Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AN ELECTRICAL POWER DISTRIBUTION METHOD
FOR A WIRELINE TOOL STRING DOWNHOLE
Field of the invention
The present invention relates to an electrical power distribution method
between
two or more operating units of a wireline tool string downhole performing at
least
one operation. Furthermore, the present invention relates to a wireline system
for carrying out the method according to the invention.
Background art
Downhole wireline tool strings are becoming increasingly complex, as they
typically consist of several specialised operational tools to perform more
complex
operations downhole, e.g. operations involving different types of operations
such
as drilling, closing valves, setting patches, or logging formation or casing
characteristics etc.
As the complexity and number of tools increase, the amount of electrical power
required in the wireline tool string also increases. In order to provide
significant
power downhole, typically the voltage applied to the wireline is increased to
overcome the huge voltage drop over the long length of a wireline. However,
increasing the voltage may lead to dangerous situations such as electrical
breakdown, electrical discharge, and is therefore limited. Also, the possible
power
transmitted through the wireline is limited due to ordinary heat dissipation
in a
long wire. Therefore, power transmitted through a wireline to provide power to
downhole operating tools is inherently limited.
One currently used way of accommodating the increased need for electrical
power is to increase the number of conductive wires in the wireline and thus
increase the total thickness of the conducting part of the wireline delivering
the
electrical power. Also, many attempts have been made to make the tools use
less
electrical power while maintaining their ability to perform the same tasks.
Using a thicker wireline or a wireline containing more conductors increases
the
weight and cost of the wireline. Furthermore, it increases the power required
to
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transport the wireline, e.g. by use of a tractor, in horizontal parts of a
well. This
again increases the electrical power required for the tool string, thereby
using
some or more of the additional power facilitated by the thicker wireline.
Minimising energy consumption by the electrical components downhole may be a
long and expensive process, since the components used downhole already
represent state-of-the-art in respect of minimisation of power consumption due
to the inherent shortage of power for power tools and components downhole.
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 able to perform several operations downhole by a
normal cable and an improved method for controlling system downhole.
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 an electrical power
distribution method for distributing power between two or more operating units
of a wireline tool string downhole performing at least one operation, the
method
comprising the steps of:
- recording information indicative of at least one operating condition,
using one
or more sensors comprised in the tool string,
- comparing the recorded information to a set of predefined intervals of
the at
least one operating condition,
- defining a power distribution between the two or more operating units
based on
the comparison of the recorded information and a predefined interval of the at
least one operating condition,
- controlling the electrical power distribution of the operating units.
By having a method for distributing the electrical power between two or more
operating units in the wireline tool based on an operation, it is possible to
utilise
the limited available electrical power to and in the wireline tool string. By
comparing the operating condition to a predefined interval, the recorded
operating condition may be detected to determine if the operating condition
lies
in a dangerous interval for an operating unit and thus affects the electrical
power
to the operating unit.
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The electrical power distribution method as described above may further
comprise a step of classifying the set of predefined intervals.
By classifying the predefined intervals of the at least one operating
condition
according to classification parameters with the same level of importance
independent of the predefined intervals, the classification parameter may be
linked to the operating condition, and the distribution of the electrical
power
according to the most important classification parameter of the operating
condition is thus distributed in a smarter way than by just comparing the
operating condition to a single interval.
Moreover, the step of comparing the recorded information may comprise
comparing the recorded information to at least one additional predefined
interval.
Also, the electrical power distribution method as described above may further
comprise the step of prioritising the operating conditions of two or more
operating units and basing the step of defining the appropriate electrical
power
distribution on the prioritisation of the operating conditions.
Furthermore, by comparing the classification parameters, a better decision on
what operating condition to consider and how to distribute the electrical
power to
the operating unit comprising the operating condition may be made.
By using the information concerning which operating unit is performing an
operation, the information may be useful in deciding how to distribute the
electrical power if two or more classification parameters from two or more
operating units are equal.
Additionally, the operating unit may comprise a plurality of operating
conditions.
Further, using the information of a predefined order of the operating units in
the
system may be useful in terms of how to distribute the electrical power if two
or
more classification parameters are equal and two or more operating units are
performing an operation.
Also, using the information of a predefined order of the rank of the operating
units in the system and having the operating conditions in an operating unit
to
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also be ordered according to a predefined rank may be useful in terms of how
to
distribute the electrical power when using a plurality of operating units and
a
plurality of operation conditions comprised in the operating unit, if two or
more
classification parameters are equal and two or more operating units are
performing an operation.
By having an operating unit comprising at least one operating condition and by
recording, evaluating, deciding and controlling according to the method, a
master-slave relationship between the two or more operating may be configured.
The steps of comparing the recorded information, defining the appropriate
electrical power distribution and controlling the electrical power
distribution of the
wireline tool string may be performed uphole at a surface.
The evaluation, decision and control may be performed at the surface by a
computer or by human interaction.
Moreover, the steps of comparing the recorded information, defining the
appropriate electrical power distribution, controlling the electrical power
distribution, evaluating, deciding and/or controlling the wireline tool string
may
be performed downhole in the wireline tool string.
The evaluation, decision and control may be performed downhole by a computer
or logic.
In the electrical power distribution method described above, the operating
condition may be a temperature, a pressure, a power, a vibration, a sound, a
voltage, a current, a light, an angle, a velocity or a frequency or another
operating condition during downhole operations.
Also, the sensor may be a temperature sensor, a pressure sensor, a wattmeter,
an accelerometer, a microphone, a voltmeter, an ammeter, a light sensor, an
angle measuring tool, a transducer, a laser or other sensors for measuring
operating conditions downhole.
Further, the operating unit may be a downhole tractor, a milling tool, a
cleaning
tool, a stroker tool, a key tool, a capacitance tool, a laser tool, a laser, a
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computer, a sensor, processing unit, an electrical circuit or other operating
units
for downhole use.
The present invention also relates to a wireline system for carrying out the
5 method as described above, wherein the wireline system comprises a power
distribution unit, two or more operational tools and two or more sensors for
measuring operating conditions.
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 schematic diagram of a method for distributing electrical power
in
a wireline tool,
Fig. 2 shows a schematic diagram of another method for distributing electrical
power in a wireline tool string,
Fig. 3 shows an example of a temperature range divided into predefined
intervals,
Fig. 4 shows a schematic diagram of yet another method for distributing
electrical
power in a wireline tool string,
Fig. 5 shows a schematic diagram of another method for distributing electrical
power in a wireline tool, and
Fig. 6 shows a cross-sectional view of a well comprising a wireline tool
string.
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.
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Detailed description of the invention
Fig. 1 shows a schematic diagram of an electrical power distribution method
for
distributing power between two or more operating units of a wireline tool
string
performing at least one operation downhole. The operating units may be used to
perform operations such as milling, cleaning, measuring, stroking, etc. Power
is
highly limited downhole due to the loss of power in the long wireline when the
wireline tool string operates several thousands of metres downhole, and the
electrical power distribution method intelligently distributes the power
available
to ensure that operations demanding high amounts of electrical power can be
performed. By basing power distribution between operating units on information
recorded by means of various sensor inputs, the power available for a given
tool
string downhole may therefore always be distributed optimally. Also, depending
on the type of operation, different distribution schemes may be set by the
present method.
A first step 10 of the method concerns recording information of at least one
operating condition 15 of at least one operating unit. The operating condition
15
is recorded by using one or more sensors comprised in the wireline tool string
in
order to control the electrical power distribution. The operating condition 15
may
be e.g. a temperature in the borehole, a pressure in the borehole, a power
usage
of an electrical motor, a vibration during drilling, a sound during drilling,
a
magnitude of a supply voltage, a current, a light, an angle, a frequency or a
velocity. The sensor may be e.g. a temperature sensor, a pressure sensor, a
wattmeter, an accelerometer, a microphone, a gyroscope, a voltmeter, an
ammeter, a light sensor, an angle measuring tool, a transducer, a laser or
another appropriate sensor. The operating unit may be a driving unit, such as
a
downhole tractor, a milling tool, a drilling tool, a cleaning tool, a stroker
tool, a
key tool, a capacitance tool, a laser tool, a laser, a computer, a sensor,
processing unit, an electrical circuit or another operating tool for downhole
use.
Thus, the step of recording information may be to measure a temperature in a
milling tool. The step of recording information 10 of the operating condition
15
may be performed by the sensor itself or by sending the information to a
computing unit. By separating the sensor and the computing unit, the sensor
can
for example be made more resistant to vibrations as compared to sensors
comprising means for recording the information.
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A second step 20 of the method, as shown in Fig. 1, concerns comparing the
recorded information to a set of predefined intervals 25, e.g. comparing a
temperature of a milling tool during operating condition 15 to a predefined
temperature interval 25 for optimal operation temperature.
When the recorded information has been compared in step 20 to the set of
predefined intervals 25, a next step 30 is to define an appropriate electrical
power distribution between the two or more operating units. The comparison
step
20 of comparing the recorded information and the predefined intervals 25 is
used
as basis for deciding on an appropriate distribution of the electrical power
between operating tools in step 30. For example, if information is recorded
which
is indicative of a temperature in a drill head, and if the recorded
information is
found to be within a predefined interval 25 which is e.g. considered to be
dangerous for the drilling operation, the electrical power distribution may be
re-
distributed by changing the distribution of electrical power between the drill
bit
and a cooling unit, i.e. by decreasing the amount of electrical power for the
drill
bit and increasing the amount of electrical power for the cooling unit in
order to
increase the cooling of the drill bit. Due to the limited power available, the
cooling unit may only be used when necessary, since the main purpose of the
drilling operation is to drill and not to cool the drill bit if not needed.
The last step 40 of the method shown in Fig. 1 is a step of controlling the
electrical power distribution 40 between the two or more operating units based
on the step of defining an appropriate electrical power distribution 30, such
as
decreasing the amount of power to the drill bit and increasing the amount of
power to the cooling unit. The step of controlling 40 may be performed by
using a
computer, a circuit or other electronics capable of distributing the amount of
power to the two or more operating units based on the step of defining an
appropriate electrical power distribution 30. The step of controlling of the
electrical power distribution 40 may, in its simplest form, be to control two
operating units, e.g. where one of the two operating units gets more
electrical
power and the other consequently gets less electrical power, the purpose being
to ensure that all the electrical power available downhole is used for
performing
the operation. In a more advanced form of the step of controlling the
electrical
power distribution 40, a plurality of operating units may be controlled by
distributing the electrical power by powering down one or more operating units
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and distributing the remaining available electrical power to one operating
unit, or
vice versa.
An example of a wireline tool string 80 in a casing 78 is shown in Fig. 6 in
which
the tool string comprises a downhole tractor 66 having an electronic section
72, a
drill bit 60 comprising a temperature sensor 62, and a cooling unit 63. The
wireline tool string 80 may have been programmed to establish a flow path
through an isolation valve in the casing that failed to open by drilling a
hole in
the isolation valve with the drill bit 60. The temperature sensor 62 records
information of a temperature in the drill bit 60 during the operation and
sends
the recorded information to the electronic section for comparison with a
predefined interval.
A predefined interval may represent a temperature interval, e.g. T>150 C. When
the milling tool drills a hole in the valve, the downhole tractor 66 provides
a force
by which the drill bit 60 presses against the valve to drill and penetrate the
valve.
If the temperature in the drill bit 60 reaches 160 C during the operation
because
the pressure generated by the downhole tractor 66 is too high when the drill
bit
60 is pressed against the valve, the information in the step of comparing the
recorded information is found to be within the predefined interval of T>150 C.
The electronic section 72 comprising the processing means defines, based on
the
comparison and a programmed knowledge, e.g. the predefined interval T>150 C
considered dangerous for the drill bit 60, how to appropriately distribute the
electrical power, e.g. by lowering the electrical power to the downhole
tractor 66,
thus reducing the force by which the drill bit 60 is pressed against the
valve. The
definition of the appropriate power distribution may also be based on another
appropriate power distribution to avoid overheating, e.g. to increase
electrical
power to a cooling unit, allowing the cooling unit to increase the cooling
effect on
the drill. Finally, the computing means controls the distribution of
electrical power
between the operating units, such as the downhole tractor 66 and the cooling
unit 63, by distributing less electrical power to the downhole tractor 66 and
thus
more to the cooling unit 63 and utilise the new available amount of electrical
power to perform the operation.
By using the method comprising the steps described above for distributing
electrical power between two or more operating units in a wireline tool string
80
performing at least one operation, it may be detected if one or more
operations
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is/are performed on inappropriate or even dangerous operating conditions for
the
two or more operating units and therefore distribute(s) the power
appropriately
to avoid problems. The steps of comparing the recorded information, defining
an
appropriate electrical power distribution and controlling the electrical power
distribution of the wireline tool string 80 may be performed uphole by a
computer, aided by human interaction, an electronic circuit or similar
electrical
devices capable of performing the steps mentioned above in part or as a whole.
To minimise data transfer over the wireline, the steps may, however,
preferably
be performed downhole in the wireline tool string 80 by the electronic section
72
comprising the computing means 61 capable of performing the steps mentioned
above.
As shown in Fig. 2, the step of comparing 20 may further comprise a subroutine
with a step of classifying the predefined intervals 27 with a set of
classification
parameters, e.g. according to a level of importance, level of risk, etc. of
the
operating condition 15. The classification parameter may be a grade, a number
or
similar indication of whether the operating condition 15 is within an
appropriate
or inappropriate interval and/or to which degree of risk, such as whether it
is
classified as no risk, moderate risk or high risk. The classification of the
predefined intervals 27 allows the different operating conditions to be
categorised
based on their criticality to the operation or the tool breakdown. When
defining a
power distribution, in step 30, between different operating units in a
downhole
tool, it is very important to secure critical processes requiring electricity.
An
example may be a drilling operation with a drilling tool having a maximum
critical
temperature. The temperature may be classified as a high risk predefined
interval
if the entire tool may break down as a consequence of exceeding the predefined
interval. The drilling speed may be another operating condition classified as
a low
risk predefined interval. The predefined interval of the speed may be given
maximum priority during drilling operations seeking to go fast as opposed to
e.g.
during precise operations or commencement of laterals. However, even when the
speed is prioritised based on the purpose of the operation, it is important
that the
speed is classified as less important than critical operating conditions like
temperature. The step of classification of the predefined intervals 27 is not
to be
mixed with prioritising the operating conditions, since the classification of
parameters is used to ensure safe operation of the downhole tool, while the
prioritising of operating conditions allows the user to set up an operation
where
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the operating conditions important to this specific type of operation are
prioritised
over less important operating conditions.
Fig. 3 shows an example of three predefined intervals 25; a first 50, a second
51
5 and a third 52 predefined interval 25 that may be classified by three
classification
parameters A, B and C. As seen in the example of predefined intervals 25 shown
in Fig. 3, the set of predefined intervals 25 may be temperature intervals,
which
further may be classified by parameters A, B and C, where A<150 C,
150 C13175 C and C>175 C, wherein the classification parameter A may be
10 defined as no risk of damaging the operating unit, B may be defined as
moderate
risk of damaging the operating unit, and C may be defined as high risk of
damaging the operating unit during operation.
Using classification parameters A, B, C, the method of distributing the
electrical
power to two or more operating units facilitates distribution of the
electrical
power in a more intelligent way than when only comparing the information of
the
operating condition to the predefined intervals 25.
The schematic diagram in Fig. 4 shows a method in which the step of defining
an
appropriate electrical power distribution 30 further comprises a step of
comparing
classification parameters 35 of at least two different operating conditions
15, e.g.
temperature, rotational speed, current draw, etc. As an example, a milling
tool
performs an operation of drilling a hole in a valve blocking a flow path
inside the
well according to the described method. A temperature sensor records
information of the operating condition 15 indicative of a temperature of the
drill
in the milling tool, and the sensor for measuring the rotation of the drill
records
information of the operating condition 15 indicative of revolutions per minute
(RPM) of the drill during the step of recording of information 10. The
operating
conditions 15 indicative of the temperature and the RPM of the drill bit are
each
compared to a set of predefined intervals 25 classified by a set of
classification
parameters. The classification of the predetermined interval is chosen, e.g.
to
define that one operating condition 15, e.g. the temperature of the drill bit,
always has to be within an acceptable tolerance interval of 100-150 C,
depending
on the material used, since the drill bit may simply break down during too
high
temperatures, whereas a second operating condition 15, such as the RPM of the
drill bit, would have an acceptable tolerance interval of 10000-15000 RPM due
to
e.g. optimal drilling performance. Comparing the classification parameters of
the
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predefined intervals 25 between the two operating conditions 15 therefore
allows
an appropriate power distribution 30 to be defined, and it is thereby possible
to
control the operating units accordingly.
By having several operating units each performing the steps of recording
information 10, the step of comparing the recorded information 20 and the step
of defining an appropriate electrical power distribution 30 for operating
conditions
of the specific operating units, a master-slave configuration between the two
or more operating units may be configured such that a master unit comprises
the
10 comparison of classification parameters based on inputs of classification
parameters and corresponding appropriate power distributions from each of the
operating units, and furthermore, the master unit controls the power
distribution.
Basing the power distribution on a comparison of classification parameters
may,
15 in some instances, be difficult if e.g. all operating conditions 15
suddenly lie
within a high risk interval. However, as shown in Fig. 5, the definition of an
appropriate electrical power distribution 30 may further be based on the
preference of the classification parameter of the operating unit performing
the at
least one operation by a prioritising step 37 prioritising the classification
parameters. If, during the comparison of classification parameters 35, two or
more classification parameters with equal values from two or more operating
units are identified, an optimal power distribution between the units may be
achieved by prioritising the operating conditions 37. Furthermore, specific
operations may need specific priorities such that during e.g. movement of the
tool string 80, the prioritisation is different than the prioritisation during
drilling.
With respect to the above example, the comparison 35 compares the
classification parameter of the temperature of the drill bit. The comparison
35
may then identify that the classification parameters are equal, and additional
information may be needed to make a decision. If the operating classification
parameters are prioritised, e.g. if the temperature is prioritised over the
RPM of
the drill bit, the drill bit may be given as much power as possible to perform
the
drilling operation without compromising the tool by overheating, i.e. if the
temperature has higher priority, the drill bit may be given as much power as
possible as long as the temperature stays below a certain predefined interval
25.
On the other hand, if the temperature increases to above a critical
temperature,
power to the drill bit may not be increased even though the drill bit may
operate
at RPM's which are not optimal for the drilling process. Alternatively, during
a
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temperature increase, the electrical power to the drill bit may be kept
constant,
and the electrical power to a drill cooling unit may be increased, etc. By
prioritising the classification parameters, the prioritisation may be used to
define
an appropriate electrical power distribution if two or more classification
parameters are equal. The prioritisation of the operating units may be
selected
based on e.g. temperature tolerances, power tolerances, pressure tolerances,
vibration tolerances, cost/benefit, time consumption, etc. of the operating
units
and/or other parameters.
Prioritising the plurality of operating conditions 15 and/or prioritising the
plurality
of the operating units allows appropriate power distributions during complex
operations involving many operational tools and many operating conditions 15.
Fig. 6 shows a wireline tool string 80 comprising a drive unit, such as a
downhole
tractor 66, a hydraulic section 68, an electric motor 70, a power distribution
unit
73 and a wireline 74.
By a casing is meant any kind of pipe, tubing, tubular, liner, string etc.
used
downhole in relation to oil or natural gas production.
The downhole tractor may have projectable arms having wheels, wherein the
wheels contact the inner surface of the casing for propelling the tractor and
the
tool forward in the casing. A downhole tractor is any kind of driving tool
capable
of pushing or pulling tools in a well downhole, such as a Well Tractor .
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.
