WO2010002270A2

WO2010002270A2 - Trigger device for activating an action

Info

Publication number: WO2010002270A2
Application number: PCT/NO2009/000246
Authority: WO
Inventors: Sven Revheim; Espen Revheim
Original assignee: Peak Well Solutions As
Priority date: 2008-07-04
Filing date: 2009-07-02
Publication date: 2010-01-07
Also published as: WO2010002270A3; NO327949B1; NO20083040A

Abstract

A trigger device (10) for activating an action by detection of a predetermined sequence, the sequence being given by characteristic changes in a natural magnetic field, and where the trigger device (10) comprises one or more magnetic field sensors and means for detecting and interpreting said changes in a natural magnetic field. The trigger device (10) is constituted further by an independent unit with no moving parts which is signal- connected and/or mechanically connected to one or more device that are to be activated to perform an action. The device can be implemented to activate and operate different types of tools.

Description

Trigger device for activating an action

Introduction The present invention relates to a device for detection of changes in a natural magnetic field. On recognising a specific movement pattern which constitutes a sequence, the device will be able to activate an action. More specifically, the invention relates to a trigger device with no moving parts which detects changes in a natural magnetic field and which activates an action on recognising one or more predetermined sequences which are given by changes in a natural magnetic field.

Prior art

Motion detection of devices introduced into elongate pipes, such as tools, has been found to be difficult. This applies in particular to cases where a device is attached to an elongate cable. Owing to long stretches, a movement at one end of the cable will be reduced at the other end thereof, so that the movement cannot necessarily be detected by the tool.

In oil and gas wells it has proven to be particularly difficult to detect motion. When running different tools into a well, it is important to receive feedback as to whether the tool responds to various activation signals that are sent to the tool. As a consequence of large well depths, it may be difficult to know whether a tool is in fact performing a given action. It may take a long time before motion or standstill of a tool can be uniquely determined at the surface. Traditionally, it has simply been established whether a tool is moving by observing the motion of a string, such as a drill string, coiled tubing or the like at the surface. This works nicely if the well is not too deep, and also provided that a string is in fact used, such as a drill string, coiled tubing or the like. As deeper wells have been drilled, it has been desirable to use to a greater extent tools which do not hang down from said string, such as a drill string, coiled tubing or the like because the long connections involve greater costs, are more subject to failure in the form of cable breaks etc., and take a long time to run up and down the well. At great depths, the traditional way of detecting motion or standstill is inadequate. The string, drill string, coiled tubing or the like can be moved relatively far on the surface without it being possible to determine unequivocally whether the tool is actually moving in the well, because the connection between the tool and the surface may expand or be compressed quite substantially without the tool far down in the well moving. This is shown in Figs. 2a-d. The broken line indicates the drill string under tension. The difference between the broken line and the solid line indicates slack that must be drawn out before movement on the drill floor is registered downhole. Fig. 2a shows slack in a drill string, Fig. 2b shows vertical tension and no slack apart from stretch in the string, Fig. 2c shows a delayed motion downhole as movement on the surface is taken to draw in slack, Fig. 2d shows horizontal tension and how a delayed motion will occur downhole as movement on the surface is taken to draw in slack.

Instruments that are used for motion detection may be arranged on the tool that is run down into the well without their comprising any means of communication, or their only comprising means for one-way communication. Such instruments may, for example, be used to prevent other equipment from being activated when a tool is in motion, for one-way communication from the surface to a tool etc.

Measuring motion by using one or more accelerometers is a well-known, tried and tested method. An accelerometer measures acceleration, not motion, but as all motion starts and stops with an acceleration, the accelerometer can be used for motion detection. However, the use of accelerometers to detect motion is associated with a number of drawbacks. The accelerometer is inaccurate and requires relatively large and powerful motions in order to provide readings. At great depths, as mentioned, large motions at the surface can be dampened substantially in that the connection expands or is compressed, and the resultant movement of the tool downhole may be so weak and slow that the accelerometer does not give a clear, unambiguous reading. In addition, an accelerometer will not distinguish between a steady motion and standstill, as both these situations are characterised by the absence of acceleration.

Fig. Ib shows measurements from an accelerometer. The figure shows no values, but is intended to illustrate how an accelerometer merely registers change of speed, positive or negative, not constant speed.

Measuring motion by using pressure sensors has also been used to determine whether a tool is in motion or is at a standstill. As a tool moves up or down in a well, the fluid column above the tool and the resulting pressure to which the tool is subjected will change. These changes in pressure can be used to determine whether the tool has moved further up or down in the well. This method requires the tool to move a relatively long way in the vertical direction in order to establish clearly that motion has taken place. Movements over smaller distances will not give clear readings on a pressure sensor. In addition, the method is not suitable for detection of motion or standstill in a horizontal direction or rotational motions.

Various forms of wave signal analysis have also been used to detect motion or standstill. A wave signal analysis system as a rule emits a wave signal, either in the form of light, sound or radio waves, and listens for an echo or a reflection. By measuring the delay, it is possible to determine distance to the object that reflects the wave signal. If this distance changes, it may be concluded that a motion has taken place. By looking in addition at the change in frequency, it is possible to determine the speed of the reflecting object. If the speed is greater than zero, motion has been detected. Wave analysis can be very difficult to implement in environments where there is no homogeneous medium in which the wave signals can travel. In an oil or gas well, the wave signals will have to propagate in many different types of media, for example, oil, natural gas, water, oil-based mud, water- based mud, metal, air, etc. Each of these materials will distort and/or reflect the wave signals differently. Although widely used for motion detection in oil and gas wells, wave signal analysis has many and clear limitations. It is costly, complex, time-consuming and gives unreliable measurements.

Different types of magnetic field measurements have been in use for many years and are, in some applications, a well-known, tried and tested technology. The most common application of these measurements is direction finding. In such an application, the Earth's magnetic field is used to determine direction. Magnetic field measurements can also be used to detect joints (ref. Patent GB-2422622), or irregularities (ref. Patent US-6768299) in, for example, steel pipes. These are common areas of application in the oil and processing industries. Systems have also been developed which are so advanced that they can, for example, determine thread type in joints (ref. Patent US-7095223). Detection of joints can also be used to determine position in a well. If a certain number of joints have been detected and the distance between the joints is known, the distance the measuring point has covered can be found.

US-2006/254768 relates to a solution for measuring movement of a tool down in a borehole based on emitting and detecting magnetic fields. This is different from the present invention which detects a natural magnetic field, and which further uses this to recognise a sequence in order to then trigger or start an action.

WO-2007/015087 describes a method for determining a feature of a downhole device. The method comprises determining a variation in an ambient magnetic field and determining features of the downhole device from the variation. The method may include comparison of the Earth's natural magnetic field with magnetic fields due to the presence of the downhole device. The comparison can be used to identify the location of casing collars.

US-6237404 describes a device and a method for NMR-based detection of properties of a borehole in an earth formation. A plurality of measurements are made in different modes. These comprise pressure, temperature, and motion of the drill string with the aid of magnetometers and/or accelerometers. The object is to measure different properties of the formation.

What is considered to be novel and advantageous about the present invention is the use of magnetic field sensors which measure changes in a natural magnetic field over time which give a sequence, and then use this information to activate an action when a recognisable sequence of motions is registered. By "natural magnetic field" is meant a magnetic field set up by the surroundings in which the magnetic field sensors are located. This includes stable fields such as the Earth's magnetic field, the magnetic field of a casing pipe, the magnetic field of motionless magnetic materials or the magnetic field of ground rock.

The inventive device is a trigger device that may be constituted by an independent unit with no moving parts, and which can move in any direction in relation to the surroundings, and where the trigger device is mounted in connection to an object or device whose motion it is desired to detect. The trigger device may also be stationary in that it is anchored to a stationary device in order to detect motions of nearby objects that move in relation to the stationary device.

The fact that the trigger device is not based on the emission of electromagnetic fields, but makes use of a passive detection of a natural magnetic field from the surroundings makes the trigger device according to the invention a low-energy device that is well suited for use in an autonomous system.

US-7245229 (PathFinder) is regarded as describing the closest prior art. The document describes a method for communicating with a downhole device in order to be able to send control signals to, for example, a directional drilling tool.

The said document describes a method involving the use of different speeds of rotation or duration of rotation of a drill string. From this a code can be derived that can be interpreted in order to then control, for example, a drilling tool.

The activation of an action based on an interpretable code has features in common with the present invention, but the way in which the present invention differs from PathFinder is that the trigger device is constituted by an independent unit with no moving parts, and where the detected magnetic field may be the magnetic field set up naturally by the surroundings. This design means that the trigger device according to the present invention is very flexible as regards implementation and areas of application.

The use of a magnetic sensor to measure rotational speed is mentioned in PathFinder as one way of determining rotational speed. Another way that is mentioned is the use of an optical sensor. The essential aspect of the Pathfinder patent is not the actual device for activating an action, but the method that is used inasmuch as it is the rotational motion per se that is used to derive control signals. The magnetic fields that are measured are set up by permanent magnets mounted on a drill string and with a sensor mounted on a sleeve, where the drill string rotates and the sleeve remains stationary. The measurement of rotational speed is therefore dependent on two mechanical parts which move relative to one another, ref. Fig 2a in the PathFinder patent, and the explanation thereof. This is different from the present invention where the device for deriving control signals for activating an action is constituted by an independent unit with no moving parts. This is possible in that, as mentioned, it is magnetic fields set up by the surroundings that are registered. This means that the detector according to the invention can be used in different ways and not least in different environments.

The use of rotational motion as a signal means will impose a limitation of having to perform the method described in PathFinder during a typical drilling operation in which the drill string rotates. The speed and duration of rotation will then be controlled by operators on the surface. If the sleeve equipped with magnet-sensitive elements and the mandrel equipped with magnets become interlocked, it will not be possible to communicate with the tool. The implementation of the invention in just one unit without any moving parts will ensure that communication is always possible. There is also no need for contact with casing pipes or a rock wall in order to create friction and thus motion between sleeve and mandrel.

The present invention is more flexible since it is not limited to rotational motion only, but some form or other of motion which also includes a rotational motion. By distinguishing between motion and non-motion, it will be possible to derive a code that can be used to activate an action as, for example, controlling a tool. The device that constitutes the invention can thus be used under conditions where a rotational motion cannot be made, i.e., for operations other than drilling, such as well completion, maintenance and inspection. The device is thus not limited to use in the offshore industry. Other areas of use may be in onshore industry. Examples of use will be described in the detailed description below.

Summary of the invention

The present invention relates to a trigger device for use in the oil and gas industry for activating one or more actions by detection of one or more predetermined sequences, the sequences being given by recognised changes in a natural magnetic field detected over time in that the trigger device moves in relation to the surroundings or in that the surroundings move in relation to the trigger device, said trigger device comprising one or more magnetic field sensors to detect said magnetic field, means for interpreting said changes in the magnetic field, means for storing said sequences and means for sending an activation signal. The trigger device is characterised in that it comprises means for checking the type of sequence or sequences received by comparing the sequence or sequences with stored sequences; means for checking whether the trigger device at the same time receives other parameters, and using these in further evaluation of whether an action should be activated or not, thereby enabling activation to take place on conditional coincidence of a predetermined sequence or sequences and at least one other parameter, and that it further comprises means for sending an activation signal via electric and/or mechanical means to one or more device that activate said action on the basis of the type of sequence received and any other measured parameters. Although the exemplary embodiments below are for the most part based on problem complexes related to the detection of motion or standstill in oil and gas wells, it should be understood that the invention is not limited to such areas of use and that it can be used in different situations and areas of application where detection of motion is of interest to be able to control and activate all forms of actions. A number of examples of this are described below.

The object of the present invention is achieved with a trigger device that is characterised by the features disclosed in independent claims 1 and 14, and by additional advantageous embodiments and features as disclosed in the dependent claims. The invention is very flexible since it does not contain moving parts, and can be implemented in different ways and adapted to different areas of application and operational conditions.

Detailed description The invention will now be described in detail with reference to the attached drawings which are an aid to understanding the invention by showing some exemplary embodiments.

Fig. 1 has been included to show the measuring principle used in the present invention and the difference between measured values from a magnetic field sensor and an accelerometer. The graphs do not show any values, but illustrate how an accelerometer only registers a change in speed, positive or negative, but where constant speed will not be registrable. By "magnetic field measurements" as used by the invention is meant the difference between a current and a previous measurement of a natural magnetic field.

Fig. Ia shows an example of a movement pattern of a random object;

Fig. Ib shows an example of what type of measurement signals an accelerometer will give in the case of a movement pattern as indicated in Fig. Ia; and

Fig. 1 c shows an example of what type of measurement signals a magnetic field sensor will give in the case of a movement pattern as indicated in Fig. 1 a. Fig. 2 shows examples of how tension in a drill string will result in a different movement pattern for a tool that is located far downhole than for the part of the drill string that is on the surface. The broken line indicates the drill string under tension. The difference between the broken line and the solid line indicates slack that must be drawn out before movement on the drill floor is registered downhole.

Fig. 2a shows slack in a drill string;

Fig. 2b shows vertical tension and no slack apart from stretch in the string;

Fig. 2c shows vertical tension and how a delayed motion will occur downhole as movement on the surface helps to take in slack; and

Fig 2d shows horizontal tension and how a delayed motion will occur downhole as movement on the surface helps to take in slack.

Fig. 3 shows an example of a trigger device that is constituted by an independent unit with no moving parts.

Fig. 4 shows an example of implementation of a trigger device in a well operation.

Fig. 5 shows an example of a trigger device mounted on a casing.

Fig. 6 shows a trigger device mounted on a running tool.

Fig. 7 shows a trigger device mounted on a plug.

Fig. 8 shows a trigger device mounted on a shoetrack.

Fig. 9 shows a trigger device mounted on a sub.

Fig. 10 shows a trigger device used passively as a logger.

Fig. 11 shows means for transmitting activation signals from a trigger device to an device that is to be activated.

The present invention is described, as mentioned, as a trigger device for activating one or more actions by detection of one or more predetermined sequences, the sequence or sequences being given by recognised changes in a natural magnetic field, and the trigger device comprising one or more magnetic field sensors for detecting a natural magnetic field, means for interpreting said changes in a natural magnetic field, means for storing sequences and means for sending an activation signal.

The trigger device is characterised in that the magnetic field sensors and all said means permitting interpretation of a natural magnetic field and transmission of the activation signal are constituted by an independent unit with no moving parts, and where the trigger device is further signal-connected and/or mechanically connected to one or more device that are to be activated to carry out said action when the trigger device recognises said predetermined sequence or sequences.

By "natural magnetic field" is meant all types of magnetic field, such as those that are set up naturally by magnetic surroundings as, for example, pipes with magnetic properties or tools moving in the pipes. Moving the trigger device in relation to its surroundings will result in a change in both the direction and signal strength of natural magnetic field. Alternatively, the trigger device itself can remain stationary whilst objects affected by a natural magnetic field on the trigger device move. The trigger device will detect and interpret the change in a natural magnetic field, and in the event of recognised characteristic changes, it will be able to activate one or more actions.

Changes in the Earth's natural magnetic field are another type of natural magnetic field that the trigger device is well suited to detect. This means that the trigger device is not limited to use in or together with structures and device which emit a magnetic field. The trigger device is therefore suitable for use as an independent device without any influence from other device.

That the trigger device activates an action means to say that the trigger device emits an activation signal which activates one or more devices to perform a desired action. The activation signal may comprise information for switching the device on or off, or for putting the device in a particular mode, such as switching to a low- energy mode or hibernation mode, and waiting for a new sequence before it become fully operative again. The switching on or off may include switching on or off a series of consecutive actions.

The activation signal from the trigger device can be sent via signals to one or more device that are to perform an action. One example of this is the transmission of signals via an electromagnetic coil. These signals can then be detected by receiver means in the devices that is or are to carry out the action.

The trigger device may also comprise means for receiving signals from one or more devices that are to perform said action. In this way, the trigger device can, for example, receive feedback as to whether the device does perform the action that was activated by the trigger device. An example of means for transmitting signals may be the same coils as mentioned in the paragraph above, but where the signals in this case pass in the other direction, i.e., from the device that is to perform the action to the trigger device.

The activation signal from the trigger device can also activate mechanical means which relay activation signals to a device that is to perform the action. Examples of this are moving rods, or the use of compressed air to open and close valves. Examples of this will be described in more detail with reference to the figures.

As mentioned, the action that is activated may be any action that is performed by a device which receives the activation signal.

The detection of changes in a natural magnetic field occurs when the magnetic field changes direction. The trigger device will detect this either in that it moves in relation to its surroundings or in that the surroundings move in relation to the trigger device. The means for detecting such a change may comprise a level filter that is arranged in such a way that noise which develops as small changes in the magnetic field can be filtered away, thereby preventing the noise from affecting the measurements. Thus, the sensitivity of what is to be detected as a motion and standstill can be adjusted.

The trigger device may further include a coil that sets up an opposing electromagnetic field to reduce the magnetic field in the case where the trigger device is used in surroundings in which the field is stronger than the sensitivity range of the measuring device. This means that the trigger device will be self- calibrating and adapt itself to the magnetic field in the surroundings in which it operates.

Detecting a predetermined sequence which is produced by recognised changes in a natural magnetic field means that the trigger device has means for comparing stored sequences with the sequence that is produced when the trigger device interprets characteristic changes in a natural magnetic field. When a sequence is recognised in that a stored sequence matches a detected sequence, the trigger device in one embodiment will emit an activation signal. In another embodiment, the trigger device does not emit an activation signal until one or more other parameters have a preset value. This will be described in more detail below.

There are, as mentioned, several ways in which a detected sequence can be produced. For example, it may be ensured that a natural magnetic field is changed in accordance with a specific pattern that produces the sequence. This can be done in that the trigger device is anchored to a moving device which moves in relation to the surroundings, such that changes in the natural magnetic field can be detected.

It may also be done in that the trigger device is anchored to a stationary device, and where nearby devices move in relation to the trigger device and the stationary device such that changes in the natural magnetic field can be detected.

A predetermined sequence is a sequence that is stored in a memory in the trigger device, or which during operation of the trigger device is stored in the memory after the sequence has been detected. Sequences which are in the memory are used to compare other detected sequences. Different recognised sequences can cause the trigger device to emit different activation signals as, for example, to switch on or off a device which in turn starts or stops an action.

Different types of activation signal can further activate one or more device which are to perform different actions based on the type of activation signal sent.

A sequence can be stored in the memory before the trigger device is put into operation in that the trigger device is programmed with relevant sequences that are stored in the memory. A sequence can, as mentioned also be stored in the memory during operation in that the trigger device is switched to a programming mode or logging mode in order to receive specific sequences which then are stored in the memory. This can take place in that the trigger device first recognises a sequence which means that the trigger device is to switch to logging mode. It can then log and store in the memory subsequent sequences. The logged sequence can further be linked to a specific activation signal that activates a specific action when the trigger device recognises the logged sequence.

A typical scenario for such a use is that during the use of the trigger device it is registered that the same sequence is received at a specific location. This may be at a specific location in, for example, a formation or a casing that gives the same sequence with changes of a natural magnetic field, and thus a characteristic detected sequence that can be recognised. This pattern can be produced in that the trigger device, for example, passes perforations in a casing, or in that the trigger device passes formations that emit a characteristic magnetic field. By putting such a sequence in the memory, location will be known on later recognition of this sequence in order then, if so desired, to activate an action.

In addition to different magnetic field sensors, the trigger device may comprise sensors for measuring other parameters, where the other measured parameters are combined with detection of the said sequence that is given by recognised changes in a natural magnetic field. In this way, activation of an action may be dependent on the coincidence of a recognised sequence and one or more different measured parameters. The other measured parameters may be pressure, temperature, flow and time which should have or be within a certain value.

When implemented thus, the trigger device will only activate an action when a sequence is recognised and further that, for example, the pressure at the same time is within a specific range.

It will be understood that the trigger device according to the present invention is flexible and can be implemented in different ways according to need and depending on the surroundings in which it is to operate.

The trigger device may be incorporated in and constitute a part of the device that is to perform the action. Alternatively, it can be mounted in connection with the device that is to perform the action.

Different uses and implementations will be described in more detail below with reference to the figures.

Figure 3 shows an example of an embodiment of a trigger device 10 which, when assembled and functional, is constituted by an independent unit with no moving parts. Furthermore, the trigger device 10 is configured as an elongate cylindrical body having an inner through cavity and an outer delimiting cavity 12 in a cylindrical core 14 that can be sealed. The cavities 12 house electronics, power supply and magnetic field sensors, and can be closed in that an outer cylindrical enclosing sleeve 16 is passed over the cylindrical core 14 which is then held in place by locking means 18. The trigger device 10 may be configured with or without a through hole in the centre. Furthermore, the enclosing sleeve 16 and the locking means 18 may be one and the same part. In order that the device should be leakproof, seals are disposed between the different elements.

Figure 4 shows an embodiment of a well operation with an example of the implementation of a trigger device 10 corresponding to that shown in Figure 3. The trigger device 10 here is anchored to a moving device which in this case is a string 5 with a running tool 20 and a VMB plug 35. By "anchored" is meant that the trigger device 10 is mounted on the same string 5 and thus has the same movement pattern as the part of the string 5 to which the trigger device 10 is mounted. By moving the string 5 in the casing 25, changes in the natural magnetic field can be detected in that the trigger device 10 moves in relation to its surroundings.

The trigger device 10 will register all forms of changes of a natural magnetic field. Even small changes will be registrable. The string 5 can therefore have different movement patterns, and is not limited to only a rotating or transversal motion. The movement pattern may be a combination of different motions that together form a registrable predetermined sequence of motions or standstill, thereby enabling the trigger device 10 to activate the running tool so that the VMB plug 35 can, for example, set a packer against the casing 25.

With the configuration as shown in Figure 4 where the trigger device 10 is incorporated in a separate unit and further mounted in connection with a device, which is the running tool 20 that is to perform the action, it may be expedient to have a wireless transmission of signals to the running tool 20. With such a set-up, the trigger device 10 preferably comprises activating means in the form of one or more electromagnetic coils for emission of electromagnetic signals. The coils may be pulsed with a sequence that is recognised by receiving means in the running tool 20. An alternative may be a mechanical connection between the trigger device 10 and the running tool 20. With such a set-up, the coils can also be used to emit electromagnetic fields that result in reflections in surrounding magnetic elements which in turn are detected by the trigger device 10. This may then be an additional function of the trigger device 10.

Figure 5 shows another example of the implementation of a trigger device 10 where the device is anchored to a stationary device which in this figure is a casing 25. In this case, changes in the natural magnetic field will be detected by the trigger device 10 in that a nearby device, which in this case is a drill pipe 45, moves in relation to the trigger device 10 which remains stationary since it is anchored in the casing 25.

As can be seen from Figure 5, the trigger device 10 is further incorporated in a electromechanical device 40 capable of opening and closing openings 42 between the casing 25 and the borehole so that fluid mass or liquid can flow freely from the cavity in the casing through the open holes 42 in the walls and into the formation. By moving the drill pipe 45, which introduces, for example, cement, in a sequential motion that the trigger device 10 is able to recognise, it will be able to activate the electromechanical device 40 which will open or close said openings 42.

When the trigger device 10 is incorporated in the tool that is to be activated as shown in Figure 5, it is not necessary to have wireless transmission of signals, as the electromagnetic activation signals mentioned by way of example. Other signal means may be used in such a case. Examples of this are activation by means of wire-based signal transmission or a mechanical activation.

Figure 6 shows the trigger device 10 mounted on a running tool 20 which in turn controls a plug 50 that may be a barrier plug. This is an example showing the trigger device 10 mounted on the running tool 20, which is a movable device, and where the trigger device 10 will be an actuator for the well tool.

This works in that the trigger device 10 activates, for example, valves which in turn activate the plug 50 at the end of the running tool 20. There is a mechanical transmission in the plug 50 that then ensures that a seal 48 is set. The running tool 20 can first set the plug 50 and then be detached therefrom. When the running tool 20 is again attached to the plug, a new sequence can be sent by rotating the running tool 20. This will in turn be able to activate valves via the electromechanical device 40 so that it ensures that the plug 50 dislodges in that the seal 48 is no longer compressed.

Figure 7 shows the trigger device 10 incorporated in a plug 50. This arrangement is also used to set a plug 50 at a specific location in the casing. The principle is the same as described in connection with Figure 6, i.e., that it is the trigger device 10 that moves together with the tool and the drill pipe in order to create a new sequence.

Figure 8 shows the trigger device 10 mounted on a shoetrack 60. Here, a cementing valve/valve 62 can be controlled to open or close based on activation signals from the trigger device 10 without their having mechanical contact. By moving the drill pipe with motions that constitute a sequence, the trigger device 10 will recognise the sequence and the valve 62 can be controlled by activating an action.

Figure 9 shows the trigger device 10 mounted on a sub. Here, the trigger device 10 activates an electromechanical device 40 which may be connected to valves that admit pressure from the well path which in turn ensures that a piston opens to allow balls to be dropped to close the drill pipe so that a possible pressure build-up can take place.

Figure 10 shows a trigger device 10 used passively as a logger. By switching the trigger device 10 to a logging mode, it can be programmed with specific sequences that are stored in the memory. This can be done in that the trigger device 10 first recognises a sequence which means that the device itself is to switch to a logging mode, or that a logging mode is set before the trigger device is put into operation. The method may advantageously be used when the trigger device is incorporated in a tool in order obtain a better calibrated trigger device 10 in cooperation with the tool by optimising the sequence that the trigger device 10 is to recognise. In this way, the function of the trigger device 10 can be adjusted and adapted to the surroundings in which it is used and the tools it is to work together with. Figure 11 shows means for transmitting activation signals from a trigger device 10 to an electromagnetic device 40 that is to be activated. The transmitting means are electromagnetic coils 55 which work according to the transformer principle. This is then a wireless transmission system.

The present invention is also characterised by a method for activating one or more actions by detection of a predetermined sequence, where the sequence is given by characteristic changes in a detected magnetic field,

The method is characterised by using a trigger device 10 as described above, and where the trigger device 10 is used to activate and control operations by carrying out the following steps:

- checking the type of sequence received by comparing the sequence with stored sequences; - checking whether the trigger device 10 at the same times receives other parameters than magnetic field, and using these in a further evaluation of whether an action should be activated or not, such that activation can take place on conditional coincidence between two or more measured parameters;

- sending an activation signal to one or more device based on the type of sequence that is received and any other measured parameters for activating said action.

As mentioned above, the stored sequences may be stored prior to use and/or they may be stored during operation of the trigger device in that the device, as mentioned above, can be switched to a logging mode. Sequences are, as mentioned, given by detected changes in the magnetic field of the surroundings in which the trigger moves, e.g., previously registered "signatures" in the formation, joints in pipes, perforations in pipes etc.

The method can be further repeated so as to obtain multifunction triggering controlled by new characteristic changes in a detected magnetic field and/or other parameters. In this way, it is possible, for example, to first start an action, then wait for a certain time, indicated by the type of trigger signal, and then stop the action.

Multifunction triggering is well suited for controlling and activating different forms of energy. An example of a form of energy is pressure which via the trigger signal controls a set of valves included in an autonomous system. A systematic control of the valves will be able to cause advance of the autonomous system. The control of the valves will be dependent on changes in a detected magnetic field and/or other parameters, and thus information about the advance of the autonomous system. The motion of the valves can, for example, be operated by changes in, for instance, supplied compressed air. Such an autonomous system may be a self-propelling unit, such as a tractor comprising one or more trigger devices and which moves inside pipes in order to carry out various operations. This tractor, in addition to it own advance, which is controlled by activation signals, can also receive further activation signals which cause the self-propelling unit to carry out dedicated tasks.

An example of the use of the said tractor is to drop it in a vertical borehole. As the borehole goes from a vertical direction to a horizontal direction, the speed of the tractor will decrease, and ultimately it will stop. The trigger device will then be able to detect that it is no longer in motion, and will send an activation signal to start the tractor so that it moves forwards in a horizontal direction. The advance of the tractor can be controlled by using valves, which are activated by a trigger device, and existing pressure in the well can be utilised to operate the valves.

To make the trigger device more flexible, it can be supplemented with means for generating magnetic fields so as to detect received changes in the magnetic field. The said signal transmission means, in such a set-up, may be used to generate a magnetic field that is detected by the trigger device. They can also be used to send and receive signals to and from the device that the trigger device is to activate.

As can be seen from the examples above, the inventive trigger device is highly suitable for use in operations in an oil or gas well to activate barrier plugs and cementing valves so that they perform a predetermined action.

The use of a trigger device according to the present invention is not limited to use only in the offshore industry. The trigger device will also be well suited for use in other industries such as onshore industry and in maritime activities.

The examples described thus far have shown a trigger device used in connection with elongate pipes in the offshore industry. However, the pipes may also be pipes used in the infrastructure onshore for the pulling of electric cables. It is, moreover, not necessary that it must be a pipe. There could also be ducts which permit the pulling or laying of equipment.

In what follows other alternative uses of the trigger device will be described.

An action that may affect the natural magnetic field of the trigger device is flow of fluid in pipes or ducts. Thus, the trigger device can be used to detect whether something is flowing in a pipe or not, and on the basis thereof activate an action. When there is a strong flow, the pipe through which the flow passes will vibrate so much that the trigger device will be able to register the vibrations as motions if the pipe has magnetic properties. If the flow is not strong enough to cause the pipe to vibrate, there will be other ways in which the trigger device can detect whether there is a flow in the pipe.

If the trigger device is placed in connection with a pipe which is configured as a U- shaped pipe with a magnetic ball inside, the trigger device will be able to detect changes in a natural magnetic field if the ball moves inside the pipe.

An example of the use of a trigger device implemented in connection with a U-pipe is where the U-pipe is placed on a boat that heels from side to side. If the heeling is of a certain magnitude, the trigger device will give a reading and thus result in a sequence which initiates an activation signal that, for example, can warn that the cargo on a cargo ship is at risk of moving and should be secured so as not to become displaced.

The sending one or more magnetic bodies through a straight pipe will affect the detected magnetic field in a similar way as in the U-pipe mentioned above. An example of such a use is to drop, for example, three consecutive balls with magnetic properties down into a casing. When these pass a trigger device that is mounted on the casing, a sequence will be detected and the trigger device can activate an action.

Another relevant example of the use of the trigger device, in onshore activities, is to optimise acceleration of a locomotive that draws behind it several carriages. As is known, it is the case that carriages will begin to roll one after the other only when the carriage in front begins to pull the one behind. Thus, the last carriage will move some time after the locomotive and all the other carriages have started to roll. Each carriage will therefore often start with a jerk. By implementing the trigger device in such a system, motion or absence of motion in one or more carriages will be detectable. This information will in turn be useful for controlling a gradual and uniform acceleration of the locomotive based on information of the motion of one or more carriages. Thus, each carriage will be able to start its motion without a jerk, this being obtained in that the acceleration of the locomotive is controlled by the trigger device.

Another example of the use of the invention is to use a trigger device in proximity to live cables. The trigger device will be able to detect whether there is current flowing in the cable or not, since live cables generate a magnetic field that is detectable. Furthermore, a specific on/off sequence in the cable can be pulsed so that the trigger device interprets this as a sequence which makes it activate a specific action.

A person of skill in the field will understand that although the description of the invention has discussed exemplary implementations within the scope of the invention as defined in the independent claims, there will be other relevant implementations of the invention.

Claims

PATENT CLAIMS

1. A trigger device (10) for use in the oil and gas industry for activating one or more actions by detection of one or more predetermined sequences, the sequence or sequences being given by recognised changes in a natural magnetic field detected over time in that the trigger device (10) moves in relation to the surroundings or in that the surroundings move in relation to the trigger device (10), said trigger device (10) comprising one or more magnetic field sensors for detecting said magnetic field, means for interpreting said changes in the magnetic field, means for storing said sequences and means for sending an activation signal, and where the trigger device (10) is characterised in that it is constituted by an independent unit with no moving parts, and which further comprises:

- means for checking the type of sequence or sequences that are received by comparing the sequence or sequences with stored sequences;

- means for checking whether the trigger device (10) at the same time receives other parameters, and using these in a further evaluation of whether an action should be activated or not, such that activation can taken place on conditional coincidence of a predetermined sequence or sequences and at least one other parameter; and

- means for sending an activation signal via electrical and/or mechanical means to one or more device that activate said action on the basis of the type of sequence that is received and any other measured parameters.

2. A trigger device (10) according to claim 1, characterised in that it further comprises sensors for measuring said other parameters than magnetic field.

3. A trigger device (10) according to claim 2, char act eri s e d in that the sensors for measuring other parameters are sensors for measuring pressure, temperature and flow.

4. A trigger device (10) according to claim 1, char act eri s e d in that it is anchored to a movable device, such that changes in the natural magnetic field are detected in that the trigger device (10) and the movable device move in relation to the surroundings.

5. A trigger device (10) according to claim 1, ch ar act e r i s e d in that it is anchored to a movable device, such that changes in the natural magnetic field are detected in that nearby device move in relation to the trigger device (10) and the stationary device.

6. A trigger device (10) according to claim 1, characterised in that it comprises means for sending activation signals to one or more device that are to perform the action.

7. A trigger device (10) according to claim 1, char a c t e ri s e d in that it comprises means for receiving signals from one or more device that are to perform the action.

8. A trigger device (10) according to claims 6 and 7, characterised in that the means for sending and receiving signals comprise electromagnetic coils (55).

9. A trigger device (10) according to claim 1, characterised in that it comprises mechanical means for transmitting activation signals to a device that is to perform the action.

10. A trigger device (10) according to claims 1-5, characterised in that the trigger device (10) is incorporated in and forms a part of the device that is to perform the action

11. A trigger device (10) according to claims 1-5, characterised in that the trigger device (10) does not form a part of the device that is to perform the action, but is mounted in connection therewith.

12. A trigger device (10) according to claim 4, characterised in that the movable device is an actuator for a well tool.

13. A trigger device (10) according to claim 5, characterised in that the stationary device is a casing (25).

14. A method for use in the oil and gas industry for activating one or more actions by detection of one or more predetermined sequences, the sequence or sequences being given by recognised changes in a natural magnetic field detected over time and where the method comprises the use of a trigger device (10) which moves in relation to the surroundings or in that the surroundings move in relation to the trigger device (10), said trigger device (10) comprising one or more magnetic field sensors for detecting said magnetic field, means for interpreting said changes in the magnetic field, means for storing said sequences and means for sending an activation signal, and where the method is characterised by the use of a trigger device which is constituted by an independent unit with no moving parts, and the method further comprising:

- checking the type of sequence or sequences that are received by comparing the sequence or sequences with stored sequences;

- checking whether the trigger device (10) at the same time receives other parameters, and using these in a further evaluation of whether an action should be activated or not, so that activation can taken place on conditional coincidence of a predetermined sequence or sequences and at least one other parameter; and

- sending an activation signal via electrical and/or mechanical means to one or more device that activate said action on the basis of the type of sequence that is received and any other measured parameters.

15. A method according to claim 14, characterised in that stored sequences are stored prior to use and/or are stored during operation of the trigger device (10).

16. A method according to claim 14, characterised in that the method is repeated so as to obtain multifunction triggering controlled by new characteristic changes in a detected magnetic field and/or other parameters.

17. A method according to claim 14, characterised in that the activation comprises starting and/or stopping an action.

18. A method according to claims 14-16, char act eri s ed in that the activation signal is used to control and activate different forms of energy.

19. A method according to claim 18, characterised in that the energy form is pressure and where the trigger signal controls a set of valves included in an autonomous system, the control of the valves causing advance of the autonomous system, and where controlling the valves is dependent on changes in a detected magnetic field and/or other parameters, and thus information about the advance of the autonomous system.

20. A method according to claim 19, characterised in that the autonomous system is a self-propelling unit that carries out different operations, and where the method further comprises using further activation signals that cause the self-propelling unit to perform dedicated tasks.

21. A method according to claims 14-20, characterised in that it is used to detect actions in elongate pipes and/or ducts.

22. A method according to claim 21, characterised in that the action is flow of fluids in pipes that affect a detected magnetic field.

23. A method according to claim 21, characterised in that the action is one or more magnetic bodies that pass through the pipe and that affect the magnetic field.

24. A method according to claim 21, characterised in that the elongate pipes are pipes used in the infrastructure onshore.

25. A method according to claim 21, characterised in that the elongate pipes are pipes for the pulling of electric cables.