[0001] The present invention relates to a downhole completion system for being arranged
in a wellbore, comprising several casing sections having a casing length of 10-14
metres mounted as one well tubular metal structure by means of casing collars. The
present invention also relates to a downhole method for completing a well having a
wellbore.
[0002] During the completion of a well, annular barriers are positioned at predetermined
positions for providing zone isolation between different zones, for instance between
a non-producing zone and a production zone. However, if the annular barriers are positioned
incorrectly, they may isolate inaccurately which results in the well not producing
as intended.
[0003] 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 completion system having a high flexibility in relation to providing zone
isolation and production zones.
[0004] 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 completion system for being
arranged in a wellbore, comprising several casing sections having a casing length
of 10-14 metres mounted as one well tubular metal structure by means of casing collars,
wherein a number of the several casing sections each comprises at least three annular
barriers each comprising an expandable metal sleeve configured to be expanded to abut
the wellbore, the annular barriers of each casing section having a common longitudinal
extension of at least 50% of the casing length.
[0005] Furthermore, at least one of the expanded metal sleeves may have a plurality of perforations.
[0006] In addition, each section may have a first end part and a second end part, at least
the first end part may having at least 1 metre which is free from annular ba rriers.
[0007] Moreover, the annular barriers may be arranged with a mutual distance of less than
100 cm, preferably less than 50 cm.
[0008] Also, each annular barrier may have a barrier length of 1-2.5 metres.
[0009] Furthermore, each casing section may have a base pipe.
[0010] Each of the expandable metal sleeves may surround and may fasten to the same base
pipe, forming an annular space between each expandable metal sleeve and the base pipe.
[0011] In addition, each space may comprise at least one thermally decomposable compound,
which compound is thermally decomposable below a temperature of 400°C and is adapted
to generate gas or super-critical fluid upon decomposition.
[0012] Moreover, the compound may comprise nitrogen.
[0013] The compound may be selected from a group consisting of: ammonium dichromate, ammonium
nitrate, ammonium nitrite, barium azide, sodium nitrate or a combination thereof.
[0014] Also, the compound may decompose at temperatures above 100°C, preferably above 180°C.
[0015] Furthermore, the annular space is pre-pressurised to a pressure above 5 bar, preferably
above 50 bar and more preferably above 100 bar, even more preferably above 250 bar.
[0016] The compound may be present in the form of a powder, a powder dispersed in a liquid
or a powder dissolved in a liquid.
[0017] In addition, the base pipe may have at least one opening opposite each of the expandable
metal sleeves for expanding the expandable metal sleeves by allowing pressurised fluid
to enter the openings.
[0018] The annular barriers may comprise a valve in fluid communication with the openings.
[0019] Furthermore, the expandable metal sleeves may be fastened to the base pipe by means
of welding, crimping or connection parts connecting the expandable metal sleeves to
the base pipe.
[0020] Also, the expandable metal sleeves of each casing section may be connected to form
part of the base pipe, so that an inner face of the expandable metal sleeves forms
part of an inner face of the base pipe.
[0021] The expandable metal sleeves of each casing section may be connected directly or
indirectly, forming a connection area.
[0022] Moreover, the expandable metal sleeves of each casing section may be connected indirectly
by means of a tubular connection part.
[0023] In addition, the expandable metal sleeves of each casing section may be connected
directly end to end in an overlapping manner.
[0024] The downhole completion system may further comprise a patch to be expanded inside
the casing section, so that each end of the patch overlaps the connection area.
[0025] Furthermore, each expandable metal sleeve may comprise a plurality of sealing elements.
[0026] Also, each expandable metal sleeve may comprise sections having an increased thickness,
which sections are expanded less than other sections of the expandable metal sleeve.
[0027] A number of the several casing sections may each comprise at least four or five annular
barriers.
[0028] In addition, the sealing elements may comprise key rings, coiled springs or a combination
thereof.
[0029] The present invention also relates to a downhole method for completing a well having
a wellbore, comprising:
- mounting a well tubular metal structure from several casing section of the downhole
completion system ad described above,
- providing the well tubular metal structure in the wellbore, and
- expanding the expandable metal sleeves of the annular barriers to abut the wellbore.
[0030] Furthermore, the expansion of the expandable metal sleeves of the annular barriers
may be performed sequentially.
[0031] The downhole method may further comprise perforating at least one of the expandable
metal sleeves, creating access of reservoir fluid into the casing sections and into
the well tubular metal structure.
[0032] The downhole method may further comprise expanding a patch inside the well tubular
metal structure opposite the perforated expandable metal sleeve for sealing off the
perforations.
[0033] 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
Fig. 1 shows a partly cross-sectional view of a downhole completion system arranged
in a wellbore of a well having several casing sections,
Fig. 2 shows a perspective of a casing section comprising four annular barriers configured
to be expanded to abut the wellbore,
Fig. 3A shows a side view of another casing section having four annular barriers,
Fig. 3B shows a cross-sectional view of the casing section of Fig. 3A,
Fig. 4A shows a side view of another casing section having four annular barriers,
Fig. 4B shows a cross-sectional view of the casing section of Fig. 4A,
Fig. 5A shows a cross-sectional view of an embodiment of an annular barrier,
Fig. 5B shows a cross-sectional view of another embodiment of an annular barrier,
Fig. 6 shows a cross-sectional view of another embodiment of an annular barrier,
Fig. 7 shows a cross-sectional view of another casing section having four annular
barriers,
Fig. 8 shows a cross-sectional view of a sealing element of an annular barrier,
Fig. 9 shows a cross-sectional view of another sealing element of an annular barrier,
and
Fig. 10 shows a cross-sectional view of another sealing element of an annular barrier.
[0034] 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.
[0035] Fig. 1 shows a downhole completion system 100 arranged in a wellbore 2 of a well
5. The downhole completion system 100 comprises several casing sections 3 having a
casing length of 10-14 metres which is a standard length, so that the casing section,
also called casing joints, can fit into the conventional rig equipment when mounting
the well tubular metal structure 1 and lowering the well tubular metal structure into
the wellbore. The several casing sections 3 are mounted as one well tubular metal
structure 1 by means of casing collars 4. A number of the several casing sections
3 each comprises at least three annular barriers 10 so that when expanded, each of
these casing sections 3 provides three isolations dividing the annulus in four zones.
Each annular barrier 10 comprises an expandable metal sleeve 11 configured to be expanded
to abut the wellbore 2. The annular barriers 10 of each casing section have a common
longitudinal extension L
A of at least 50% of the casing length L
C as seen in Fig. 2.
[0036] By having several casing sections 3 each comprising at least three annular barriers
10, the operator of the well is not limited to arranged the hydra-carbon-producing
zones in predetermined areas, but can freely make perforations where the hydra-carbon-producing
zones are very long after the system has been completed. The operator can thus quickly
complete the well and subsequently make more accurate measurements for determining
exactly where the hydra-carbon-producing layers are in the formation, and then perforate
through the expandable metal sleeves of the annular barriers and even through the
casing collars. The adjacent non-perforated annular barriers will provide the zonal
isolation around the hydra-carbon-producing zone. Furthermore, when producing, the
hydra-carbon-producing zones move and then the perforated zone can easily be patched
off and new perforations at another location can be made for providing access to the
hydra-carbon-producing zone.
[0037] As can be seen from Fig. 1, after perforation some of the expanded metal sleeves
of the annular barriers have a plurality of perforations 21 and fractures 22 extending
further into the formation. The fractures are mainly created by a subsequent fracturing
operation.
[0038] In Fig. 2, the casing section having annular barriers has a first end part 23 and
a second end part 24, and at least the first end part has at least 1 metre which is
free from annular barriers, so that the casing section can be mounted by a rough neck.
The annular barriers 10 are arranged with a mutual distance D
AB of less than 100 cm, preferably less than 50 cm. Each annular barrier 10 has a barrier
length L
B of 1-2.5 metres as shown in Fig. 3B. The annular barriers of Fig. 3A have a common
longitudinal extension L
A of at least 50% of the casing length L
C. In Fig. 3B, the casing section is shown having a base pipe 25 and each of the expandable
metal sleeves 11 surrounds and fastens to the same base pipe 25, forming annular spaces
26 between the expandable metal sleeves 11 and the base pipe 25.
[0039] Each annular space may comprise at least one thermally decomposable compound, which
compound is thermally decomposable below a temperature of 400°C and is adapted to
generate gas or super-critical fluid upon decomposition. Thus, the decomposition of
the compound is activated by a temperature increase, and the annular barriers are
in this way expanded without pressurising the well tubular metal structure from within.
The compound comprises nitrogen. The compound is selected from a group consisting
of: ammonium dichromate, ammonium nitrate, ammonium nitrite, barium azide, sodium
nitrate or a combination thereof. The compound decomposes at temperatures above 100°C,
preferably above 180°C. The annular space is pre-pressurised to a pressure above 5
bar, preferably above 50 bar and more preferably above 100 bar, even more preferably
above 250 bar. The compound is present in the form of a powder, a powder dispersed
in a liquid or a powder dissolved in a liquid.
[0040] As seen in Fig. 9, the base pipe may also have at least one opening 27 opposite each
of the expandable metal sleeves 11 for expanding the expandable metal sleeves by allowing
pressurised fluid to enter the openings. In another embodiment, the annular barriers
may further comprise a valve or valve assembly in fluid communication with the openings.
The valve assembly operates between a first position in which fluid is allowed to
enter the annular space to expand the expandable metal sleeve and a second position
in which the opening is blocked and even permanently blocked. The valve assembly may
be arranged outside the base pipe and connected to the opening by means of flow lines.
The valve assembly may, in the second position, also equalise the pressure within
the space with the pressure in the annulus surrounding the well tubular metal structure.
[0041] In Figs. 3A and 3B, the expandable metal sleeves 11 are fastened to the base pipe
25 by means of welding, but in another embodiment the expandable metal sleeve may
be fastened to the base pipe by means of crimping and/or connection parts connecting
the expandable metal sleeves to the base pipe in known ways.
[0042] In Figs. 4A and 4B, the expandable metal sleeves 11 of the casing section 3 are connected
to form part of the base pipe 25, so that an inner face 28 of the expandable metal
sleeves 11 forms part of an inner face 29 of the base pipe 25. The expandable metal
sleeves thus form the base pipe together with tubular connection parts 31, and the
expandable metal sleeves of the casing section are connected indirectly by means of
the tubular connection parts.
[0043] In another embodiment, the expandable metal sleeves of the casing section are connected
directly end to end in an overlapping manner, forming a connection area in the overlapping
part. Thus, the expandable metal sleeves of each casing section having annular barriers
may be connected directly or indirectly, forming the connection area 32, as seen in
Figs. 4A and 4B. In a subsequent operation, a patch may be expanded inside the casing
section, so that each end of the patch overlaps the connection area. The connection
area is an area which is more rigid than the expandable metal sleeves, and the connection
area does not expand when the expandable metal sleeves expand. Thus, the connection
areas can be used for support for the patch. The connection areas also provide the
base pipe with stability both before and after expansion of the expandable metal sleeve.
[0044] In Fig. 4B, the expandable metal sleeve 11 forms an end of the casing section 3,
so that the expandable metal sleeve 11 is connected to the next casing section 3 by
means of a casing collar 4.
[0045] In Figs. 3A-4B, each expandable metal sleeve 11 comprises a plurality of sealing
elements 33 and the expandable metal sleeves also comprises sections 34 having an
increased thickness, which sections 34 are expanded less than other sections 35 of
the expandable metal sleeve 11.
[0046] In Figs. 6 and 8, each sealing element 33 comprises a sealing part 36 and key rings
37 as back-up to the sealing part 36. The section 34 having an increased thickness
creates a groove 39 in which the sealing part 36 and key rings 37 are arranged. As
seen in Fig. 8, the expandable metal sleeve may have a first thickness T1 opposite
the groove 39 and a second thickness T2 outside the groove in the other sections 35.
So the other sections 35 may have different thicknesses but thicknesses that are smaller
than the thickness of section 34 having the increased thickness. In Fig. 10, an intermediate
element 38 is arranged between the split ring-shaped retaining element in the form
of key rings 37 and the sealing element 36. In this embodiment, the split ring-shaped
retaining element 37 partly overlaps the intermediate element 38. The intermediate
element 38 may be made of a flexible material and is adapted to maintain the split
ring-shaped retaining element 37 in position and function as protection and support
of the sealing element 36. The split ring-shaped retaining element or key rings 37,
the intermediate element 38 and the sealing element 36 are placed in the groove 39
between the first and second projections, i.e. sections 34.
[0047] In Fig. 9, each sealing element 33 comprises a coiled spring or coiled springs 41
underneath a sealing sleeve 42 having an aperture 43. All the components of the sealing
elements 33 in Fig. 9 are of metal and are thus very suitable in high temperature
wells.
[0048] In Figs. 5a and 5B, the expandable metal sleeve 11 has a first end 14 and a second
end 15 and an outer face 16 facing the wellbore/borehole. The annular barrier 10 comprises
a first end part 17 having a first end 17A connected to the first end 14 of the expandable
metal sleeve and a second end 17B for being mounted as part of the base pipe 25 of
the casing section 3 of the well tubular metal structure 1. The annular barrier 10
further comprises a second end part 18 having a first end 18A connected to the second
end of the expandable metal sleeve and a second end 18B for being mounted to another
annular barrier and as part of the well tubular metal structure. The first end 17A
of the first end part 17 is connected end to end to the first end 14 of the expandable
metal sleeve 11, and the first end 18A of the second end part 18 is connected end
to end to the second end 15 of the expandable metal sleeve. The second ends 17B, 18B
of the end parts are provided with male or female thread connections for being mounted
to corresponding male or female thread connections of other annular barriers of the
casing sections. Sealing means 46 is provided between the connections.
[0049] The invention also relates to a downhole method for completing a well having a wellbore,
in which the well tubular metal structure 1 is mounted from several casing sections
3 of the downhole completion system 100, then the well tubular metal structure is
provided in the wellbore, and subsequently the expandable metal sleeves of the annular
barriers are expanded to abut the wellbore. The expansion may be performed substantially
simultaneously by pressurising the well tubular metal structure or may be performed
sequentially, e.g. by means of a tool isolating part of the well tubular metal structure
opposite the opening(s).
[0050] Subsequently, at least one of the expandable metal sleeves is perforated, e.g. by
intervening by means of a perforation tool/gun, creating access of reservoir fluid
into the casing sections and into the well tubular metal structure. Prior to perforation,
measurements may be performed in order to determine where to perforate, i.e. where
the hydro-carbon fluid is present.
[0051] In the event that the well starts producing in a non-optimal manner, a patch 51 (shown
by dotted line in Fig. 1) made be inserted by means of a tool and expanded inside
the well tubular metal structure opposite of perforated expandable metal sleeve for
sealing off the perforations. Subsequently, new perforations across and through the
annular barriers can be made to provide access for the hydro-carbon containing fluid
to be produced up the well tubular metal structure.
[0052] 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.
[0053] By a casing string or well tubular metal structure is meant any kind of pipe, tubing,
tubular, liner, string etc. used downhole in relation to oil or natural gas production.
[0054] In the event that the perforation 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®.
[0055] 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.
1. A downhole completion system (100) for being arranged in a wellbore (2), comprising
several casing sections (3) having a casing length of 10-14 metres mounted as one
well tubular metal structure (1) by means of casing collars (4), wherein a number
of the several casing sections each comprises at least three annular barriers (10)
each comprising an expandable metal sleeve (11) configured to be expanded to abut
the wellbore, the annular barriers of each casing section having a common longitudinal
extension (LA) of at least 50% of the casing length (LC).
2. A downhole completion system according to claim 1, wherein at least one of the expanded
metal sleeves has a plurality of perforations (21).
3. A downhole completion system according to any of the preceding claims, wherein each
section has a first end part (23) and a second end part (24), at least the first end
part having at least 1 metre which is free from annular barriers.
4. A downhole completion system according to any of the preceding claims, wherein the
annular barriers are arranged with a mutual distance (DAB) of less than 100 cm, preferably less than 50 cm.
5. A downhole completion system according to any of the preceding claims, wherein each
annular barrier has a barrier length (LB) of 1-2.5 metres.
6. A downhole completion system according to any of the preceding claims, wherein each
casing section has a base pipe (25).
7. A downhole completion system according to claim 6, wherein each of the expandable
metal sleeves surrounds and fastens to the same base pipe, forming an annular space
(26) between each expandable metal sleeve and the base pipe.
8. A downhole completion system according to claim 7, wherein each space comprises at
least one thermally decomposable compound, which compound is thermally decomposable
below a temperature of 400°C and is adapted to generate gas or super-critical fluid
upon decomposition.
9. A downhole completion system according to claim 6, wherein the base pipe has at least
one opening (27) opposite each of the expandable metal sleeves for expanding the expandable
metal sleeves by allowing pressurised fluid to enter the openings.
10. A downhole completion system according to any of the claims 6-9, wherein the expandable
metal sleeves are fastened to the base pipe by means of welding, crimping or connection
parts connecting the expandable metal sleeves to the base pipe.
11. A downhole completion system according to claim 6, wherein the expandable metal sleeves
of each casing section are connected to form part of the base pipe, so that an inner
face (28) of the expandable metal sleeves forms part of an inner face (29) of the
base pipe.
12. A downhole completion system according to claim 11, wherein the expandable metal sleeves
of each casing section are connected directly or indirectly, forming a connection
area (32).
13. A downhole method for completing a well (5) having a wellbore (2), comprising:
- mounting a well tubular metal structure (1) from several casing section (3) of the
downhole completion system (100) according to any of the claims 1-12,
- providing the well tubular metal structure in the wellbore, and
- expanding the expandable metal sleeves (11) of the annular barriers (10) to abut
the wellbore.
14. A downhole method according to claim 13, further comprising perforating at least one
of the expandable metal sleeves, creating access of reservoir fluid into the casing
sections and into the well tubular metal structure.
15. A downhole method according to claim 14, further comprising expanding a patch (51)
inside the well tubular metal structure opposite the perforated expandable metal sleeve
for sealing off perforations (21).