DOWNHOLE COMPLETION
Field of the invention
The present invention relates to a downhole completion comprising a production
casing and a sliding sleeve assembly connected as part of a production casing,
comprising a tubular part and a tubular sleeve.
Background art
In a casing downhole, it is often necessary to pressurise the interior of the
casing, or parts of it, during completion or operation of the well.
The interior is pressurised to expand one or more components in predetermined
positions along the casing string. These components may be expandable annular
barriers, rock anchors, etc.
Common for these components is that a high pressure is necessary to expand
them. The high pressure may influence on other components and in severe
circumstances in fact damage these components.
Therefore, these components are protected by for instance sliding elements
which are adapted to be positioned in front of the components. However, since
the components to be expanded require higher and higher pressure to obtain
expansion, the sealing properties of the sliding elements are not sufficient to
secure that the other components are not damaged.
Summary of the invention
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 comprising a sliding sleeve assembly
which is adapted to protect and seal an opening in a tubular section and/or a
component inserted in the opening, even during high interior pressurising.
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,
comprising
- a production casing, and
- a sliding sleeve assembly connected as part of a production casing, comprising:
- a tubular part forming part of the production casing and having a
recess, an inner face, an opening and an axial extension, and
- a tubular sleeve slidable within the recess and having an outer face and
being slidable in the axial extension along the inner face between a first
position, wherein fluid is allowed to flow through the opening, and a second
position, wherein the fluid is hindered from flowing through the opening,
wherein a sealing element is arranged in connection with the sleeve at its outer
face.
In an embodiment, the opening may have a width in the axial extension and the
sealing element may have a width which is larger than the width of the opening.
Furthermore, the tubular sleeve may have at least one circumferential groove
arranged at its outer face.
Moreover, the sealing element may be arranged in the groove.
In addition, the sleeve may have at least two circumferential grooves, each
groove comprising a sealing element.
Also, the tubular part may have a recess in which the sleeve slides.
In an embodiment, the opening may have a width in the axial extension and the
sealing elements may be arranged with an axial distance which is larger than the
width of the opening.
Moreover, the sealing element may be a chevron seal or an O-ring.
Additionally, the sleeve may have an inner face comprising indentations.
Furthermore, the opening may comprise a valve, such as an inflow control valve,
a flow restriction, a throttle or similar restriction.
Also, the tubular part may have threads for connecting the tubular part with
other tubular parts to form a casing.
The invention furthermore relates to use of the downhole completion described
above in connection with a casing string in a borehole.
Brief description of the drawings
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 sliding sleeve assembly connected as part of a casing in its first
and open position,
Fig. 2 shows the sliding sleeve assembly of Fig. 1 in its second and closed
position,
Fig. 3 shows another embodiment of the sliding sleeve assembly,
Fig. 4 shows another embodiment of the sliding sleeve assembly,
Fig. 5 shows yet another embodiment of the sliding sleeve assembly, and
Fig. 6 shows a downhole system according to the invention.
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
Fig. 1 shows a partial view of a downhole completion 100 of a sliding sleeve
assembly 1 connected as part of a production casing 4. The sliding sleeve
assembly 1 comprises a tubular part 2 having an inner face 3, an opening 5 and
an axial extension 28. The tubular part 2 is connectable with other tubular parts
to form a production casing or casing string. The connection between the tubular
part 2 and the production casing 4 is most often a threaded connection. The
sliding sleeve assembly 1 further comprises a tubular sliding sleeve 26 having an
outer face 8 and being slidable in the axial extension 28 along the inner face 3 of
the tubular part. In Fig. 1, the sliding sleeve assembly 1 is shown in a first
position, wherein fluid is allowed to flow through the opening 5, and in Fig. 2, the
sliding sleeve assembly 1 is shown in a second position, wherein the fluid is
hindered from flowing through the opening. The sliding sleeve assembly 1 further
comprises a sealing element 9 arranged in connection with the sleeve in
circumferential grooves 10 at the outer face 8 of the tubular sleeve 26.
By having a sliding sleeve 26 in a production casing of a completion 100 or
system 100, a production section producing water can be closed off.
Furthermore, such sliding sleeve can be used to protect a completion component
50 (shown in Figs. 4-6) pressurising a casing in order to expand e.g. an annular
barrier. Not all components 50 can withstand the high pressure required to
expand annular barriers, and thus it may be necessary to seal off these
components 50 when making the completion and subsequently open them in
order to use the functionality of the component 50.
The sliding sleeve slides in a recess in the tubular part 2 so that the sleeve 26
does not limit the space within the casing, and thus a sliding sleeve in a recess
27 does not decrease the overall inner diameter of the tubular part 2 and thus of
the casing 4. When making the completion, it is very important that the inner
diameter is not reduced unnecessarily as further components or tubulars are to
pass the already installed casing 4.
As can been seen in Fig. 1, the opening 5 has a width w in the axial extension of
the tubular part 2, and the sealing element 9 has a width ws which is larger than
the width of the opening. The width ws of the sealing element 9 being larger than
the width w of the opening 5 ensures that the sealing element does not get
stuck when the sliding sleeve assembly 1 passes the opening 5. If the sealing
element 9 is smaller than the width w of the opening, the sealing element may
get stuck at an edge of the opening 5 and be pulled up and squeezed between
the outer face 8 of the tubular sleeve 26 and the inner face of a recess 27. In this
situation, the sealing element 9 is no longer able to seal off the opening 5.
The sliding sleeve 26 has an inner face 15 comprising indentations 11 for moving
the sleeve in the recess by means of a key tool extending into the indentations
and forcing the sleeve 26 to slide axially along the inner face of the recess 27.
In Figs. 1 and 2, the sealing elements 9 are arranged with an axial distance
between them which is larger than the width w of the opening 5 so that the
sealing elements 9 in the second position is arranged on opposite sides of the
opening 5, thereby sealing the opening 5.
In Fig. 3, the sliding sleeve assembly 1 comprises one sealing element 9 and one
indentation 11. The sliding sleeve assembly 1 is shown in its closed and second
position. The width ws of the sealing element 9 is more than twice the width w of
the opening 5, meaning that the sealing element 9 covers the opening 5 and part
of the inner face of the recess 27 surrounding the opening 5 in order to seal the
opening.
The sealing element 9 is a chevron seal in Figs. 1-3 and an O-ring in Fig. 4. The
chevron seals have V-shaped parts, the tips of which point towards the outer face
8 of the sliding sleeve 26 or in the opposite direction. In Fig. 4, the opening 5
comprises a completion component 50, such as a valve 13, such as an inflow
control valve, a flow restriction, a throttle or similar restriction. The sliding sleeve
assembly 1 is shown in its first and open position, in which fluid may flow from
the surrounding annulus or formation into the interior of the tubular part 2.
The sliding sleeve assembly 1 of Fig. 5 is shown in its second and closed position,
in which fluid from the surrounding annulus or formation is hindered from
entering into an interior of the production casing 4. When the sleeve is moved to
its open position, the fluid may enter from the formation into the interior of the
tubular part 2 through the valve 13. The V-shaped parts of the chevron seal point
in a direction perpendicular to the direction shown in Figs. 1-3 and thus point in a
direction along the axial extension.
The sliding sleeve 26 is shown in its closed position, in which fluid from the valve
13 is prevented from flowing into the production casing 4, but also preventing the
fluid in the production casing from escaping through the inflow control valve. The
sliding sleeves 26 are arranged opposite the valves 13 and are slidable from an
open position to a closed position, causing the sleeves 26 to slide back and forth
in recesses 27 in the wall of the production casing 4 and form part of the wall
thickness.
Having a slidable sleeve 26 opposite a valve 13 as part of a casing wall allows for
closing of the sliding sleeve 26 when the production casing 4 is pressurised from
within to perform an operation requiring highly pressurised fluid, such as when
expanding annular barriers. When the operation requiring high pressure is
finalised, the sliding sleeve 26 can be opened, and fluid from the annulus is able
to flow into the production casing 4 through the valve 13.
Having a sleeve sliding in a recess in the production casing 4 ensures that the
inner diameter of the production casing is not decreased, which is advantageous
as such a decrease may limit subsequent operations in the well.
In Fig. 5, the sliding sleeve assembly 1 comprises an inflow control valve, such as
a constant flow valve. In order to control the flow, the valve comprises a spring
element 12A, 12B. The spring element 12A, 12B is springy along the axial
direction of the valve perpendicular to the axial extension of the production
casing for providing a spring force. The housing has a seat 35 and a membrane
31, and the spring element is a diaphragm moving towards the seat to close any
valve openings 36 in the valve 13. The spring element 12A, 12B comprises two
spring plates, each formed as a star, arranged one on top of the other and
displaced in relation to each other so that the tips of the star-shaped plates 12A,
12B form openings there between. When the pressurised fluid from a reservoir
flows in through a screen 20 in the inlet, the fluid forces the star-shaped plates
12A, 12B down towards the seat 35 and the membrane 31, thereby minimising
the passage through the openings. The membrane 3 1 has an aperture in its
centre through which the fluid passes before entering the outlet 7 and after
passing the openings.
The tubular part 2 of the sliding sleeve assembly 1 has fastening means for being
fastened to the production casing 4 and thereby form part of a production casing
string. The fastening means may be threads for creating a threaded connection
with the rest of the production casing 4.
Fig. 6 shows a downhole system 100 comprising a casing string or production
casing 4 and at least one sliding sleeve assembly 1 connected with the casing
string 4. The downhole system 100 comprises several sliding sleeve assemblies 1
along the casing string, also called the production casing. In this way, the entry
of fluid from the formation can be controlled by opening and closing the sliding
sleeves. Furthermore, the casing can be pressurised from within by closing the
sliding sleeve assemblies 1 when performing an operation requiring high
pressurised fluid to expand expandable sleeves of annular barriers or a fixation
device, such as a rock anchor.
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 oilcontaining
fluid, etc. Gas, oil, and water fluids may thus all comprise other
elements or substances than gas, oil, and/or water, respectively.
By a production casing is meant any kind of pipe, tubing, tubular, liner, string
etc. used downhole in relation to oil or natural gas production and thus the
production casing is the casing in which the hydro carbons, such as oil and/or
gas, flow in order to bring up oil and/or gas from the reservoir. The production
casing may comprise a surface casing and a hanging casing. The sliding sleeve is
used to seal off or expose an opening through which the oil and/or gas or water
from the formation/reservoir could flow through, and thus closing the sleeve
seals off the opening so that oil and/or gas and/or water can no longer flow into
the production casing.
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.
Claims
1. A downhole completion (100), comprising
- a production casing (4), and
- a sliding sleeve assembly (1) connected as part of a production casing (4),
comprising:
- a tubular part (2) forming part of the production casing and having a
recess (27), an inner face (3), an opening (5) and an axial extension (28),
and
- a tubular sleeve (26) slidable within the recess and having an outer face
(8) and being slidable in the axial extension along the inner face between a
first position, wherein fluid is allowed to flow through the opening, and a
second position, wherein the fluid is hindered from flowing through the
opening,
wherein a sealing element (9) is arranged in connection with the sleeve at its
outer face.
2. A downhole completion according to claim 1, wherein the opening has a
width (w ) in the axial extension and the sealing element has a width (ws)which
is larger than the width (w ) of the opening.
3. A downhole completion according to claim 1 or 2, wherein the tubular
sleeve has at least one circumferential groove (10) arranged at its outer face.
4. A downhole completion according to claim 3, wherein the sealing element is
arranged in the groove.
5. A downhole completion according to any of the preceding claims, wherein
the sleeve has at least two circumferential grooves, each groove comprising a
sealing element.
6. A downhole completion according to claim 5, wherein the opening has a
width (w ) in the axial extension and the sealing elements are arranged with an
axial distance which is larger than the width of the opening.
7. A downhole completion according to any of the preceding claims, wherein
the sealing element is a chevron seal or an O-ring.
8. A downhole completion according to any of the preceding claims, wherein
the sleeve has an inner face (15) comprising indentations (11).
9. A downhole completion according to any of the preceding claims, wherein
the opening comprises a valve (13), such as an inflow control valve, a flow
restriction, a throttle or similar restriction.