U.S. patent application number 11/671401 was filed with the patent office on 2008-08-07 for apparatus and method for cleaning a well.
Invention is credited to Irvine Cardno Brown.
Application Number | 20080185150 11/671401 |
Document ID | / |
Family ID | 39675184 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080185150 |
Kind Code |
A1 |
Brown; Irvine Cardno |
August 7, 2008 |
Apparatus and Method for Cleaning a Well
Abstract
The present invention relates to apparatus and a method for
cleaning a well. In an embodiment, the apparatus (10) includes a
well cleaning tool (12) coupled to a support string 26, which may
be located in well tubing (14) to permit cleaning of the well
tubing (14). The cleaning tool (10) may restrict fluid flow past
the tool, for example, in an annular space between the tool (12)
and the well tubing (14). Further, the tool (12) can be translated
relative to the well tubing (14) to displace fluid along the well
tubing (14) and thus clean the well.
Inventors: |
Brown; Irvine Cardno;
(Aberdeen, GB) |
Correspondence
Address: |
LUNDEEN & LUNDEEN, PLLC
PO BOX 131144
HOUSTON
TX
77219-1144
US
|
Family ID: |
39675184 |
Appl. No.: |
11/671401 |
Filed: |
February 5, 2007 |
Current U.S.
Class: |
166/311 ;
166/173 |
Current CPC
Class: |
E21B 37/00 20130101 |
Class at
Publication: |
166/311 ;
166/173 |
International
Class: |
E21B 37/00 20060101
E21B037/00 |
Claims
1. A well cleaning tool for location in well tubing to be cleaned
on an associated support string, the cleaning tool adapted to be
configured to restrict fluid flow past the tool and to be
translated relative to the well tubing to displace fluid along the
well tubing and thereby clean the well.
2. A well cleaning tool as claimed in claim 1, wherein the tool is
adapted to be configured such that fluid flow past the tool is
substantially prevented.
3. A well cleaning tool as claimed in claim 1, wherein the tool is
adapted to be configured to restrict fluid flow past the tool along
an annulus defined between the well tubing and the support
string.
4. A well cleaning tool as claimed in claim 1, wherein the cleaning
tool is movable between a first configuration where fluid flow past
the cleaning tool is permitted, and a second configuration where
fluid flow past the cleaning tool is substantially prevented.
5. A well cleaning tool as claimed in claim 4 wherein the first
configuration is a deactivated, running configuration, and the
second configuration is an activated, cleaning configuration.
6. A well cleaning tool as claimed in claim 1, wherein the cleaning
tool is adapted to permit fluid flow in one direction past the
tool, and to restrict fluid flow past the tool in an opposite
direction.
7. A well cleaning tool as claimed in claim 1, wherein the cleaning
tool is arranged such that the tool automatically restricts fluid
flow when the tool is translated in one direction along the well
tubing, but permits fluid flow when the tool is translated in an
opposite direction.
8. A well cleaning tool as claimed in claim 1, wherein the cleaning
tool is adapted to abut a wall of the well tubing in order to
restrict fluid flow.
9. A well cleaning tool as claimed in claim 1, wherein the cleaning
tool is coupled to tubing of the support string.
10. A well cleaning tool as claimed in claim 9, wherein the tubing
of the support string is adapted to permit flow of completion fluid
therethrough and into the well.
11. A well cleaning tool as claimed in claim 1, wherein the
cleaning tool comprises at least one abutting element for abutting
the wall of the well tubing, the element serving for permitting and
restricting fluid flow past the tool.
12. A well cleaning tool as claimed in claim 11, wherein the
abutting element is movable between a deactivated configuration and
an activated configuration, which corresponds to deactivated and
activated configurations of the tool, for selectively engaging an
internal surface of the tubing.
13. A well cleaning tool as claimed in claim 10, wherein the
abutting element is adapted to be biased into abutment with the
well tubing wall.
14. A well cleaning tool as claimed in claim 4, wherein the tool
comprises an actuating mechanism for moving the tool between the
deactivated and activated configurations.
15. A well cleaning tool as claimed in claim 14, wherein the
actuating mechanism is adapted to exert a radial actuating force on
the abutting element.
16. A well cleaning tool as claimed in claim 10, wherein the
abutting element defines a cleaning surface for cleaning an
internal wall of the well tubing during translation of the cleaning
tool through the tubing.
17. A well cleaning tool as claimed in claim 16, wherein the
cleaning tool is adapted to be movably mounted relative to the
support string, and comprises a body mounted for movement relative
to the support string along a length thereof.
18. Apparatus for cleaning a well, the apparatus comprising: a
support string adapted to be located in well tubing to be cleaned;
at least one well cleaning tool coupled to the support string, the
well cleaning tool adapted to be configured to restrict fluid flow
past the tool and to be translated relative to the well tubing to
displace fluid along the well tubing and thereby clean the
well.
19. Apparatus as claimed in claim 18, wherein the apparatus
comprises a plurality of cleaning tools, and comprises a first
cleaning tool adapted to define a first cleaning diameter for
cleaning a first section of well tubing of a corresponding first
diameter and a second cleaning tool adapted to define a second
cleaning diameter for cleaning a second section of well tubing of a
corresponding second diameter.
20. Apparatus as claimed in claim 19, wherein at least one of the
cleaning tools is adapted to be movably mounted relative to the
support string, and comprises a body mounted for movement relative
to the support string along a length thereof.
21. Apparatus as claimed in claim 19, wherein at least one of the
cleaning tools is movable relative to at least one other cleaning
tool.
22. Apparatus as claimed in claim 19, wherein a lower cleaning tool
is secured against movement relative to the support string, and an
upper cleaning tool is movably mounted relative to the support
string.
23. Apparatus as claimed in claim 19, wherein upper cleaning tool
is adapted to initially be provided in a deactivated configuration
permitting fluid flow past the tool, lower cleaning tool is adapted
to be provided in an activated configuration, restricting fluid
flow past the tool so as to urge fluid along the well tubing and
past the upper tool during movement of the lower cleaning tool.
24. Apparatus as claimed in claim 18, wherein the support string is
adapted to permit fluid to be pumped therethrough and into the well
to facilitate cleaning the wellbore.
25. Apparatus as claimed in claim 18, wherein the apparatus
comprises a flow restrictor, the restrictor adapted to be located
within the support string, to define a barrier between fluid within
the string above the restrictor and fluid below the restrictor.
26. Apparatus as claimed in claim 25, wherein the flow restrictor
is adapted to be pumped down the support string using completion
fluid for defining a barrier between the completion fluid and fluid
present in the well and in the string below the restrictor.
27. A method of cleaning a well, the method comprising the steps
of: locating a well cleaning tool in well tubing to be cleaned on
an associated support string; configuring the well cleaning tool to
prevent fluid flow past the tool; and translating the well cleaning
tool relative to the well tubing to displace fluid along the well
tubing to thereby clean the well.
28. A method as claimed in claim 27, wherein the cleaning tool is
translated along the support string relative to the well tubing in
a direction from surface to a downhole location, to displace fluid
in the well tubing and up the support string to surface.
29. A method as claimed in claim 27, wherein the cleaning tool is
secured relative to the support string and translated relative to
the well tubing in a direction towards the surface, to displace
fluid in the well tubing along the tubing to surface, by
translating the support string along the well tubing.
30. A method as claimed in claim 27, wherein the method comprises
the step of defining a barrier between fluid in the well tubing and
replacement fluid pumped into the well tubing.
Description
[0001] The present invention relates to well cleaning in the field
of the oil and gas exploration and production industry. In
particular, but not exclusively, the present invention relates to
apparatus and a method for cleaning a well.
[0002] In the oil and gas exploration and production industry, a
borehole is drilled from surface to gain access to well fluids in
subterranean rock formations. The borehole is typically drilled to
a first depth, and well tubing known as casing is then located in
the drilled section and cemented in place, both to support the
drilled rock formations and to prevent formation fluids from
entering the borehole. The borehole is then extended to a further
depth, and a smaller diameter well tubing known as a liner is
run-in to the extended section, coupled to the lower end of the
casing, and also cemented in place. Once the borehole has been
extended and lined to a desired depth, a completion string is
run-in to enable completion of the well and recovery of well fluids
from a particular rock formation.
[0003] However, during drilling of the borehole, a drilling fluid
known in the industry as `drilling mud` is utilised to carry drill
cuttings to surface; to form a skin on drilled rock formations to
prevent mud loss; to cool the drill bit; to drive a downhole motor
coupled to the drill bit (if used); and to maintain hydrostatic
pressure overbalance across the rock formations, to prevent blowout
of formation fluids.
[0004] Accordingly, before the well can be completed, it is
necessary to clean the borehole by removing residual drilling mud,
formation fluids, drill cuttings and the like from the well tubing.
This has conventionally been achieved by pumping relatively large
volumes or `pills` of a viscous fluid downhole. The viscous fluid
is often of greater weight (density) than the drilling mud, and
serves to carry the drilling mud, cuttings and the like to surface.
These pills of viscous fluid are followed by a completion fluid,
typically a saturated salt solution known as `brine`, which is used
to replace the fluids removed from the borehole. The weight of the
brine is chosen to suit the particular well, to ensure that the
well remains overbalanced both during and subsequent to the
cleaning operation.
[0005] This cleaning operation presents a number of problems,
particularly on offshore rigs where deck space is at a premium. In
particular, a great deal of deck space is required to store the
concentrates of chemicals needed to make the pills of viscous fluid
needed to clean the well. Furthermore, a number of valuable mixing
pits are needed to store the prepared completion brine and to
prepare the pills of viscous fluid, and these tanks need to be
cleaned before the brine or viscous fluid can be pumped into the
tanks, as they may previously have been used for storing drilling
mud.
[0006] Also, when the viscous pills and completion brine are pumped
downhole, a large fluid interface is formed between the drilling
mud and the viscous fluid/brine. This interface fluid is a mixture
of fluids including drilling mud, brine and the viscous fluid and
cannot be cleaned to recover the valuable drilling mud. The
interface fluid must therefore be temporarily stored on the rig
either for subsequent shipping offsite, or for injection into an
abandoned well. As the volume of interface fluid is relatively
large, this utilises a significant number of mixing pits.
[0007] Additionally, as the drilling mud is designed to coat the
surfaces of the drilled formations, it has been found difficult to
remove the mud from the walls of the well tubing. To overcome this,
it is necessary to pump the pills of viscous fluid and the brine at
relatively high fluid flow rates, whilst rotating the drill string
in the well tubing. This promotes turbulent flow, which assists in
removing mud solids adhered to the wall of the casing; carrying the
removed solids to surface; and in reducing the size of the fluid
interface.
[0008] However, maintaining a high fluid flow rate has a consequent
effect upon costs. Also, if it is desired to re-inject the
interface fluids into an abandoned well, it is necessary to reduce
the fluid flow rate to suit the injection rate that may be achieved
using a cuttings re-injection unit, with a consequent effect upon
the injected fluid flow rate and thus on the volume of interface
fluids. Also, it is often necessary to continue pumping the viscous
fluid/brine for long periods of time, often twenty-four hours or
more, in order to achieve a desired level of cleaning. This results
in significant delays in completing the well, with associated cost
implications.
[0009] Even when this cleaning operation has been carried out, it
has been found that the well is often not sufficiently clean, which
can create problems both when the well is completed, and during
subsequent recovery of well fluids. For example, it has been found
that the cleaning operation often does not remove relatively large
or heavy solids from the cased borehole. In an effort to address
this problem, tools have been developed for scraping the casing and
for filtering solids from the fluid in the cased borehole. However,
it has been found that solids often still remain in the completion
fluid, as the cleaning tool simply filters the fluid in the
borehole.
[0010] It is amongst the objects of embodiments of the present
invention to obviate or mitigate at least one of the foregoing
disadvantages.
[0011] According to a first aspect of the present invention, there
is provided a well cleaning tool for location in well tubing to be
cleaned on an associated support string, the cleaning tool adapted
to be configured to restrict fluid flow past the tool and to be
translated relative to the well tubing to displace fluid along the
well tubing and thereby clean the well.
[0012] The invention therefore provides a cleaning tool which may
be utilised to remove or displace fluids and any entrained solids
from the well tubing by translation of the cleaning tool along the
tubing. Thus, for example, drilling mud, well fluids and any drill
cuttings or other solids present in the well tubing following
drilling and installation of the well tubing may be removed using
the cleaning tool, in preparation for completion of the well.
[0013] It will be understood that the cleaning tool cleans the well
tubing by urging fluid/solids along the tubing ahead of the
cleaning tool in the direction of travel of the tool.
[0014] Preferably, the tool is adapted to be configured such that
fluid flow past the tool is substantially or completely prevented.
The tool may be adapted to be configured to restrict fluid flow
past the tool along an annulus defined between the well tubing and
the support string.
[0015] The cleaning tool may be movable between a first
configuration where fluid flow past the cleaning tool is permitted,
and a second configuration where fluid flow past the cleaning tool
is restricted. Preferably, in the second configuration of the tool,
fluid flow past the tool is substantially or completely prevented.
The first configuration may be a deactivated, running configuration
and the second configuration may be an activated, cleaning
configuration. The cleaning tool may be adapted to be run into the
well tubing in the deactivated configuration and subsequently moved
to the activated configuration for cleaning the well tubing. This
may facilitate positioning of the cleaning tool at a desired
location within the well tubing, and subsequent activation of the
cleaning tool for carrying out a cleaning operation. Alternatively,
the cleaning tool may be adapted to be run into the well tubing in
the activated configuration and subsequently moved to the
deactivated configuration. This may facilitate cleaning of the well
tubing when the tool is run-in, and subsequent movement of the tool
to the deactivated configuration for recovery of the tool.
[0016] In a further alternative, the cleaning tool may be adapted
to permit fluid flow in one direction past the tool, and to
restrict fluid flow past the tool in an opposite direction. The
cleaning tool may be adapted to be configured such that when the
tool is translated in a first direction along a length of the well
tubing, fluid flow past the cleaning tool is permitted; and when
the tool is translated in a second, opposite direction along the
length of the tubing, fluid flow past the cleaning tool is
restricted. The cleaning tool may therefore be arranged such that
the tool automatically restricts fluid flow when the tool is
translated in a first direction along the well tubing, but permits
fluid flow when the tool is translated in a second, opposite
direction. For example, in embodiments of the invention, fluid flow
past the tool may be permitted during run-in of the tool into the
well tubing, and may be restricted when the tool is pulled-out of
the well tubing. The first direction may therefore be a run-in
direction and the second direction a pull-out or run-out direction.
In alternative embodiments, fluid flow past the tool may be
restricted during run-in of the tool into the well tubing, and
permitted when the tool is pulled-out of the well tubing. The first
direction may therefore be a run-out direction and the second
direction a run-in direction.
[0017] Preferably, the cleaning tool is adapted to abut or engage a
wall of the well tubing in order to restrict fluid flow.
Accordingly, when the cleaning tool is brought into abutment with
the tubing wall, translation of the tool along the well tubing
urges fluid along the tubing. The cleaning tool may be adapted to
sealingly abut or engage the wall of the well tubing to
substantially or completely restrict fluid flow past the cleaning
tool. In embodiments of the invention, the cleaning tool may be
movably mounted relative to a support string, and may also be
adapted to abut or engage a surface of the support string, and
optionally to sealingly abut or engage the surface of the support
string. Alternatively, the cleaning tool may be coupled to tubing
of the support string, for example through a threaded connection,
and therefore it may not be necessary to arrange the cleaning tool
to sealingly abut or engage the surface of the support string.
[0018] Most preferably, the cleaning tool comprises at least one
abutting element for abutting or engaging the wall of the well
tubing, the element serving for permitting and restricting fluid
flow past the tool. The abutting element may be radially movable or
otherwise outwardly movable relative to a body of the tool. The
abutting element may be adapted to extend from or to be upstanding
from a body of the tool. The abutting element may be movable
between a deactivated configuration and an activated configuration,
which may correspond to deactivated and activated configurations of
the tool, for selectively engaging an internal surface of the
tubing. For example, it may only be desired to arrange the abutting
element to abut an internal surface of the tubing during passage of
the tool in a selected direction along a length of the tubing. The
abutting element may be movable between a collapsed and extended or
deployed positions corresponding to the deactivated and activated
configurations, for abutting the well tubing. The abutting element
may be adapted to be biased into abutment with the well tubing
wall. In a variation, the abutting element may be adapted to be
moved between a deactivated configuration where the abutting
element abuts the well tubing wall but permits fluid flow, and an
activated configuration where the abutting element is arranged to
restrict fluid flow. For example, the abutment element may be urged
into enhanced abutment with the tubing wall to restrict fluid flow.
In preferred embodiments, the tool comprises a plurality of
abutting elements which may be fins, ridges or the like extending
from a surface of a body of the tool.
[0019] Alternatively, the abutting element may be resilient and may
be adapted to be deflected to permit fluid flow past the tool in
one direction and to restrict fluid flow past the tool in an
opposite direction. To facilitate this, the abutting element may
comprise a resilient annular ring or the like extending from a body
of the tool.
[0020] The tool may comprise an actuating mechanism for moving the
tool, in particular the abutting element, between the deactivated
and activated configurations. In particular preferred embodiments,
the actuating mechanism may be adapted to exert a radial actuating
force on the abutting element through an axial force applied to or
generated by the mechanism. Where the tool comprises a plurality of
fins or the like, the fins may be compressed and thus urged
radially outward to abut the tubing wall.
[0021] The cleaning tool may be adapted to be hydraulically
actuated for configuring the tool to restrict fluid flow, and may
comprise a hydraulic actuating mechanism for moving the tool
between the first and second configurations. For example, the tool
may comprise at least one piston for configuring the tool to
restrict fluid flow. The actuating mechanism may be adapted to urge
the abutting element between the deactivated and activated
positions. The piston may be actuated in response to an applied
control signal or applied fluid pressure, for example via control
line or by differential fluid pressure between an interior and an
exterior of the tool. The actuating mechanism may comprise a burst
disc or the like for isolating the piston from applied fluid
pressure until such time as fluid at a determined pressure is
applied to rupture the disc. Thus the tool may be run-in to a
desired location within the tubing with the abutting element held
in a deactivated or activated position until fluid pressure at a
determined level is applied to rupture the burst disc and move the
abutting element from the deactivated configuration to the
activated configuration, or vice-versa. It will be understood that
this determined level may be significantly higher than the fluid
pressure normally experienced by the tool, and this may prevent
premature actuation of the abutting element.
[0022] Alternatively, the cleaning tool may be mechanically or
electro-mechanically actuated for configuring the tool to restrict
fluid flow, and may comprise a mechanical or electro-mechanical
actuating mechanism for moving the tool between the first and
second configurations. For example, the tool may comprise a biasing
mechanism for urging the tool between the deactivated and activated
configurations, and a shear pin, locking ring or the like for
retaining the tool in one of said configurations. The shear pin may
be arranged to maintain the tool in the deactivated configuration,
permitting fluid flow past the tool until such time as the pin is
sheared, whereupon the tool may move to the activated
configuration, restricting fluid flow, or vice-versa. This may
prevent premature actuation of the abutting element. The shear pin
may be sheared by applying a jarring force to the support string,
or by a release mechanism arranged to exert a force on the shear
pin to release the pin. Where the cleaning tool comprises an
electro-mechanical actuator, the tool may be actuated in response
to an applied control signal.
[0023] It will be understood that in further alternative
embodiments, the tool may comprise a combination of hydraulic,
mechanical and/or electro-mechanical actuators.
[0024] The tool, in particular the abutting element may define a
cleaning surface for cleaning or wiping an internal wall of the
well tubing. Alternatively, the tool may comprise at least one
cleaning element separate from the abutting element, the cleaning
element defining the cleaning surface. The cleaning surface may be
adapted to scrape, wipe or abrade the internal wall of the well
tubing during translation of the cleaning tool through the tubing,
to remove solids such as mud residues, scale or the like adhered to
the wall of the well tubing. The cleaning surface may take the form
of a blade, fin, scraper, abrader, brush or the like, or the tool
may comprise a combination thereof.
[0025] The cleaning tool may be adapted to be movably mounted
relative to the support string, and may comprise a body mounted for
movement relative to the support string along a length thereof.
This may facilitate movement of the tool along the string, and/or
movement of the string within and thus relative to the tool.
Accordingly, the cleaning tool may be adapted to be run-in to the
well tubing along a support string already located within the
tubing, without requiring the string to be pulled out. For example,
the cleaning tool may be run-in on a drill string located in the
well tubing. The cleaning tool may therefore comprise a generally
annular member in the form of a swab, plug or the like, adapted to
be pumped down the well tubing along the support string.
[0026] Alternatively, the cleaning tool may be adapted to be
secured against movement relative to the support string and may be
coupled to sections of the support string by threaded connections
or the like. This may facilitate translation of the tool relative
to the well tubing by translation of the support string along a
length of the tubing. It will be understood however that where the
tool is movably mounted relative to the support string, the tool
may also be adapted to be secured relative to the support string,
to facilitate translation of the tool along the well tubing using
the support string, if desired.
[0027] According to a second aspect of the present invention, there
is provided apparatus for cleaning a well, the apparatus
comprising:
a support string adapted to be located in well tubing to be
cleaned; at least one well cleaning tool coupled to the support
string, the well cleaning tool adapted to be configured to restrict
fluid flow past the tool and to be translated relative to the well
tubing to displace fluid along the well tubing and thereby clean
the well.
[0028] The cleaning tool may be adapted to be translated along the
support string relative to the well tubing from a downhole location
and in a direction towards the surface, to displace fluid in the
well tubing along the tubing to surface. To achieve this,
replacement fluid such as completion fluid may be pumped into the
well tubing down the support string, to create a pressure
differential across the tool and urge the cleaning tool along the
support string.
[0029] Alternatively, the cleaning tool may be adapted to be
translated along the support string relative to the well tubing in
a direction from surface to a downhole location, to displace fluid
in the well tubing and up the support string to surface. To achieve
this, replacement fluid such as completion fluid may be pumped into
the well tubing down an annulus between the tubing and the string,
to create a pressure differential across the tool and urge the
cleaning tool along the string.
[0030] In a further alternative, the cleaning tool may be adapted
to be secured relative to the support string and to be translated
relative to the well tubing in a direction towards the surface, to
displace fluid in the well tubing along the tubing to surface, by
translating the support string along the well tubing. Replacement
fluid such as completion fluid may be adapted to be pumped into the
well tubing along the support string. In a variation, the cleaning
tool may be adapted to displace fluid along the well tubing during
run-in of the support string, displaced fluid passed to surface
through the support string and completion fluid pumped into the
well tubing behind the cleaning tool.
[0031] Preferably, the apparatus comprises a plurality of cleaning
tools, and may comprise a first cleaning tool adapted to define a
first, cleaning diameter for cleaning a first section of well
tubing of a corresponding first diameter and a second cleaning tool
adapted to define a second, cleaning diameter for cleaning a second
section of well tubing of a corresponding second diameter. This may
facilitate cleaning of a length of well tubing having varying
internal diameter along a length thereof, such as is typically
found downhole, for example, in a transition from larger diameter
casing to smaller diameter liner.
[0032] At least one of the cleaning tools may be adapted to be
movably mounted relative to the support string, and may comprise a
body mounted for movement relative to the support string along a
length thereof. This may facilitate movement of the tool along the
string, and/or movement of the string within the tool. At least one
other one of the cleaning tools may be adapted to be secured
against movement relative to the support string and may be coupled
to sections of the support string by threaded connections or the
like. This may facilitate translation of the tool relative to the
well tubing by translation of the support string along a length of
the tubing. Accordingly, at least one of the cleaning tools may be
movable relative to at least one other cleaning tool.
[0033] Preferably, a lower cleaning tool is secured against
movement relative to the support string, and an upper cleaning tool
is movably mounted relative to the support string. This may
facilitate translation of the support string within and relative to
the upper cleaning tool, the support string carrying the lower
cleaning tool to bring the lower cleaning tool to a position
adjacent or close to the upper tool. This may enable the lower tool
to be used to clean a lower section of well tubing, and to carry
fluid out of said lower section and past the upper cleaning tool,
whereupon the upper cleaning tool may be translated relative to an
upper section of well tubing, to carry the fluid displaced from the
lower section, as well as fluids in the upper section, along the
well tubing. To achieve this, the upper cleaning tool may be
adapted to initially be provided in a deactivated configuration
permitting fluid flow past the tool, whilst the lower cleaning tool
may be adapted to be provided in an activated configuration,
restricting fluid flow past the tool so as to urge fluid along the
well tubing and past the upper tool during movement of the lower
cleaning tool. Once the lower tool has been brought adjacent to the
upper tool, the upper tool may be adapted to be moved to an
activated configuration, to restrict fluid flow past the upper
tool. It will be understood that references herein to upper and
lower cleaning tools are relative to the apparatus when assembled
and prior to running-in to well tubing, which may be deviated from
the vertical.
[0034] The apparatus may comprise a flow restrictor such as a ball,
dart or the like, the restrictor adapted to be located within the
support string, to define a barrier between fluid within the string
above the restrictor and fluid below the restrictor. The flow
restrictor may be adapted to be pumped or passed down the support
string using completion fluid such as brine, and may therefore
define a barrier between the completion fluid and fluid present in
the well and in the string below the restrictor. This avoids or
substantially reduces any interface between fluids such as drilling
mud in the well tubing and the completion fluid. The flow
restrictor may be adapted to be passed down the support string
prior to or during translation of the cleaning tool relative to the
well tubing. In this fashion, drilling mud and other fluid removed
from the well tubing using the cleaning tool may be replaced with
clean completion fluid, preparatory to completion of the well. The
apparatus, in particular the cleaning tool, may comprise a catcher
or the like for catching or retaining the flow restrictor to
prevent discharge of the flow restrictor into the well tubing. The
apparatus, in particular the cleaning tool, may also comprise a
bypass such as a bypass port adapted to permit fluid flow past the
restrictor once the flow restrictor has seated on the catcher. This
facilitates flow of completion fluid or the like past the
restrictor to replace fluids removed from the well tubing. The
apparatus may also comprise a valve seat for the restrictor, or a
separate valve or the like, for preventing return flow of fluid up
the support string past the restrictor.
[0035] Further features of the cleaning tool of the cleaning
apparatus are defined above.
[0036] According to a third aspect of the present invention, there
is provided a method of cleaning a well, the method comprising the
steps of:
locating a well cleaning tool in well tubing to be cleaned on an
associated support string; configuring the well cleaning tool to
prevent fluid flow past the tool; and translating the well cleaning
tool relative to the well tubing to displace fluid along the well
tubing to thereby clean the well.
[0037] The method may comprise translating the cleaning tool along
the support string relative to the well tubing from a downhole
location and in a direction towards the surface, to displace fluid
in the well tubing along the tubing to surface. Replacement fluid
such as completion fluid may be pumped into the well tubing down
the support string, to create a pressure differential across the
tool and urge the cleaning tool along the support string.
[0038] Alternatively, the cleaning tool may be translated along the
support string relative to the well tubing in a direction from
surface to a downhole location, to displace fluid in the well
tubing and up the support string to surface. Replacement fluid such
as completion fluid may be pumped into the well tubing down the
annulus, to create a pressure differential across the tool and urge
the cleaning tool along the string.
[0039] In a further alternative, the cleaning tool may be secured
relative to the support string and translated relative to the well
tubing in a direction towards the surface, to displace fluid in the
well tubing along the tubing to surface, by translating the support
string along the well tubing. Replacement fluid such as completion
fluid may be pumped into the well tubing along the support string.
In a variation, the cleaning tool may displace fluid along the well
tubing during run-in of the support string, with displaced fluid
passed to surface through the support string and completion fluid
pumped into the well tubing behind the cleaning tool.
[0040] The method may comprise cleaning a first section of well
tubing of a first diameter using a first cleaning tool of a
corresponding first, cleaning diameter, and cleaning a second
section of well tubing of a second diameter using a second cleaning
tool of a corresponding second, cleaning diameter.
[0041] Preferably, a lower cleaning tool is provided and is secured
against movement relative to the support string, and an upper
cleaning tool is provided and is movably mounted relative to the
support string. The support string may be translated within and
relative to the upper cleaning tool, to carry the lower cleaning
tool to a position adjacent to the upper tool to clean a lower
section of well tubing, and to carry fluid out of said lower
section and past the upper cleaning tool. The upper cleaning tool
may then be translated relative to an upper section of well tubing,
to carry the fluid displaced from the lower section, as well as
fluids in the upper section, along the well tubing. To achieve
this, the upper cleaning tool may initially be provided in a
deactivated configuration permitting fluid flow along the annulus
past the tool, whilst the lower cleaning tool may be provided in an
activated configuration, restricting fluid flow past the tool so as
to urge fluid along the well tubing during movement of the lower
cleaning tool. Once the lower tool has been brought adjacent to the
upper tool, the upper tool may be moved to an activated
configuration, to restrict fluid flow past the upper tool.
[0042] The method may further comprise defining a barrier between
fluid in the well tubing and replacement fluid, such as completion
fluid, pumped into the well tubing. The barrier may be defined by a
flow restrictor or the like, which may be run into the well tubing
through the support string, and which may define a barrier between
fluid within the string above the restrictor and fluid below the
restrictor. The flow restrictor may be adapted to be passed down
the support string prior to or during translation of the cleaning
tool relative to the well tubing. The flow restrictor may engage a
catcher to prevent discharge of the flow restrictor into the well
tubing. Once the flow restrictor has seated on the catcher, bypass
flow around the restrictor may be permitted, to facilitate flow of
completion fluid or the like past the restrictor to replace fluids
removed from the well tubing.
[0043] According to a fourth aspect of the present invention, there
is provided a well cleaning tool for location in well tubing to be
cleaned on an associated support string, the cleaning tool adapted
to be configured to restrict fluid flow past the tool along an
annulus defined between the well tubing and the support string,
such that translation of the cleaning tool relative to the well
tubing urges fluid in the well tubing along the annulus to thereby
clean the well tubing.
[0044] Embodiments of the present invention will now be described
by way of example only, with reference to the accompanying
drawings, in which:
[0045] FIG. 1 is a schematic, longitudinal part-sectional view of
apparatus for cleaning a well and of a well cleaning tool forming
part of the cleaning apparatus, in accordance with a preferred
embodiment of the present invention, the tool and apparatus shown
during an initial step in a method of cleaning a well; and
[0046] FIGS. 2 to 5 are views of the cleaning tool and apparatus
during further steps in the method of cleaning a well.
[0047] Turning firstly to FIG. 1, there is shown apparatus for
cleaning a well in accordance with a preferred embodiment of the
present invention, the apparatus indicated generally by reference
numeral 10 and including a well cleaning tool indicated generally
by reference numeral 12. The apparatus 10 is shown in FIG. 1 during
run-in to a well borehole 16 which has been drilled from surface
and lined with well tubing 14. Specifically, the borehole 16 has
been drilled to a first depth and a casing 18, comprising a number
of threaded casing sections coupled together end-to-end, has been
located in the drilled section and cemented in place. An extension
20 has then been drilled and a smaller diameter liner 22, also
comprising a number of tubing sections coupled together end-to-end,
has been installed in the section 20 extending from the lower end
or shoe 24 of the casing 18, and also cemented in place.
[0048] As will be understood by persons skilled in the art, the
casing 18 and liner 22 initially contain a volume of fluids such as
drilling mud and formation fluids, and solids such as drill
cuttings, cement residue and the like. These fluids and solids must
be removed from the well tubing 14 before the well can be completed
by running in a completion string to gain access to well fluids in
a particular rock formation. As discussed above, this has
conventionally been achieved by pumping pills of viscous fluid down
a tubing string (not shown) located in the well tubing 14, followed
by a completion fluid such as brine. These viscous pills transport
fluids and entrained solids along the well tubing 14 to surface
along an annulus defined between the tubing string and the well
tubing 14. A filtering tool may then be utilised to filter out
remaining solids present in the well tubing 14. However, as
discussed above, this prior art procedure suffers from various
disadvantages which are obviated by the present invention.
[0049] The cleaning apparatus 10 of the present invention is shown
in FIGS. 1 to 5 at various stages in a method of cleaning the well
tubing 14 utilising the cleaning apparatus 10. For ease of
illustration, only part of the borehole 16 is shown, in FIG. 1.
[0050] As shown in FIGS. 1 to 5, the cleaning apparatus 10
generally comprises a support string 26 adapted to be located in
the well tubing 14 to be cleaned, and at least one well cleaning
tool 12 in the form of a plug or swab which is adapted to be
configured to restrict fluid flow past the tool. In the illustrated
embodiment, the apparatus 10 comprises two such well cleaning tools
12 and 12a, and the cleaning tools 12, 12a are adapted to be
translated relative to the well tubing 14 to displace fluid along
the tubing to thereby clean the well.
[0051] In more detail, the cleaning apparatus 10 includes an upper
cleaning tool in the form of the tool 12, and a lower cleaning tool
in the form of the tool 12a. The lower cleaning tool 12a is secured
to an end 30 of the support string 26, whilst the upper cleaning
tool 12 is mounted for selective movement relative to the string
26. Each of the cleaning tools 12, 12a are moveable between a
first, deactivated configuration where they permit fluid flow and a
second, activated configuration where they restrict fluid flow.
[0052] The cleaning tools 12, 12a are both shown in FIG. 1 in
deactivated configurations, during run-in to the well tubing 14. In
this configuration, the upper cleaning tool 12 is initially
retrained against movement relative to the support string 26 by a
shear pin or locking ring, or by a shoulder or upset (not shown) on
the support string 26.
[0053] The upper cleaning tool 12 is of a larger external diameter
than the lower cleaning tool 12a, and serves for cleaning the
larger diameter casing 18, whereas the lower cleaning tool 12a
serves for cleaning the smaller diameter liner 22. The cleaning
tool 12 comprises a plurality of abutting elements in the form of
fins or ridges 32 provided on a body 34 of the tool 12, which
define a wiper for cleaning an inner surface of the well tubing 14.
It will be understood that like components of the lower cleaning
tool 12a with the upper tool 12 are indicated by the same reference
numerals, with the addition of the suffix a.
[0054] The cleaning tools 12, 12a each include an actuating
mechanism (not shown) for moving the fins 32 between retracted and
extended positions corresponding to the deactivated and activated
configurations of the tools. The actuating mechanism may be a
hydraulic actuator such as a piston, a mechanical actuator such as
a mandrel and cam surface arrangement, or a suitable
electro-mechanical actuator. In each case, the actuating mechanism
serves for axially compressing the body 34, to urge the fins 32
radially outwardly into abutment with the well tubing wall. The
fins 32 thus abut or engage the inner wall of the casing 18/liner
22 to restrict fluid flow past the tool 12, 12a. In this fashion,
subsequent translation of the tool 12, 12a relative to the casing
18/liner 22 displaces fluid along the well tubing, to clean the
well.
[0055] The cleaning apparatus 10 is shown in FIG. 2 following
location of the upper cleaning tool 12 at a junction 36 between the
casing 18 and liner 22, with the lower cleaning tool 12a located
partway along a length of the liner 22. The upper cleaning tool 12
is then released to permit movement of the support string 26
relative to the upper tool, such that the lower cleaning tool 12a
may be advanced along the liner 22 and located adjacent an end or
shoe 38 of the liner 22, as shown in FIG. 3. It will be noted that
the string 26 may carry further tools such as a jetting sub 39,
bypass sub 41 and a scraper 43, if required for a particular
downhole operation.
[0056] A flow restrictor in the form of a ball 40 is then inserted
into the support string 26 at surface and is pumped down the string
to the lower cleaning tool 12a. The ball 40 forms a barrier between
drilling mud 42 in the string 26 below the ball 40 and in the
casing 18/liner 22, and completion brine 44 behind the ball 40,
which is used to pump the ball 40 down the string. In this regard,
where the weight of the brine 44 pumped into the tubing 14 is
similar to or less than that of the mud 42, it may be desired or
necessary to maintain the brine pressure higher than that of the
mud to avoid mud leakage across the tool 12.
[0057] When the ball 40 reaches the end of the string 26, it is
caught by a ball catcher 44 in the lower tool 12a, shown in FIG. 4,
which prevents discharge of the ball 40 into the liner 22. The
lower cleaning tool 12a also includes a bypass port for fluid
bypass around the ball 40 once the ball has seated on the ball
catcher 44, to enable the completion brine to be pumped into the
liner 22, to replace displaced drilling mud. Accordingly, as the
ball 40 passes down the string 26, drilling mud 42 in the string 26
is pumped out of the string though the bypass port, and flows up
around the cleaning tool 12a into the annulus 28 and thus to
surface. The support string 26 is then filled with clean completion
brine 44 and a small volume of drilling fluid 42 (if any) remains
in the liner 22 below the lower cleaning tool 12a.
[0058] After the ball 40 has been collected by the ball catcher 44,
the lower cleaning tool 12a is moved to the activated configuration
by the actuating mechanism, which urges the fins 32a radially
outwardly into abutment with an inner wall 46 of the liner 22. In
this position, the fins 32a restrict fluid flow past the lower
cleaning tool 12a, facilitating displacement of fluid along the
liner 22. The support string 26 is then retracted through the upper
cleaning tool 12 whilst completion brine is pumped into the liner
22 through the string 26. The lower cleaning tool 12a thus defines
a barrier between the drilling mud in the liner above the tool 12a
and the completion brine pumped into the liner 22 below the tool
12a.
[0059] As the lower tool 12a is translated towards the upper tool
12, the fins 32a scrape or wipe clean the inner wall 46 of the
liner 22, removing any adhered solids such as mud residue. The tool
12a thus drives the scraped solids and the drilling mud along the
liner 22, and past the upper cleaning tool 12 through annulus 28
and along an annulus (not shown) between the tool 12 and string 26,
and thus to surface, as shown in FIG. 4.
[0060] This movement of the lower cleaning tool 12a is continued
until the lower tool is brought to a position where the upper tool
12 is seated on the lower tool 12a, with the lower tool remaining
in the liner 22. The upper cleaning tool 12 is then moved to the
activated configuration by urging the fins 32 radially outwardly
into engagement with the casing wall 48, as shown in FIG. 5. The
tool 12 is also sealed relative to the string 26.
[0061] The upper cleaning tool 12 thus forms a barrier between the
drilling mud 42 in the annulus 28 above the tool 12 and the clean
completion brine 44 pumped into the liner 22 and casing 18 below
the upper tool 12. The support string 26 is then translated further
along the casing 18, carrying the upper tool 12, whilst pumping
further brine 42 through the string 26 and into the well tubing 14.
In a similar fashion to the lower cleaning tool 12a, the fins 32 of
the upper tool 12 scrape clean the inner wall 48 of the casing 18,
to remove any adhered solids. The cleaning apparatus 10 is then
returned to surface, carrying the drilling mud and entrained
solids, and the drilling mud may be cleaned for subsequent re-use.
The well tubing 14 has thus been cleaned and the fluid present in
the tubing 14 removed to surface and replaced with clean completion
brine.
[0062] The apparatus and method of the present invention offers
significant advantages over prior cleaning methods and apparatus.
For example, the apparatus and method of the invention avoids
creating a large fluid interface, by providing a barrier between
the fluids. Also, mechanical interference between the cleaning
tools 12, 12a and the well tubing 14 wipe the tubing to provide
superior, assured cleaning of mud and solids from the well. There
is no need to store chemicals for use in viscous pills, with
associated Health & Safety benefits, and there is a reduced
requirement to use and clean mud pits, this also freeing up deck
space for other equipment. In use, it is not necessary to circulate
at high fluid flow rates whilst rotating the support string, with
associated time and cost savings. The weight of the apparatus is
also much reduced compared with prior cleaning assemblies.
[0063] Various modifications may be made to the forgoing within the
scope of the present invention.
[0064] For example, in an alternative embodiment, the apparatus 10
may be run-in to the well tubing 14 with the cleaning tools 12, 12a
in their respective activated configurations, so that the tools
wipe the casing 18 and liner 22 during their passage down through
the tubing. In this case, drilling mud and scraped solids may be
driven ahead of the tools 12, 12a and removed from the well tubing
14 along the string 26 to surface, with completion brine pumped
into the well tubing behind the cleaning tools 12, 12a. The string
may include suitable valves or the like to ensure the mud does not
return into the well through the string 26. Once the apparatus 10
has been fully run-in, the cleaning tools 12, 12a may then be moved
to their deactivated configurations for removal of the apparatus
from the tubing 14, with additional brine pumped downhole during
run-out.
[0065] In a further alternative embodiment, the or each of the
tools 12, 12a may be movably mounted on the support string 26,
which may be already located within the well tubing 14. The tools
12, 12a may be pumped downhole from surface by the completion
fluid, by creating a positive pressure differential across the
tool, the tools 12, 12a wiping the casing 18/liner 22 wall during
passage downhole, and driving drilling mud and the like into the
string 26 and thus to surface. The tools 12, 12a may then be
discharged into a rathole (not shown) at the bottom of the borehole
16.
[0066] In a still further alternative embodiment, the or each of
the tools 12, 12a may again be movably mounted on the support
string 26, and the apparatus 10 may be located downhole with the
tools 12, 12a in their deactivated configurations. The tools may
then be moved to the activated configuration and pumped to surface
along the string 26 by completion fluid passed down the string 26,
to create a positive pressure differential across the tool. The
tools 12, 12a may thus wipe the casing 18/liner 22 wall during
passage to surface, driving drilling mud and the like along the
well tubing 14.
[0067] In a yet further alternative embodiment, the tools 12 and/or
12a may be configured to permit fluid flow in one direction and to
restrict fluid flow in a second, opposite direction past the tool.
For example, The cleaning tools 12, 12a may be adapted to be
configured such that when the tool is translated in a first
direction along a length of the well tubing 14, fluid flow past
tool is permitted; and when the tool 12, 12a is translated in a
second, opposite direction along the length of the tubing 14, fluid
flow past the tool is restricted. Thus fluid flow past the tools
12, 12a may be permitted during run-in of the tool into the well
tubing 14, and restricted when the tool is pulled-out of the well
tubing. The first direction may therefore be a run-in direction and
the second direction a pull-out or run-out direction.
Alternatively, fluid flow past the tools 12, 12a may be restricted
during run-in, and permitted when the tool is pulled-out of the
well tubing 14. The first direction may therefore be a run-out
direction and the second direction a run-in direction. To achieve
this, the cleaning tool may include an abutting element in the form
of a resilient, annular ring or the like, which may scrape the well
tubing when passed in one direction and be deflected when passed in
the opposite direction.
[0068] The cleaning tool may be adapted to be run on wireline or
slickline.
* * * * *