EA039708B1 - Downhole communication - Google Patents

Abstract

Provided are downhole electrical energy harvesting and communication in systems for well installations having metallic structure carrying electric current, for example CP current. In some instances there is a harvesting module (4) electrically connected to the metallic structure (2) at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure (2); and the harvesting module (4) being arranged to harvest electrical energy from the electric current. In addition or alternatively, there may be communication apparatus (4, 5, 6) for communication by modulation of the current, for example CP current, in the metallic structure (2).

Description

The field of technology to which the invention belongs

The present invention relates to downhole communication. In particular, it relates to methods and systems for communicating with devices in a downhole installation having a metal structure provided with cathodic protection. The present invention also relates to methods and systems using energy harvesting methods and systems, as well as apparatus for use in such methods and systems.

Background Art Information

There is a general desire to be able to extract data from oil and/or gas wells, as well as from control devices located in oil and/or gas wells, such as valves, such as underground safety valves.

However, supplying power to such downhole devices presents certain difficulties. In some circumstances, power may be supplied directly from the surface through a cable, or power may be supplied to devices directly from the surface in a hydraulic manner. However, in other circumstances, such methods of power supply are not applicable. In some circumstances, batteries may be the solution. However, such a solution presents challenges in itself, especially in downhole environments where fairly high temperatures tend to shorten battery life.

The essence of the invention

Thus, there is a need for alternative power sources for downhole devices that can be used in circumstances where power supply directly from the surface via a cable or hydraulically is difficult, impossible or undesirable, which would overcome the limitations encountered in cases where rely on battery power supply. It is also necessary to provide alternative means of communication between different locations within a well, as well as with areas of another well and/or areas on the surface.

In the present description, the term surface refers to the surface of the earth in the case of a subsurface well, where the wellhead is located; seabed/bottom level in the case of a subsea well; and the wellhead site on the platform. When appropriate, the term also refers to areas above said areas. In general, the term surface is used to refer to any suitable area, for example, for supplying and/or receiving power/signals, that is outside the wellbore.

According to a first aspect of the present invention, there is provided a downhole electrical energy collection system for collecting electrical energy in a downhole installation having a metal structure carrying electric current, said system comprising: a collection module electrically connected to the metal structure in a first section and to a second section spaced from the first section, while the first and second sections are selected so that in use there is a potential difference between them due to the electric current flowing through the structure; wherein the collection module is configured to collect electrical energy from said electrical current.

The downhole installation may be a cathodic protection installation, then the electric current is the cathodic protection current. Although the solutions presented here can be used in a system where current is specifically applied to the downhole structure to supply power, it has been found that power can also be collected from cathodic protection systems. In this case, the collection of power from already existing currents is particularly advantageous.

In general, the second section will be the downhole section.

In some cases, the connection to the second site may be a connection to the rock via an electrode. A more typical case, however, would be one in which the collection module would be connected to the metal structure at the first and second spaced sections.

Such systems and methods have certain advantages in that power can be provided to the downhole tool without the need for a separate power source. Moreover, power can be provided without relying on local batteries, which will often have a limited lifespan. It can also be provided without the need for a cable through the wellhead. Similarly, the proposed solutions can be implemented without the use of toroids for signal injection and extraction. This reduces the complexity and technical problems that may arise when implementing the system.

The collection module may be configured to collect electrical energy from direct currents.

Preferably, the current flow in the sections of the metal structure in the areas between the first section and the second section occurs in the same longitudinal direction.

Preferably, between the first section and the second section, a continuous current flow path is provided, which would at least partially pass through the metal structure.

- 1 039708

This description presents the elements that will generally be present in the installation, unless its design is modified. The ideas presented here generally do not require modification of a standard downhole installation as a whole, i.e. they are oriented to work with a standard installation.

The collection module may be electrically connected to the metal structure in the second section.

A single or each connection to the metal structure may be formed with the metal extension section/metal pipe section.

In several embodiments, the spaced portions may be axially spaced. Connections may be formed to a common section of metal elongated members, such as a common section of metal pipe that is part of a metal structure. The uppermost of the two offset sections may be located in close proximity to the location of the liner hanger provided in the well. Often this option will correspond to the most practical location of the uppermost section. In some cases, a top connection may be formed to the riser.

Both connections, for example, may be formed with a production string provided in the well, or both connections may be formed with a first casing section separated from the production string by a first annulus A, or both connections may be formed with a second casing section, separated from the first casing section by a second annulus B, etc.

In other cases, axially spaced connections can be formed with different sections of metal extensions, for example, with different sections of metal pipe, which will lead to similar results, but in general, it is more appropriate to create connections with the same section of metal extensions. /metal pipe if there is no reason to use other solutions.

Where spaced sections are axially spaced and a potential difference between them is required, the distance between the sections should preferably be significant, typically 100 m or more. Preferably between 300 and 500 m.

The electrical connection to the metal structure in the first section may be a galvanic connection.

The electrical connection to the metal structure in the second section may be a galvanic connection.

The collection module may be located in one or more elongated elements external to the well, inside the annulus of the well, and inside the inner wellbore.

The connection to at least one of the sections, the first or the second, can be provided by means of a cable running along the metal structure.

If the second spaced contact is formed with at least one section of metal elongate elements, it is preferable that the electric current flowing through said at least one section of metal elongate elements, on which the first contact is formed, moves in the same longitudinal direction as the electric current , flowing along at least one section of metal elongated elements, on which the second contact is formed.

If the first spaced contact and the second spaced contact are both formed with the same section of metal elongated elements, it is preferred that said section of metal elongated elements be continuously conductive between said first and second sections.

At least one connection between at least one of the electrical contacts and the collection module may be provided with an insulated cable.

The cable may be selected to have a conductor with a relatively large cross-sectional area. When selecting a cable, the goal is to select a cross-sectional area that is large enough to provide the required level of collection, one that provides a sufficiently low resistance in the cable.

Preferably, the insulated cable has a conductive area of at least 10 mm ² , preferably at least 20 mm ² , more preferably at least 80 mm ² .

The cable may be a conductor placed in the column.

One of the connections can be formed in the absence of an external cable. One of the connections may be formed by the conductive housing of the collection module (or surrounding the collection module).

Usually there is some optimal value for the distance between connections. The greater the distance, the greater the change in potential between the contact areas, but the greater the resistance of the cable. The method presented here may include the step of determining the optimal distance between spaced sections. This distance can be determined by simulation for

- 2 039708 specific installation.

The distance between sites can be at least 100 m.

In other embodiments, the spaced portions may be radially spaced. The first of the connections can be formed with a first section of metal elongated elements, for example, the first section of a metal pipe, which is part of a metal structure, and the second of the connections can be formed with a second, different section of metal elongated elements, for example, with a second, different section of metal pipe, which is part of a metal structure. Therefore, the connection can cross the annulus formed by the two sections of the metal pipe.

For example, one connection may be formed to the production string provided in the well and one to the first casing section separated from the production string by the first annulus A, or one connection may be formed to the first casing section provided in the well and one with a second casing section separated by a second annulus B from the first casing section, and so on.

In some cases, the spaced sections may be spaced both axially and radially.

Connections can be formed with a common section of metal elongated elements that is part of the metal structure.

In some embodiments, the first of the connections is formed with a first section of metal elongated elements that is part of the metal structure, and the second of the connections is formed with a second, different section of metal elongated elements that is part of the metal structure.

For electrical isolation of the first section of metal elongated elements from the second section of metal elongated elements, isolation means may be provided in the connection area.

Isolation means may be provided to electrically isolate the first section of the elongated elements/metal pipe from the second section of the elongated elements/metal pipe in the region of at least one of the connections. This can help ensure that there is a potential difference between the elongate/metal pipe sections in the areas where the connections are made. This is achieved by having different ground paths from each element/pipe section.

It should be noted that in the solutions described here, the currents from which the energy is harvested will generally flow in the same direction on the first and second sections of the metal elongated elements/pipe. Therefore, the isolation is not intended to form a separate short path, but rather to change the ground path for one of the sections relative to the other.

The insulation means may comprise an insulating layer or coating provided on at least one of the elongate/metal pipe sections. The means of isolation may comprise at least one insulating centralizer to keep the sections of elongated elements/metal pipe at a distance from each other.

Means of isolation may be provided to prevent electrical contact between the two sections of elongated members/metal pipe at a distance of at least 100 m, preferably 300 m.

At least one of the connections may be in the isolated area. Both connections can be in an isolated area. At least one of the connections may be located near the center point of the isolated area. The location of at least one of the connections can be determined by modeling a particular installation to determine the optimal location, which is then selected.

The collection module can be provided in the wellbore of the central section of the string, in the annulus or outside the casing - between the casing and the rock. Thus, among other possible locations, the collection module may be provided in annulus A, annulus B, annulus C, annulus D, or any other annulus.

This makes it possible to supply power to areas where it is generally not possible and/or undesirable to run cables from the surface, which is especially useful in the case of subsea wells. In addition, this possibility is provided without the need to use primary batteries or other local power sources, which means that it is possible to supply power to such areas throughout the life of the well.

The collection module may contain variable impedance means for varying the load between two connections. The variable impedance means may be controlled by a microprocessor.

Variable impedance means can be used to vary the load in order to optimize power collection.

Variable impedance means can be used to modulate the load in order to transfer data from the acquisition module towards the surface.

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Downhole communications may be provided to transmit data from within the wellbore towards the surface. Downhole communications may also be configured to receive data from, for example, the surface.

The acquisition module may include downhole communications. In other cases, downhole communications may be located separately. The downhole device powered by the acquisition module may include downhole communications.

The downhole communication means may comprise variable impedance means.

The overhead communication means may be provided at the exit portion of the wellbore and include a detector to detect changes in current, such as cathodic protection current flowing through the metal structure, to enable retrieval of data encoded by the load modulation in the acquisition module. For example, the detector may be configured to detect the potential of the metal structure relative to a reference value, or to detect a drop in potential across the structure; or current from a power source used to deliver superimposed cathodic protection current to a metallic structure.

In other embodiments, other forms of communication may be used instead of communicating with the surface by modulating the load. For example, an acoustic and/or electromagnetic signal may be used. Load modulation is one example of applying an electromagnetic signal, but other, more direct, methods of applying an electromagnetic signal can be used.

The downhole communication means may be configured to provide data-carrying acoustic signals to the metallic structure, while the upper communication means may be configured to receive data-carrying acoustic signals.

The downhole communication means may be configured to provide data-carrying electromagnetic signals to the metallic structure, while the upper communication means may be configured to receive data-carrying electromagnetic signals.

The overhead communication means may be configured to deliver data-carrying acoustic and/or electromagnetic signals to the metallic structure, while the downhole communication means may be configured to receive data-carrying acoustic and/or electromagnetic signals.

In some instances, uphole communications and downhole communications may be configured to communicate using both types of signals: acoustic and electromagnetic signals. This creates a useful redundancy in that if one link fails, the other link will continue to function.

A collection module may be placed at a predetermined position within the well to collect power, and a cable may be provided to supply electrical power downhole downhole to the downhole tool. The cross-sectional area of the cable used to deliver electrical power downhole downhole will typically be smaller than the cross-sectional area of any cable used to collect that power, and the power will typically be delivered downhole downhole at a higher voltage than the voltage generated between the downhole contacts with current flowing through a metal structure, for example, cathodic protection currents.

In some embodiments, the current flowing through the elongated elements is supplied from the surface of the well.

In some embodiments, the current flowing through the elongated element is supplied from one or more sacrificial anodes.

In some embodiments, the current flowing through the elongated members is superimposed current from an external power source.

In some embodiments, the well surface voltage in use is limited to -0.7V to -2V relative to the silver/silver chloride reference cell.

Preferably, the potential difference between spaced contacts is less than 1 V, preferably less than 0.5 V, more preferably less than 0.1 V.

Optionally, the resistance of the well structure between the contacts does not exceed 0.1 ohm, preferably does not exceed 0.01 ohm.

The optimum site for collecting power will usually be located near the site where currents, such as cathodic protection currents, are superimposed on the metal structure.

Where spaced portions are axially spaced, it is preferable to position the upper portion in close proximity to the portion in which currents, such as cathodic protection currents, are superimposed on the metallic structure. It should be noted that in the case of a platform structure, current, such as cathodic protection currents, may be supplied to the downhole metal structure through a galvanic connection to the platform structure. In some cases, the solutions proposed here may include controlling the location of this connection.

Often, the optimal site for collecting power will be located near the wellhead, where the highest rate of potential change occurs as one moves into the well. FROM

- 4 039708 On the other hand, the downhole device to which power is supplied may be located below, inside the well. Therefore, the collection module and downhole device may be located at different locations, in particular at different depths in the well.

In other cases, the collection module and downhole device may be located together. Such a system may include a downhole assembly including a collection module and a downhole device.

The top offset contact may be: within 100 m, preferably within 50 m, of the ground if the well is a subsea well, and within 100 m, preferably within 50 m, of the bottom if the well is a subsea well.

The upper spacer contact may be in close proximity to the area corresponding to the potential of the maximum value caused by the electric current flowing through the structure.

The system may also include downhole communications for transmitting and/or receiving data.

The downhole communication means can be configured to transmit data by varying the load between the connections in the spaced sections.

In accordance with another aspect of the present invention, a downhole tool control system is provided, comprising the downhole electrical energy collection system disclosed above and the downhole device, wherein the collection module is electrically coupled to the downhole tool and configured to supply power to the downhole tool.

The downhole device may include a downhole sensor, such as a pressure and/or temperature sensor. The sensor can be installed, for example, in the annulus A, B, C or D.

A sensor located in one annulus or wellbore may be configured to monitor some parameter in a nearby annulus or wellbore in addition to monitoring in the annulus or wellbore in which it is located, or instead of monitoring in the annulus or wellbore in which it is located. To enable measurement of parameters in a nearby annulus or wellbore, a port may be provided through a section of metal structure.

A sensor may be provided to detect leaks in the cemented annulus.

The sensor may include a set of sensors.

The downhole device may comprise at least one of the following elements: a downhole sensor; downhole actuator; annular sealing device, such as a packer or packer element; valve; downhole communication module, such as a transceiver or repeater.

The communication module may include a downhole communication repeater. It may be a repeater for acoustic communication, or electromagnetic communication, including wireless electromagnetic communication and cable electromagnetic communication, or for a hybrid communication system. For example, the repeater may receive acoustic signals from areas downhole downhole and signals towards the surface using electromagnetic coupling, or vice versa. Similarly, both types of communication, acoustic and electromagnetic communication, can be used in one or both directions. The supply of electromagnetic signals can be carried out by applying electrical signals downhole or by modulating the load in the collection module, as described above. The supply of electromagnetic signals can be carried out, at least in part, through cables, as described above.

If the downhole device is a repeater or transceiver, the system can be pre-installed into the well structure to create a wireless ready well. Thus, the system may be set up to provide a wireless communication channel even if the communication capability is not initially used. Here, again, the term wireless means that there is at least one wireless branch in the communication channel, other branches can go over the cable.

In other situations, the specified system can be installed after the fact.

The valve may include at least one of the following: an underground relief valve; a flow control valve in the wellbore; wellbore-annulus valve; valve annulus-annulus; valve wellbore-pressure compensation chamber; valve annulus-pressure compensation chamber; valve through the packer or bypassing the packer.

It should be noted that each device may be a device controlled remotely, for example, may be a device controlled by wireless communication. This could mean

- 5 039708 for example, that when controlled from the surface, at least one wireless branch can be present in the communication channel. Other branches may run along the cable, for example, between the area where the sensor is located and the area where the collection takes place.

The supply of electromagnetic signals may involve the use of DC or AC signals and suitable modulation schemes. The collection module may include a DC/DC converter to collect power from cathodic protection currents or other present currents. The collection module may include an energy storage device for storing the collected power. The power storage device may include a charge storage device that may include at least one capacitor and/or at least one rechargeable battery. Where there are energy storage means, the collection module may be configured to selectively supply power from the storage device or directly from the collected energy. Such selection may be based on predetermined conditions. Alternatively, in the absence of a power storage device, the collection module may be configured to continuously supply power on demand.

For selective use, a primary battery may also be provided in the acquisition module.

The DC/DC converter may include a FET to form a resonant boost oscillator. The DC/DC converter may also include a step-up transformer and may include a coupling capacitor.

The acquisition module may be configured to control the turn ratio of the step-up transformer to modify the load generated by the DC/DC converter. The secondary winding of the step-up transformer may comprise a plurality of taps and/or the step-up transformer may comprise a plurality of secondary windings, and the collection module may be configured to select the windings and/or taps to provide the required turns ratio. A microprocessor controlled switch can be used to select taps and/or windings.

According to another aspect of the present invention, there is provided a downhole assembly comprising the collection module disclosed above and at least one device capable of receiving power from the collection module.

One or more of the sensor module, communication module, and collection module may be provided in the annulus, such as annulus B or annulus C, or other annulus. The sensor module and the acquisition module may be part of a common downhole assembly, however, it is more typical that they are separated so that the sensor may be located deeper than the collection module.

The downhole device may be provided at a different location in the well relative to the collection module.

A collection module may be placed at a predetermined location within the well to collect power, and a cable may be provided to supply electrical power downhole downhole to a downhole tool at another location in the well.

The cross-sectional area of the conductive strand or strands of the cable used to deliver electrical power downhole downhole may be less than the cross-sectional area of the cable used to connect the collection module to the downhole power collection structure.

According to another aspect of the present invention, a downhole monitoring system is provided for monitoring at least one parameter in a downhole installation having a metallic structure carrying electrical current, said system comprising the electrical energy collection system disclosed above; a sensor module for measuring at least one parameter; and a communication module for sending encoded data readings from the sensor module towards the surface, wherein the electrical power collection system is configured to supply electrical power to at least one of the devices to the sensor module or communication module.

According to another aspect of the present invention, a downhole monitoring system is provided for monitoring at least one parameter in a downhole installation having a metal structure carrying an electrical current, said system comprising a sensor module for measuring at least one parameter; a communication module for sending coded data readings from the sensor module towards the surface; and an electrical energy collection system comprising a collection module electrically connected to a metal structure in the first section and to a second section spaced apart from the first section, the first and second sections being selected such that, in use, there is a potential difference between them due to an electric current flowing through constructions; moreover, the collection module is configured to collect electrical energy from an electrical current, while the electrical energy collection system is configured to supply electrical power to at least one of the devices of the sensor module or communication module.

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Said system may include at least one cable having a first length for connecting the collection module to one of the spaced sections.

Said system may include at least one cable having a second length for supplying power from the collection module to the sensor module.

The cross-sectional area of the conductive portion of the cable having the first length may exceed the cross-sectional area of the conductive portion of the cable having the second length.

The communication module may be configured to modulate the electric current flowing through the metal structure in the signal delivery area for data encoding to enable said data to be retrieved in the acquisition area remote from the signal delivery area by detecting the effect of said modulation on the electric current in said area. receipt.

The well monitoring system may include a detector for detecting the effect of modulation on the electrical current at the specified acquisition site to extract encoded data.

The communication module may be configured to control the load generated by the collection module to perform said electric current modulation in the metal structure in the signaling area.

The sensor module may include a pressure sensor.

The pressure sensor may be configured to monitor formation pressure.

The pressure sensor may be configured to monitor pressure in the annulus of the well.

The pressure sensor may be configured to monitor pressure in the closed annulus of the well.

According to another aspect of the present invention, there is provided a downhole communication repeater system for use in a downhole installation having a metal structure carrying electrical current, said system comprising: an electrical energy collection system as disclosed above; and a communication repeater placed downhole in said well and configured to communicate with the first device outside the wellhead via a communication channel that is wireless at least in a section passing through the wellhead and configured to communicate with the second device located in the well, i.e. below the wellhead, so that the connected repeater can act as a repeater between the first and second devices, while the electrical power collection system is configured to supply electrical power to the connected repeater.

According to another aspect of the present invention, a downhole communication repeater system is provided for use in a downhole installation having a metal structure carrying an electrical current, said system comprising a communication repeater located downhole in the well and configured to communicate with a first device outside the wellhead with using a communication channel that is wireless, at least in a section passing through the wellhead, and configured to communicate with a second device located in the well, i.e. below the wellhead so that a connected repeater can act as a repeater between the first and second devices; and an electrical energy collection system comprising a collection module electrically connected to a metal structure in the first section and to a second section spaced apart from the first section, the first and second sections being selected such that, in use, there is a potential difference between them due to an electric current flowing through metal structure; wherein the collection module is configured to collect electrical energy from an electrical current, wherein the electrical energy collection system is configured to supply electrical power to the connected repeater.

It should be understood that reference herein to the first device outside the wellhead refers to the device on the other side of the wellhead from the second device which is located in the well, i.e. communication through the wellhead is preferred. As such, the first device may be located anywhere near the wellhead or remotely, as long as appropriate communication is provided.

The communication repeater may be configured to modulate the electric current flowing through the metal structure at the signal injection site for data encoding to allow data to be retrieved at the acquisition site remote from the signal injection site by detecting the effect of said modulation on the electric current at said acquisition site. .

A connected follower and/or collection module may be provided in the annulus, such as annulus B or annulus C or other annulus.

The communication repeater and collection module may be part of a common downhole unit.

Said system may comprise at least one cable having a first length for

- 7 039708 connection of the collection module with one of the remote sections.

Said system may include at least one cable having a second length for supplying power from a collection module to a communication repeater.

The cross-sectional area of the conductive portion of the cable having the first length may exceed the cross-sectional area of the conductive portion of the cable having the second length.

The downhole communication repeater system may include a detector for detecting the effect of said modulation on the electrical current at said acquisition site to extract encoded data.

The connected repeater may be configured to control the load generated by the collection module to effect said electrical current modulation in the metallic structure at the signaling site.

According to another aspect of the present invention, there is provided a downhole tool control system for controlling a downhole tool in a downhole installation having a metal structure carrying an electrical current, said system comprising the downhole tool; an electrical energy collection system comprising a collection module electrically connected to a metal structure in a first section and to a second section spaced apart from the first section, wherein the first and second sections are selected such that, in use, there is a potential difference between them due to electric current flowing through the structure ; wherein the collection module is configured to collect electrical energy from an electrical current, wherein the electrical energy collection system is configured to supply electrical power to the downhole device.

The downhole device may comprise at least one of the following: a downhole sensor; downhole actuator; annular sealing device, such as a packer or packer element; valve; downhole communication module, such as a transceiver or repeater.

The specified valve may contain at least one of the following elements: underground safety valve; a flow control valve in the wellbore; valve wellbore annulus; valve annulus-annulus; valve wellbore-pressure compensation chamber; valve annulus-pressure compensation chamber; valve through the packer or bypassing the packer.

Power may be supplied to actuate the valve, with the power to move the valve coming from another source (eg spring, differential pressure). Alternatively, power may be supplied to move the valve, or to both control and move the valve. The valve may include a trigger mechanism, such as a servo valve, controlled by power from the power supply system.

The device control system may be configured to supply varying power levels. Thus, the first power level may be supplied at times other than when a second, higher power level is required. Injected currents, such as cathodic protection currents, can be increased if a higher power level is required by switching to more anodes or by applying a higher injected current. This may be at a level undesirable for long term periods due to the potentially damaging effects of too much potential difference due to cathodic protection-hydrogen embrittlement currents, but it is acceptable for short term periods. Therefore, the system, apparatus, method can be configured to temporarily increase the supplied current, such as cathodic protection current. A higher power level may be used, for example, to move a valve from one state to another, while a lower power level may be used at other times, such as when monitoring and/or controlling signals.

The downhole device may be located at a different location in the well relative to the collection module.

A collection module may be placed at a selected location within the well to collect power, and a cable may be provided to supply electrical power downhole downhole to a downhole tool located at another location in the well.

The cross-sectional area of the conductive strand or strands of the cable used to deliver electrical power downhole downhole may be less than the cross-sectional area of the cable used to connect the collection module to the downhole power collection structure.

Another source of power may be available to the downhole tool in addition to the electrical power supplied by the electrical power harvesting module.

In each of the apparatuses described above, the collection module may include variable impedance means for varying the load between two connections. The variable impedance means may be controlled by a microprocessor.

Variable impedance means can be used to vary the load to optimize power harvesting.

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Variable impedance means can be used to modulate the load to transfer data from the acquisition module towards the surface.

Impedance modulation can also be used to transfer from the top section towards the collection module to modulate the applied current (eg cathodic protection current). One way is to turn the anode on and off, which will modulate the potential observed downhole. Thus, data can be encoded by turning the anode on and off. For example, the connection between the anode and the structure can be selectively formed and broken by said switching means. Thus, the upper communication unit may contain switching means for turning the anode on and off. In a superimposed current system, the applied signals can be modulated to encode the data.

According to another aspect of the present invention, a method is provided for supplying power to a downhole tool in a downhole installation having a metal structure carrying an electric current, said method comprising the steps of electrically connecting a collection unit to the metal structure in a first section and to a second section spaced from the first. section, while the first and second sections are selected so that there is a potential difference between them due to the electric current flowing through the structure, while the collection unit is configured to collect electric energy from the electric current, being connected between the sections with a potential difference existing between them;

collect electric power from electric current in the collection unit;

electrical power is supplied from the collection unit to the downhole device.

Said method may include the steps of determining the section where the potential due to the electric current flowing through the structure is maximum in magnitude, and depending on the section of the specified maximum, the first section is selected, in which the collection unit is connected to the metal structure.

According to another aspect of the present invention, a downhole electrical energy collection system is provided for use in a downhole installation having a metal structure comprising at least one section of metal elongated electrical current-carrying members, the collection system comprising an energy collection module comprising an electrical circuit connected between spaced contacts for collecting energy from a potential difference between spaced contacts, wherein the first of the spaced contacts is formed with at least one section of metal elongated elements in the first section, and the second of the spaced contacts is formed with at least one section of metal elongated elements in the second section, with this potential difference is caused by the current flowing through said at least one section of elongated elements, and, at least in part, by the impedance of said at least one section of elongated elements.

Electric current flowing through at least one section of metal elongated elements, on which the first contact is formed, can flow in the same longitudinal direction as the electric current flowing through at least one section of metal elongated elements, on which the second contact is formed.

Preferably, the first spaced contact and the second spaced contact are both formed with the same section of metal extensions; wherein this section of metallic elongate members is continuously conductive between the first and second portions.

Preferably, the metal structure provides a continuous current path between the first section and the second section.

Preferably, the flow of current between parts of the metal structure in the areas between the first section and the second section occurs in the same longitudinal direction.

Preferably, the collection module is configured to collect electrical energy from direct currents.

The electrical connection to the metal structure in the first section may be a galvanic connection.

The electrical connection to the metal structure in the second section may be a galvanic connection.

An electrical connection to the metal structure in the first section can be formed with one of the following elements: casing, liner, string, coiled tubing string, sucker rod.

An electrical connection to the metal structure in the second section can be formed with one of the following elements: casing, liner, string, coiled tubing string, sucker rod.

Spaced sections can be spaced along the axis.

The spaced sections can be spaced radially.

At least one connection between at least one of the electrical contacts and

- 9 039708 the electric circuit can be provided with an insulated cable.

Preferably, the insulated cable has a conductive area of at least 10 mm ² , preferably at least 20 mm ² , more preferably at least 80 mm ² .

The cable may be a conductor placed in a column.

The distance by which the plots are separated can be at least 100 m.

Connections can be formed with a common section of metal elongated elements that is part of the metal structure.

In some embodiments, the first of the connections is formed with a first section of metal elongated elements that is part of the metal structure, and the second of the connections is formed with a second, different section of metal elongated elements that is part of the metal structure.

For electrical isolation of the first section of metal elongated elements from the second section of metal elongated elements, isolation means may be provided in the connection area.

The isolation means may comprise an insulating layer or coating provided on at least one of the sections of the metal elongated elements.

The means of isolation may include at least one insulating centralizer to keep the metal elongated elements at a distance from each other.

Means of isolation may be provided to avoid electrical contact between two sections of metal elongated members at a distance of at least 100 m.

The current flowing through the elongated elements may be supplied from the well surface.

The current flowing through the elongated element may be supplied from one or more sacrificial anodes.

The current flowing through the elongated elements may be superimposed current from an external power source.

The well surface voltage, in use, can be limited to between 0.7V and -2V relative to the silver/silver chloride reference cell.

The potential difference between spaced contacts may be less than 1 V, preferably less than 0.5 V, more preferably less than 0.1 V.

The resistance of the well structure between the contacts may be less than 0.1 ohms, preferably less than 0.01 ohms.

The upper offset contact may be within 100 m, preferably within 50 m of the earth's surface if the well is an inland well; and within 100 m, preferably within 50 m of the bottom if the well is a subsea well.

The upper spacer contact may be located in close proximity to the area corresponding to the potential of the maximum value caused by the electric current flowing through the structure.

Said system may include downhole communications for transmitting and/or receiving data.

The downhole communication means may be configured to transmit data by varying the load between connections in distant areas.

According to another aspect of the present invention, a downhole tool control system is provided, comprising the downhole electrical energy collection system disclosed above and the downhole device, wherein the collection module is electrically connected to said downhole device and configured to supply power to said downhole device.

Said downhole device may comprise at least one of the following elements:

downhole sensor;

downhole actuator;

annular sealing device, such as a packer or packer element;

valve;

downhole communication module, such as a transceiver or repeater.

The specified valve may contain at least one of the following elements:

underground safety valve;

a flow control valve in the wellbore;

wellbore-annulus valve;

valve annulus-annulus;

valve wellbore-pressure compensation chamber;

valve annulus-pressure compensation chamber;

- 10 039708 valve through the packer or bypassing the packer.

The downhole device may be provided at a different location in the well relative to the collection module.

A collection module may be placed at a selected location within the well to collect power, and a cable may be provided to supply electrical power downhole downhole to a downhole device located at another location in the well.

The cross-sectional area of the conductor, or conductors, of the cable used to deliver electrical power downhole downhole may be smaller than the cross-sectional area of the cable used to connect the collection module to the downhole power collection system.

According to another aspect of the present invention, there is provided a method for supplying power to a downhole tool in a downhole installation having a metal structure carrying an electrical current, said method comprising the steps of:

the electrical connection of the collection unit with the metal structure in the first section and with the metal structure in the second section, spaced from the first section, is carried out, while the first and second sections are selected so that there is a potential difference between them due to the electric current flowing through the structure, while the block collection is configured to collect electrical energy from the electric current, being connected between sections with a potential difference between them;

collecting electrical power from the electrical current in the collection unit;

electrical power is supplied from the collection unit to the downhole device.

Said method may also comprise the following steps, in which the section is determined where the potential caused by the electric current flowing through the structure is maximum in magnitude, and the first section is selected, in which the collection unit is connected to the metal structure, depending on the section of the specified maximum.

According to another aspect of the present invention, a downhole electrical energy collection system is provided for collecting electrical energy in a downhole installation having a cathodically protected metal structure, said system comprising a collection module electrically connected to the metal structure in a first section and to a second section spaced from the first. section, and the first and second sections are selected so that when used between them there is a potential difference due to cathodic protection currents flowing through the structure;

wherein the collection module is configured to collect electrical energy from cathodic protection currents.

The collection module may be configured to collect electrical energy from direct currents.

The flow of current between parts of the metal structure in the areas between the first section and the second section may occur in the same longitudinal direction.

A continuous current path can be provided between the first section and the second section, which at least partially passes through the metal structure.

The collection module may be electrically connected to the metal structure in the second section.

Spaced sections can be spaced along the axis.

The spaced sections can be spaced radially.

At least one connection between at least one of the electrical contacts and the collection module may be provided with an insulated cable.

The insulated cable may have a conductive area of at least 10 mm ² , preferably at least 20 mm ² , more preferably at least 80 mm ² .

The cable may be a conductor placed in a column.

The distance at which these sections are separated may be at least 100 m.

Connections can be formed with a common section of metal elongated elements that is part of the metal structure.

The first of the connections can be formed with the first section of metal elongated elements, which is part of the metal structure, and the second of the connections can be formed with the second, different section of metal elongated elements, which is part of the metal structure.

For electrical isolation of the first section of metal elongated elements from the second section of metal elongated elements, isolation means may be provided in the connection area.

The isolation means may comprise an insulating layer or coating provided on at least one of the sections of the metal elongated elements.

The means of isolation may include at least one insulating centralizer for holding sections of metal elongated elements at a distance from each other.

- 11 039708

In order to avoid electrical contact between two sections of metal elongated members, means of isolation may be provided at a distance of at least 100 m.

The current flowing through the elongated elements may be supplied from the well surface.

The current flowing through the elongated element may be supplied from one or more sacrificial anodes.

The current flowing through the elongated elements may be superimposed current from an external power source.

The well surface voltage, in use, may be limited to -0.7V to -2V relative to the silver/silver chloride reference cell.

The potential difference between the spaced contacts may be less than 1 V, preferably less than 0.5 V, more preferably less than 0.1 V.

The resistance of the well structure between the contacts may be less than 0.1 ohms, preferably less than 0.01 ohms.

The upper offset contact may be within 100 m, preferably within 50 m of the earth's surface if the well is inland; and within 100 m, preferably within 50 m of the bottom if the well is subsea.

The upper spacer contact may be located in close proximity to the area corresponding to the potential of the maximum value caused by the electric current flowing through the structure.

Said system may also include downhole communications for transmitting and/or receiving data.

The downhole communication means may be configured to transmit data by varying the load between connections in distant areas.

According to another aspect of the present invention, a downhole tool control system is provided, said system comprising the downhole electrical energy collection system disclosed above and a downhole device, the collection module being electrically connected to the downhole device and configured to supply power to said downhole device.

The downhole device may comprise at least one of the following:

downhole sensor;

downhole actuator;

annular sealing device, such as a packer or packer element;

valve;

downhole communication module, such as a transceiver or repeater.

The specified valve may contain at least one of the following elements:

underground safety valve;

a flow control valve in the wellbore;

wellbore-annulus valve;

valve annulus-annulus;

valve wellbore-pressure compensation chamber;

valve annulus-pressure compensation chamber;

valve through the packer or bypassing the packer.

The downhole device may be located at a different location in the well relative to the collection module.

A collection module may be placed at a selected location within the well to collect power, and a cable may be provided to supply electrical power downhole downhole to a downhole tool at another location in the well.

The cross-sectional area of the conductor, or conductors, of the cable used to deliver electrical power downhole downhole may be less than the area of the cable used to connect the collection module to the downhole power collection structure.

According to another aspect of the present invention, a downhole data communication apparatus is provided for use in a downhole installation having a metal structure equipped with a cathodic protection system, such that there is an electrical circuit containing a metal structure and an earth fault, through which an electric current flows, which is a product of the system cathodic protection, wherein the downhole data transmission apparatus comprises a first communication module for location in the first section, comprising modulation means for modulating electric current in the first section for encoding data; and a second communication module for location in the second area spaced from the first area, containing a detector for detecting the effect of modulation on the electric current in the first area to extract the specified data.

- 12 039708

The modulation means may be configured with at least one of the following possibilities:

i) superimposed cathodic protection system signal source control to directly modulate the cathodic protection current applied to the metallic structure if the cathodic protection system is a superimposed cathodic protection system;

ii) modifying the connection between at least one anode of the cathodic protection system and the metallic structure; and iii) changes in the impedance of the electrical circuit.

The first communication module may be configured to be located downhole.

The second communication module may be configured to be positioned within the well.

Said apparatus may comprise a sensor module for measuring at least one parameter, wherein the first communication module is configured to send encoded data readings from the sensor module to the second communication module.

The sensor module may include a pressure sensor.

The second communication module may be configured to provide data to the downhole device in response to data received by the second communication module from the first communication module.

The downhole device may comprise at least one of the following:

downhole sensor;

downhole actuator;

annular sealing device, such as a packer or packer element;

valve;

downhole communication module, such as a transceiver or repeater.

The specified valve may contain at least one of the following elements:

underground safety valve;

a flow control valve in the wellbore;

wellbore-annulus valve;

valve annulus-annulus;

valve wellbore-pressure compensation chamber;

valve annulus-pressure compensation chamber;

valve through the packer or bypassing the packer.

At least one of the communication modules, the first or second communication module, may comprise a communication repeater for location downhole in the well, configured to communicate with the first device outside the wellhead using a communication channel that is wireless, at least in the area, passing through the wellhead, and configured to communicate with a second device located in the well, i.e. below the wellhead so that a connected repeater can act as a repeater between the first and second devices.

Said apparatus may comprise a downhole electrical power collection module configured to be electrically connected between two spaced apart sections in a downhole installation and containing an electrical circuit configured to collect electrical energy, when in use, from the potential difference between the spaced sections used for collection, acting in the role of the input voltage, and the collection module is configured to supply power to at least one component of the specified data transmission apparatus.

The first communication module may be configured to control the load generated by the collection module to perform said electric current modulation in the metal structure at the signaling site.

The collection module may be configured to collect electrical energy from direct currents.

According to another aspect of the present invention, a downhole data communication system is provided comprising the downhole data communication apparatus disclosed above located in a downhole rig having a cathodically protected metal structure.

According to another aspect of the present invention, a downhole data communication system is provided for use in a downhole installation having a metallic structure equipped with a cathodic protection system such that there is an electrical circuit comprising the metallic structure and an earth fault carrying an electrical current which is the product of the system. cathodic protection, said system comprising a downhole data transmission apparatus, which includes a first communication module located in the first section and containing modulation means for modulating electric current in the first section for data encoding; and a second communication module located in the second section spaced from the first section and containing a detector for detecting the effect of modulation on the electric current in the first section for

- 13 039708 extraction of the indicated data.

Said apparatus may comprise a downhole electrical energy collection module electrically connected between two spaced apart sections in a downhole installation and containing an electrical circuit configured to collect electrical energy, in use, from the potential difference between the spaced sections used for collection, acting as an input voltage , wherein the acquisition module is configured to supply power to at least one component of said data communication apparatus.

The flow of current in parts of the metal structure in the areas between the spaced areas used for collection may occur in the same longitudinal direction.

Between the spaced areas there may be a continuous path for the flow of the current used for collection, which, at least partially, passes through the metal structure.

At least one of the modules, the first communication module and the second communication module, may be located in the closed well annulus.

Said system or apparatus may include a pressure sensor configured to monitor the formation pressure of the well.

Said system or apparatus may include a pressure sensor configured to monitor pressure in the annulus of the well.

Said system or apparatus may include a pressure sensor configured to monitor pressure in a closed well annulus.

According to another aspect of the present invention, there is provided a downhole electrical energy harvesting module configured to be electrically connected between two spaced locations in a downhole installation, and comprising an electrical circuit configured to collect electrical energy, in use, from a potential difference between the spaced locations acting as an input voltage. .

The collection module may be configured to collect electrical energy from direct currents.

The acquisition module may include controls for modifying the input impedance of the electrical loop to match the source impedance of the electrical loop to optimize power conversion efficiency.

The electrical circuit may comprise a DC/DC converter.

The DC/DC converter may be configured to operate with input voltages greater than a minimum threshold, wherein the minimum threshold is not greater than 0.5 V, preferably the minimum threshold is not greater than 0.25 V, and even more preferably the minimum threshold is not greater than 0.05 V.

The DC/DC converter may include self-starting means that allow power harvesting to start when the available input voltage is less than a voltage corresponding to the semiconductor bandgap of the components in the DC/DC converter.

The DC/DC converter may contain self-starting means that allow power harvesting to start when the available input voltage is below 0.5 V.

The DC/DC converter may include a step-up transformer.

The self-starting means may comprise a FET coupled with a step-up transformer to form a resonant step-up oscillator.

The DC/DC converter may comprise an H-bridge of transistors operable, under control of the controls, to supply an input signal to a step-up transformer, while the self-starting means may comprise an auxiliary power supply for the controls to enable starting.

The acquisition module may include controls configured to control the turns ratio of the step-up transformer to modify the load generated by the DC/DC converter.

The secondary winding of the step-up transformer may contain several taps and/or the step-up transformer may contain several secondary windings, while the controls can be configured to select the windings and/or taps to provide the desired ratio of turns.

The collection module may contain at least a pair of terminals from which connections can be formed to two spaced areas.

The collection module may have more than two terminals, with each of the terminals providing connectivity to a respective site, the collection module further comprising switching means for selectively electrically connecting two of the terminals to an electrical circuit, thereby allowing a choice between which of the respective plots connected to the electrical circuit.

As a result, a structure is obtained, at the time of installation of which multiple

- 14 039708 direct contacts to a metal structure, with a choice of which connections to use after installation. For example, the design may include one bottom connection and two top connections at different locations. After installation, it can be determined that more power can be collected if the first of the top connections is used, so the first connection can be used. Alternatively, a second top connection may be preferred.

A switch can also be used to switch between connections, used dynamically at the time of use.

Alternatively, two bottom connections may be provided in addition to or instead of the two top connections, or a different number of top and/or bottom connections may be provided.

The collection module may include an energy storage device for storing the collected energy. The power storage device may include a charge storage device that may include at least one capacitor and/or a rechargeable battery.

The collection module may contain variable impedance means for varying the load between two connections.

The variable impedance means may be controlled by a microprocessor.

The collection module may be configured to use variable impedance means to vary the load to optimize energy collection.

The acquisition module may be configured to use variable impedance load modulation means to transmit data from the acquisition module.

The collection module may comprise a primary battery such that, in use, power can be selectively supplied from the power collected by the loop and from the primary battery.

According to another aspect of the present invention, a downhole tool is provided, comprising a collection module as disclosed above, and a downhole device for receiving power from the collection module.

The downhole tool may include charge storage means and power control means for controlling the power supplied to the downhole device when sufficient power is available to supply power to said device.

The downhole tool may include impedance modulation means for varying the input impedance of the collection module to modulate the load to transmit data from at least one element of the electrical power collection unit or downhole device.

The downhole tool may include modulation means for applying a modulated voltage over spaced data connections.

The downhole tool may include a primary battery such that, in use, power can be selectively supplied from the collected power and from the primary battery.

The downhole device may comprise at least one of the following: a downhole sensor;

downhole actuator;

annular sealing device, such as a packer or packer element;

valve;

downhole communication module, such as a transceiver or repeater.

The specified valve may contain at least one of the following elements:

underground safety valve;

a flow control valve in the wellbore;

wellbore-annulus valve;

valve annulus-annulus;

valve wellbore-pressure compensation chamber;

valve annulus-pressure compensation chamber;

valve through the packer or bypassing the packer.

According to another aspect of the present invention, a downhole electrical energy collection system is provided for collecting electrical energy in a downhole installation having a metal structure carrying an electric current, said system comprising a collection module as disclosed above electrically connected to the metal structure in a first section and to a second section, spaced apart from the first section, and the first and second sections are selected so that in use there is a potential difference between them due to the electric current flowing through the structure;

wherein the collection module is configured to collect electrical energy from the electric current.

According to another aspect of the present invention, a downhole power supply system is provided for supplying power to a downhole device in a downhole installation having a metal structure carrying an electrical current, said system comprising a collection module as disclosed above, electrically connected to the metal structure at a lane.

- 15 039708 the first section and with the second section spaced from the first section, the first and second sections being selected so that between them, in use, there is a potential difference due to the electric current flowing through the structure, while the collection module is configured to collect electrical power from electric current and supply of electric power to the specified downhole device.

Moreover, according to another aspect of the present invention, a downhole power supply system is provided for supplying power to a downhole device in a downhole installation having a metal structure provided with cathodic protection, while said system comprises the collection module disclosed above, electrically connected to the metal structure at two spaced apart sections, which are selected so that, in use, there is a potential difference between them due to cathodic protection currents flowing through the structure;

wherein the collection module is configured to collect electrical power from cathodic protection currents and supply electrical power to the downhole device.

Meanwhile, according to another aspect of the present invention, a method is provided for transmitting data in a downhole installation having a metal structure equipped with a cathodic protection system, such that there is an electrical circuit containing a metal structure and an earth fault, through which an electric current flows, which is a product of the cathodic protection system. protection, while the specified method contains stages, which carry out the modulation of the electric current in the first section for encoding data; and in a second section spaced from the first section, the effect of said modulation on the electric current in the first section is detected to extract said data.

One of the sections may be an area located outside the wellbore, for example, the specified area may be the surface, and the other section may be inside the well.

The step of effecting the modulation of the current may, inter alia, provide, and the means of modulation may, inter alia, be configured to

i) superimposed cathodic protection system signal source control to directly modulate cathodic protection signals applied to the metallic structure if the cathodic protection system is a superimposed cathodic protection system;

ii) modulating the connection between the at least one anode and the metal structure, i. e. at least one anode can, for example, be connected to or disconnected from a connection to a metal structure to modulate electrical signals, or the impedance between said anode and the structure can be changed; or iii) changing the impedance of the electrical loop, for example, this can be achieved by means of variable impedance, or by connecting components to a connection or disconnecting from a connection to a loop.

Desirably, methods i) and ii) are available only in the upper section, while method iii) can be available both downhole and in the upper section.

Communication using the principle described above can be used for unidirectional communication, such as communication of the surface with the interior of the well; unidirectional communication, such as communication of the interior of the well with the surface, and bidirectional communication.

These methods enable communication, which is part of a hybrid communication system, when some parts of the signal channel are provided by the modulation of cathodic protection signals, and some are provided by other methods, for example, wireless methods, including electromagnetic methods and acoustic methods.

In any of the cases described above, cathodic protection, if any, can be provided both by a passive cathodic protection system, when sacrificial anodes are connected to the metal structure of the downhole installation, and by a superimposed cathodic protection system, when the protective current is applied to the metal structure of the downhole installation.

In the methods and systems presented here, the goal is to use existing cathodic protection systems (or other current sources if available), in particular, the use of existing anodes, if available, for example, in subsea installations, without the need to modify them.

So, anodes, if any, are usually located outside, i.e. from above, wellbore, in water. Moreover, the anodes are usually located at some distance from the area where you want to provide power and/or signal.

Thus, any of the systems described above may include one or more of the following: at least one existing anode; at least one anode located in the water, for example, in the water column in which the subsea well installation is located; at least one anode located at some distance from the area where it is necessary to provide power and/or signal, using the current generated by the specified anode.

Moreover, any of the systems described above may be designed to allow power to be transferred from a location where a current is applied to the structure, such as a cathodic protection (SC) current, to a signal collection and/or signaling area. This applies to both the current being passive cathodic protection current, superimposed cathodic protection current, or other applied current. Typically, the source of cathodic protection current or other current is at some distance from the area of collection and/or signaling.

Moreover, the metal structure may be continuous in the area of at least one anode and/or the area of the collection module.

When the description above mentions optimization of the simulation, for example, in relation to the distance that the connections are spaced, the use of insulation, the choice of only the radial or axial distance that the connections are spaced, and the choice of a given collection load, then at least one from the following options:

1) attenuation rate at the top of the well, derived from casing and tubular dimensions, material weight and type (resistivity) and overburden resistivity (environment surrounding the well);

2) the location of the top connection;

3) the location of the lower connection;

4) cross-sectional area and type of material (resistivity) of the upper cable used at the inputs to the collector;

5) number, location, material (electric potential) and surface area of wellhead anodes;

6) well resistivity at seabed/wellhead level, also derived from casing and tubular dimensions, weight, and material type (resistivity) and overburden resistivity (environment surrounding the well), but this time for the entire well structure.

In each case, the systems described above may include a primary battery for power supply, independent of the power collected. The primary battery may comprise a collection module. Where a primary battery is provided, its use may be preferred as long as it has power. For example, it may be used to allow higher capacity to be used initially, while it may stop operating when only the collected power is available.

According to another aspect of the present invention, a downhole installation is provided, comprising a metal structure carrying an electrical current and any of the systems or apparatus described above, for example, a downhole tool or an electrical energy harvesting system; device or downhole control system; downhole tool or communication repeater system; apparatus or power supply system; or collection module; or downhole tool or well monitoring system; or the downhole tool or data communication system disclosed above. Such an installation may also contain a cathodic protection system to protect the metallic structure.

It should be noted that, in general, each of the optional features following each of the aspects of the invention above are equally applicable optional features with respect to any other aspect of the present invention and may be given after each aspect with any necessary wording changes. Not all of these optional features are written after each aspect solely for the sake of brevity.

For example, it should be understood that any of the systems, methods, apparatus and installations mentioned above may use a collection module having any combination or partial combination of the features disclosed above, etc.

The well referred to in any of the above described methods, systems, apparatuses, or installations may be a subsea well.

List of figures

For purposes of example only, some embodiments of the present invention are described below with reference to the accompanying drawings.

In FIG. 1 is a schematic representation of a downhole installation including a well monitoring apparatus including a downhole power supply system;

in fig. 2A is a schematic representation of the collection module of the power supply system shown in FIG. one; while in FIG. 2B shows an alternative downhole assembly;

in fig. 2C is a circuit diagram of a DC/DC converter circuit that can be used in an acquisition module;

in fig. 2D is a circuit diagram of a DC/DC converter circuit that can be used in an acquisition module;

in fig. 3 is a schematic representation of a downhole installation including a downhole data communication apparatus comprising a downhole communication repeater and a downhole power supply system for supplying power to the downhole communication repeater;

- 17 039708 in FIG. 4 is a schematic representation of a downhole installation including a valve control apparatus comprising a remote controlled downhole valve and a power supply system for supplying power to the remote controlled downhole valve;

in fig. 5 is a schematic representation of a downhole installation including an alternative well monitoring system comprising a downhole sensor and a downhole power supply system for supplying power to the downhole sensor;

in fig. 6 is a schematic representation of an alternative downhole installation;

in fig. 7 for a design similar to that shown in FIG. 1 is a plot of the optimal power to be collected versus bottom connection depth;

in fig. 8 is a block diagram of energy harvest optimization;

in fig. 9 is a block diagram of downhole control;

in fig. 10 is a schematic representation of a downhole installation including a platform.

Information confirming the possibility of carrying out the invention

In FIG. 1 shows a downhole installation of an oil and/or gas well. It should be understood that such an oil and/or gas well may be an inland well or a subsea well (i.e., the well may be under some water column), while the wellhead is under water at the bottom of the sea, river, lake, etc. or on the platform. Downhole installations are often equipped with a cathodic protection (SC) system. In the case of inland wells, it most often takes the form of a superimposed current cathodic protection system, while the protective current is applied to the metal structure of the well. On the other hand, for subsea wells, cathodic protection is most commonly a passive cathodic protection system in which a plurality of anodes of relatively reactive material, such as magnesium alloy, are bonded to a metal structure while being exposed to the water in which the downhole rig is located.

It should be noted that the solutions described herein are also relevant to injection wells used to inject water into a formation to assist oil and/or gas recovery from other wells in the field. Therefore, the well installation in the present description may be an injection well. Such a well will have a design similar to the design of the installations described in detail in this application. Similarly, the solutions presented here can be used both during drilling and during operation and subsequent abandonment of the site. Therefore, the downhole rig may be a partially complete rig when drilling is in progress. In a broad sense, the solutions presented here can be used in any period of the life cycle of a downhole installation.

Moreover, while this description is given in relation to installations in which cathodic protection is present, which is the preferred case, many of the systems and solutions presented here also work in other situations in which electrical current flows in and out of a metal structure. power can be collected.

The downhole installation shown in Fig. 1 comprises a wellhead 1 and a downhole metal structure 2 leading down into the wellbore from the surface P. The downhole installation is equipped with a cathodic protection system 3A, 3B. As mentioned above, the system is either a 3A superimposed current cathodic protection system or a passive cathodic protection system comprising a plurality of anodes 3B connected to the metal structure of the downhole rig, i. e. with the wellhead or other metal components connected to it.

Downhole metal structure 2 contains the first section of the metal pipe 21, which is the production string going down into the wellbore. Surrounding this is a first casing 22. Outside this layer is a second casing 23 and then a third casing 24. It should be understood that there is a corresponding annulus between each section of metal pipe. Thus, the first annulus between the production string 21 and the first casing 22 is commonly referred to in the oil and gas industry as annulus A and is denoted as A in the drawings. Between the first casing 22 and the second casing 23 there is a second annulus, commonly referred to as annulus B and also referred to in the drawings, and between the second casing 23 and the third casing 24, there is a third annulus, commonly referred to as annulus C and so on. as indicated in the drawings. Wells can usually have the following, D, annulus, and sometimes more annulus.

In other cases, the metal structure may contain other elongated elements, in particular, one or more of the following elements: casing, liner, string, coiled tubing string, sucker rod.

The monitoring apparatus provided in the downhole installation comprises a power collection module 4 located in the annulus A in this embodiment. The collection module 4 is electrically connected via cables 41 to a pair of spaced sections 41a, 41b on the production string 21. Alternatively, the module 4 collection can be electrically connected to one of the sections by means of a cable, while it can be connected to another section without

- 18 039708 cable. With one of the sections, the collection module 4 can be electrically connected through a conductive housing of the collection module (or surrounding the collection module). Therefore, only one such cable may need to be led out of said enclosure.

It should be noted that a galvanic connection takes place between the collection module 4 and the metal structure 21 at the spaced sections 41a, 41b. In particular, a galvanic connection takes place with the metal structure 21 instead of, for example, an inductive connection. This simplifies the design and eliminates engineering complexities. In this case, the galvanic connection takes place throughout the entire area from the metal structure to the inputs of the circuit, which is part of the collection module to collect energy.

Moreover, it should be noted that the installation of such a system, in general, does not have any effect on the specified metal structure of the well. No insulating inserts were added to any section of the metal pipe to ensure the efficiency of the system, and the normal flow of cathodic protection current in the structure was not altered except, of course, by the collection process taking place. For example, between spaced areas, the section of the metal structure to which connections are formed is solid, more broadly, all sections of the metal structure are solid in all areas. This is not essential for operation, but it is possible and is the prevailing situation in a downhole installation, i.e. the standard metal structure of the installation is not changed. Similarly, in a metallic structure, current can, and does, flow in the same direction at the joints and between the joints. Again, this is the prevailing situation in the downhole installation - modifications to the downhole installation are avoided. The current can flow on one section of the metal structure with which the connections are made, or jump from one section to another, or flow in parallel in several sections. current flow, and the current flow through the metal structure occurs in the same longitudinal direction.

It should be noted that access to the annulus A is often provided by a cable passing through the wellhead 1 . Regardless, the configurations presented here are advantageous because they minimize the number of penetrators at the wellhead, reducing risk and using and/or freeing the penetrator for other purposes.

The monitoring apparatus also includes a downhole sensor 5 located deeper in the well than the collection module 4 and connected to it via a cable 42. In this embodiment, the downhole sensor 5 is located directly above the PR packer. Typically, the cables 41 connecting the collection module 4 to the production unit 21 are tubing encased conductors (TEC) commonly used in the oil and gas industry, while the cable 42 connecting the collection module 4 to the downhole sensor 5 is also is a conductor placed in a column. Typically, the cross-sectional area of the conductor along the length of the cable 41 connecting the collection module 4 to the production string 21 will be greater than the cross-sectional area of the cable 42 connecting the collection module 4 to the downhole sensor 5.

If cathodic protection is provided in the downhole installation, the potential of the metal structure of the well is chosen negative enough at the injection point, for example, at the wellhead 1, to suppress corrosion at the wellhead and other points along the downhole metal structure 2 as it is lowered into the well. However, the magnitude of this negative potential decreases as one moves deeper into the well due to losses in the system. Therefore, the potential of the metal structure 2 near the wellhead will be more negative than in deeper areas in the well. Therefore, when cathodic protection currents flow through the downhole installation, between the section 41a, where the first of the cables 41 from the collection module is connected to the production string 21, and the section 41b, where the other of the cables 41 from the collection module 4 is connected to the production string 21, there will be potential difference. Therefore, there will be a potential difference in the collection module 4 and it will be able to extract energy from the cathodic protection currents.

It should be noted that although the energy recovery will use the power from the cathodic protection system, the impact on the effectiveness of the cathodic protection system or the acceleration of corrosion of the anodes will be negligible. Typically, cathodic protection currents will be on the order of 10 A, while the systems presented here will draw, for example, 10-100 mA. That is, the amount of extracted current falls within the allowable range, usually included in the design of cathodic protection systems. If necessary, an increased level of superimposed current may be provided, or the number of anodes provided may exceed their normal number. This will increase the cathodic protection current and therefore improve collection.

Electrical power may be collected from the downhole system of the collection module 4 and this collected power may be used for other purposes.

In the embodiment shown in FIG. 1, this collected power is used to supply

- 19 039708 power downhole sensor 5 and makes it possible to extract readings from it and transfer these readings to the surface P.

In the present embodiment, the upper communication unit 6 is used to communicate with the acquisition module 4 and the downhole sensor. In this case, the upper communication unit 6 is provided on the surface P, in this case on the surface of the earth.

It should be appreciated that configurations such as those presented here can be used instead of a traditional permanent downhole gauge PDG, with the advantage that they help to avoid the use of a penetrator passing through the wellhead, while making it possible, in many cases, continuous monitoring of the well. The monitoring may be reservoir pressure monitoring, if necessary, or similarly closed annulus pressure monitoring, for example, to detect a leak or problem or failure in the system. In this case, the sensor and collection module can be located in a closed annulus.

All of these options are possible, for example, in a subsea well installation, where there will usually be a ready source of current for collection, i.e. cathodic protection current, usually generated by sacrificial anodes, located in the water in which the subsea installation is located, and where other options for supplying power and signal are difficult to implement.

In a well with a subsea wellhead, it is usually not possible (practically or economically) to provide hydraulic or electrical communication with the outer annulus (B, C, etc.). In particular, when these annulus are sealed in the base, it makes sense to monitor and, optionally, regulate the pressure in such annulus, for example, to reduce the risk of high pressures leading to the destruction of the casing structure. In particular, flow movement or drilling of a well can increase the temperature of the sealed outer annulus and therefore increase the pressure therein. The ability to monitor in such a case, and optionally regulate the pressure in such a case (for example, by means of a drain valve between the annulus, such as those described above) is preferred. In particular, monitoring pressure in a closed annulus may allow production at higher rates than can be achieved if only simulated expected pressure increases are used, since the use of simulated pressure would require the adoption of large safety margins, and potentially lead to corresponding decrease in production rate. It should be understood that the solutions presented here may assist in such monitoring and/or regulation.

Another particular embodiment of the solution presented here will include a sensor module located in the same location as a conventional, traditional fixed downhole sensor, provided for the same purpose as the traditional fixed downhole sensor.

Thus, the sensor module can be placed in the annulus A and is designed to monitor the formation pressure by measuring the pressure in the string through the pressure transmission port passing through the string, thereby making it possible to determine the formation pressure based on the pressure obtained by measuring the pressure taking into account the static pressure and flow effects. As with traditionally used PDGs, formation pressure is often determined in this way rather than directly measuring the placement of the sensor directly in the formation, in general, is not practical (while it should be clear that the implementation of reservoir pressure monitoring replaces the use of such measurements).

An acquisition module may also be provided in the area of the sensor module.

Various methods can be used to retrieve data from the downhole sensor 5 in the direction of the surface.

In the present embodiment, the acquisition module 4 is configured to receive a signal from a downhole sensor indicative of the value of a measured parameter, such as pressure and/or temperature, and transmit this data towards the surface by modulating the load that the acquisition module 4 performs between the offset connections 41a and 41b. In response, this change in load will change the amount of current drawn from the cathodic protection currents supplied to the system. This, in turn, is detected at the surface or at another suitable location by changing the potential of the metal structure at the surface or at another suitable location. This can be detected, for example, by detecting a potential change at the wellhead 1 or by detecting a voltage or an observed current in the power supply used in the superimposed cathodic protection system 3A. In the present embodiment, the effect of the modulation is detected by the upper communication unit 6 by monitoring the wellhead potential relative to a reference ground level to extract pressure and/or temperature measurement data.

Preferably, the distance between spaced connections 41a, 41b is

- 20 039708 at least 100 m or more likely to be in the range of 300-500 m. The optimal distance for spaced connections 41a, 41b can be determined by modeling a particular installation. As the distance between these junctions increases, there is a tendency for the potential difference between said junctions to increase (although the rate of increase in potential difference decreases as the depth of the lower junction increases). On the other hand, as the distance increases, the total length, and therefore the resistance of the cables 41, increases. Therefore, in most systems there will be some optimal distance.

In FIG. 2A shows in more detail the assembly module 4 of the apparatus shown in FIG. 1. In this embodiment, the collection module 4 has a pair of terminals 43a, 43b to which respective cables 41 are connected. A galvanic connection takes place between the metal structure and the terminals 43a, 43b. Between these terminals 43a, 43b, a low-voltage DC/DC converter (DC/DC converter) is connected where there is a potential difference between the terminals 43a, 43b to collect electric power. DC/DC converter 44 is connected to charge storage means 45 including at least one low leakage capacitor and is also connected to and controlled by microprocessor controlled central unit 46. The charge storage means 45 and the central unit 46 are also connected via a respective terminal 43c to a cable 42 leading to the downhole sensor 5. Alternatively, the charge storage means 45 can be omitted, i. if necessary, enough power can be collected to make continuous operation possible.

During operation, the central unit 46 controls the operation of the DC/DC converter 44 to optimize the load it gives to the current received by the collection module 4 from the cathodic protection currents, in order to maximize the energy that can be collected and used or stored in the charge storage means 45. It should be noted that the central unit may be configured to selectively directly use and/or send the collected energy when required, and store energy and extract the stored energy when required.

It should be noted that, alternatively, the central unit 46, controlled by a microprocessor, can be replaced by alternative electronics, including, for example, an analog feedback loop, or so-called. a state machine, or even a fixed collection load based on simulations done for a particular setup.

When using the stored energy, the power from the charge storage means 45 is supplied through the cable 42 to the downhole sensor 5, and through the cable 42 the central unit 46 receives readings from the downhole sensor 5. The central unit 46 also controls the operation of the DC converter 44 to modulate the load introduced between the terminals 43a and 43b to send signals back to the surface carrying readings from the downhole sensor 5 as described above.

It should be noted that in the described embodiment, DC/DC converter 44 and central unit 46 together act as variable impedance means by controlling central unit 46 to operate DC/DC converter 44 to input variable impedance between terminals 43a and 43b.

It should be noted that instead of locating the sensor in a separate downhole sensor 5, a suitable sensor may be provided in the same area as the acquisition module 4.

In particular, the downhole block 4a shown in FIG. 2B, comprising both the acquisition module 4 and at least one downhole device that needs to be powered. In such a case, downhole block 4a includes both a pressure sensor 47 and a communication block 48 .

In such a case, the secondary cable 42 leading from the downhole unit 4a may be omitted. On the other hand, in some other cases, the downhole unit 4a may still be used to supply power to an external device, even with its own sensor 47 and/or communication unit 48, and therefore the secondary cable 42 may be present.

In alternative embodiments, instead of communicating in the surface direction using the load modulation method disclosed above, the downhole unit 4a may use its own communication unit 48 for feedback in the surface direction. Such communication may be in the form of electromagnetic coupling signals which may be fed back to the downhole metal structure 21 via cables 41. transmission in the direction of the surface. In such a case, the upper communication unit will be configured to receive acoustic signals. It should be understood that bi-directional communication may be provided, as and when required, over any or all portions of the communication channels. Moreover, two communication methods can be used in parallel on any branch of the communication channels, so electromagnetic signals and acoustic signals can be used in parallel.

In other alternatives, collection module 4 or downhole unit 4a may include at least one power converter to control the voltage at which the

- 21 039708 power is harvested to supply the charge storage means 45 and/or other components such as the central unit 46. It may be preferable to store energy at a different voltage than that at which it is collected and/or at a different voltage than that in which it is used by the central unit 46 or other components. For example, it may be preferable to store power at a higher voltage than that at which it is collected and/or consumed. This can be useful, for example, if there is a large consumption of stored power, for example, during transmission.

A possible embodiment of the DC/DC converter is to use a commercially available integrated circuit. The alternative is to create a similar circuit using separate components. For efficient operation, a DC/DC converter that can handle low input voltages is preferred. One way to achieve this is to use a FET such as a JFET switch to create a resonant boost oscillator using a step-up transformer and a coupling capacitor. To improve the optimization of energy collection, the ratio of turns on the transformer can be selected, preferably dynamically selected, during operation. A plurality of taps may be provided on the secondary of the transformer, which may be selectively used to provide an appropriate turn ratio.

The processor of, for example, the central unit may be configured to control a switch to dynamically select the appropriate taps and thus control the load generated by the DC/DC converter.

In FIG. 2C is a circuit diagram of a circuit for a possible implementation of a resonant boost oscillator similar to that described above. The available input potential difference can be connected to the input terminals (indicated as Vin), and the output signal Vout is shown at the output terminals. The circuit contains a field effect transistor 201, a step-up transformer 202 acting together as an oscillator, and a rectifying output structure 203 containing a pair of parallel diodes 204 connected with opposite polarity (the so-called crossed diodes, from the English. crossed diodes), and the corresponding capacitors 205 communications. The primary winding 202a of the transformer 202 is connected in series with the FET 201, and the input signal Vin is applied to them. The gate of the FET 201 is connected to the secondary winding 202b of the transformer 202. The output signal Vout is shown on coupling capacitors 205, each of which is connected to the secondary winding 202b through respective diodes 204.

The secondary winding 202b of the transformer 202 contains a plurality of taps 202c which can be selected with the switch 206, which makes it possible to adjust the turn ratios. The switch 206 may be controlled by a microprocessor, in this case the central unit 4b.

This type of DC/DC converter can operate even with a low potential difference across the terminals (input voltage), i.e. 0.5V or less. In practice, the input voltage can be as low as 0.25V, and possibly even as low as 0.05V. Since these values are much smaller than the semiconductor bandgap voltages (e.g. 0.7V), many DC/DC converters will not work. to collect energy at such low input voltages. However, DC/DC converters relying on the principles described above can operate even at these low voltages. Such a DC/DC converter may include triggering means to enable operation both when the input voltage is 0.5V or less and at higher voltages.

An alternative approach is to provide a loop with a separate power supply that acts as part of the launcher. For example, a primary battery may be provided to start the system after installation. Moreover, the stored energy in the energy store can be used to restart the system if the energy collection is temporarily stopped.

In FIG. 2D shows a circuit diagram of a circuit for a possible implementation of a DC/DC converter operating in this manner. The DC/DC converter shown in FIG. 2D includes an H-bridge 207 of transistors 207a to which an input voltage is connected. The gates of the transistors 207a are connected to a control unit 208 configured to control the switching of the transistors 207a to generate an AC output signal. The AC output of the H-bridge 207 is connected to the primary winding 202a of the step-up transformer 202. The secondary winding 202b of the transformer 202 is connected to the rectifier 209. One output of the rectifier 209 is connected through a diode 204 to the input of the power supply 210, and the other output is grounded. The battery 211 is also connected to the specified input of the power supply unit 210 through another diode 204.

The power supply unit 210 is configured to supply power to the control unit 208. Power supply 210 may use power from battery 211 to start operation.

- 22 039708 from rectifier 209, i.e. collected power.

While in the present example the power is used directly in the collection, in alternative embodiments, the collected energy can also be stored in the storage means and used from said storage means. As described elsewhere in the application, in such a case, the storage means may, for example, include one low leakage capacitor and/or at least one rechargeable cell. The storage of energy, when it occurs, allows the mechanism to restart the system in case of termination of collection at some point in time after the battery 211 is discharged.

Battery 211 may be a primary (disposable) battery, or may be a rechargeable battery, provided it is charged when installed. When the battery is a rechargeable battery, in some embodiments, power supply 210 may be configured to store power therein when available; or alternatively, it may be convenient to have separate energy storage means (which may include a rechargeable battery).

It should be noted that in another alternative, the DC/DC converter shown in FIG. 2D may be designed to be able to control the load generated by the DC/DC converter. Thus, for example, a configuration similar to that shown in FIG. 2C, in which the secondary winding 202b has a plurality of taps, and a switch is provided to allow the taps to be selected. Such a switch may be located between the windings and the input to the rectifier 209. In another alternative, separate secondary windings may be provided instead of multiple taps to achieve the same result. The switch can be controlled by the control unit shown in the configuration of FIG. 2C.

It should be noted that in other embodiments, acquisition module 4 and downhole sensor 5 (or downhole assembly 4a) may be located in a different annulus in the well installation than annulus A. Moreover, the sensor may be configured to measure a parameter in the annulus space other than the one in which it is located.

For example, such components may be located in the annulus B or C, while the sensor located, for example, in the annulus B, can be configured to measure one or more parameters in the annulus A, B, C, or any combination of them. . It should be noted that these are areas where, in general, it is not possible or at least undesirable to have direct cable connections to the surface. Therefore, the solutions presented here increase the ability to monitor, for example, the pressure in the annulus B or C throughout the life of the downhole rig, which would be difficult and/or impossible with conventional power delivery methods. The solutions presented here do not require the use of wellhead penetrators, reducing risk and cost. They also offer relatively simple, neat and easy installation solutions.

In FIG. 3 shows a downhole installation similar to that shown in FIG. 1, but including a downhole communication repeater 7 instead of a downhole sensor. The repeater 7 is located in the annulus B together with a collection module 4 of the same type as described above with respect to FIG. 1, 2A-2D. Here, again, the collection module 4 collects power from the cathodic protection currents in the metal structure 2 and provides this power to the downhole communication repeater 7.

The design and operation of the downhole rig, cathodic protection system, and power delivery system in the configuration shown in FIG. 3 is essentially the same as the system described with reference to FIG. 1, 2A-2D. The only difference is that the downhole component that is powered by the power supply system is the communication repeater 7 and not the downhole sensor 5.

Therefore, a detailed description of the downhole installation and power supply system is omitted here for the sake of brevity. For the components referred to with respect to this embodiment, which are the same components as in FIG. 1 and 2A-2D, the same reference numbers are used.

The downhole communication repeater 7 is configured to pick up signals from the downhole metal structure 2 in the area of the repeater 7 and transmit relevant data outward towards the surface. In this embodiment, the signals are applied to the downhole metal structure 2 in the form of electromagnetic signals by a transmission tool 71 located downhole, such as in the production string 21. Accordingly, the repeater 7 is configured to capture the electromagnetic signals.

In alternative embodiments, another type of transmission tool may be provided to send signals picked up by the repeater. Such an instrument can, for example, be placed

- 23 039708 guns of the specified column.

In alternative embodiments, the communication repeater 7 may be configured to pick up acoustic signals from the downhole metal structure 2 that have been fed downhole.

Similarly, the downhole communication repeater 7 may be configured to provide acoustic signals to the downhole structure 2 for transmission towards the surface, or configured to provide electromagnetic signals to the downhole metal structure 2 for transmission to the surface, or to use the impedance modulation signaling method disclosed above.

For example, the communication repeater 7 can pick up signals in its area and transmit them along the cable 42 to the collection module 4, giving it signals and modulating the load that it applies to the power supply in the collection module 4. Similarly, the acquisition module 4 may be configured to signal the metal structure 2 for transmission in the direction of the surface, or configured to modulate the load it generates between the spaced connections 41a, 41b for detection on the surface by the upper communication unit 6.

It should be noted that in the case of a downhole communication repeater 7, electromagnetic signals can, for example, be captured and/or supplied by the repeater 7 using spaced contacts formed with a metal structure, or using an inductive connection containing a toroid, or by applying a signal through an insulating element, if available, etc. Similarly, traditional methods of capturing and applying acoustic signals can be used.

In alternative embodiments, communication may be provided from the surface downhole to downhole sections, and in general, two-way communication. Again, the two communication methods can be used in parallel on at least one channel branch to provide redundancy.

It should be noted that downhole communication repeater 7 can be located so as not to be in the path of the product, thereby not interfering with the implementation of downhole operations.

Below are two specific examples with respect to FIG. 3.

1. Repeater 7 contains an electromagnetic repeater that is constantly powered and located at a depth of 3-500 m, this repeater either receives and decodes messages, or simply constantly redirects them using high frequency load impedance modulation, the source data / signal for decoding on a surface.

2. The repeater 7 contains an acoustic repeater which is constantly powered and located at a depth of 3-500 m, said repeater receives and decodes messages and then redirects the data to the surface using load impedance modulation.

It should be noted that in both cases, the repeater 7 can be located in the downhole block together with the collection module or separately from it. Again, the repeater may be a two-way repeater.

In any of the systems presented herein, devices can be configured to control the energy budget, i.e. in general, less energy use due to the variable operation of components such as electromagnetic or acoustic receivers and/or transmitters.

In FIG. 4 is a schematic representation of a downhole installation including a remote controlled valve and a power delivery system generally similar to that described above.

The overall design and operation of the downhole installation and power delivery system is again essentially the same as described above with respect to the configurations shown in FIGS. 1, 2A-2D. Therefore, a detailed description of these common elements is omitted here for the sake of brevity, while the same reference numbers are used to refer to these characteristics - common to these two embodiments.

In this embodiment, the downhole installation comprises a first hydraulically actuated sub-surface safety valve (SSSV) located in the production string 21, similar to conventional solutions.

However, in this case, an additional underground safety valve 8 is also located in the production string 21, downhole. In the present case, said underground safety valve 8 is provided as an additional, safety or emergency means. However, in alternative embodiments, the hydraulically actuated underground relief valve SSSV may be omitted.

The second underground relief valve 8 is powered and operated by using the power supply system. In particular, the collection module 4 is connected to the second underground safety valve 8 via a cable 42, while the collection module is provided with the ability to supply power and control signals directed to the second underground safety valve.

- 24 039708 valve 8 via cable 42. Thus, energy is collected from cathodic protection currents, and it is used both to control the second underground safety valve 8 and for its operation.

Such a subterranean safety valve 8 may be located deeper in the well compared to the traditionally used hydraulically actuated subsurface safety valve SSSV. This is because it is not subject to the same limitations that are imposed on systems with a hydraulic drive - there is no need to supply hydraulic fluid to it.

It should be noted that in this case, control signals for the second subsurface safety valve 8 may be transmitted by the upper communication unit 6 through the metal structure of the well 1, 2 for detection by the collection module 4 and further transmission to the subsurface safety valve 8. In some embodiments, the implementation of the valve 8 may be forced operate in safety mode so that the valve will close in the absence of power and/or control signals. It should be noted that alternatively, the valve 8 and the collection module may be part of a common downhole tool 4a. Moreover, in some embodiments, the power to close the valve may come from another source, while the power to control the operation and/or control the trigger mechanism is received from the downhole power supply system.

In FIG. 5 shows an alternative downhole installation including a well monitoring apparatus. Here, again, there are similarities with the configuration shown in and described with reference to FIG. 1, 2A-2D. Again, there is a collection module 4 provided in the downhole metal structure 2 and connected to the off-site portions on the downhole structure 2, and there is also a downhole sensor 5 connected to the collection module 4. In this case, the acquisition module 4 and the downhole sensor 5 are both located in the annulus B to enable monitoring of conditions in said annulus. The downhole sensor 5 may, for example, comprise a pressure and/or temperature sensor.

In this case, the spaced sections 41a, 41b are located on different sections of the downhole metal structure 2. In particular, in this embodiment, the first of the connections 41a is formed with the second casing 23, while the other of the connections 41b is formed with the first casing 22. The specified system works following a similar principle to that described above, and therefore its operation is based on the potential difference present between the two said connections 41a, 41b. In this embodiment, the specified potential difference is realized by isolating the two sections of the metal structure 22, 23 from each other, at least in the area of these connections. This means that for cathodic protection currents there are different paths to earth from said two metal structure sections 22, 23. In the present embodiment, the means of isolating said two metal structure sections 22, 23 from each other includes surfaces of the first casing 22; and a plurality of isolating centralizers 92 provided on the first casing 22 to keep it away from the second casing 23.

Preferably, this insulation 91 and these centralizers 92 are at least 100 m apart along the first casing 22, and more likely at a distance of 300-500 m. insulating separators were installed to form the annulus. For example, they can be installed on the second casing pipe 23 in the above example. It should be noted that the insulation does not have to be completely continuous to provide a positive effect. The goal is to create another trajectory towards the ground. Although insulation may be provided at a distance of 100 m, it may be either non-continuous or may provide continuous insulation throughout the distance.

An advantage of the configuration shown in FIG. 5 is that the large lengths of cable 41 between collection module 4 and metal structure 2 are not necessary in the configuration shown in FIG. 1. This means that the system can be easier to install. For example, the installation of this system can be carried out by mounting the body of the collection module 4 on a piece of metal pipe, provided with a sliding contact to create contact with another piece of pipe through the annulus. To further simplify positioning, the downhole sensor 5 may be omitted and the sensor may be located together with the collection module 4 in the downhole block 4a. This configuration can reduce the installation time required for installation.

Thus, in some circumstances, the presence of means 91, 92 of isolation may be preferable to the presence of cables 41. Which system is preferable for a particular installation may be determined by external factors regarding the installation, or perhaps by simulation of a particular installation.

Typically, however, the configuration shown in FIG. 1 is likely to work better than the one shown in FIG. 5 when its application is practicable.

In a configuration similar to that shown in FIG. 5, the acquisition module may observe a relatively higher current but a relatively lower potential difference. Thus, in the configuration of FIG. 5, the potential difference can be, for example, 10-20 mV, and the current, for example, be 1 A. On the other

- 25 039708 sides, in the configuration of FIG. 1, the potential difference may be, for example, 100-200 mV, and the current, for example, be 100-150 mA. The higher potential difference is achieved by the greater distance provided by the cable(s) 41 in the configuration of FIG. 1 and the lower current is due to the resistance of the cable(s).

In addition to these differences in how the connections are formed and how the potential difference is achieved, as well as differences in the advantages and disadvantages of use, the design and operation of the system shown in FIG. 5 is similar to that shown in Fig. 1. Similarly, the various alternatives described above with respect to FIGS. 1-4 are also applicable where the system shown in FIG. 5.

It should be noted that the insulation and connection configuration shown in FIG. 5 may be used in each of the embodiments shown in FIG. 1, 3 and 4. Similarly, the different forms of collection module 4 and downhole unit 4a described above can be used in a configuration similar to that shown in FIG. 5.

It should be noted that, in some circumstances, it may be preferable to use existing power delivery systems to create a wireless-ready downhole installation, even if there is no intention to use wireless capabilities in the initial installation of said well.

Therefore, the configuration shown in FIG. 3, where a communication repeater 7 and associated power delivery system is included in the annulus B, may be provided during initial well installation to make the well ready for wireless communication. This will provide communication with the surface if it is later decided to use, for example, a downhole wireless signaling tool 71 to signal the surface. It should also be noted that the term wireless is used in relation to the spaces between the downhole space and the outer space, i.e. concerns the absence of cables/wires passing through the wellhead.

In other circumstances, the systems presented here may be installed after the fact. For example, a system similar to that shown in FIG. 1, installed in annulus A, can be installed after the fact when replacing the production string. Alternatively, the system may be installed in the main bore of the production string. It should be noted that each of the configurations and solutions presented in the present description does not need a cable passing through the wellhead 1. Therefore, these systems can be used where no penetrator is available or its use is not preferred.

While the configuration shown in FIG. 4 illustrates the presence of an additional underground safety valve 8, in other circumstances another type (possibly remote controlled) valve or component may be provided. For example, a configuration similar to that shown in FIG. 4 may be used with an annular vent valve provided in the well to allow controlled hydraulic communication or venting between one annulus and another annulus, or between the annulus and the wellbore. Said valve may include a gas lift injection valve to allow gas to enter the wellbore of the production string from the annulus A. Similarly, the valve may be a packer, or a valve through the packer, or a valve bypassing the packer. Again, to provide ventilation to a particular annulus under control from the surface. In another example, the valve may comprise a flow control valve, for example, to control the proportion of a certain zone, or it may provide a means to enable improved collection of pressure rise data by eliminating the wellbore volume effect. It should be noted that the valve, in each case, may be a flow control valve which does not provide a complete flow shut-off but, for example, may function as a variable diameter nozzle.

The valve or component in each example may be a wirelessly controlled valve or component.

In another alternative, the solutions presented herein may be used to communicate with and/or control a tool supported by a wireline/solid wire, or attached to a coiled tubing in production string 21. Such a tool may be configured to signal to and /or capturing signals from the specified column, while the specified signals pass through the repeater 7.

With systems similar to the one described here, it may be possible to extract power at a probable level of 50 mW. That is, the amount of power that can be extracted is not necessarily large, but what is of interest in this case is that this power can be available throughout the life of the well, and it is enough to perform useful functions such as control of downhole devices, making important measurements and enabling the transmission of these measurements to the surface.

It should be noted that, in general, in the general type embodiments shown in FIGS.

- 26 039708

1-4, the biggest impact on collection efficiency will be the cross-sectional area of cable(s) 41 and that the source impedance provided by connections 41a and 41b is low. This means that when multiple collection systems are included in one downhole installation, there is a slight decrease in the efficiency of any one of the collection modules 4 . It should be noted that, in general, any additional collection system will have its own cables 41 when appropriate. This relies on the fact that cable losses mean that having more acquisition systems sharing the same cable is not of much benefit.

In general, multiple collection modules of any type of those described above may be provided in a single downhole installation. So, for example, one sensor can be provided to monitor conditions in the production string, one sensor can be provided to monitor the annulus, in addition, one valve can be provided, while all of these devices are powered by a separate, appropriate module collection. Likewise, any of the collection modules can be used to supply power to multiple devices. In some examples, each device may have a dedicated cable running from such a collection module. In other examples, a multipoint system may be envisaged in which a single cable from the collection module is used to connect to multiple downhole devices. A multipoint system may be designed to provide power and communication to multiple downhole devices. Thus, said cable may carry power signals, transmitted data and address information. Also, the acquisition module may be configured to administer a multipoint system.

It should be noted that while in the embodiments above the cables 41, 42 pass through unobstructed annulus, in other cases one or more cables 41, 42 may pass through a packer (including a swellable packer), cement, or other annulus. sealing.

It should be noted that, in at least some cases, the characteristics of the systems and apparatuses presented here may take a distributed form. This means that, for example, a collection module can be represented as several separate parts, components or sub-modules, which can be located in different areas.

In FIG. 6 shows an alternative downhole rig that has similar features to the rig shown in FIG. 1, with the same reference numerals used here to refer to characteristics in common with FIG. 1, while a detailed description of these general characteristics is omitted.

The downhole installation shown in Fig. 6 helps illustrate in more detail some of the alternatives described above in relation to the downhole installations shown in and described with respect to FIG. 1-5.

The downhole installation includes a monitoring apparatus similar to that shown in FIG. 1. Therefore, there is a collection module 4 connected via cables 41 to a pair of spaced sections 41a and 41b. However, in this case, the first of the sections 41a is located on the production string 21, so the first of the cables 41 is connected to the production string, while the second of the spaced sections 41b is located on the casing 22. Thus, the distance between the connections 41a, 41b is provided as axially and radially, so that the collection module 4 is connected through the annulus A. Moreover, on the production string 21 in the area of the second connection 41b is the insulation 91, passing axially on both sides of it. It should be noted that in another alternative, one connection is more likely to be to the rock than to the metal structure. In some cases, all apparatus of the power supply system may be located outside the casing, i.e. between casing and rock. This option would generally not be preferable in terms of risk/difficulty of installation, but it is possible.

In addition, in the present embodiment, second and third collection modules 4', 4 (which are part of the respective downhole blocks) are provided located in the annulus A. In such an embodiment, each of these other collection modules 4', 4 uses the same first cable 41. Thus, one of the terminals of each of the collection modules 4', 4 is connected to the first connection point 41a. It should be noted that in other embodiments, separate cables may be used to create such connections to the first connection point, and such an option would be preferred as it results in increased efficiency. Using a single top cable as shown is undesirable but helps simplify the image. In some cases, there may be several collection modules distributed in different annulus.

In the present embodiment, the first acquisition module 4 is connected to the downhole sensor 5 via a secondary cable 42, similar to the embodiments shown in FIG. 1. However, here the downhole sensor 5 is located below the PR packer, and the cable 42 passes through it. The sensor 5 in this case is configured to measure the pressure and/or temperature conditions inside the production casing 21 through the port 21a provided in

- 27 039708 the wall of the production string 21. That is, despite the fact that the downhole sensor 5 is located in the annulus A, it is configured to measure parameters inside the production string 21.

Moreover, in this embodiment, second and third downhole sensors 5' and 5 are provided. In this embodiment, each of the downhole sensors 5, 5', 5 is connected to the collection module 4 via the same secondary cable 42. multipoint system, and cable 42 is used to carry power signals, control signals, parameter data and address information to allow power to be supplied to and read from each of the sensors 5, 5', 5.

It should be noted that in alternative embodiments, a number of downhole sensors or other downhole devices are more likely to be powered from a single acquisition module 4 via separate dedicated cables 42 than a single cable as shown in the present embodiment. Moreover, as mentioned above, while the present embodiment provides for multiple sensors radiating from a single acquisition module, in other embodiments, a single acquisition module may be used to supply power to different types of downhole devices. Thus, one acquisition module, for example, can be used to supply power to a downhole sensor, a downhole repeater, and a downhole valve.

In the present embodiment, the second acquisition module 4' is part of a downhole tool that contains both the acquisition module and the sensor. In the present embodiment, the sensor is configured to measure parameters in the annulus B through port 22a provided in the first casing 22. For example, the sensor in the second collection module 4' may be configured to measure pressure and/or temperature in the annulus AT.

Moreover, in the present embodiment, the third acquisition module 4 is also part of the downhole tool, which in this case includes an acquisition module and a communication unit for communicating with the sensors 605 located in the annulus B and the annulus C. Here, the communication between the sensors 605 and the second collection module 4 is provided by wireless means. For example, an inductive signal or an acoustic signal can be provided between the sensors 605 and the collection module 4 . The sensors 605 may be physically located as close as possible to the acquisition module 4 .

It should be understood that once the data reaches the upper communication unit 6, it can be transferred outside to the required site using standard communication methods such as mobile communication methods, the Internet, etc., to the PM workstation for further processing and /or study. Of course, wired connections can also be provided between the workstation and the upper communication unit 6 .

Moreover, data can also be sent from the RM workstation to the upper communication node 6 for downhole transmission. So, for example, control signals can be transmitted from the PM workplace through the upper communication unit 6 downhole to control the operation of the collection module, or sensor, or downhole valve, or repeater, etc., thus any necessary data.

In another alternative, outside the outermost casing, such as the third casing 24 in the embodiment shown in FIG. 6, isolation may be provided in the region near the wellhead 1. It can contribute to the supply of the maximum negative potential caused by cathodic protection currents deeper into the well. This is achieved by minimizing leakage in the area near the wellhead. Therefore, the presence of insulation on the outermost casing can help to allow the uppermost connection 41a to be located lower, while avoiding a significant reduction in the efficiency of the system. Looking at the potential loss curve due to the presence of insulation on the outermost casing 24, the negative potential may decrease very slowly in the isolated region near the wellhead, and then may begin to decrease more rapidly after reaching the non-isolated region.

Fig. 7 is a graph showing an example of how the optimum power available to collect in a downhole installation varies with the depth of the well. As noted above, due to the increase in the potential difference provided by the increase in the distance between the connections, on the one hand, and the resistance of the cable, on the other hand, there is an optimal depth for the bottom connection 41b, or, in other words, the optimal distance between the two connections 41a and 41b. The graph shown in Fig. 7 refers to an arrangement in which the top connection 41a is about 5 m below the wellhead, i. e. located in the area of the liner hanger. In this example, it can be seen that the optimal depth of the lower connection is in the region of 550 m inside the well. However, it can also be seen that a significant portion of the optimal power can be obtained at depths around 300 and 950 m.

- 28 039708 connection. However, there may be circumstances in which the advantage of locating the collection module deeper within the well can be used.

The optimal location for the top connection may depend on where the cathodic protection current (or other current) is injected and where the specified current is maximum, or the potential caused by the current is maximum. The methods and systems presented herein include the steps of first determining where the applied current (or potential) is at its maximum and selecting a site for the top connection depending on that.

The top connection may be within 100 m of the surface, preferably within 50 m if the well is an inland well.

The top connection may be within 100 m of the bottom, preferably within 50 m if the well is a subsea well.

As noted above, although the above description refers to collecting from cathodic protection currents, and although this option is preferred, if there are other currents in the metal structure, they can be similarly used.

It should be noted that while some specific examples are given above, in general, any of the components of the system can be located in any available annulus.

When the description above mentions optimization by simulation, for example, with regard to the spacing of connections, the use of insulation, choosing only the radial or axial spacing of the connections, and choosing a given collection load, such a model can use at least one of the following options:

1) attenuation rate at the top of the well, derived from casing and tubular dimensions, material weight and type (resistivity) and overburden resistivity (environment surrounding the well);

2) the location of the top connection;

3) the location of the lower connection;

4) cross-sectional area and type of material (resistivity) of the upper cable used at the inputs to the collector;

5) number, location, material (electric potential) and surface area of wellhead anodes;

6) wellbore resistivity at seabed/wellhead level, also derived from casing and tubular dimensions, material weight and type (resistivity) and overburden resistivity (environment surrounding the well), but this time for the entire well designs.

In specific examples of the above systems, the cable or cables 41 used to connect the collection module to the structure/environment may have a cross-sectional area of, for example, 10-140 mm ² . 10 mm ² can be considered the lower limit of the preferred cable size for operation. Generally, a larger cross-sectional area will be preferred. The ^140mm2 cable can be Kerite (RTM) LTF3 type flat cable. It corresponds to the upper limit of what is currently available on the market, but larger sizes can be used if available.

Fig. 8 is a flowchart showing the energy collection optimization process of the collection module disclosed above.

In step 801, the DC/DC converter 44 starts up using the initial settings/configuration and supplies the available power to the charge storage means 45 .

At step 802, it is determined if there is sufficient voltage to supply power to the microprocessor in the central unit 46. If the answer is no, then step 802 is repeated until the answer is yes, and when the answer is yes, the process proceeds to step 803, at which the microprocessor in the central unit 46 is supplied with power.

Next, at step 804, the microprocessor measures the power output from the energy collector, and at step 805, the microprocessor modifies the settings of the DC converter 44 for a slight increase in load. Next, at step 806, it is determined whether this results in an increase in output from the collector. If the answer is yes, then the process loops back to step 805 so that the settings of DC/DC converter 44 can be changed again for a slight increase in load.

On the other hand, if it is determined at step 806 that the output has not increased, then the process proceeds to step 807 where the microprocessor modifies the settings of the DC/DC converter 44 to slightly decrease the load, and the process returns to the step before step 806 to determine if this is to increase the output.

Thereafter, steps 805, 806, and 807 are alternately repeated during power harvesting so that the load is gradually increased and decreased depending on the result obtained in step 806. This results in dynamic optimization of power harvesting.

As mentioned above, when the DC/DC converter 44 uses a FET and an associated transformer, the step of changing the settings of the DC/DC converter in the steps

- 29 039708

805 and 807 may include the step of changing the tap used on the secondary transformer to modify the load as appropriate. This is also true when the variable transformer is equipped with the H-bridge shown in FIG. 2D. Alternatively, in such a case, the mode of operation of the transistors in the H-bridge can be adjusted to vary the load.

In FIG. 9 is a block diagram illustrating the operation of the downhole unit 4a in a manner similar to that described above.

At step 901, it is determined if there is enough power to supply power to the processor in the central unit 46. If the answer is no, then the process remains at the same step until there is enough power.

When enough power is available, the process proceeds to step 902 where it is determined whether a command has been received or whether a scheduled data set needs to be sent. If the answer is no, then the process remains in the same state of determining whether some action is required until a moment arrives at which action is required.

When action is required, the process proceeds to step 903 where data from the sensor or storage device is retrieved as required and the load represented by the energy collector between connections 41a is modulated to encode this data.

Separately, at the wellhead, in step 904, the wellhead voltage potential is monitored and the data is decoded in the second microprocessor. The retrieved data may then be exported or re-transmitted to the client at step 905, for example, via an underwater acoustic line or communication channel.

Fig. 10 illustrates a well installation including a platform 1000. The wellhead 1 is located on the pad 1001 of the platform 1000. In this case, the metal structure includes a riser 1002 between the bottom level and the platform 1001. The production string 21 extends in the riser 1002 downhole. Casings 22, 23 are provided within the well. The innermost casing 22 is an extension of the riser 1002. Cathodic protection anodes 3B are provided on the platform structure 1000. There will be an electrical connection between the platform and the downhole structure 2 (casing and production string). It may be provided through the drilling base plate 1003 and/or through the wellhead, riser and other components such as riser guides. In such cases, it can be difficult to know where to make the top connection of the collection structure, similar to that shown in Fig. 1, 3, 4 or 6 for best performance. It will not always be known where the cathodic protection current will be injected into the conductive pipe (sections of elongated members) that runs downhole. As mentioned above, it may be preferable to make the top connection in close proximity to the area where the cathodic protection current is injected. When aiming for optimization, one of the options would be to manage this entry point, i.e. guaranteeing a galvanic connection at a known point. Another alternative would be to provide the system with multiple alternative top connection points for the collection module and allow the most efficient connection point to be selected after installation. Typically, in such a case, the power supply system will be installed with a plurality of overhead cable connections to the metal structure, with the most efficient being selected, for example, by control of a switch controlled by the central unit.

Alternatives for signal, device and sensor.

Various specific signaling solutions have been described above. For the avoidance of doubt, a wide range of signaling solutions can be used either alone or in combination with various parts of the signal path in systems similar to those described here. Thus, wireless signals can be transmitted in at least one of the following forms: electromagnetic, acoustic, through inductively coupled tubular elements and coded pressure pulses, while references to the wireless nature of transmission refer to these forms, unless otherwise stated.

Signals, unless stated otherwise, may include control signals and data signals. Control signals can control the operation of downhole devices, including sensors. Sensor data can be transmitted in response to a control signal. Moreover, data acquisition and/or transmission of parameters, such as acquisition and/or transmission of rate or resolution, can be changed by respective control signals.

The pressure pulses include methods of communicating from/to the well space(s)/wellbore(s), at least from/to one of the deeper locations in the well/wellbore, and surface of the well/wellbore using positive and/or negative changes in pressure and/or changes in fluid flow in the tubular and/or annulus.

Encoded pressure pulses are pressure pulses for which a modulation scheme has been used to encode commands and/or data into pressure and/or flow rate changes. In this case, a transducer is used in the well/wellbore to detect and/or generate these changes, and/or an electron is used in the well/wellbore

- 30 039708 system for encoding and/or decoding commands and/or data. Thus, pressure pulses used in conjunction with an electronic downhole/wellbore interface are defined herein as encoded pressure pulses. An advantage of encoded pressure pulses, similar to those defined here, is that they can be sent to electronic interfaces and may provide better baud rate and/or range than pressure pulses sent to mechanical interfaces.

Where coded pressure pulses are used to transmit control signals, a variety of modulation schemes can be used to encode control signals, for example, pressure change or rate of change of pressure, amplitude keying (English on / off keyed, OOK), phase-pulse modulation ( pulse position modulation (PPM), pulse width modulation (PWM), frequency shift keying (FSK), pressure shift keying (PSK), manipulation by amplitude shift keying (ASK), combinations of modulation schemes can be used, for example OOK-PPM-PWM. The rates of coded pressure modulation schemes are typically low, typically less than 10 bps, and may be less than 0.1 bps.

Encoded pressure pulses may be induced in static or flowing fluids and may be detected directly or indirectly by measuring changes in pressure and/or flow rate. Fluids include liquids, gases, and multiphase fluids, and may be statically controlled fluids and/or well-produced or injected fluids.

Wireless signals may be able to pass through a barrier such as a plug or annular seal when it is fixed in place. Therefore, wireless signals can be transmitted in at least the following forms: in the form of an electromagnetic signal, an acoustic signal, or inductively coupled tubular elements.

The electromagnetic/acoustic delivery and the delivery of coded pressure pulses use the borehole, the wellbore and the rock as the transmission medium. The electromagnetic/acoustic or pressure signal can be sent from the well or from the surface. When applied downhole, the electromagnetic/acoustic signal may be able to pass through any annulus seal, although in some embodiments it may bypass, for example, around any annular seal.

Electromagnetic and acoustic signals are useful as they can be transmitted through/through an annulus sealing device without special inductively coupled tubular infrastructure, and in the case of data transmission, the amount of information that can be transmitted is usually greater compared to the supply of coded pressure pulses, especially when receiving data from a well.

When inductively coupled tubulars are used, there are typically at least ten, usually many more, individual lengths of inductively coupled tubulars that are connected together during use to form a column of inductively coupled tubulars. They have a solid wire and may be in the form of tubular elements such as production pipe, drill pipe or casing. At each connection of adjacent segments there is an inductive connection. The inductively coupled tubular elements used are available from NOV under the Intellipipe® brand.

Thus, electromagnetic/acoustic or wireless pressure signals can be transmitted over relatively long distances as wireless signals sent to a distance of at least 200 m, optionally more than 400 m or further, which is obviously an advantage over short range signals. Inductively coupled tubulars have the advantage/effect of a combination of solid wire and inductive connections. The distance traveled can be much longer depending on the length of the well.

The data and commands in the signals may be relayed or transmitted by other means. Thus, wireless signals can be converted to other types of wireless or wired signals, optionally retransmitted, by the same or other means, such as hydraulic, electrical and fiber optic lines. For example, the signals may be transmitted over a cable over a first distance, such as over 400 m, and then transmitted via acoustic or electromagnetic coupling over a shorter distance, such as 200 m. In another example, they may be transmitted over a distance of 500 m by sending coded pressure pulses and then 1000 m using a hydraulic line.

In addition to wireless means, wired means may be used for signal transmission. The distance traveled by the signals depends on the depth of the well, often a wireless signal, including repeaters, but excluding any non-wireless transmission, travels more than 1000 m, or more than 2000 m.

Different wireless signals can be used in the same well to communicate from the well to the surface and to communicate from the surface to the downhole.

- 31 039708 Zhinu.

The wireless signals may be sent to the communication device directly or indirectly, for example, through the use of downhole relays above and/or below any annulus sealing device. The wireless signal can be sent from the surface or from a wireline/coiled tubing (or hoist) section anywhere in the well, optionally above any annulus sealing device.

Acoustic signals and communication may include transmission through vibration of the well structure, including pipes, casing, liner, drill pipe, drill collars, string, coiled tubing, pump rod, downhole tools; transmission through a liquid medium (including transmission through a gas), including transmission through a liquid medium in sections of a well without casing, inside pipes, inside annulus; transmission through static or flowing liquid media; mechanical transmission through a wire line, solid wire or flexible wire; ground transmission; transmission through wellhead equipment. Communication through the structure and/or through the liquid medium is preferred.

Acoustic transmission can be low frequency (<20 Hz), can be within the audible range (20 Hz - 20 kHz) and have ultrasonic frequencies (20 kHz - 2 MHz). Preferably, the acoustic transmission is within the audible range (20 Hz - 20 kHz).

Acoustic signals and communications may include modulation techniques such as Frequency Shift Keying (FSK) and/or Phase Shift Keying (PSK) and/or more advanced derivatives of these. methods, such as Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM), and preferably the inclusion of signal transmission methods with spread spectrum (English Spread Spectrum Techniques). They are typically adapted to automatically adjust transmission frequencies and methods to match downhole conditions.

Acoustic signals and communication can be unidirectional or bidirectional. A piezoelectric, inductive, or magnetostrictive transducer may be used to send and/or receive a signal.

Electromagnetic (sometimes referred to as Quasi-Static, QS) wireless communications are typically found in the following frequency bands (selected based on propagation characteristics):

sub-very low frequency (below VLF) range (extremely low frequency) <3 Hz (typically above 0.01 Hz);

VLF (extra low frequency) 3-30 Hz;

super low frequency 30-300Hz;

ULF (ultra-low frequency) 300 Hz - 3 kHz and

VLF (very low frequency) 3-30 kHz.

An exception to the above frequencies is electromagnetic communication using a waveguide tube, in particular, but not limited to, when the tube is filled with gas, while frequencies from 30 kHz to 30 Hz can usually be used depending on the dimensions of the tube, the liquid in the tube, and communication range. The liquid medium in the pipe is preferably non-conductive. US 5,831,549 discloses a remote sensing system including gigahertz transmission in a gas-filled tubular waveguide.

Bands below VLF and/or VLF are useful for downhole to surface communications (eg over 100 m). For more local communications, such as less than 10 m, the VLF band is useful. The terminology used here for the ranges indicated is defined by the International Telecommunication Union (ITU).

Electromagnetic communication may include the transmission of messages through one or more of the following: applying a modulated current to an elongated element and using ground to complete the loop; transmitting current to one tubular element and providing a return path in the second tubular element; using the second well as part of the current path; transfer to the area near the deposit or remote from the deposit; creating a current loop in a part of the metal structure of the well to create a potential difference between the metal structure and the ground; using spaced contacts to create an electrical dipole transmitter; using a toroidal transformer to apply current to the metal structure of the well; using an insulating block; a loop antenna for generating a modulated magnetic field that varies over time or through rock transmission; transmission in the well casing; using an elongated element and earth as a coaxial transmission line; using a tubular element as a waveguide; transmission outside the well casing.

Particularly useful is the imposition of a modulated current on an elongated element and the use of ground for shorting; creation of a current loop in a part of the metal structure of the well for

- 32 039708 creating a potential difference between a metal structure and the ground; using spaced contacts to create an electrical dipole transmitter and using a toroidal transformer to inject current into the metal structure of the well.

Many different solutions can be used to effectively control and direct the current. For example, one or more of the following: the use of an insulating coating or separators on the tubular elements of the well; selecting well control fluids or cements in or outside of the tubulars for electrical connection to the tubulars or isolation of the tubulars; the use of a toroid of high magnetic permeability to create induction and, as a result, impedance; use of an insulated wire, cable, or insulated elongated conductor as part of a transmission path or antenna; the use of a tubular element as a round waveguide, the use of ultra-high frequencies (3-30 GHz) and ultra-high frequencies (300 MHz - 3 GHz).

Various methods may be used to obtain the transmitted signal, these may include current flow detection; potential difference detection; use of a dipole antenna; use of a loop antenna; use of a toroidal transformer; use of the Hall effect or similar magnetic field detector; use of sections of the metal structure of the well as part of a dipole antenna.

When the term elongated element is used in relation to electromagnetic transmission, it can mean any elongated (extended or elongated) electrical conductor, including a shank; casing pipe; column or tubular element; flexible coiled tubing string; pump rod; wire line; drill pipe; solid wire or induction wire.

The sensors may comprise one or more different types of sensors. A single or each of the sensors may be connected (physically or wirelessly) to a wireless transmitter, and data may be transmitted from the wireless transmitter to above the annular seal or, conversely, to the surface. The data may be transmitted in at least one of electromagnetic, acoustic, and inductively coupled tubular forms, especially acoustic and/or electromagnetic form, as described above.

Such short range wireless connections can be provided by electromagnetic coupling in the very low frequency range.

The sensors provided can measure any parameter and therefore be any type of sensor, including, but not necessarily limited to, temperature, acceleration, vibration, torque, displacement, movement, cement integrity, pressure, direction and slope, load, various pipe/casing angles , corrosion and erosion, radiation, noise, magnetism, seismic movements, stresses and deformations in pipes/casings, including torsion, shear, compression, expansion, bending and any form of deformation; detection of chemical and radioactive indicators; identification of a liquid medium, such as gas detection; water detection; carbon dioxide detection; production of hydroxide, paraffin and sand; and fluid properties, such as (but not limited to) flow rate, density, water volume, resistivity, acidity, viscosity, boiling point, gas/oil ratio, hydrocarbon composition, fluid color, or fluorescence. Sensors can be imaging, mapping, and/or scanning devices such as, but not limited to, camera, video camera, infrared, magnetic resonance, acoustic, ultrasonic, electrical, optical, impedance, and capacitance devices. Sensors can also monitor downhole equipment, such as valve position, or motor rotation. Moreover, sensors can be adapted to produce a signal or parameter detected by incorporating suitable transmitters and mechanisms.

The apparatus, in particular the sensors, may comprise a storage device which may store data for later retrieval. The storage device may also be ejected in some circumstances, and data may be recovered after the device is ejected. The storage device may be configured to store information for at least 1 minute, optionally for at least 1 hour, optionally for at least one week, preferably at least one month, more preferably at least for one year or more than five years.

Claims (20)

1. A downhole data communication apparatus for use in a downhole installation having a metal structure provided with a cathodic protection system, such that an electrical circuit is formed containing a metal structure and an earth fault, through which the electric current generated by the cathodic protection system is allowed to flow, when This downhole data transmission apparatus contains - 33 039708 the first communication module for location in the first section inside the well, containing modulation means for modulating electric current in the first section for encoding data; a second communication module for location in a second area spaced from the first area, containing a detector for detecting the effect of electric current modulation in the first area to extract the specified data; and a downhole electrical power collection module configured to electrically connect between two spaced apart sections in a downhole installation and containing an electrical circuit configured to collect electrical energy, in use, from a potential difference between said spaced sections used for collection, acting as an input voltage, while the collection module is configured to supply power to at least one component of the data transmission apparatus, and the first communication module is configured to control the load generated by the collection module to carry out said electric current modulation in the metal structure in the signal supply section. 2. Apparatus according to claim 1, wherein the modulation means is configured with at least one of the following possibilities: i) controlling the signal source of the superimposed cathodic protection system, if the cathodic protection system is a superimposed cathodic protection system, to directly modulate the cathodic protection current applied to the metallic structure; ii) modifying the connection between at least one anode of the cathodic protection system and the metallic structure; and iii) changing the impedance of the electrical circuit. 3. Apparatus according to any one of the preceding claims, wherein the second communication module is arranged to be positioned downhole. 4. Apparatus according to any one of the preceding claims, comprising a sensor module for measuring at least one parameter, the first communication module being configured to send encoded data readings from the sensor module to the second communication module. 5. The apparatus of claim 4, wherein the sensor module comprises a pressure sensor. 6. An apparatus according to any one of the preceding claims, wherein the second communication module is configured to provide data to the downhole device in dependence on data received by the second communication module from the first communication module. 7. The apparatus of claim 6, wherein the downhole device comprises at least one of the following: downhole sensor; downhole actuator; annular sealing device, such as a packer or packer element; valve; downhole communication module, such as a transceiver or repeater. 8. Apparatus according to claim 7, wherein said valve comprises at least one of the following: underground safety valve; a flow control valve in the wellbore; valve wellbore - annulus; valve annulus - annulus; wellbore valve - pressure compensation chamber; valve annulus - pressure compensation chamber; valve through the packer or bypassing the packer. 9. An apparatus according to any one of the preceding claims, wherein at least one of the first and second communication modules comprises a downhole communication repeater configured to communicate with the first device outside the wellhead using a communication channel that is wireless, at least in a section extending through the wellhead and configured to communicate with a second device located in the wellhead and therefore below the wellhead such that the communication repeater can act as a repeater between the first and second devices. 10. Apparatus according to any one of the preceding claims, wherein the collection module is configured to collect electrical energy from direct currents. 11. A downhole data communication system comprising a downhole data communication apparatus according to any of the preceding claims, located in a downhole installation having a metal structure provided with cathodic protection. 12. The system of claim 11 wherein the well is a subsea well. 13. The system of claim 11 or 12, wherein said apparatus comprises a downhole electrical power collection module electrically connected between two spaced apart sections in the downhole installation and comprising an electrical circuit configured to collect electrical power. - 34 039708 cal energy, when used, from the potential difference between the specified spaced areas used for collection, acting as an input voltage, while the collection module is configured to supply power to at least one component of the data transmission apparatus. 14. The system according to claim 13, wherein the current flow in the sections of the metal structure in the areas between the spaced areas used for collection is provided in the same longitudinal direction. 15. The system according to claim 13 or 14, in which between the spaced areas there is a continuous current path, which, at least partially, passes through the metal structure. 16. The system of any one of claims 11-15, wherein at least one of the first communication module and the second communication module is located in a closed well annulus. 17. The system according to any one of claims 11-16, comprising a pressure sensor configured to monitor the formation pressure of the well. 18. The system according to any one of claims 11-17, comprising a pressure sensor configured to monitor the pressure in the annulus of the well. 19. The system of any one of claims 11-18, comprising a pressure sensor configured to monitor pressure in a closed well annulus. 20. A downhole installation, comprising a downhole metal structure provided with a cathodic protection system, such that an electrical circuit is formed, containing a metal structure and a ground fault, through which an electric current generated by the cathodic protection system is allowed to flow; and the downhole communication tool of claim 1, wherein the first communication module is located downhole in said downhole installation.