APPAREIL ET METHODE DE PENETRATION DU CIMENT ENTOURANT UN TUBE

APPARATUS AND METHOD FOR PENETRATING CEMENT SURROUNDING A TUBULAR

Abrégé français

Un appareil et un procédé pour pénétrer le béton (300) entourant une tubulure (200) cimentée à une formation (400). Lappareil comprend un orifice (10) à travers la paroi de la tubulure (200) et un canal de fluide intermédiaire (102) dans un élément rapporté (100) à lintérieur de lorifice. Un manchon intérieur (120) peut être disposé sur la surface intérieure de la paroi de la tubulure (200). Le manchon intérieur (120) est mobile entre une position fermée à laquelle la communication fluidique entre lintérieur de la tubulure et lorifice est empêchée, et une position ouverte à laquelle la communication fluidique entre lintérieur de la tubulure et lalésage est permise. Un fluide abrasif ou un fluide de gravure est acheminé par le canal (102) pour retirer le béton ou lélément rapporté (100) ou lensemble piston.

Abrégé anglais

Apparatus and method for penetrating cement (300) surrounding a tubular (200) cemented to a formation (400). The apparatus comprises a bore (10) through the tubular wall (200), and an intermediate fluid channel (102) in an insert (100) within the bore. An inner sleeve (120) may be disposed on the interior surface of the tubular wall (200). The inner sleeve (120) is movable between a closed position wherein fluid connection between the interior of the tubular and the bore is prevented, and an open position wherein fluid connection between the interior of the tubular and the bore is allowed. An abrasive and/or etching fluid is supplied through the channel (102) to remove cement and/or the insert (100) or piston assembly.

Revendications

8
CLAIMS
1. Apparatus for penetrating cement (300) surrounding a tubular (200)
cemented to a formation (400), the apparatus comprising:
- a bore (10) through the tubular wall (200), and
- an intermediate fluid channel (102) in an insert (100) within the bore,
and
being characterized by:
an inner sleeve (120) disposed on an interior surface of the tubular wall
(200), the inner sleeve being movable between a closed position wherein fluid
connection between the interior of the tubular and the bore (10) is prevented,
and
an open position wherein fluid connection between the interior of the tubular
and
the bore (10) is allowed, and where the insert (100) is a piston assembly
disposed
in the bore (10) and movable in an axial direction of the bore (10), the
piston
assembly comprising a hardened tip (105) at an outer end and a piston (110) at
an
inner end, and the fluid channel (102) being provided through the piston
assembly
to the vicinity of the tip (105).
2. Apparatus according to claim 1, wherein the bore (10) through the
tubular
wall (200) is in a direction perpendicular to the tubular wall (200).
3. Apparatus according to claim 1 or 2, wherein the bore is provided with a
removable seal (140) near an exterior surface of the tubular.
4. Apparatus according to any one of the claims 1 to 3, wherein the insert
(100) within the bore (10) is erodible by an abrasive and/or etching fluid.
5. Apparatus according to any one of the claims 1 to 4, wherein the insert
is
disposed in a housing (101) made from a material that is more resistant to
abrasion and/or corrosion than the material of the tubular wall (200).
6. Apparatus according to any one of the claims 1 to 5, further comprising
a
substance (150) capable of swelling when a liquid is added thereto, the
swelling
substance (150) being disposed between the piston (110) and an interior wall

9
(103), and the interior wall (103) comprising ports (102) that are opened or
closed
by the inner sleeve (120).
7. .. Method for penetrating cement (300) surrounding a tubular (200) cemented
to a formation (400), the method comprising the following steps:
- providing a bore (10) through the tubular wall (200),
- providing a fluid from an interior of the tubular through an intermediate
fluid channel (102) being arranged in an insert (100) within the bore (10),
the fluid
being capable of removing cement and/or material from the insert (100)
surrounding the fluid channel,
wherein the method, before the step of providing the fluid, is further
characterized by the steps of:
- providing an inner sleeve (120) on an interior surface of the tubular
wall
(200),
- moving the inner sleeve (120) from a closed position wherein fluid
connection between the interior of the tubular and the bore (10) is prevented,
to an
open position wherein fluid connection between the interior of the tubular and
the
bore (10) is allowed, and
- forcing a hardened tip (105) from the interior of the tubular wall (200)
into
the cement with sufficient force to cause a groove and/or cracks in the cement
where the insert (100) is a piston assembly (110) disposed in the bore (10),
and
the fluid channel (102) is provided through the piston assembly (110) to the
vicinity
of the tip (105), and
where the step of forcing the hardened tip (105) into the cementing involves
applying hydraulic pressure from the interior of the tubular on the piston
(110)
rigidly connected to the tip (105).
8. .. Method according to claim 7, wherein the step of forcing the hardened
tip
into the cementing involves opening the fluid channel (102) from the interior
of the
tubular to an expandable substance (150) being disposed between the piston
(110) and an interior wall (103) and being arranged to exert a force on the
piston
(110), wherein the interior wall (103) comprises ports (102) that are opened
or
closed by the inner sleeve (120).

10
9. Method according to claim 7 or 8, wherein the step of providing the
fluid
involves providing an abrasive and/or etching fluid.
10. Method according to any one of the claims 7 to 9, wherein the step of
providing the fluid involves providing at least one chemical capable of
etching
cement and/or the material of the insert.

Description

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1
Apparatus and method for penetrating cement surrounding a tubular
INTRODUCTION
[0001] The present invention relates to an apparatus and a method for
penetrating cement surrounding a tubular.
BACKGROUND
[0002] A well extending through geological formations may be used for
exploration and production of oil and/or gas, water production and/or in
geothermal
applications. Building a well typically involves drilling a borehole,
inserting a steel
casing into the wellbore and cementing the casing to the formation. The casing
provides structural stability, for example by preventing weak rock or sand
from
caving into the borehole. When the cement is set, the next section is drilled
through the formation in the extension of the existing casing. A liner is then
hung
off of the casing, and cemented to the formation. This process can be repeated
until the well has reached the desired depth. A well may also comprise
sections of
uncased or open borehole, sections of casing or lining with sand screens,
sections
surrounded by gravel packs etc, as is well known in the art. However, for the
purposes of the following disclosure, only wellbores with a tubular steel
lining
cemented to the formation are considered. Further, a casing and a liner will
be
collectively referred to as a tubular in the following description and
accompanying
claims. In other words, no distinction will be made between a casing and a
liner in
the following.
[0003] In order to allow fluid flow from the formation into the wellbore, the
steel
tubular and cement must be penetrated at depths corresponding to a layer
containing oil and/or gas, an aquifer or the like, hereinafter referred to as
a
production zone. Conventionally, the perforation has been performed by using
an
explosive charge in a device known as a perforation gun. However, explosives
require special handling according to strict safety rules, they may damage the
formation and they have other disadvantages. Hence, there is a tendency to
avoid
explosives whenever possible.

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[0004] Any time after penetration, i.e. when a fluid path is established
between
the formation and the interior of the well bore, the production zone may be
`stimulated' in order to facilitate the fluid flow. Techniques for stimulating
a zone
involve hydraulic fracturing, in which hydraulic pressure is applied to force
open
cracks in the rock and insert sand or other granular material into the cracks.
When
the fracturing pressure is removed, the granular material remains in the
cracks and
keeps them open. Known stimulation techniques also include injection of acid,
solvents, surfactants etc in order to reduce the viscosity of the production
fluid or
the adhesion of production fluid to the surrounding rock.
[0005] The purpose of the present invention is to overcome the problems of
prior
art, while keeping the benefits of well known techniques and equipment, in
particular to penetrate the cement surrounding a tubular cemented to a
formation
without using explosives.
SUMMARY OF THE INVENTION
[0006] According to the present invention, in a first aspect, this is
accomplished
by an apparatus for penetrating cement surrounding a tubular cemented to a
formation, the apparatus comprising a bore through the tubular wall and an
intermediate fluid channel disposed within an insert within the bore. In an
embodiment, an inner sleeve may be disposed on the interior surface of the
tubular wall, the inner sleeve being movable between a closed position wherein
fluid connection between the interior of the tubular and the bore is
prevented, and
an open position wherein fluid connection between the interior of the tubular
and
the bore is allowed. The bore through the tubular wall (200) may be provided
in a
direction perpendicular to the tubular wall.
In one embodiment, the insert is a piston assembly movably disposed in the
bore,
the piston assembly comprising a hardened tip at an outer end and a piston at
an
inner end, and the fluid channel being provided from the piston to the
vicinity of the
tip. In a further embodiment, the apparatus comprises a substance capable of
swelling when a liquid is added thereto, the swelling substance being disposed

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between the piston and an interior wall, and the interior wall comprising
ports that
are opened or closed by the inner sleeve.
[0007] In another aspect, the invention concerns a method for penetrating
cement
surrounding a tubular cemented to a formation, the method comprising the steps
of: providing a fluid from an interior of the tubular through an intermediate
fluid
channel, the fluid being capable of removing cement and/or material from an
insert
surrounding the fluid channel.
[0008] One embodiment of the method further comprises the step of forcing a
hardened tip from the tubular wall into the cement with sufficient force to
cause a
groove and/or cracks in the cement before providing the fluid. The groove
and/or
cracks provide a larger area of attack for the fluid. Forcing the hardened tip
into
the cementing may involve applying hydraulic pressure from the interior of the
tubular on a piston rigidly connected to the tip. Forcing the hardened tip
into the
cementing may also involve opening a fluid channel from the interior of the
tubular
to an expandable substance arranged to exert a force on the piston. Providing
the
fluid may involve providing an abrasive fluid or providing at least one
chemical
capable of etching cement and/or the material of the insert.
[0009] In an embodiment, the method further comprises prior to providing the
fluid, providing an inner sleeve on an interior surface of the tubular wall,
and
moving the inner sleeve from a closed position wherein fluid connection
between
the interior of the tubular and the bore is prevented, to an open position
wherein
fluid connection between the interior of the tubular and the bore is allowed.
[0010] Further embodiments and advantages of the invention will be apparent
from the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the invention will now be described with reference to
the
followings drawings, where:

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[0012] Fig. 1 is a schematic cross sectional view of an embodiment of the
invention;
[0013] Fig. 2 is a schematic cross sectional view of a further embodiment of
the
invention;
[0014] Fig. 3 is a schematic cross sectional view of an alternative embodiment
of
the invention;
DETAILED DESCRIPTION
[0015] The drawings are schematic and intended to illustrate the principles of
the
present invention. Hence, the figures are not to scale, and a number of
details are
omitted for the sake of clarity.
Figure 1 illustrates an embodiment of an apparatus to penetrate the cement 300
surrounding a tubular (200) cemented to a formation (400). A bore 10 extends
through the tubular wall 200. In figure 1 the bore extends through the tubular
wall
200in a direction perpendicular to the wall, i.e. radially with respect to the
tubular.
However, the bore 10 may also extend through the tubular wall 200 in a sloping
direction. The bore is provided with a removable seal (140) near an exterior
sur-
face of the tubular.
[0016] An intermediate fluid channel 102 within an insert 100 essentially
provides
a fluid path through the wall of the tubular. However, the diameter of the
intermediate fluid channel is considerably less than the diameter of the bore.
This
may be useful in applications where a number of ports are to be opened, e.g.
by a
drop ball, and a small pressure difference is desired over each port
corresponding
to the bore 10. Later, an abrasive fluid, for example slurry for hydraulic
fracturing,
can abrade the insert in order to fully open the port or bore. In such an
application,
the bore could be lined 101 with a hard material, e.g. tungsten carbide (WC),
ceramic material or hardened steel, and the insert would be manufactured form
a
softer material, for example a softer steel or other metal e.g. aluminium.
This

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method can also be used to penetrate the cement around the casing as
illustrated
in figure 1.
[0017] An inner sleeve 120 is disposed on the interior surface of the tubular
wall
200. The inner sleeve is movable between a closed position wherein fluid
5 connection between the interior of the tubular and the bore is prevented,
and an
open position wherein fluid connection between the interior of the tubular and
the
bore is allowed. The sleeve is provided to close the bore during run in, and
may be
rotated around, or alternatively displaced axially along, the axis of rotation
of the
tubular. In both cases, at least one opening in the inner sleeve is aligned
with the
bore in the open position, and not aligned in the closed, or run-in, position
shown
in the figures 1-3.
[0018] Fig. 2 illustrates a preferred embodiment of the apparatus, wherein the
insert 100 is a piston assembly disposed in the bore 10. The bore is provided
with
a removable seal (140) near an exterior surface of the tubular. The piston
assembly can be displaced in the axial direction of the bore 10, which
corresponds
to the radial direction of the tubular. When the inner sleeve 120 is moved to
its
open position, hydraulic pressure may work in the interior surface of the
piston
110, i.e. to the left on Fig. 2. It is readily seen that the pressure and
piston area
can be adapted such that the piston assembly is forced radially outwards with
respect to the tubular, i.e. towards the right hand side of Fig. 2, such that
the
hardened tip 105 penetrates the seal 140 and enters a distance into the cement
300.
[0019] To achieve this, the piston assembly comprises a hardened tip 105 at an
outer end rigidly connected to a piston 110 at an inner end of the bore. The
tip can
be made of a ceramic material, as ceramics tend to withstand compression
forces
quite well even if they are brittle and break easily when subjected to tensile
forces.
Alternatively, the tip 105 can be made of hardened steel or another suitable
material. The tip is sufficiently hard to penetrate a distance into the cement
and
provide a groove and/or cracks. Typical compressive strength of the cement is
from about 3000 psi and above, and the tip is forced into the cement with
sufficient

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force in order for the pressure against the cement under the tip to become
larger
than the compressive strength. The enlarged surface of the groove and/or
cracks
provides an area of attack for an etchant or abrasive fluid as described
below. This
fluid is supplied from the interior of the tubular (to the left on figures 1-
3) through
the fluid channel(s) 102, which are provided through the piston assembly to
the
vicinity of the tip 105.
[0020] The seal 140 in the figures 1-3 is intended to protect the bore during
run
in. It can be provided as a lid as illustrated. Alternatively, the seal 140
can be a
portion of the tubular wall 200 with reduced thickness, or a plug made from a
suitable material such as a plastic or resin. In particular, the tip 105 in
figs. 2 and 3
should penetrate seal 140 without requiring too much force, so the seal 140
should
just be able to withstand the forces it may encounter during run-in.
[0021] Figure 3 resembles figure 2 in that it comprises a piston assembly
within a
housing. In Fig. 3, however, a swelling substance 150 is disposed between the
piston 110 and an interior wall 103. The interior wall 103 is provided in the
bore 10
facing the inner sleeve 120. The interior wall 103 has ports or fluid channels
102
as discussed above. The ports 102 may be opened by the inner sleeve 120, such
that liquid can be supplied to the swelling material. When liquid is supplied,
the
swelling material will exert equal forces in opposite directions on the
interior wall
103 and the piston 110. Hence, the interior wall 103 must be able to withstand
the
forces required to drive the tip 105 into the cement 300.
[0022] In all of the embodiments above, a fluid is provided from the interior
of the
tubular through an intermediate fluid channel 102. The fluid must be capable
of
removing cement and/or material from an insert surrounding the fluid channel.
A
slurry containing sand or ceramic particles, such as a slurry used for
hydraulic
fracturing, is known to abrade metal inserts and cement. The amount of abraded
material is proportional to the area in which the abrasive fluid is allowed to
work.
Hence, a small groove tends to be enlarged by the abrasion. Similarly, cracked
cement tends to be abraded more easily than solid cement. Alternatively, the
fluid
may be corrosive or etching. For example, it is well known that NaOH etches
aluminium, and hence could be used to remove aluminium inserts. Similarly, HCI

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could be used for etching the cement 300 and/or stimulate a limestone
formation.
Obviously, different fluids could be used at separate times. The choice of
suitable
materials and chemicals are known in the art, and hence left to the skilled
person.
[0023] While the invention has been described with reference to certain
embodiments, the scope of the invention is defined by the following claims.

Dessin représentatif