Note: Descriptions are shown in the official language in which they were submitted.
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GAS LIFT KICKOVER SYSTEM
Field of the Invention
The present invention relates to a valve changing system for retrieving and
installing a valve in a well. Furthermore, the invention relates to a valve
changing
method.
Background Art
Gas lift kickover tools are used to take out a gas lift valve in a side pocket
in a
well and, in a next run, to put in a new gas lift valve. Gas lift valves are
arranged
in a side pocket in the production casing for letting gas into the casing from
the
annulus surrounding the casing which is filled with gas. The gas lift valves
are,
together with the casing, part of the primary barrier in a well and it is
therefore
extremely important that a gas lift valve is not leaking as pressure is then
built
up in the annulus. If pressure builds up in the annulus due to a leaking valve
or if
the production decreases, the valve is changed. After having changed a gas
lift
valve, a new valve is installed in a next run and the well is tested by taking
off
the pressure in the annulus to verify that the valve is mounted correctly and
functions as intended. If the pressure in the annulus does not increase, the
valve
does not leak and the primary barrier is maintained. The process of taking off
the
pressure and pressurising the annulus again lasts around three days in which
the
well is not producing. Thus, the changing of a gas lift valve is performed in
two
runs if the operation is successful on the first attempt and subsequently, the
well
is out of production for at least three days to be tested. When intervening a
well
to change a gas lift, the well is not producing, and the sooner the operation
is
completed, the sooner production can be resumed.
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 system for changing gas lift valves which is capable of
changing a gas lift valve and verify that the valves are mounted correctly so
that
they do not leak and function satisfactorily in less time than the known
systems.
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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 valve changing
system for retrieving and installing a valve in a well, comprising:
- a tool string comprising:
- a retrieving tool for taking out the valve, comprising a housing and an
arm pivotally connected with the housing, said arm having a connector for
connection to the valve, and
- an installation tool for installing another valve connected with the
retrieving tool forming a tool string, the installation tool comprising a
housing and an arm which is pivotally connected with the housing and has a
connector for connection to another valve,
- a driving tool connected with the installation tool and the retrieving tool
for
providing an axial movement in order to install or retrieve the valve, and
- a leak detection device for detecting temperature and/or acoustic
variations,
the leak detection device being arranged in one end of the tool string.
By having a system comprising both a retrieval and installation tool,
replacing of
a valve can be performed in one run. Furthermore, by having a leak detection
device, testing of the valve can be made in the same run by submerging the
system into the well so that the leak detection device is arranged opposite
the
valves and all the valves can be tested without having to decrease the
pressure
in the annulus. A replacement operation can then be performed in half a day
instead of in three days.
When having a leak detection device to test the valves, also horizontal wells
having valves can easily be tested.
By having the leak detection device in the end of the tool string, the leak
detection device can be arranged so that it is affected by any variations all
around the interior of the casing. The leak detection device arranged in front
of
or behind the tool string is not shielded and influenced by the tool string
itself.
Leak detection devices arranged at one side of the tool housing are not
influenced by the variations at the opposite side of the housing since the
tool
housing shields for these variations. The leak detection device arranged in
front
of the tool string or behind the tool string is equally affected by all
variations
along the circumference of the casing and is thus not shielded by the tool
string.
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In one embodiment, the tools may be aligned along a tool string centre axis
and
the leak detection device may be arranged substantially in line with the tool
centre axis.
Also, the leak detection device may be arranged in front of one of the
installation
tool and the retrieving tool or arranged behind one of the installation tool
and the
retrieving tool closest to a well head of the well.
Further, the leak detection device may be a pressure sensor, a temperature
sensor, a flow meter or an acoustic sensor, such as a microphone.
In an embodiment, the leak detection device may be a fibre optical cable
sensor.
Moreover, the fibre optical cable sensor may comprise a single mode fibre
operating at a wavelength of 1000 nm-2000 nm, preferably at a wavelength of
1200 nm-1800 nm, and more preferably at a wavelength of 1400 nm-1600 nm,
such as at a wavelength of 1550 nm.
Further, the fibre optical cable sensor may operate at an attenuation of 0.1-
0.3
dB/km.
The valve changing system as described above may further comprise a wireline
for powering the tools.
Additionally, the leak detection device is fibre optical cable sensor which
may be
part of a wireline, an e-line or a slickline connected to the tool string in
order to
retrieve the tool string.
Furthermore, the fibre optical cable sensor may be a distribution temperature
sensor and/or a distribution acoustic sensor.
Additionally, the tool may comprise a laser for sending light pulses through
the
leak detection device being a fibre optical cable sensor.
In an embodiment, the tool may comprise a detector for detecting the intensity
of the reflected light pulses.
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Furthermore, the retrieving tool may further comprise a contact for detecting
a
connection between the connector and the valve.
Hereby it is ensured that the valve changing system is not retracted from the
well
before the defect valve is removed.
Said contact may be in communication with an activation device of the
installation tool.
Hereby it is ensured that the installation tool is not activated until the
installation
tool has proper contact with the defect valve to be retrieved, and thus the
installation of a functioning valve can be initiated.
The valve changing system according to the present invention may further
comprise a tool connection for connecting the retrieving tool with the
installation
tool.
In one embodiment, the driving tool may comprise a stroking tool comprising a
motor and a pump driven by the motor, the pump pumping fluid into a piston
chamber in the stroking tool moving a piston connected with a piston shaft,
said
shaft being connected with the retrieving tool or installation tool for
transferring
the axial movement.
Moreover, the driving tool may comprise a downhole tractor, said driving tool
also being capable of driving the system forward in the well.
Also, the driving tool may comprise wheels arranged on a wheel arm and may
have an electrical motor driving a pump which drives the wheel to move the
system forward in the well.
Further, the driving tool may comprise an electrical power device to power the
tools.
In one embodiment, the piston may divide the piston chamber of the stroking
tool into a first chamber part and a second chamber part, and the pump may
pump fluid into the first chamber part and suck fluid out of the second
chamber
part.
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Also, the stroking tool may comprise several pistons, each piston being
arranged
in a piston chamber.
The valve changing system according to the present invention may further
5 comprise an anchoring section.
Said valve changing system may comprise sensors arranged to detect if the arm
is in its retracted or extending position.
Furthermore, the present invention relates to a valve changing method for
changing a valve in a well, comprising the steps of:
- entering the valve changing system according to the present invention,
- moving the valve changing system so that the leak detection device passes
a
plurality of valves in order to detect which valve is defect,
- moving the valve changing system to a position so that the retrieving tool
is
opposite the defect valve,
- retrieving the defect valve by means of the retrieving tool,
- moving the valve changing system so that the installation tool is in the
position,
and
- installing another valve by means of the installation tool.
Moreover, the valve changing method as described above may further comprise
the step of moving the valve changing system so that the leak detection device
passes the installed valve, and detecting temperature and/or acoustic
variations
opposite the at least one valve by means of the leak detection device.
Also, the present invention relates to a valve changing method comprising the
steps of:
- entering the valve changing system according to the present invention,
- moving the valve changing system to a position in which the retrieving tool
is
opposite at least one valve in the well,
- retrieving the valve by means of the retrieving tool,
- moving the valve changing system so that the installation tool is in the
position,
- installing another valve by means of the installation tool,
- moving the valve changing system so that the leak detection device passes
the
installed valve, and
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- detecting temperature and/or acoustic variations opposite the at least one
valve
by means of the leak detection device.
The step of detecting acoustic variations may be performed using Rayleigh
scatter based sensing.
In the valve changing method as described above, the leak detection device may
be a fibre optical sensor and may further comprise the step of sending a
coherent
laser light pulse along the leak detection device being a fibre optical cable
sensor.
In addition, the valve changing method as described above may comprise the
step of measuring of the intensity of the reflected laser light as a function
of time
after transmission of the laser pulse.
A laser pulse may be sent through the optic fibre and in the event of a leak,
sound and temperature may influence the fibre at that position to scatter the
laser light. The intensity of the reflected light is measured as a function of
time
after transmission of the laser pulse. The reflected light at the position of
the leak
returns before the rest of the laser pulse has had time to travel the full
length of
the fibre and back, and thus the position of the leak and thus which gas lift
valve
is leaking can be determined. The next laser pulse can be sent along the fibre
when the previous laser pulse has travelled the full length and back. Changes
in
the reflected intensity of successive pulses from the same region of fibre
opposite
the leak are caused by changes in the optical path length of that section of
fibre
and confirm the position of the leak. This type of system is very sensitive to
both
strain, noise and temperature variations of the fibre, and measurements can be
made simultaneously at all sections of the fibre.
In addition, the valve changing method as described above may further comprise
the step of adjusting the installed valve to be more open or closed.
Moreover, the valve changing method as described above may further comprise
the step of closing the well while conducting an acoustic detection by means
of
the leak detection device.
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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 valve changing system in a casing in a well,
Fig. 2 shows another valve changing system in a casing in a well,
Figs. 3A-D show a retrieving tool retrieving a valve,
Figs. 3E-H show an installation tool installing another valve,
Fig. 4 shows a cross-sectional view of a wireline comprising a fibre optical
cable
sensor, and
Fig. 5 shows another embodiment of the valve changing system.
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 valve changing system 1 for retrieving a valve 2 in a well 3
and
installing another valve. The valve changing system 1 comprises a retrieving
tool
4 for taking out the valve and an installation tool 9 for installing another
valve.
The installation tool 9 is connected with the retrieving tool forming a tool
string 8.
The tool string 8 is connected with a driving tool 13 for providing an axial
movement in order to install or retrieve the valve. The valve changing system
1
further comprises a leak detection device 14 for detecting temperature and/or
acoustic variations. The leak detection device is arranged in one end of the
tool
string closest to the top of the well so that when the tools are moved forward
in
the well, the leak detection device can test the valves in the well. This end
of the
tool string comprises an electrical power device 20 powering a motor 15 which
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drives a pump 16. The pump 16 is part of the driving tool 13 providing the
axial
movement of the retrieving tool and the installation tool.
The tools are aligned along a tool string centre axis and the leak detection
device
is arranged substantially in line with the tool centre axis. By having the
leak
detection device in the end of the tool string, either in the end closest to
the top
of the well or in the opposite end in front of the tool string, the leak
detection
device can be arranged so that it is affected by any variations all around the
interior of the casing. A leaking gas lift valve leaks bubbles into the well
fluid and
thus generates sound variations, and the gas most often has a temperature
different from that of the well fluid, resulting in the gas leak also
generating
temperature variation. Furthermore, the gas expands in the fluid, resulting in
an
increased flow. The leak detection device arranged in front of or behind the
tool
string is not shielded and influenced by the tool string itself. If the leak
detection
device is arranged at one side of the tool housing, the leak detection device
is not
influenced by the variations at the opposite side of the housing since the
tool
housing shields for these variations. Thus, if the leak detection device is
arranged
on the side opposite to where the side pocket is located, the variations may
not
be detected and the defect valve may seem in order. The leak detection device
arranged in front of the tool string or behind the tool string is equally
affected by
all variations along the circumference of the casing and is thus not shielded
by
the tool string. Hence, the leak detection device arranged at one end of the
tool
string is capable of detecting a gas leak and thus a defect valve even though
such leak is positioned in a side pocket. Furthermore, the detection of the
valve
leaking and hence requiring replacement can be performed using only one fibre
cable since it is arranged in line with the centre axis.
In Fig. 3A, the leak detection device 14 is arranged in front of one of the
installation tool and the retrieving tool and in Figs. 1 and 2 the leak
detection
device 14 is arranged behind one of the installation tool and the retrieving
tool
closest to a well head of the well.
The leak detection device may be any kind of leak detection device such as a
pressure sensor, a temperature sensor, a flow meter or an acoustic sensor,
such
as a microphone. A leaking gas lift valve leaks bubbles into the well fluid
and thus
generates sound variations, and the gas most often has a temperature different
from that of the well fluid, resulting in the gas leak also generating
temperature
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variation. Furthermore, the gas expands in the fluid, resulting in an
increased
flow. Thus, leak detection devices capable of sensing acoustic changes,
temperature changes, pressure changes and/or flow changes can be suitable as a
leak detection device.
In Fig. 1, the tool comprises a laser 51 for sending light pulses through the
leak
detection device 14 being a fibre optical cable sensor 14. A laser pulse is
sent
through the optical fibre of the fibre optical cable sensor and in the event
of a
leak, sound and perhaps also a temperature difference influence the optic
fibre at
that position by scattering the laser light. The intensity of the reflected
light is
measured as a function of time after transmission of the laser pulse of a
detector
52 in the sensor 14. The reflected light at the position of the leak returns
before
the rest of the laser pulse has had time to travel the full length of the
fibre and
back, and thus the position of the leak and thus which gas lift valve is
leaking can
be determined.
The next laser pulse can be sent along the fibre when the previous laser pulse
has travelled the full length and back. Changes in the reflected intensity of
successive pulses from the same region of fibre opposite the leak are caused
by
changes in the optical path length of that section of fibre and confirm the
position
of the leak. This type of system is very sensitive to strain, noise and
temperature
variations of the fibre.
The retrieving tool comprises a housing 5 and an arm 6 pivotally connected
with
the housing. The arm has a connector 7 for connecting to the valve to be
retrieved. The installation tool 9 also comprises a housing 10 and an arm 11
pivotally connected with the housing, and the arm has a connector 12
releasably
connected to the new valve. The arms of the tools comprise two arm parts
pivotally connected so that the first arm part is connected to the housing 10
and
the second arm part is connected to the valve 2. Both the retrieving tool and
the
installation tool are a kind of kickover tool. The installation tool has a
tool
connection 39 arranged in an end opposite the driving tool transferring the
axial
movement of the driving tool to the retrieving tool so that only one driving
tool is
needed for movement of both arms of the tools. If the retrieving tool is
arranged
closest to the driving tool, the retrieving tool has a tool connection
arranged in an
end opposite the driving tool transferring the axial movement of the driving
tool
to the installation tool.
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In Fig. 3A, the retrieving tool 4 is arranged opposite the valve 2 to be
replaced.
In Fig. 3B, the arm 6 of the retrieving tool 4 is in its extended position,
ready to
be subjected to an axial movement from the driving tool 13 to engage the valve
2 by the connector of the arm 6. In Fig. 3C, the retrieving tool 4 has been
5 subjected to the axial movement and the arm 6 is connected to the valve
2,
ready for retrieval. In Fig. 3D, the retrieving tool 4 is retrieving the valve
2 and
the retrieving tool 4 is moved further down the well so that the installation
tool 9
is arranged in the position opposite the opening 40 in which the valve is to
be
installed. In Fig. 3E, the arm 11 of the installation tool 9 is extended and
the
10 valve is arranged opposite the opening 40 into which the valve is to be
inserted.
In Fig. 3G, the valve is in its inserted position and in Fig. 3H, the
installation tool
9 is pulled back in order to retract the arm 11. Subsequently, the tool string
8 is
moved forward in the well so that the leak detection device is arranged
opposite
the valves to verify that the valve has been installed correctly and is
working as
intended and that it was in fact that valve that needed to be changed in order
to
solve the problem.
As can be seen in Fig. 3C, the retrieving tool 4 comprises a contact 50 for
detecting a connection between the connector 7 and the valve 2. It is hereby
ensured that attempts to replace a malfunctioning valve with a new valve do
not
result in the new valve being arranged on top of the unmoved malfunctioning
valve.
In the valve changing system, the contact 50 may furthermore be in
communication with an activation device 53 of the installation tool shown in
Figs.
3E and 3F. This is to ensure that the installation tool is not activated until
the
installation tool has proper contact with the defect valve to be retrieved,
and thus
the installation of a functioning valve can be initiated. If the defect valve
cannot
be removed, the operation is abandoned without damaging the new valve.
The tool connection 39, as shown in Figs. 1 and 5, comprises a cylindrical
tube
having an internal thread corresponding to external threads of the retrieving
and
installation tools, or the tool connection 39 comprises latches hooking onto a
corresponding groove or corresponding grooves in the retrieving and
installation
tools.
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In Fig. 1, the driving tool is a downhole tractor which is also capable of
driving
the system forward in the well. Hereby, the valves in a horizontal part of the
well
can be tested in the same run as the valves in the vertical part of the well.
The
driving tool comprises wheels arranged on a wheel arm and has an electrical
motor 15 driving a pump 16 which drives the wheel to move the system forward
in the well. The wheels thus provide the axial movement needed for retrieving
or
installing a valve. The arm of the retrieving and installation tool is
extending
when a latch of the tool hooks onto a trail 25 or groove in the vicinity of
the valve
and is thus pulled back again by means of the trail 25.
In Fig. 2, the driving tool is a stroking tool which comprises a motor 15 and
a
pump 16 driven by the motor. The pump pumps fluid into a piston chamber 17 in
the stroking tool moving a piston 18 connected with a piston shaft 19, the
shaft
being connected with the retrieving tool or installation tool for transferring
the
axial movement. In order to transfer the axial movement to the retrieving or
installation tool, the valve changing system 1 comprises an anchoring section
24
which is activated by the pump before providing the stroking movement.
The piston 18 divides the piston chamber of the stroking tool into a first
chamber
part 22 and a second chamber part 23, and the pump pumps fluid into the first
chamber part and sucks fluid out of the second chamber part. In another
embodiment, the stroking tool comprises several pistons, each piston being
arranged in a piston chamber 17 providing greater axial force than one piston
as
the pump pumps fluid into every first chamber parts to apply pressure on the
piston from one side and to pull from the other side by pumping fluid out of
the
second chamber part. In order to pull the retrieving or installation tool
back, the
pump pumps fluid into the second chamber parts and pumps fluid out of the
first
chamber parts.
The fibre optical cable sensor 14 is a distribution acoustic sensor. The fibre
optical cable sensor comprises a single mode fibre operating at a wavelength
of
1000 nm-2000 nm, preferably at a wavelength of 1200 nm-1800 nm, and more
preferably at a wavelength of 1400 nm-1600 nm, such as at a wavelength of
1550 nm. The fibre optical cable sensor operates at an attenuation of 0.1-0.3
dB/km.
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The leak detection device may furthermore comprise a distribution temperature
sensor. The valve changing system is moved back and forth in the well so that
the leak detection device is located opposite each of the valves in order to
detect
which valve is leaking or stuck.
In Fig. 4, the fibre optical cable sensor is part of a wireline, e-line or
slickline
connected to the tool string 8 in order to retrieve the tool string. The wires
26 are
arranged on the outside and the optical fibre 14 on the inside. The wireline
may
also comprise electrical cables 27 as illustrated in Fig. 4.
In Fig. 5, the valve changing system 1 has the retrieving tool 4, the
installation
tool 9, the leak detection device 14 and two driving tools 13 in the form of a
stroking tool and a downhole tractor. The stroking tool provides the axial
force to
replace the valve and the downhole tractor drives the valve changing system 1
back and forth in the well so as to move the valve changing system 1 into a
specific position to perform a certain operation.
The valve changing system 1 is thus used to determine if a valve needs to be
replaced or which valve needs to be replaced, to replace the valve and verify
that
the valve has been correctly installed and functions as intended.
If the well only has one gas lift valve and production is not running, the
valve
changing system is entered into the well and the valve changing system is
moved
to a position in which the retrieving tool is opposite at least one valve in
the well.
Subsequently, the valve is retrieved by means of the retrieving tool, and the
valve changing system is moved so that the installation tool is in the
position
opposite the opening in which the valve is to be installed and the
installation tool
installs another valve by means of the installation tool, and then the valve
changing system is moved backwards so that the leak detection device passes
the installed valve and detects the temperature and/or acoustic variations
opposite the at least one valve by means of the fibre optical cable sensor. If
the
valve is functioning perfectly, the valve changing system is pulled out of the
well.
If e.g. a dummy valve is leaking and the well has been closed, the leak
detection
device 14 is able to detect the flow around the valve by means of acoustic
sensing. When the gas lift valve is functioning, the leak detection device 14
is
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able to detect the gas flowing in by means of acoustic sensing. Temperature
sensing is another way of detecting flow as the temperature will change
locally.
When having several valves in the well, the defect valve needs to be located.
After lowering the system into the well, the valve changing system is moved so
that the leak detection device 14 passes a plurality of valves in order to
detect
which valve is defect, and then the valve changing system is moved to a
position
so that the retrieving tool is opposite the defect valve, the defect valve is
retrieved by means of the retrieving tool, and then the valve changing system
is
moved again so that the installation tool is in the position, and another
valve is
installed by means of the installation tool. Subsequently, the valve changing
system 1 is moved back and forth so that the leak detection device 14 passes
the
installed valve 2 and detects any temperature and/or acoustic variations
opposite
the at least one valve by means of the leak detection device 14. By having
such
system, the detection of which valve to replace, the replacement operation and
the verification step can be performed in one run instead of in many runs as
is
the case when using prior art tools.
The invention further relates to the valve changing method for changing a
valve
in a well by entering the aforementioned valve changing system into the well
for
detecting which valve of a plurality of valves is leaking by moving the valve
changing system so that the leak detection device 14 passes all the valves 2
in
order to detect which valve is defect. When the leaking valve is located, the
valve
changing system is moved to the position so that the retrieving tool is
opposite
the defect valve, and then the connector 7 of the retrieving tool connects
with
the defect valve by moving the arm of the retrieving tool. When the defect
valve
has been removed by retracting the arm, the valve changing system is moved so
that the installation tool is in the position and the new valve is installed
by means
of the arm of the installation tool.
The invention further relates to the valve changing method for changing a
valve
in a well by entering the aforementioned valve changing system into the well
for
detecting if the valve is leaking by moving the valve changing system. The
valve
changing system is moved so that the leak detection device passes the
installed
valve and detects temperature and/or acoustic variations opposite the at least
one valve by means of the fibre optical cable sensor. If the valve is defect,
the
valve changing system is moved to a position in which the retrieving tool is
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opposite at least one valve in the well and the defect valve is removed. Then
the
installation tool is moved opposite the position for installing another valve.
When the defect valve has been replaced, the valve changing system verifies
that
the valve is functioning. The system is moved so that the leak detection
device
passes the installed valve and the leak detection device detects acoustic
variations or even temperature variation opposite the at least one valve by
means of the leak detection device. The verification may be performed in two
steps. First, the valve is in its closed position and the leak detection
device 14 is
moved past to verify that the valve is installed correctly in that the leak
detection
device 14 senses no variations opposite the newly installed valve apart from
the
normal variations in the well. Second, the valve is set in its operation mode
so
that gas is let in through the valve and the leak detection device 14 is moved
past to verify that sound variations is detected opposite the valve.
In one embodiment, the step of detecting acoustic variations by the fibre
optical
cable sensor is performed using Rayleigh scatter based sensing as known by a
person skilled in the art. The laser thus sends coherent laser light pulse
along the
fibre optical cable sensor and the intensity of the reflected laser light as a
function of time after transmission of the laser pulse is detected in the
detector
and a position of the defect valve is determined.
The system may further comprise an adjustment device for adjusting the
installed valve to be more open or closed. In order to determine if the valve
is
leaking, the well may be closed while conducting an acoustic detection by
means
of the leak detection device.
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.
By a casing is meant any kind of pipe, tubing, tubular, liner, string etc.
used
downhole in relation to oil or natural gas production.
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In the event that the tool is not submergible all the way into the casing, a
downhole tractor can be used to push the tool all the way into position in the
well. A downhole tractor is any kind of driving tool capable of pushing or
pulling
tools in a well downhole, such as a Well Tractor .
5
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.
