well tubular structure
having a wall and being configured to be arranged in a borehole of
the well; a first annular barrier for being expanded in an annulus
between the downhole well tubular structure and a wall of the
borehole; and a first aperture in the wall of the downhole well
tubular structure. Furthermore, the invention relates to a
completion method for completing a downhole system.
BACKGROUND ART
[0002] Hydrocarbon-containing wells may be completed in very
different manners and with very different designs, and the design
used depends on the geological structure and composition of the
formation in which the well is formed. In sub-salt fields that
experience high losses during drilling and completion, it is very
important that the well tubular structure is closed off until the
annular barriers are expanded so that a zone experiencing a high
pressure loss can be closed off after opening for production from
that zone.
[0003] Also, when using expandable annular barriers where the well
tubular structure is pressurised to expand several annular barriers
in one run, the well tubular structure needs to be sealed off so
that the well tubular structure can be pressurised to a certain
pressure. Subsequently, the well tubular structure needs to be
opened to let hydrocarbon-containing fluid from the formation into
the well tubular structure. For this reason, well tubular
structures are often opened for production by perforating the well
tubular structure by means of perforation guns after the expansion
of the annular barriers. However, such detonation entails a risk of
the well tubular structure leaking in unintended areas, and sliding
sleeves are therefore often preferred. However, operating such
sliding sleeves by intervening the well with a tool takes time and
cannot be done remotely as demanded by oil companies nowadays.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to wholly or partly
overcome the above disadvantages and drawbacks of the prior art.
More specifically, it is an object to provide an improved downhole
system having annular barriers configured to be expanded by
pressurising the well tubular structure, in which system opening
for production may be done remotely and easily.
[0005] The above objects, together with numerous other objects,
advantages and features, which will become evident from the below
description, are accomplished by a solution in accordance with the
present invention by a downhole system for completing a well,
comprising: [0006] a downhole well tubular structure having a wall
and being configured to be arranged in a borehole of the well,
[0007] a first annular barrier for being expanded in an annulus
between the downhole well tubular structure and a wall of the
borehole, the first annular barrier comprising: [0008] a tubular
part for mounting as part of the downhole well tubular structure,
the tubular part having a first expansion opening and an outer
face, [0009] an expandable metal sleeve surrounding the tubular
part and having an inner face facing the tubular part and an outer
face facing the wall of the borehole, [0010] a first connection
part and a second connection part configured to connect a first end
and a second end, respectively, of the expandable metal sleeve with
the tubular part, and [0011] an annular space between the inner
face of the expandable metal sleeve and the tubular part, the
expandable metal sleeve being expanded by pressurising the annular
space to an expansion pressure by pressurising the tubular part
opposite the expansion opening, and [0012] a first aperture in the
wall of the downhole well tubular structure, wherein the aperture
is at least partly plugged with an acid-soluble material.
[0013] The downhole well tubular structure may have a first end
nearest a top of the well and a second end, the second end may be
configured to be closed or may be closed when inserting the
downhole well tubular structure into the well, and the second end
may comprise a second aperture in which a burstable element is
arranged for closing the second end. By having a burstable element
in the second end, the annular barrier can be expanded in that the
downhole well tubular structure is closed, and subsequently the
well tubular structure is pressurised to a pressure above the
expansion pressure to burst the burstable element so that acid can
be circulated down past the acid-soluble material to dissolve the
plug.
[0014] In an embodiment, the material may comprise aluminium.
[0015] Moreover, the first aperture plugged with a plug of the
material may be configured to withstand a first pressure higher
than the expansion pressure.
[0016] Further, the plug may have a body part and a flange, the
body part extending into the aperture and the flange abutting an
inner face of the well tubular structure.
[0017] Also, the body part of the plug may have a bore. By having a
hollow body part, fluid communication between the inside of the
well tubular structure and the annulus can be established by the
bore.
[0018] The body part may have a notch for initiating separation
between the body part and the flange.
[0019] Furthermore, the first aperture plugged with the material
may be configured to withstand a first pressure being higher than
the expansion pressure.
[0020] Moreover, the burstable element may be configured to burst
at a burst pressure.
[0021] The first aperture plugged with the material may be
configured to withstand a first pressure higher than the burst
pressure.
[0022] The downhole system may further comprise a second annular
barrier, and the aperture may be arranged between the first annular
barrier and the second annular barrier.
[0023] Furthermore, the downhole system may further comprise a
sliding sleeve arranged opposite the aperture and having a first
initial position uncovering the aperture.
[0024] In another embodiment, the annular barrier may have only one
or no connection parts.
[0025] In addition, the downhole system may further comprise:
[0026] an inner well tubular structure arranged inside the downhole
well tubular structure, the inner well tubular structure comprising
a wall, [0027] a first inner annular barrier and a second inner
annular barrier, each inner annular barrier comprising: [0028] a
tubular part for mounting as part of the inner well tubular
structure, the tubular part having an inner expansion opening,
[0029] an expandable metal sleeve surrounding the tubular part and
having an inner face facing the tubular part and an outer face
facing the wall of the downhole well tubular structure, [0030] a
first connection part and a second connection part configured to
connect a first end and a second end, respectively, of the
expandable metal sleeve with the tubular part, and [0031] an
annular space between the inner face of the expandable metal sleeve
and the tubular part, the expandable metal sleeve being expanded by
pressurising the annular space to an inner expansion pressure by
pressurising the tubular part opposite the inner expansion opening,
and [0032] a second aperture in the wall of the inner well tubular
structure.
[0033] In an embodiment, a burst disc may be arranged in the second
aperture and be configured to burst at a burst pressure higher than
the inner expansion pressure.
[0034] Moreover, the inner well tubular structure may comprise a
sliding sleeve arranged opposite the second aperture.
[0035] Also, the downhole well tubular structure may comprise other
annular barriers.
[0036] In addition, the inner well tubular structure may comprise
other inner annular barriers.
[0037] Furthermore, the downhole well tubular structure may
comprise other first apertures arranged between two annular
barriers.
[0038] Additionally, the inner well tubular structure may comprise
other second apertures arranged between two inner annular
barriers.
[0039] The downhole system may further comprise a tool configured
to close and/or open the sliding sleeves.
[0040] In an embodiment, the tool may be arranged at the bottom of
the well or be inserted when needed.
[0041] Furthermore, the downhole system may further comprise a dart
tool having projecting elements for engaging a groove in the
sliding sleeve and an inflatable element.
[0042] The present invention furthermore relates to a completion
method for completing a downhole system as described above
comprising [0043] inserting the downhole well tubular structure
into the borehole, [0044] pressurising the downhole well tubular
structure to expand the annular barriers, and [0045] acidising the
acid-soluble material to clear the first aperture.
[0046] Said completion method as described above may, before
acidising the acid-soluble material, further comprise pressurising
the well tubular structure to a pressure above the expansion
pressure to burst a burstable element in a second end of the well
tubular structure below the annular barrier.
[0047] Also, the well tubular structure may comprise a sliding
sleeve which is run in hole in an open position, uncovering the
first aperture.
[0048] In an embodiment, the completion method may, before
acidising the acid-soluble material, further comprise inserting an
inner well tubular structure.
[0049] Furthermore, the completion method may, before acidising the
acid-soluble material and after inserting the inner well tubular
structure, further comprise pressurising the inner well tubular
structure to the inner expansion pressure to expand inner annular
barriers connected with the inner well tubular structure.
[0050] In addition, the completion method may, before acidising the
acid-soluble material and after pressurising the inner well tubular
structure to the inner expansion pressure, further comprise
pressurising the inner well tubular structure to the burst pressure
to burst a burst disc.
[0051] Finally, the completion method may, after pressurising the
inner well tubular structure to the burst pressure to burst the
burst disc, let acid through a second aperture into a second
annulus between the inner well tubular structure, the downhole well
tubular structure and the inner annular barriers to acidise the
acid-soluble material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] The invention and its many advantages will be described in
more detail below with reference to the accompanying schematic
drawings, which for the purpose of illustration show some
non-limiting embodiments and in which
[0053] FIG. 1 shows a partially cross-sectional view of a downhole
system having a downhole well tubular structure connected with
unexpanded annular barriers,
[0054] FIG. 2 shows a partially cross-sectional view of the
downhole system of FIG. 1 where the annular barriers are in the
expanded position,
[0055] FIG. 3 shows a partially cross-sectional view of another
downhole system having an inner well tubular structure arranged
within the downhole well tubular structure, before the inner
annular barriers connected with the inner well tubular structure
are expanded,
[0056] FIG. 4 shows a partially cross-sectional view of the
downhole system of FIG. 1 where the inner annular barriers are in
the expanded position,
[0057] FIG. 5 shows a partially cross-sectional view of another
downhole system having a tool inserted for operating sliding
sleeves covering/uncovering the second apertures in the inner well
tubular structure,
[0058] FIG. 6 shows a partially cross-sectional view of yet another
downhole system having a dart tool for sequentially operating the
sliding sleeves,
[0059] FIG. 7 shows a partially cross-sectional view of yet another
downhole system having a burst disc in the second end of the well
tubular structure,
[0060] FIG. 8 shows a cross-sectional view of part of the downhole
system having a plug and a sliding sleeve in its open position,
[0061] FIG. 8A shows a partial view of FIG. 8, and
[0062] FIG. 9 shows a cross-sectional view of part of the downhole
system of FIG. 8 in which the sliding sleeve has released the
flange from the bode part.
[0063] All the figures are highly schematic and not necessarily to
scale, and they show only those parts which are necessary in order
to elucidate the invention, other parts being omitted or merely
suggested.
DETAILED DESCRIPTION OF THE INVENTION
[0064] FIG. 1 shows a downhole system 100 for completing a well 2,
comprising a downhole well tubular structure 1 having a wall la and
being configured to be arranged in a borehole 3 of the well. The
downhole system 100 comprises a first annular barrier 10, 10a
configured to be expanded in an annulus 4 between the downhole well
tubular structure 1 and a wall 5 of the borehole 3, as shown in
FIG. 2. The first annular barrier 10, 10a comprises a tubular part
11 configured to be mounted as part of the downhole well tubular
structure 1. The tubular part 11 has a first expansion opening 12
and an outer face 14. The first annular barrier 10, 10a further
comprises an expandable metal sleeve 15 surrounding the tubular
part 11 and having an inner face 16 facing the outer face 14 of the
tubular part, the expandable metal sleeve further having an outer
face 17 facing the wall of the borehole 3. A first connection part
18 is configured to connect a first end 20 of the expandable metal
sleeve 15 with the tubular part 11, and a second connection part 19
is configured to connect a second end 21 of the expandable metal
sleeve with the tubular part. An annular space 22 (as shown in FIG.
2) is defined between the inner face of the expandable metal sleeve
15 and the outer face 14 of the tubular part 11. The first annular
barrier 10, 10a is set and thus expanded by the expandable metal
sleeve 15 being expanded by pressurising the annular space 22 with
fluid to an expansion pressure by pressurising the fluid inside the
tubular part 11 opposite the first expansion opening. The wall of
the downhole well tubular structure 1 has a first aperture 23 which
is at least partly plugged with an acid-soluble material 24 so that
the aperture is configured to withstand a first pressure being
higher than the expansion pressure. The material 24 mainly
comprises aluminium so that acid can dissolve the material and
clear the aperture 23.
[0065] When having well tubular structures with annular barriers
which are expanded by pressurising fluid inside the well tubular
structure and letting the pressurised fluid in through the
expansion opening and into the annular space, the apertures for the
subsequent production of hydrocarbon-containing fluid need to be
sealed off to be able to pressurise the well tubular structure.
After the pressurisation and the expansion, the production
apertures in known completions need to be opened by sliding sleeves
arranged opposite the apertures. However, this has to be done in a
separate run and with the risk of not being able to slide the
sleeve and thus not being able to open for production in one or
more production zones. For this and other reasons, well tubular
structures are often opened for production by perforating the well
tubular structure by means of perforation guns after the expansion
of the annular barriers. However, such detonation entails a risk of
the well tubular structure leaking in unintended areas, and sliding
sleeves are therefore preferred. After sliding the sliding sleeves
and thereby uncovering the apertures, the well tubular structure is
pressurised with acid to acidise the formation and increase the
production contact area and thus increase formation contact.
[0066] By having the first aperture at least partly plugged with an
acid-soluble material, the step or run of intervening the well in
order to slide the sliding sleeves can be avoided since the acid
provides access through the aperture to the formation. In the event
that one production zone opposite one of the first apertures 23
produces too much water, that zone can be shut off by sliding the
sliding sleeve to close off the flow through the first aperture
opposite that zone. Thus, the sliding sleeve 26 is run in hole in
its open position.
[0067] As can be seen in FIG. 2, the downhole system 100 further
comprises a second annular barrier 10, 10b for isolating a first
production zone 101, and the first aperture 23 is arranged between
the first and second annular barriers 10, 10a, 10b. The downhole
system 100 further comprises a third annular barrier 10, 10c for
isolating a second production zone 102 between the second and third
annular barriers 10, 10b, 10c. The downhole well tubular structure
1 is closed at the bottom by a ball 46 fitting into a ball seat 47.
In this way, the entire well tubular structure 1 can be pressurised
from its top to expand the annular barriers 10. The well tubular
structure 1 may also be closed, e.g. by a plug or the like.
[0068] The downhole system 100 further comprises a sliding sleeve
26 arranged opposite the first aperture 23 and having a first
initial position uncovering the first aperture so that a second run
is not necessary to open the first apertures. However, the sliding
sleeves 26 can be closed later, e.g. if one of the production zones
starts producing water, that zone can be closed by sliding the
sliding sleeve arranged opposite that aperture through which the
water flows from that zone.
[0069] In order to expand the expandable metal sleeves 15 of the
annular barriers 10, 10a, 10b, 10c, the inside of the well tubular
structure 1 is pressurised so that several annular barriers 10 are
set in one pressurising step. The first apertures 23 between the
annular barriers 10a, 10b, 10c are plugged by a plug 9 of an
acid-soluble material 24 and the plugs 9 are configured to
withstand a first pressure being higher than the expansion
pressure. The downhole well tubular structure 1 has a first end 6
and a second end 7 as shown in FIG. 7. The first end 6 is nearest a
top of the well and the second end 7 is closed when inserting the
downhole well tubular structure 1 into the borehole of the well.
The second end 7 comprises a second aperture 52 in which a
burstable element 8 is arranged, and the second aperture 52 is also
arranged below all the annular barriers 10. By having a burstable
element 8 in the second end 7, the annular barriers 10 can be
expanded in that the downhole well tubular structure 1 is closed by
the burstable element 8, and subsequently the well tubular
structure 1 is pressurised to a pressure above the expansion
pressure to burst the burstable element 8 so that acid can be
circulated down past the acid-soluble material 24 to dissolve the
plug 9. In known solutions, the ball dropped for closing the well
tubular metal structure in order to be able to pressurise it has to
be drilled out before fluid can be circulated in the well tubular
metal structure. By the present solution, the combination of the
burstable element 8 in the second aperture 52 in the second end 7
for closing the well tubular structure 1 and plugs 9 of
acid-dissoluble material 24 in the first apertures 23 between the
annular barriers 10a, 10b, 10c allows the annular barriers to be
expanded, and then the burstable element 8 is burst to open the
second aperture 52 of the second end 7, and acid can be circulated
to dissolve the plugs 9, and the well tubular structure 1 is thus
open for production without having to intervene the well by tools.
A burstable element 8, such as a burst disc, is set to burst at a
certain pressure, meaning within a certain pressure range. If all
first apertures were plugged with burst discs, the first burst disc
bursting would cause the pressure to drop and the remaining burst
discs would not burst, and then a tool isolating a zone opposite
each of the burst discs has to be inserted into the well. The
present invention thus presents a downhole system 100 in which
annular barriers 10 can be expanded and no intervention is needed
to open for production subsequently.
[0070] In FIG. 8, the plug 9 has a body part 27 and a flange 28,
the body part extending into the aperture and the flange abutting
an inner face 44 of a groove 43 in the well tubular structure 1.
The flange 28 has a sealing means 48 in order to seal against the
inner face 44. The body part has a bore 51 closed by the flange 28.
The body part has on its outer face a notch 25, also shown in FIG.
8A, so that if the plug is not dissolved when acidising, a tool 50
as shown in FIG. 9 can intervene the well and a projectable part 55
of the tool 50 can slide the sleeve and separate by force the
flange 28 from the body part 27. When separating the flange 28 from
the body part 27, as shown in FIG. 9, the bore 51 in the body part
27 provides access to the production zone and the production can
begin as indicated by arrows.
[0071] In FIG. 3, the downhole system 100 further comprises an
inner well tubular structure 29 arranged inside the downhole well
tubular structure 1. The inner well tubular structure 29 comprises
a first inner annular barrier 30, 30a and a second inner annular
barrier 30, 30b. Each inner annular barrier 30 comprises a tubular
part 31 for mounting as part of the inner well tubular structure
29. The tubular part 31 has an inner expansion opening 32 through
which pressurised fluid enters to expand an expandable metal sleeve
33 surrounding the tubular part and having an inner face 34 facing
the tubular part and an outer face facing the wall of the downhole
well tubular structure 1. A first connection part 35 is configured
to connect a first end 37 of the expandable metal sleeve 33 with
the tubular part 31, and a second connection part 36 is configured
to connect a second end 38 of the expandable metal sleeve with the
tubular part. An annular space 39 is formed between the inner face
34 of the expandable metal sleeve 33 and the tubular part 31. The
expandable metal sleeve 33 of the inner annular barriers 30, 30a,
30b is expanded by pressurising the annular space to an inner
expansion pressure by pressurising the tubular part 31 and letting
the pressurised fluid in through the inner expansion opening 32.
The wall of the inner well tubular structure 29 comprises a second
aperture 40 through which acid is let into a second annulus 45
between the inner well tubular structure 29, the downhole well
tubular structure 1 and the inner annular barriers 30 to acidise
the acid-soluble material in the first aperture 23 in the wall of
the downhole well tubular structure 1.
[0072] By having an inner well tubular structure 29 arranged in the
downhole well tubular structure 1, the completion is double-skinned
and the production fluid flows from the first production zone 101
in through the first aperture 23, into the second annulus 45 and
further into the inner well tubular structure 29 through the second
aperture 40.
[0073] As can be seen in FIG. 3, the inner well tubular structure
29 comprises a key mechanism 49 at its toe at the bottom of the
inner well tubular structure 29. The purpose of this is that when
the inner well tubular structure 29 is recovered for recompletion
or abandonment, the sliding sleeves of the valves of the downhole
well tubular structure 1 are closed as the inner well tubular
structure is retrieved to surface. The key mechanism 49 slides
along the downhole well tubular structure 1 and engages a profile
of the sliding sleeves 26 and slides the sliding sleeves into their
closed position one by one as the inner well tubular structure 29
is pulled out of the well. This prevents commingling of the zones
or significant losses during work-over operations.
[0074] The inner well tubular structure 29 may be an intelligent
completion with surface control of the inner valves, e.g. sliding
sleeves 26 or other types of valves, for controlling the flow from
the multiple zones. By using an acid-dissoluble material in the
apertures in the downhole well tubular structure 1, the risk of
losing mud out of the apertures when running the inner well tubular
structure is decreased, while it is ensured that the zones are open
for flow once the inner well tubular structure has landed in its
position downhole.
[0075] In order to be able to expand the inner annular barriers 30
as shown in FIG. 4, the second apertures 40 need to be sealed off,
e.g. closed by a sliding sleeve 42 covering the second aperture 40.
In order to move the sliding sleeves 42 to open the second aperture
40, an additional run is necessary. However, when a burst disc 41
is arranged in the second aperture 40 and configured to burst at a
burst pressure higher than the inner expansion pressure, the inner
well tubular structure just needs to be pressurised to the burst
pressure to open the second apertures. When supplying acid down the
inner well tubular structure, the acid fluid can be pressurised to
a pressure above the burst pressure and can thus burst the burst
disc just before the acid is fed to the second annulus to dissolve
the material 24 in the first aperture 23. Thus, the step of
acidising entails bursting the burst disc opening the second
aperture, acidising the acid-soluble material in the first aperture
23 and acidising the formation to increase formation contact, all
in one run without intervening the well.
[0076] Furthermore, when having an inner well tubular structure, it
is not easy to operate the sliding sleeves 42 covering/uncovering
the first apertures 23 as soon as the inner well tubular structure
has been inserted. Therefore, the combination of having a burst
disc in the second apertures 40 in the inner well tubular structure
and having the acid-soluble material 24 in the downhole well
tubular structure 1 makes it possible to make a very operationally
safe completion, since the first and second apertures are inserted
in the uncovered position, but "plugged" with acid-soluble material
or a burst disc, respectively, so that the apertures can be opened
in one run after expanding the inner annular barriers 30.
[0077] As shown in FIGS. 3 and 4, the downhole well tubular
structure 1 may be connected with other annular barriers 10, and
the inner well tubular structure may be connected with other inner
annular barriers 30. The downhole well tubular structure 1 may
comprise other first apertures 23 arranged between two adjacent
annular barriers 10, and the inner well tubular structure may
comprise other second apertures 40 arranged between two adjacent
inner annular barriers 30. The downhole system 100 may in this way
have a plurality of production zones other than the first and the
second production zones.
[0078] In FIG. 5, the downhole system 100 further comprises a tool
50 configured to close the sliding sleeves 42 and reopen them when
needed. The tool 50 comprises a flexible element (not shown) which
is forced radially outwards, but when moving along the inner face
34 of the inner well tubular structure, it is forced to retract,
and when being opposite the groove 62 of the sliding sleeve 42, the
flexible element is allowed to project radially outwards and engage
the groove 62, and as the tool 50 continues to move in one
direction, the sliding sleeve 42 is moved to either open or close
the aperture 40. The tool 50 may be arranged in the bottom of the
well 2 and be engaged by a drill pipe inserted in the inner or
downhole well tubular structure when the sliding sleeves 42 need to
be closed, e.g. before the inner well tubular structure is
retracted for repair or replacement.
[0079] As shown in FIG. 6, the downhole system 100 further
comprises a dart tool 60 having projecting elements 61 configured
to engage a groove 62 in the sliding sleeve 42 and an inflatable
element 63. The dart tool 60 can be used if the inner well tubular
structure is inserted with the sliding sleeves 42 in a closed
position, covering the second aperture 40, and the production zones
need to be opened and fractured sequentially. This is e.g. the case
if only one zone is opened and treated with acid, and when that
production zone produces water, the zone is closed and another
production zone is opened and treated with acid. The dart tool 60
is then inserted into the inner well tubular structure, and when
detecting the sliding sleeve 42 to be operated, the projecting
elements 61 engage the groove 62 of the sliding sleeve 42 and the
inflatable element 63 is inflated. Upon further pressurisation of
the fluid above the inflatable element 63, the dart tool 60 is
moved downwards and the sliding sleeve 42 is forced open, and the
acid is let into the second annulus 45, the acid-soluble material
24 is dissolved and the acid enters the first aperture 23 and the
formation. The dart tool 60 may be used to open and treat several
zones with acid. When this is done, the sliding sleeves 42 are
self-closing.
[0080] The well 2 is completed by inserting the downhole well
tubular structure 1 into the borehole 3, by pressurising the
downhole well tubular structure to expand the annular barriers 10,
and by subsequently acidising the acid-soluble material 24 to clear
the first aperture 23 and allow the acid to enter the first
aperture to acidise the formation as well.
[0081] When completing a double-cased completion as shown in FIG.
4, an inner well tubular structure is inserted after the annular
barriers 10 connected with the downhole well tubular structure 1
are expanded and before the acid treatment. After the step of
inserting the inner well tubular structure, the inner well tubular
structure is pressurised to the inner expansion pressure to expand
the inner annular barriers 30, 30a, 30b and thus isolate the second
annulus 45 between the downhole well tubular structure 1 and the
inner well tubular structure into several second annuluses 45.
Then, the inner well tubular structure is pressurised to the burst
pressure to burst the burst discs 41 and provide access to the
second annulus 45. The burst discs 41 may be burst one at a time
and thus be rated at different burst pressures so that e.g. the
burst disc arranged furthest away from the top of the well is rated
to the lowest burst pressure to ensure that it is burst before
bursting the next burst disc closer to the top of the well. In this
way, it is ensured that all burst discs 41 are burst to prevent
that once the first burst disc arranged closest to the top is
burst, all fluid is lost in that zone so the other burst discs are
not burst.
[0082] The first apertures may also comprise a burst disc
configured to burst at a burst pressure higher than the expansion
pressure in order to expand the annular barrier.
[0083] A flow control valve may be arranged in one of the apertures
in the well tubular structures to control flow in or out of the
well tubular structures.
[0084] By fluid or well fluid is meant any kind of fluid that may
be present in oil or gas wells downhole, such as natural gas, oil,
oil mud, crude oil, water, etc. By gas is meant any kind of gas
composition present in a well, completion, or open hole, and by oil
is meant any kind of oil composition, such as crude oil, an
oil-containing fluid, etc. Gas, oil, and water fluids may thus all
comprise other elements or substances than gas, oil, and/or water,
respectively.
[0085] By a casing, well tubular structure, downhole well tubular
structure, inner well tubular structure, or production casing is
meant any kind of pipe, tubing, tubular, liner, string etc. used
downhole in relation to oil or natural gas production.
[0086] In the event that the tool is not submergible all the way
into the casing, a downhole tractor can be used to push the tool
all the way into position in the well. The downhole tractor may
have projectable arms having wheels, wherein the wheels contact the
inner surface of the casing for propelling the tractor and the tool
forward in the casing. A downhole tractor is any kind of driving
tool capable of pushing or pulling tools in a well downhole, such
as a Well Tractor.RTM..
[0087] Although the invention has been described in the above in
connection with preferred embodiments of the invention, it will be
evident for a person skilled in the art that several modifications
are conceivable without departing from the invention as defined by
the following claims.
* * * * *