EA043424B1 - IN-WELL ENERGY COLLECTION - Google Patents

Description

Field of technology to which the invention relates

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

Information about the prior art

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 subsurface safety valves.

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

The essence of the invention

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

As used herein, the term surface refers to the surface of the earth in the case of a continental 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 located above these 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 an electric current, the system comprising a collection module electrically connected to the metal structure at a first portion and to a second portion spaced from a first section, wherein the first and second sections are selected so that when 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, in which case the electric current is a cathodic protection current. Although the solutions presented here can be used in a system where current is specifically applied to a downhole structure to provide power, it has been discovered that power can also be harvested from cathodic protection systems. In this case, collecting power from 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 where the collection module would be connected to the metal structure at the first and second spaced sections.

Such systems and methods have certain advantages because power can be supplied to the downhole device without the need for a separate power source. Moreover, power delivery 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 passing through the wellhead. Likewise, the proposed solutions can be implemented without using toroids for signal injection and extraction. This reduces the complexity and technical problems that may arise during system implementation.

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

It is preferable that the current flow through the sections of the metal structure in the areas between the first section and the second section occurs in the same longitudinal direction.

Preferably, a continuous current path is provided between the first portion and the second portion, which at least partially passes through the metal structure.

- 1 043424

This description represents the items that will generally be present in the installation unless the design is modified. The ideas presented here generally do not require modification of the entire standard well rig, that is, they are designed to work with a standard rig.

The collection module may be electrically connected to the metal structure at the second site.

A single or each connection to a metal structure may be formed with a section of metal extensions/section of metal pipe.

In several embodiments, the spaced portions may be axially spaced. Connections may be formed to a common section of metallic elongate members, such as a common section of metal pipe that is part of a metal structure. The uppermost of the two spaced 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 area. In some cases, the top connection may be formed to the riser.

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

In other cases, axially spaced connections can be made to different sections of metallic elongates, such as different sections of metal pipe, which will produce similar results, but in general a more suitable solution is to make connections to the same section of metallic elongates /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 sections should preferably be significant - typically 100 m or more. Preferably - from 300 m to 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 well annulus, and inside the internal wellbore.

The connection to at least one of the first or second sections may 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 the 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 through at least one section of metal elongate elements on which a second contact is formed.

If the first spacer contact and the second spacer contact are both formed with the same section of metal elongate members, it is preferable that said section of metal elongate members be continuously conducted between said first and second portions.

At least one connection between at least one of the electrical contacts and the collection module may be provided by 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 will provide a low enough 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 a column.

One of the connections can be formed without an external cable. One of the connections may be formed by a conductive housing of the collection module (or surrounding the collection module).

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

- 2 043424 specific installation.

The distance between sections can be at least 100 m.

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

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

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

Connections may be formed with a common section of metallic elongate members forming part of the metallic structure.

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

To electrically isolate the first section of metallic elongate members from the second section of metallic elongated members, insulating means may be provided in the area of the connections.

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

It should be noted that in the solutions described herein, the currents from which energy is harvested will generally flow in the same direction on the first and second sections of the metal elongate elements/pipe. Therefore, the isolation is not designed to create a separate fault path, but rather to change the path leading to ground 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 element/metal pipe sections. The insulating means may comprise at least one insulating centralizer for holding the sections of elongated members/metal pipe at a distance from each other.

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

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

The collection module may be provided in the bore of the central section of the string, in the annulus, or outside the casing - between the casing and the formation. 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 would normally be impossible and/or undesirable to run cables from the surface, which is particularly useful in the case of subsea wells. In addition, this opportunity is provided without the need for primary batteries or other local power sources, which means it is possible to supply power to such areas throughout the life of the well.

The collection module may include variable impedance means to vary the load between two connections. Variable impedance means can be controlled by a microprocessor.

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

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

- 3 043424

Downhole communication means may be provided to transmit data from the interior of the well towards the surface. Downhole communications may also be configured to receive data from, for example, the surface.

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

Downhole communication means may contain variable impedance means.

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

In other embodiments, instead of communicating with the surface through load modulation, other types of communication may be used. For example, an acoustic and/or electromagnetic signal may be supplied. 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 metal structure, while the uphole communication means may be configured to receive data-carrying acoustic signals.

The downhole communication means may be configured to supply data-carrying electromagnetic signals to the metal structure, and the uphole communication means may be configured to receive data-carrying electromagnetic signals.

The topside communication means may be configured to supply data-carrying acoustic and/or electromagnetic signals to the metal structure, while the downhole communication means may be configured to receive data-carrying acoustic and/or electromagnetic signals.

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

The 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 below the well to the downhole device. The cross-sectional area of the cable used to deliver electrical power downhole will typically be less than the cross-sectional area of any cable used to collect that power, and the power will typically be delivered downhole at a higher voltage than the voltage generated between the spaced 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 elongate element is supplied from one or more sacrificial anodes.

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

In some embodiments, the well surface voltage, in use, is limited to a range of -0.7 V to -2 V 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 downhole structure between the contacts does not exceed 0.1 ohms, preferably does not exceed 0.01 ohms.

The optimal site for power harvesting will usually be located close to the site where currents, such as cathodic protection currents, are applied to the metal structure.

Where the spaced sections are axially spaced, it is preferred to locate the top section in close proximity to the section where currents, such as cathodic protection currents, are applied to the metal 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 involve controlling the location of this connection.

Often the optimal location for power harvesting will be located near the wellhead, where the rate of potential change is greatest as you move deeper into the well. WITH

- 4 043424 on the other hand, the downhole device to which the power is supplied may be located below, inside the well. Therefore, the collection module and the downhole device can be located in different areas, 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 comprise a downhole unit including a collection module and a downhole device.

The upper spaced contact may be located:

within 100 m, preferably within 50 m, from the surface of the earth if the well is a mainland well, and within 100 m, preferably within 50 m, from the bottom level if the well is a subsea well.

The upper spaced contact may be in close proximity to the area corresponding to the maximum potential caused by the electrical current flowing through the structure.

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

Downhole communications may be configured to transmit data by varying the load between connections at distant locations.

In accordance with another aspect of the present invention, there is provided a downhole tool control system comprising a downhole electrical energy collection system disclosed above and a downhole tool, 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, for example 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, or instead of, monitoring the annulus or wellbore in which it is located. in the annulus or barrel 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 a cemented annulus.

The sensor may include a plurality of sensors.

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

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

The communication module may contain 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, a repeater may receive acoustic signals from areas lower down the wellbore and signals toward the surface using electromagnetic coupling, or vice versa. Likewise, both types of communication, acoustic and electromagnetic communication, can be used in one or both directions. The supply of electromagnetic signals can be accomplished by applying electrical signals inside the well or by modulating the load in the acquisition module, as described above. The supply of electromagnetic signals may be carried out at least in part via 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 can be installed 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 may go along the cable.

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

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

underground safety valve;

wellbore flow control valve;

- 5 043424 valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - 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 remote controlled device, for example, may be a wireless controlled device. This may mean, for example, that when controlled from the surface, there may be at least one wireless leg 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 contain a direct current converter (DC/DC converter) to collect power from cathodic protection currents or other currents present. The collection module may include a power storage device for storing the collected power. The energy storage device may comprise a charge storage device, which may include at least one capacitor and/or at least one rechargeable battery. Where energy storage means are present, the harvesting module may be configured to selectively supply power from the storage device or directly from the harvested energy. This choice may be based on predetermined conditions. In alternative embodiments, in the absence of an energy storage device, the harvesting module may be configured to continuously supply power on demand.

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

The direct current converter (DC/DC converter) may include a field effect transistor to form a resonant boost oscillator. The DC/DC converter may also include a step-up transformer and may include a coupling capacitor.

The collection module may be 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 include a plurality of taps, and/or the step-up transformer may include a plurality of secondary windings, and the collection module may be configured to select the windings and/or taps to provide a desired turns ratio. A microprocessor controlled switch may be used to select taps and/or windings.

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

One or more of the sensor module, communication module, and acquisition module may be provided in an annulus, such as annulus B or annulus C, or other annulus. The sensor module and acquisition module may be part of a common downhole assembly, however, it is more typical to separate them so that the sensor may be located deeper than the acquisition 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 to a downhole device at another location in the well.

The cross-sectional area of the conductive core or cores of the cable used to deliver electrical power 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, there is provided a downhole well monitoring system for monitoring at least one parameter in a downhole installation having a metal structure carrying an electrical current, the system comprising:

the electrical energy harvesting 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 sensor module or the communication module.

According to another aspect of the present invention, there is provided a downhole well monitoring system for monitoring at least one parameter in a downhole installation having a metal structure carrying an electrical current, wherein said system

- 6 043424 topic contains:

a sensor module for measuring at least one parameter;

a communication module for sending encoded data readings from the sensor module towards the surface; and an electrical energy harvesting system comprising a collection module electrically coupled to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that, when in use, there is a potential difference between them due to an electric current flowing through designs; wherein the collection module is configured to collect electrical energy from the electric current, wherein the electrical energy collection system is configured to supply electrical power to at least one of the devices: a sensor module or a communication module.

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

Said system may comprise 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 be greater than the cross-sectional area of the conductive portion of the cable having the second length.

The communication module may be configured to modulate an electrical current flowing through a metal structure at a signal input portion to encode data to enable retrieval of said data at a receiving portion remote from the signal input portion by detecting the effect of said modulation on the electrical current at said portion. receiving.

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

The communication module may be configured to control a load generated by the acquisition module to effect said modulation of the electrical current in the metal structure at the signal supply portion.

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 well annulus.

The pressure sensor may be configured to monitor pressure in a closed annulus of a 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, the system comprising:

the electrical energy harvesting system disclosed above; and a communication repeater located downhole in said wellhead and configured to communicate with the first device outside the wellhead using a communication channel that is wireless at least over a portion passing through the wellhead, and configured to communicate with the second device , located in the well, that is, below the wellhead, so that the communication repeater can act as a repeater between the first and second devices, and the electrical energy collection system is configured to supply electrical power to the communication repeater.

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, the system comprising:

a communication repeater located downhole in the well, and configured to communicate with a first device outside the wellhead using a communication channel that is wireless at least over a portion passing through the wellhead, and configured to communicate with a second device, located in the well, that is, below the wellhead, so that the communication repeater can act as a repeater between the first and second devices; and an electrical energy harvesting system comprising a collection module electrically coupled to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that, when 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 the electric current, wherein the electrical energy collection system is configured to supply electrical power to the connected repeater.

- 7 043424

It should be understood that reference here to a first device outside the wellhead refers to a device on the other side of the wellhead relative to the second device that is located in the wellhead, that is, communication through the wellhead is preferred. As such, the first device may be located anywhere, close to the wellhead or remotely, as long as appropriate communications are provided.

The communication repeater may be configured to modulate an electrical current flowing through a metal structure at a signal supply site to encode data to enable data retrieval at a receiving site remote from the signal supply site by detecting the effect of said modulation on the electrical current at said receiving site .

The communication repeater and/or collection module may be provided in the annulus, for example in annulus B or annulus C, or other annulus.

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

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

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

The cross-sectional area of the conductive portion of the cable having the first length may be greater than 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 an electrical current at said acquisition site to retrieve the encoded data.

The communication repeater may be configured to control the load generated by the acquisition module to effect said modulation of the electrical current in the metal structure at the signal supply portion.

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 electric current, the system comprising: a downhole tool;

an electrical energy harvesting system comprising a collection module electrically coupled to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that, when in use, there is a potential difference between them due to electrical current flowing through the structure ; wherein the collection module is configured to collect electrical energy from the electric 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 elements: a downhole sensor;

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

Said valve may comprise at least one of the following elements:

underground safety valve;

wellbore flow control valve;

valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - pressure compensation chamber;

valve annulus - pressure compensation chamber;

valve through the packer or bypassing the packer.

Power may be supplied to operate the valve, while the power to move the valve comes from another source (eg, spring force, differential pressure). Alternatively, power may be supplied to move the valve, or to both control and move the valve. The valve may include an actuator, such as a servo valve, controlled by power from the power delivery system.

The device control system may be configured to supply variable power levels. Thus, the first power level may be supplied at times different from the times when the second, higher power level is required. Injected currents, such as cathodic protection currents, can be increased if higher power levels are required by switching to more anodes or by injecting a higher imposed current. This may be at a level undesirable for long periods due to the potentially damaging effects of too much potential difference due to cathodic protection currents - hydrogen embrittlement - but

- 8 043424 this is acceptable for short-term periods. Therefore, the system, apparatus, method can be configured to temporarily increase the supplied current, for example the cathodic protection current. A higher power level can be used, for example, to move a valve from one state to another, while a lower power level can be used at other times, for example, when monitoring and/or controlling signals.

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

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

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

A power source other than the electrical power supplied by the electrical energy harvesting module may be available to the downhole device.

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

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

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 transmit from the top section towards the collection module to modulate the supplied current (eg, cathodic protection current). One method is to turn the anode on and off, which will modulate the potential observed inside the well. Thus, data can be encoded by turning on the anode and excluding it from operation. 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 data.

According to another aspect of the present invention, there is provided a method of supplying power to a downhole device in a downhole installation having a metallic structure carrying an electric current, the method comprising the steps of:

an electrical connection is made between the collection block and the metal structure in the first section and with the second section spaced from the first section, wherein 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, and the collection block is made with the ability to collect electrical energy from an electric current, being connected between sections with a potential difference between them;

collect electrical power from the electric current in the collection unit; and supplying electrical power from the collection unit to the downhole device.

The specified method may contain stages in which: a section is determined in which the potential due to the electric current flowing through the structure is maximum in value, and depending on the section of the specified maximum, a first section is selected in which the collection block is connected to the metal structure.

According to another aspect of the present invention, there is provided a downhole electrical energy collection system for use in a downhole installation having a metal structure comprising at least one section of metallic elongate elements carrying electrical current, the collection system comprising:

an energy harvesting module comprising an electrical circuit connected between spaced contacts for collecting energy from a potential difference between the spaced contacts, wherein a first of the spaced contacts is formed with at least one section of metal elongate elements in a first portion, and a second of the spaced contacts is formed with at least with one section of metallic elongate members in a second portion, wherein the potential difference is caused by a current flowing through said at least one section of elongated members and at least in part by the impedance of said at least one section of elongated members.

An electric current flowing through at least one section of metal elongate elements on which a first contact is formed may flow in the same longitudinal direction as an electric current flowing through at least one section of metal elongate elements on which a second contact is formed.

Preferably, the first spacer contact and the second spacer contact are both formed with the same section of metal elongate elements; Moreover, this section of metal extensions

- 9 043424 elements are continuously conductive between the first and second sections.

Preferably, the metal structure provides a continuous path of current flow between the first portion and the second portion.

It is preferable that the current flow between the parts of the metal structure in the regions 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.

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

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

The spaced sections may be spaced along the axis.

The spaced sections may be spaced radially.

At least one connection between at least one of the electrical contacts and the electrical circuit may be provided by 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 may be formed with a common section of metallic elongate members forming part of the metallic structure.

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

To electrically isolate the first section of metallic elongate members from the second section of metallic elongated members, insulating means may be provided in the area of the connections.

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

The insulating means may include at least one insulating centralizer for holding the metal elongate elements at a distance from each other.

Isolation means may be provided to prevent electrical contact between two sections of metallic elongate members over a distance of at least 100 m.

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

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, when used, can be limited to a range of 0.7 V to -2 V 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 downhole structure between the contacts may be less than 0.1 ohms, preferably less than 0.01 ohms.

The upper spaced contact may be located:

within 100 m, preferably within 50 m, from the surface of the earth if the well is a mainland well; and within 100 m, preferably within 50 m, of the bottom level if the well is a subsea well.

The upper spaced contact may be located in close proximity to the area corresponding to the maximum potential caused by the electrical current flowing through the structure.

Said system may contain downhole communication means for transmitting and/or receiving data.

Downhole communication equipment can be configured to transmit data

- 10 043424 load transfer between connections in spaced sections.

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

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

downhole sensor;

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

Said valve may comprise at least one of the following elements:

underground safety valve;

wellbore flow control valve;

valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - pressure compensation chamber;

valve annulus - pressure compensation chamber;

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 wellbore to collect power, and a cable may be provided to supply electrical power below the wellbore to a downhole device located at another location in the wellbore.

The cross-sectional area of the conductive core or cores of the cable used to deliver electrical power 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 of supplying power to a downhole device in a downhole installation having a metal structure carrying an electric current, the method comprising the following steps:

an electrical connection is made between the collection block and a metal structure in the first section and with a metal structure in a second section spaced from the first section, wherein 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, and the block collecting is configured to collect electrical energy from an electric current, being connected between sections with a potential difference between them;

collecting electrical power from the electric current in the collection unit; and supplying electrical power from the collection unit to the downhole device.

The specified method may also contain the following steps, in which: determining the area in which the potential caused by the electric current flowing through the structure is maximum in value, and selecting the first area in which the collection unit is connected to the metal structure, depending on the area of the specified maximum .

According to another 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 provided with cathodic protection, the system comprising:

a collection module electrically connected to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that when 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 energy from cathodic protection currents.

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

Current flow 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 flow path between the first portion and the second portion may be provided that at least partially extends through the metal structure.

The collection module may be electrically connected to the metal structure at the second site.

The spaced sections may be spaced along the axis.

- 11 043424

The spaced sections may be spaced radially.

At least one connection between at least one of the electrical contacts and the collection module may be provided by 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 areas are separated may be at least 100 m.

Connections may be formed with a common section of metallic elongate members forming part of the metallic structure.

The first of the connections may be formed with a first section of metal elongate members that is part of the metal structure, and the second of the connections may be formed with a second, different section of metal elongate members that is part of the metal structure.

To electrically isolate the first section of metallic elongate members from the second section of metallic elongated members, insulating means may be provided in the area of the connections.

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

The insulating means may include at least one insulating centralizer for holding the sections of metallic elongate members at a distance from each other.

To avoid electrical contact between two sections of metallic elongate members, insulation means may be provided at a distance of at least 100 m.

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

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, when used, can be limited to a range of 0.7 V to -2 V 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 downhole structure between the contacts may be less than 0.1 ohm, preferably less than 0.01 ohm.

The upper spaced contact may be located:

within 100 m, preferably within 50 m, from the surface of the earth if the well is continental; and within 100 m, preferably within 50 m, from the bottom level if the well is subsea.

The upper spaced contact may be located in close proximity to the area corresponding to the maximum potential caused by the electrical current flowing through the structure.

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

Downhole communication means can be configured to transmit data by varying the load between connections at distant locations.

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

The downhole device may contain at least one of the following elements:

downhole sensor;

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

Said valve may comprise at least one of the following elements:

underground safety valve;

wellbore flow control valve;

valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - pressure compensation chamber;

- 12 043424 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 wellbore to collect power, and a cable may be provided to supply electrical power below the wellbore to a downhole device at another location in the wellbore.

The cross-sectional area of the conductive strand or strands of the cable used to deliver electrical power 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, there is provided a downhole data communication apparatus for use in a downhole installation having a metal structure equipped with a cathodic protection system such that there is an electrical circuit comprising the metal structure and a ground fault through which an electric current flows as a product of the system. cathodic protection, and the downhole data transmission device contains:

a first communication module for positioning in a first section, comprising modulation means for modulating an electrical current in the first section for encoding data; and a second communication module for positioning at a second site spaced from the first site, comprising a detector for detecting a modulation effect on an electric current at the first site for retrieving said data.

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

i) controlling the source of the overlay cathodic protection system signal to directly modulate the cathodic protection current applied to the metal structure if the cathodic protection system is an overlay cathodic protection system;

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

The first communication module may be configured to be located inside the well.

The second communication module may be configured to be located inside 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 depending on the data received by the second communication module from the first communication module.

The downhole device may contain at least one of the following elements:

downhole sensor;

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

Said valve may comprise at least one of the following elements:

underground safety valve;

wellbore flow control valve;

valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - 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 include 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 wellhead, that is, below the wellhead, so that the communication repeater can act as a repeater between the first and second devices.

Said apparatus may comprise an downhole electrical power collection module, configured to be electrically connected between two spaced sections in the downhole installation and containing an electrical circuit configured to collect electrical energy, when used, from the potential difference between the spaced sections, using

- 13 043424 designed for collection, acting as an input voltage, wherein the collection module is configured to supply power to at least one component of said data transmission apparatus.

The first communication module may be configured to control a load generated by the acquisition module to effect said modulation of the electrical current in the metal structure at the signal supply portion.

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

According to another aspect of the present invention, there is provided a downhole data communications system comprising the downhole data communications apparatus disclosed above located in a downhole apparatus having a metallic structure provided with cathodic protection.

According to another aspect of the present invention, there is provided a downhole communication system for use in a downhole installation having a metal structure equipped with a cathodic protection system such that there is an electrical circuit comprising the metal structure and a fault to ground through which an electric current flows as a product of the system. cathodic protection, wherein said system comprises a downhole data transmission device, which contains:

a first communication module located in the first section and comprising modulation means for modulating an electrical current in the first section for encoding data; and a second communication module located at a second portion spaced from the first portion and comprising a detector for detecting a modulation effect on an electrical current at the first portion to retrieve said data.

Said apparatus may comprise a downhole electrical energy collection module electrically connected between two spaced sections in the downhole installation and comprising an electrical circuit configured to collect electrical energy, in use, from a 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 transmission apparatus.

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

Between the spaced sections there may be a continuous path of 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 a closed annulus of the well.

The specified system or apparatus may contain a pressure sensor configured to monitor the reservoir pressure of the well.

The specified system or apparatus may contain a pressure sensor configured to monitor pressure in the annulus of the well.

The specified system or apparatus may contain a pressure sensor configured to monitor pressure in the closed annulus of the well.

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 sections in a downhole installation and comprising an electrical circuit configured to collect electrical energy, when used, from a potential difference between the spaced sections 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 contain a direct current converter (DC/DC converter).

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

The DC/DC converter may include self-triggering means that allow energy 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-triggering features that allow energy 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 contain a field-effect transistor, complete with a

- 14 043424 with a shading transformer to form a resonant step-up oscillator.

The direct current converter (DC/DC converter) may comprise an H-bridge of transistors configured, under the control of controls, to provide an input signal to a step-up transformer, wherein 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 a step-up transformer may include multiple taps, and/or the step-up transformer may include multiple secondary windings, and the controls may be configured to select the windings and/or taps to provide a desired turns ratio.

The acquisition module may comprise at least a pair of terminals from which connections can be made to two spaced sections.

The collection module may have more than two terminals, each of the terminals providing connectivity to a corresponding portion, wherein the collection module may further comprise switching means for selectively electrically connecting two of the terminals to the electrical circuit, thereby allowing a choice between which of the respective areas the electrical circuit is connected.

The result is a structure that, at the time of installation, can make multiple contacts with the metal structure, and after installation, a choice is made which connections to use. For example, the design may include one bottom connection and two top connections at different locations. After installation, it may be determined that more power can be collected if the first of the top connections is used, so the first connection may be used. In another case, the second top connection may be preferable.

A switch can also be used to switch between connections, used dynamically during 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 energy storage device may include a charge storage device, which may include at least one capacitor and/or a rechargeable battery.

The collection module may include variable impedance means to vary the load between two connections.

Variable impedance means can 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 means to modulate the load to transmit data from the acquisition module.

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

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

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

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

The downhole apparatus may include modulation means for supplying a modulated voltage over spaced data connections.

The downhole apparatus may include a primary battery such that, when 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 elements: a downhole sensor;

downhole actuator;

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

valve;

downhole communication module, such as a transceiver or repeater.

Said valve may comprise at least one of the following elements:

- 15 043424 underground safety valve;

wellbore flow control valve;

valve wellbore - annulus;

valve annulus - annulus;

wellbore valve - pressure compensation chamber;

valve annulus - pressure compensation chamber;

valve through the packer or bypassing the packer.

According to another 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 an electrical current, the system comprising:

the collection module disclosed above is electrically connected to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that, when 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 the electric current.

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

the collection module disclosed above is electrically connected to a metal structure at a first portion and to a second portion spaced from the first portion, the first and second portions being selected such that a potential difference exists between them when in use due to electric current flowing through the structure, wherein the collection module is configured to collect electrical power from the electric current and supply electrical power to the specified downhole device.

However, according to another aspect of the present invention, there is provided a downhole power delivery system for supplying power to a downhole device in a downhole installation having a metal structure provided with cathodic protection, the system comprising:

the collection module disclosed above is electrically coupled to the metal structure at two spaced locations that are selected such that, when 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.

However, according to another aspect of the present invention, there is provided a method for transmitting data in a downhole installation having a metal structure equipped with a cathodic protection system such that there is an electrical circuit comprising the metal structure and a ground fault through which an electric current flows as a product of the cathodic protection system. protection, wherein this method contains the steps of:

modulate the electric current in the first section for data encoding; and at a second section spaced from the first section, detecting the effect of said modulation on the electric current at the first section to extract said data.

One of the regions may be a region outside the wellbore, for example, the region may be the surface, and the other region may be within the wellbore.

The step of performing current modulation may, among other things, include, and the modulation means may, among other things, be configured to:

i) controlling the source of the overlay cathodic protection system signal to directly modulate the cathodic protection signals applied to the metal structure if the cathodic protection system is an overlay cathodic protection system;

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

It is desirable that methods i) and ii) be available only in the top section, while method iii) may be available both downhole and in the top section.

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

These methods make it possible to communicate as part of a hybrid communication system - to

- 16 043424 where some parts of the signal channel are provided by 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 available, can be provided either by a passive cathodic protection system, where the sacrificial anodes are connected to the metal structure of the downhole rig, or by a superimposed cathodic protection system, where protective current is applied to the metal structure of the downhole rig.

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.

Thus, anodes, if available, are usually located outside, that is, on top of the wellbore, in the water. Moreover, the anodes are usually located at some distance from the area where power and/or signal must be supplied.

Thus, any of the systems described above may include one or more of the following elements: at least one anode present; at least one anode located in 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 said anode.

Moreover, any of the systems described above may be designed to allow power to be transferred from an area where current is applied to the structure, such as a cathodic protection (CP) current, to a signal collection and/or supply area. This applies whether the current is passive cathodic protection current, imposed cathodic protection current, or other applied current. A typical option is when the source of cathodic protection current or other current is located at some distance from the signal collection and/or supply area.

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

When modeling optimization is mentioned in the description above, for example, with respect to the spacing of connections, the use of insulation, selecting only radial or axial spacing of connections, and selecting a given collection load, then such a model may use at least one from the following parameters:

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

2. Top connection location.

3. Bottom connection location.

4. The cross-sectional area and type of material (resistivity) of the overhead cable used at the inputs to the collector.

5. Number, location, material (electric potential) and surface area of wellhead anodes.

6. Effective wellbore resistivity at seabed/wellhead level, also derived from casing sizes and tubular element sizes, weight, and type of material (resistivity) and overburden resistivity (medium surrounding the well), but this time for the entire well structure.

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

According to another aspect of the present invention, there is provided a downhole apparatus comprising a metal structure carrying an electrical current and any of the systems or apparatus described above, for example, a downhole apparatus or an electrical energy collection system; downhole device control device or system; downhole apparatus or communication repeater system; apparatus or power supply system; or collection module; or a downhole apparatus or well monitoring system; or the downhole apparatus or data transmission system disclosed above. Such an installation may also contain a cathodic protection system to protect the metal 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 set forth after each aspect with any necessary modifications to the wording. Not all of these optional signs are propi

- 17 043424 san after each aspect solely for the purpose of maintaining brevity of presentation.

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

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

List of figures

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

In fig. 1 is a schematic diagram of a downhole installation including a well monitoring apparatus including an downhole power delivery system.

In fig. 2A is a schematic diagram of the power supply system acquisition module shown in FIG. 1; while in FIG. 2B shows an alternative downhole block.

In fig. 2C shows a circuit diagram of a DC/DC converter circuit that can be used in the acquisition module.

In fig. 2D shows a circuit diagram of a DC/DC converter circuit that can be used in the acquisition module.

In fig. 3 is a schematic diagram of a downhole installation including a downhole data transmission apparatus containing a downhole communication repeater and a downhole power delivery system for supplying power to the downhole communication repeater.

In fig. 4 is a schematic diagram of a downhole installation including a valve control apparatus comprising a remotely controlled downhole valve and a power supply system for supplying power to the remotely controlled downhole valve.

In fig. 5 is a schematic diagram of a downhole installation including an alternative well monitoring system comprising a downhole sensor and a downhole power delivery system for supplying power to the downhole sensor.

In fig. Figure 6 schematically shows an alternative well setup.

In fig. 7 for a structure similar to that shown in FIG. 1 shows a graph of the optimal collected power depending on the depth of the lower connection.

In fig. Figure 8 shows a flowchart for optimizing energy harvesting.

In fig. Figure 9 shows a block diagram of the downhole unit control.

In fig. 10 is a schematic diagram of a well rig including a platform.

Information confirming the possibility of implementing the invention

In fig. 1 shows a downhole installation for an oil and/or gas well. It should be understood that such an oil and/or gas well may be a mainland well or a subsea well (that is, the well may be under some water column), with the wellhead located underwater at the bottom of a sea, river, lake, etc. , or on the platform. Often, downhole installations are equipped with a cathodic protection system (CP). In the case of mainland wells, this most often takes the form of a cathodic protection system with an imposed current, with the protective current applied to the metal structure of the well. On the other hand, for subsea wells, cathodic protection is most often a passive cathodic protection system in which multiple anodes of a relatively reactive material, such as a magnesium alloy, are connected to a metal structure and are exposed to the water in which the downhole unit is located.

It should be noted that the solutions described here are also relevant for well injection wells used to inject water into the formation to facilitate 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. Likewise, 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 occurs. In a broad sense, the solutions presented here can be used at any time in the life cycle of a downhole rig.

Moreover, while this description is given in relation to installations where 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 through and away from a metal structure power harvesting can be carried out.

The downhole installation shown in FIG. 1, contains a wellhead 1 and an 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 current-imposed cathodic protection system 3A or a passive cathodic protection system comprising a plurality of anodes 3B coupled to the metallic structure of the downhole rig, ie the wellhead or other metallic components coupled thereto.

- 18 043424

The downhole metal structure 2 contains a first section of metal pipe 21, which is a production string extending 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 will be appreciated 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 usually called annulus A in the oil and gas industry and is designated 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 designated 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 space, and sometimes more annulus spaces.

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

The monitoring apparatus provided in the downhole installation includes an electrical power collection module 4, located in this embodiment in the annulus A. The collection module 4 is electrically connected via cables 41 to a pair of spaced sections 41a, 41b on the production string 21. In an alternative embodiment, the module 4 collection can be electrically connected to one of the sections via a cable, while it can be connected to another section without a cable. The collection module 4 can be electrically connected to one of the sections by means of a conductive housing of the collection module (or surrounding the collection module). Therefore, only one such cable may need to be exited from the specified housing.

It should be noted that a galvanic connection takes place between the collection module 4 and the metal structure 21 at 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 along the entire section from the metal structure to the inputs of the circuit included in the energy collection module.

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 of the metal pipe sections to ensure the effectiveness of the system, and the normal flow of cathodic protection current in the structure was not altered - except, of course, during the collection process that took place. For example, between spaced sections, the section of the metal structure with which connections are formed is continuous; in a broader sense, all sections of the metal structure are continuous in all areas. This is not essential to the operation, but it is possible and is the prevailing situation in a downhole rig - that is, the standard metal structure of the rig is not changed. Similarly, in a metal structure, current can and does flow in the same direction at the joints and between the joints. Again, this is the prevailing situation in a downhole rig - modifications to the downhole rig are avoided. The current can flow in one section of the metal structure with which connections are formed, or jump from one section to another, or flow in parallel in several sections - the main thing is that the operation of the system does not require the creation of an artificial configuration of the metal structure in the well; the specified metal structure ensures continuous path of current flow, and 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 means of a cable passing through the wellhead 1. Despite this, the use of the configurations presented here is advantageous as they minimize the number of penetrators at the wellhead, reducing risk and using and/or freeing up the penetrator for other purposes.

The monitoring apparatus also includes a downhole sensor 5 located deeper in the well than the acquisition 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 casing 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 to be sufficiently negative at the entry point, for example, at the wellhead 1, that

- 19 043424 would 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 we move 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 portion 41a where the first of the cables 41 from the collection module is connected to the production string 21, and the portion 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, the collection module 4 will have a potential difference and will be able to extract energy from the cathodic protection currents.

It should be noted that although energy extraction will use power from the cathodic protection system, the effect on the efficiency of the cathodic protection system or the acceleration of anode corrosion will be negligible. Typically cathodic protection currents will be on the order of 10 A, while the systems presented here will extract, for example, 10-100 mA. That is, the amount of current extracted falls within the permissible range usually included in the design of cathodic protection systems. If necessary, a higher level of imposed current may be provided or the number of anodes provided may exceed the normal number. This will increase the cathodic protection current and therefore improve collection.

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

In the embodiment shown in FIG. 1, this collected power is used to supply power to the downhole sensor 5 and makes it possible to extract readings from it and transmit 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 understood that configurations such as those presented here can be used in place of a traditional permanent downhole gauge PDG with the advantage that they avoid the use of a penetrator passing through the wellhead while allowing in many cases, continuous well monitoring. The monitoring may be reservoir pressure monitoring, if necessary, or similarly, closed annulus pressure monitoring, for example to detect a leak or problem or breakdown in the system. In this case, the sensor and acquisition module can be located in a closed annulus.

All of the above 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 power and signal delivery options 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 external annulus (B, C, etc.). In particular, when these annular spaces are sealed in the base, it makes sense to monitor and optionally regulate the pressure in such annular spaces, for example, to reduce the risk of high pressures leading to failure of the casing structure. In particular, flow movement or drilling of a well can increase the temperature of the hermetically sealed external 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, using an annular drain valve such as those described above) is advantageous. In particular, the implementation of pressure monitoring in a closed annulus may allow production at higher rates than can be achieved if only modeling of the expected pressure rise is used, since the use of simulated pressure will require greater safety tolerances, and potentially lead to corresponding reduction in production rate. It should be clear that the solutions presented here can assist in the implementation of such monitoring and/or regulation.

Another specific embodiment of the solution presented herein would include a sensor module located in the same location where a conventional, traditional fixed downhole sensor is typically located, and is provided for the same purpose as a 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 a pressure transmission port passing through the string, thereby making it possible to determine the formation pressure based on the pressure obtained by measuring the static pressure and the influence of flow. As is the case with traditionally used stationary in-well

- 20 043424 pressure sensors (PDG), formation pressure is often determined in this way rather than measured directly - placing the sensor directly in the formation is generally not practical (it should be understood that monitoring formation pressure replaces the use of such measurements).

A collection module may also be provided in a portion of the sensor module.

Various methods can be used to extract data from the downhole sensor 5 towards the surface.

In the present embodiment, the collection module 4 is configured to receive a signal from the downhole sensor indicating the value of the measured parameter, for example, pressure and/or temperature, and transmit this data towards the surface by modulating the load that the collection module 4 carries out between the spaced connections 41a and 41b . In response, this load change 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 other suitable location by changing the potential of the metal structure at the surface or other suitable location. This may be detected, for example, by detecting a change in potential at the wellhead 1 or by detecting a voltage or 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 at least 100 m, or more likely 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 connections increases, there is a tendency for the potential difference between said connections to increase (although the rate at which the potential difference increases decreases as the depth of the bottom connection 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 collection 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 corresponding 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 direct current converter (DC/DC converter) is connected to collect electrical energy where there is a potential difference between the terminals 43a, 43b. The 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 a central unit 46 controlled by a microprocessor. The charge storage means 45 and the central unit 46 are also connected via a corresponding terminal 43c to a cable 42 leading to the downhole sensor 5. Alternatively, the charge storage means 45 may be omitted - that is, sufficient power can be collected as needed to allow continuous operation.

During operation, the central unit 46 controls the operation of the DC/DC converter 44 to optimize the load it places on the current received by the collection module 4 from 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 the energy and retrieve the stored energy when required.

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

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

It should be noted that in the described embodiment, the DC-DC converter 44 and the central unit 46 together act as variable impedance means by controlling the central unit 46 to operate the DC-DC converter 44 to input the variable impedance between the 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, a downhole block 4a shown in FIG. 2B, comprising both a collection module 4 and at least one downhole device that requires

- 21 043424 We need to apply power. In such a case, the downhole unit 4a contains both a pressure sensor 47 and a communication unit 48.

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

In alternative embodiments, instead of providing communication in the surface direction using the load modulation method disclosed above, 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 communication signals, which may be fed back to the downhole metal structure 21 via cables 41. In other cases, a communication unit 48 provided in the downhole unit 4a may be an acoustic communications unit for providing acoustic signals to the metal structure 21 for feedback. transmission in the direction of the surface. In this case, the upper communication unit will be configured to receive acoustic signals. It should be understood that bidirectional 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 communication channels, so electromagnetic signals and acoustic signals can be used in parallel.

In other alternative embodiments, the collection module 4 or downhole unit 4a may include at least one power converter to control the voltage that collects power for supply to the charge storage means 45 and/or other components, such as the central unit 46. Storage may be preferred. energy at a different voltage than that at which it is collected and/or at a different voltage than that at 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 draw of stored power, such as during transmission.

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

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

In fig. 2C shows a schematic circuit diagram 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 (so-called crossed diodes), and corresponding capacitors 205 communications. The primary winding 202a of the transformer 202 is connected in series with the field effect transistor 201, and an input signal Vin is supplied to them. The gate of the field effect transistor 201 is connected to the secondary winding 202b of the transformer 202. The output signal Vout is shown on the coupling capacitors 205, each of which is connected to the secondary winding 202b through corresponding diodes 204.

The secondary winding 202b of the transformer 202 includes a plurality of taps 202c that can be selected by the switch 206, making it possible to adjust the turns ratios. Switch 206 may be controlled by a microprocessor, in this case 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 lower. In practice, the input voltage may be lower than 0.25 V, and possibly even lower than 0.05 V. Since these values are much less than the semiconductor bandgap voltages (eg 0.7 V), many DC-DC converters will not work to harvest energy at such low input voltages. However, DC-DC converters relying on the principles described above can operate even at such low voltages. Such a direct current converter (DC/DC converter) can

- 22 043424 provide for the inclusion of triggering means designed to enable operation both in the case of an input voltage of 0.5 V or lower and in the case of higher voltages.

An alternative approach involves a circuit with a separate power supply that acts as part of the triggering means. For example, a primary battery may be provided to start the system after installation. Moreover, the stored energy in the energy storage device can be used to restart the system if energy collection is temporarily interrupted.

In fig. 2D shows a circuit diagram of a circuit for a possible implementation of a DC-DC converter operating on this principle. The DC/DC converter shown in FIG. 2D, contains 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 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. Also connected to the specified input of the power supply unit 210 through another diode 204 is the battery 211.

The power supply unit 210 is configured to supply power to the control unit 208. To start operation, the power supply 210 may use power from the battery 211. When energy is harvested by the DC/DC converter, the power supply 210 may use the power received from the 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 may also be stored in 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 element. Energy storage, when accomplished, allows the mechanism to restart the system if collection stops at some point in time after battery 211 has been 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, the power supply 210 may be configured to store energy therein when it is 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 embodiment, the DC-DC converter shown in FIG. 2D may be designed to enable control of the load generated by the DC/DC converter. 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 enable selection of the taps. Such a switch may be located between the windings and the input to rectifier 209. In another alternative, separate secondary windings may be provided instead of multiple taps to achieve the same result. The switch may be controlled by the control unit shown in the configuration in FIG. 2C.

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

For example, such components may be located in annulus B or C, wherein a sensor located, for example, in annulus B may be configured to measure one or more parameters in annulus A, B, C, or any combination thereof. It should be noted that these are areas where it is generally impossible, or at least undesirable, to place direct cable connections to the surface. Therefore, the solutions presented here increase the ability to monitor, for example, annulus pressure B or C throughout the life of the downhole rig, which would be difficult and/or impossible using traditional 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 well setup 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

- 23 043424 in relation 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 receives power from the power delivery system is the communication repeater 7 rather than the downhole sensor 5.

Therefore, a detailed description of the downhole installation and power delivery system is omitted here in the interest of brevity. For the components referred to in relation 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, signals are supplied to the downhole metal structure 2 in the form of electromagnetic signals by a transmission tool 71 located downhole, for example, in the production string 21. Accordingly, the repeater 7 is configured to pick up the electromagnetic signals.

Alternatively, another type of transmission instrument may be provided to send the signals picked up by the repeater. Such a tool may, for example, be placed outside said 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 supplied downhole.

Likewise, the downhole communication repeater 7 may be configured to supply acoustic signals from the downhole structure 2 for transmission toward the surface, or configured to provide electromagnetic signals from the downhole metal structure 2 for transmission to the surface, or use the impedance modulation signal delivery method disclosed above.

For example, a communication repeater 7 can pick up signals in its area and transmit them via cable 42 to the collection module 4, supplying it with signals and modulating the load that it applies to the power source in the collection module 4. Likewise, the acquisition module 4 may be configured to supply signals to the metal structure 2 for transmission toward 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 picked up 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 supplying a signal through an insulating element, if available, etc. Traditional methods for capturing and delivering acoustic signals can be used in a similar manner.

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

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

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

1. Repeater 7 contains an electromagnetic repeater, which is constantly supplied with power, and which is located at a depth of 3-500 m, said repeater either receives and decodes messages, or simply forwards them constantly using high frequency load impedance modulation, the original data/signal for decoding on the surface.

2. Repeater 7 contains an acoustic repeater, which is constantly supplied with power, and which is located at a depth of 3-500 m, the 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 in this description, the devices can be configured to regulate the energy budget, i.e. overall less energy use due to variable operation of components such as electromagnetic or acoustic receivers

- 24 043424 and/or transmitters.

In fig. 4 is a schematic diagram of a downhole rig including a remote controlled valve and a power delivery system generally similar to that described above.

The general design and operation of the downhole rig and power delivery system is, again, substantially similar to those described above with respect to the configurations illustrated in FIG. 1, 2A-2D. Therefore, detailed description of these common elements is omitted here for the sake of brevity, but the same reference numerals common to the two embodiments are used to denote these characteristics.

In this embodiment, the downhole rig includes 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, lower in the well. In the presented case, the specified underground safety valve 8 is provided as an additional, safety or emergency means. However, in alternative embodiments, the hydraulically actuated underground safety valve SSSV may be omitted.

The second underground safety valve 8 receives power and operates through the use of a power supply system. In particular, the collection module 4 is connected to the second underground safety valve 8 via cable 42, wherein the collection module is provided with the ability to supply power and control signals directed to the second underground safety valve 8 via cable 42. Thus, energy is collected from the cathodic protection currents, and it is used both for the control and operation of the second underground safety valve 8.

Such a subsurface safety valve 8 may be located deeper in the well as compared to the conventionally used hydraulically actuated subsurface safety valve SSSV. This is due to the fact that it is not subject to the same restrictions that are imposed on hydraulically driven systems - there is no need to supply hydraulic fluid to it.

It should be noted that in this case, control signals for the second underground 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 underground safety valve 8. In some embodiments, 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, in an alternative embodiment, the valve 8 and 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 is supplied from the downhole power delivery system.

In fig. Figure 5 shows an alternative downhole installation that includes 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 spaced portions on the downhole structure 2, and there is also a downhole sensor 5 connected to the collection module 4. Here, the collection 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.

Here, the spaced portions 41a, 41b are located on different sections of the downhole metal structure 2. Specifically, in this embodiment, the first of the connections 41a is formed with the second casing 23, while the other of the connections 41b are formed with the first casing 22. This system operates following a similar principle as described above and therefore its operation is based on the potential difference present between the two said connections 41a, 41b. In this embodiment, said potential difference is realized by isolating the two sections of the metal structure 22, 23 from each other at least in the area of said connections. This means that the cathodic protection currents have different paths to ground from the two sections of the metal structure 22, 23. In the present embodiment, the means for isolating the two sections of the metal structure 22, 23 from each other include an insulating coating 91 provided on the outer surface of the first casing 22; and a plurality of isolating centralizers 92 provided on the first casing 22 to maintain it at a distance from the second casing 23.

Preferably, this insulation 91 and these centralizers 92 are located at a distance of at least 100 m along the first casing 22, and more likely at a distance of 300-500 m. Where preferred or practical, the outer section of the metal structure may insulating separators forming the annulus should be installed. For example, they can be installed on the second casing 23 in the above example. It should be noted that the insulation does not have to be completely continuous to provide positive

- 25 043424 effects. The goal is to create a different path to the ground. Although insulation may be provided over a distance of 100 m, it may not be continuous or may provide continuous insulation over the entire distance.

An advantage of the configuration shown in FIG. 5 is that there is no need for the large lengths of cable 41 between the collection module 4 and the metal structure 2 required 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 housing of the collection module 4 on a section of metal pipe, provided with a sliding contact to create contact with another section 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 acquisition module 4 in the downhole block 4a. This configuration can reduce the installation time required for installation.

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

Typically, however, the configuration shown in FIG. 1 will likely perform better than the one shown in FIG. 5, in the case where its use is practically feasible.

In a configuration similar to that shown in FIG. 5, the collection module can observe a relatively higher current but a relatively lower potential difference. Thus, in the configuration in FIG. 5, the potential difference may be 10-20 mV, for example, and the current, for example, 1 A. On the other hand, in the configuration of FIG. 1 potential difference can be, for example, 100-200 mV, and the current, for example, can be 100-150 mA. The higher potential difference is achieved due to the greater distance provided by the cable(s) 41 in the configuration of FIG. 1, and the lower current value is caused by the resistance of the cable(s).

Apart from the stated 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 the one shown in FIG. 1. Likewise, the various alternatives described above in relation 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. Likewise, the various shapes of the collection module 4 and the downhole block 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 without the intention of using wireless capabilities when the well is initially installed.

Therefore, the configuration shown in FIG. 3, where a communication repeater 7 and a corresponding power delivery system are included in the annulus B, may be provided during the initial installation of the well 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 signal tool 71 to provide a signal to the surface. It should also be noted that the term wireless is used to refer to the spaces between the downhole space and the outside 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 herein does not require a cable passing through the wellhead 1. Therefore, these systems can be used where a penetrator is not 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 of (possibly remotely controlled) valve or component may be provided. For example, a configuration similar to that shown in FIG. 4 may be used with an annular drain valve provided in a well to allow controlled hydraulic communication or venting between one annulus and another annulus, or between an annulus and the wellbore. Said valve may include a gas lift gas injection valve to allow gas to enter the production string bore from annulus A. Likewise, the valve may be a packer, or a valve through a packer, or a valve bypassing the packer. Again, to ensure ventilation of a specific annulus under control

- 26 043424 lineage coming from the surface. In another example, the valve may include a flow control valve, for example, to control a fraction from a certain zone, or it may provide a means to allow improved pressure build-up data collection 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 the ability to completely shut off the flow, but, for example, can function as a variable diameter fitting.

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 string in the production string 21. Such a tool may be configured to provide signals to and from /or collecting 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 is sufficient to perform useful functions such as control downhole devices, take critical measurements, and enable those measurements to be transmitted to the surface.

It should be noted that, in general, in the general embodiments illustrated in FIGS. 1-4, the greatest influence on collection efficiency will be the cross-sectional area of the 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 a single downhole installation, there is a slight reduction in the efficiency of any of the collection modules 4. It should be noted that, in general, any additional collection system will have its own cables 41 when practical. This relies on the fact that cable losses mean that having more collection systems sharing the same cable does not provide much benefit.

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

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

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

In fig. 6 shows an alternative well setup that has similar features to the setup shown in FIG. 1, the same reference numerals being used to denote characteristics common to FIG. 1, but a detailed description of these general characteristics is omitted.

The downhole installation shown in FIG. 6 helps to illustrate in more detail some of the alternatives described above with respect to the well installations shown in and described in relation 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, and therefore 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, and therefore the collection module 4 is connected through

- 27 043424 pipe space A. Moreover, on the production string 21 in the area of the second connection 41b there is an insulation 91 extending axially on either side of it. It should be noted that in another alternative, one connection may be more likely to be to rock rather than to a metal structure. In some cases, all devices of the power supply system may be located outside the casing - i.e. between the casing and the rock. This option would generally not be preferable in terms of risk/complexity of installation, but it is possible.

In addition, the present embodiment provides second and third collection modules 4' and 4 (which are part of respective downhole assemblies) 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 make such connections to the first connection point, and this would be preferred as it results in increased efficiency. Using a single top cable as shown is not advisable, but helps to simplify the image. In some cases, several collection modules may be provided, distributed in different annular spaces.

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 FIGS. 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 pressure and/or temperature conditions inside the production string 21 through a port 21a provided in 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 designed with the ability 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. This embodiment is multi-drop system, and cable 42 is used to carry power signals, control signals, parameter data and address information to enable power to be supplied to each of the sensors 5, 5', 5 and readings taken from them.

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 rather than a single cable as illustrated in the present embodiment. Moreover, as mentioned above, while the present embodiment provides multiple sensors extending from a single collection module, in other embodiments a single collection module may be used to provide 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 collection module 4' is a part of a downhole tool that contains both a collection module and a sensor. In the present embodiment, the sensor is configured to measure parameters in the annulus B through a port 22a provided in the first casing 22. Thus, for example, the sensor in the second collection module 4' may be configured to measure pressure and/or temperature in the annulus IN.

Moreover, in the present embodiment, the third collection module 4 is also a part of the downhole tool, which in this case contains a collection 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 via wireless means. For example, an inductive signal supply or an acoustic signal supply may be provided between the sensors 605 and the acquisition module 4. The sensors 605 may be physically located as close as possible to the acquisition module 4.

It should be clear that once the data reaches the upper communication unit 6, it can be transmitted externally to the required site using standard communication methods such as mobile communication methods, the Internet, etc., to the PM workstation for subsequent processing and /or studying. Of course, wire connections between the workstation and the upper communication unit 6 can also be provided.

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

- 28 043424

In another alternative, outside the outermost casing, for example, the third casing 24 in the embodiment shown in FIG. 6, insulation may be provided in the area near the wellhead 1. It can help deliver 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, having insulation on the outermost casing can help allow the uppermost connection 41a to be positioned lower while avoiding a significant reduction in system efficiency. Looking at the potential decay curve, due to the presence of insulation on the outermost casing 24, the negative potential may decrease in the isolated region near the wellhead very slowly, and then may begin to decrease more rapidly after reaching the uninsulated region.

Fig. 7 is a graph showing an example of how the optimal power available for collection in a downhole installation varies with well depth. As noted above, due to the increase in potential difference provided by the increase in the distance between the connections, on the one hand, and the cable resistance, on the other hand, there is a certain optimal depth for the lower connection 41b, or, in other words, an 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 approximately 5 meters below the wellhead, that is, in the area of the liner hanger. In this example, it can be seen that the optimal depth of the lower connection is around 550 m inside the well. However, it can also be noted that a significant portion of the optimal power can be obtained at depths of about 300 and 950 m. In general, it will be preferable to minimize the cable length, achieving optimal power collection, which involves minimizing the depth of the second connection. However, there may be circumstances in which the advantage of locating the collection module deeper within the well may be taken advantage of.

The optimal location for the top connection may depend on where the cathodic protection current (or other current) is injected and where said 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 injected current (or potential) is at its maximum value and selecting an area for the top connection based on this.

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

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

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

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

When optimization by simulation is mentioned in the description above, for example with respect to the spacing of connections, the use of insulation, selecting only the radial or axial spacing of connections, and selecting a given collection load, such a model may use at least one of the following parameters:

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

2. Top connection location.

3. Bottom connection location.

4. The cross-sectional area and type of material (resistivity) of the overhead cable used at the inputs to the collector.

5. Number, location, material (electric potential) and surface area of wellhead anodes.

6. Effective wellbore resistivity at seabed/wellhead level, also derived from casing sizes and tubular element sizes, weight, and type of material (resistivity) and overburden resistivity (medium surrounding the well), but this time for the entire well structure.

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 cable size preferred for operation. Generally, a larger cross-sectional area will be preferred. The ^140mm2 cable can be Kerite flat cable (RTM) LTF3. It represents the upper end of what is currently available on the market, but larger sizes can be used if available.

Fig. 8 is a flowchart depicting the optimization process of energy harvesting mode

- 29 043424 le collection disclosed above.

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

At step 802, it is determined whether 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 moves to step 803, at to which the microprocessor in the central unit 46 is supplied with power.

Then, at step 804, the microprocessor measures the power output from the energy harvester, and at step 805, the microprocessor modifies the settings of the DC-DC converter 44 to slightly increase the load. Next, at step 806, it is determined whether this results in increased yield from the collector. If the answer is yes, then the process returns back to step 805 so that the settings of the DC/DC converter 44 can be changed again to slightly increase the 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 reduce the load, and the process returns to the stage prior to step 806 to determine whether this is to increase output.

Thereafter, steps 805, 806, and 807 are repeated alternately during energy 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 DC-DC converter 44 uses a FET and an accompanying transformer, the step of changing the DC-DC converter settings in steps 805 and 807 may include changing the tap used on the secondary transformer to modify the load appropriately. This is also true when the variable transformer is equipped with an H-bridge, as shown in FIG. 2D.

Alternatively, in this case, the operating mode 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 similar to that described above.

At step 901, it is determined whether 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 sufficient power is available, the process proceeds to step 902, where it is determined whether the command has been received or whether the 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 the point comes at which the action is required.

When action is required, the process moves to step 903 where data from the sensor or storage device is retrieved as required and the load provided by the energy harvester between connections 41a is modulated to encode that data.

Separately, at the wellhead, at step 904, the wellhead voltage potential is monitored and the data is decoded in a second microprocessor. Then, at step 905, the extracted data may be exported or retransmitted to the client, 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 at the platform 1001 of the platform 1000. In this case, the metal structure includes a riser 1002 between the seabed level and the platform 1001. The production string 21 extends in the riser 1002 into the well. 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). This may be provided through the drilling support plate 1003 and/or through the wellhead, riser and other components such as riser guides. In such cases, it may be difficult to know where to make the top connection of a collection structure similar to the one shown in FIG. 1, 3, 4 or 6 for best performance. It will not always be known where the cathodic protection current will be introduced into the conductive pipe (sections of elongated elements) that extends into the well. As mentioned above, it may be preferable to provide the top connection in close proximity to the area where the cathodic protection current is introduced. When seeking optimization, one of the options would be to control this input 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 multiple overhead cable connections to the metal structure, with the most efficient being selected, for example, by control of a switch controlled by a central unit.

- 30 043424

Alternatives for signal, device and sensor.

Various specific signal solutions are described above. For the avoidance of doubt, it should be noted that a wide range of signal 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 may be transmitted in at least one of the following forms: electromagnetic, acoustic, through inductively coupled tubular elements and encoded pressure pulses, and references to the wireless nature of transmission refer to these forms, unless stated to the contrary.

Signals, unless otherwise stated, may include control signals and data signals. Control signals can control the operation of downhole devices, including sensors. Data from sensors can be transmitted in response to a control signal. Moreover, the reception of data and/or the transmission of parameters, for example, the reception and/or transmission of speed or permission, can be modified by corresponding control signals.

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

Encoded pressure pulses are pressure pulses for which a modulation scheme has been used to encode commands and/or data into changes in pressure and/or flow rate. In this case, a transducer is used in the well/wellbore to detect and/or generate said changes, and/or an electronic system is used in the well/wellbore to encode and/or decode commands and/or data. Thus, pressure pulses used in conjunction with the electronic downhole/wellbore interface are defined here as encoded pressure pulses. The advantage of encoded pressure pulses, similar to those defined here, is that they can be sent to electronic interfaces and can provide better transmission speed and/or range than pressure pulses sent to mechanical interfaces.

Where encoded pressure pulses are used to transmit control signals, a variety of modulation schemes can be used to encode the control signals, for example, pressure change or rate of change of pressure, amplitude shift keying (OOK), pulse phase 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. Transmission rates of coded pressure modulation schemes are typically low, typically less than 10 bps, and can be as low as 0.1 bps.

Encoded pressure pulses can be induced in static or flowing liquid media, and can 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 fluids produced by or introduced into the well.

Wireless signals may be able to pass through a barrier, such as a plug or annular sealing device, 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.

Electromagnetic/acoustic delivery and encoded pressure pulse delivery use the borehole, wellbore and formation as the transmission medium. The electromagnetic/acoustic or pressure signal can be sent from the borehole, or from the surface. When applied in a well, the electromagnetic/acoustic signal may be capable of passing through any annular seal device, although in some embodiments it may bypass, for example, around any annular seal device.

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

When using inductively coupled tubular elements, there are typically at least ten, usually many more, individual lengths of inductively coupled tubular elements that are connected together during use to form a column of inductively coupled tubular elements. They have a solid wire and can be in the form of tubular elements such as production pipe, drill pipe or casing. On each connection a neighbor

- 31 043424 of these 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 in the form of wireless signals sent over a distance of at least 200 m, optionally over 400 m or further, which is obviously an advantage over short range signals. Inductively coupled tubular elements have the advantage/effect of a combination of solid wire and inductive connections. The distance traveled can be much greater depending on the length of the well.

Data and commands in signals may be relayed or transmitted by other means. Thus, wireless signals can be converted into other types of wireless or wired signals, optionally relayed, by the same or other methods, for example, hydraulic, electrical and fiber optic lines. For example, the signals may be transmitted via cable over a first distance, such as over 400 m, and then transmitted via acoustic or electromagnetic communication 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 to transmit the signal. The distance traveled by signals depends on the depth of the borehole, 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 may be used in the same borehole to communicate from the borehole to the surface, and to communicate from the surface to the borehole.

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 annular containment device. The wireless signal can be sent from the surface or from a wireline/coiled tubing section (or lift) anywhere in the well, optionally above any annular containment device.

Acoustic signals and communications may include transmission through vibration of the well structure, including pipes, casing, liner, drill pipe, drill collars, casing, coiled tubing, sucker rod, downhole tools; transmission through a liquid medium (including transmission through gas), including transmission through a liquid medium in sections of a well without casing, inside pipes, inside annular spaces; 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 a structure and/or through a liquid medium is preferred.

Acoustic transmission may be low frequency (<20 Hz), may be within the audible range (20 Hz - 20 kHz), and may have ultrasonic frequencies (20 kHz - 2 MHz). It is preferable that the acoustic transmission be 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 techniques such as Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM), and preferably incorporating Spread Spectrum Techniques. They are typically adapted to automatically adjust signal transmission frequencies and methods to match downhole conditions.

Acoustic signals and communication can be unidirectional or bidirectional. Piezoelectric, inductive, or magnetostrictive transducers may be used to send and/or receive the signal.

Electromagnetic (sometimes called Quasi-Static (QS)) wireless communications typically reside in the following frequency ranges: (selected based on propagation characteristics) sub-ELF (extremely low frequency) <3 Hz (usually above 0.01 Hz);

VLF (ultra-low frequency) 3 Hz - 30 Hz;

super low frequency 30 Hz - 300 Hz;

ULF (ultra-low frequency) 300 Hz - 3 kHz; And,

VLF (very low frequency) 3 kHz - 30 kHz.

An exception to the above frequencies is electromagnetic communication using a pipe, in the form of a waveguide, in particular, but not limited to, when the pipe is filled with gas, frequencies from 30 kHz to 30 GHz can generally be used depending on the size of the pipe, the liquid medium in

- 32 043424 pipe, and communication range. The fluid in the pipe is preferably non-conductive. US Patent 5,831,549 discloses a remote sensing system incorporating gigahertz transmission in a gas-filled, tubular-shaped waveguide.

The sub-VLF and/or ELF bands are useful for downhole to surface communications (e.g. over 100 m). For more local communications, such as distances less than 10m, the VLF band is useful. The terminology used here for the indicated bands is defined by the International Telecommunication Union (ITU).

Electromagnetic communication may involve transmitting messages through one or more methods: 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 an area near the deposit or remote from the deposit; creating a current loop in 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 electric dipole transmitter; using a toroidal transformer to apply current to the metal structure of the well; using an insulating block; a loop antenna for creating a modulated magnetic field, varying in time, or through transmission through the rock; transmissions in the well casing; using an elongated element and the ground as a coaxial transmission line; using a tubular element as a waveguide; transmission from outside the well casing.

Particularly useful is applying a modulated current to an extended element and using ground to make the short circuit; creating a current loop in 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 electric dipole transmitter; and the use of a toroidal transformer to apply current to the metal structure of the well.

A wide variety of solutions can be used to effectively control and direct 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 the tubular elements for electrical connection to the tubular elements or insulation of the tubular elements; the use of a toroid of high magnetic permeability to create induction and, as a consequence, impedance; the use of insulated wire, cable, or insulated extended conductor as part of a transmission path or antenna; using a tubular element as a circular waveguide, using ultra-high frequency (3 GHz - 30 GHz) and ultra-high frequency (300 MHz - 3 GHz) ranges.

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

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

Sensors may contain one or more different types of sensors. One or each of the sensors may be coupled (physically or wirelessly) to a wireless transmitter, and data may be transmitted from the wireless transmitter to the space above the annular sealing device or, conversely, towards the surface. Data may be transmitted in at least one of electromagnetic form, acoustic form, and inductively coupled tubular elements, especially acoustic and/or electromagnetic form, as described above.

Such short-distance wireless connections can be provided by electromagnetic communications 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 inclination, load, various pipe/casing angles pipes, corrosion and erosion, radiation, noise, magnetism, seismic movements, stresses and deformations in pipes/casing, including torsion, shear, compression, expansion, bending and any form of deformation; detection of chemical and radioactive indicators; liquid medium identification, for example 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

- 33 043424 or fluorescence. Sensors may 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 capacitive devices. Sensors can also monitor downhole equipment, such as valve position or motor rotation. Moreover, sensors can be adapted to generate a signal or parameter detected by incorporating suitable transmitters and mechanisms.

The apparatus, in particular the sensors, may contain a storage device that can store data for later recovery. The storage device may also be removed in some circumstances, and data may be restored after the device is removed. The storage device may be configured to store information for at least one minute, optionally for at least one hour, optionally for at least one week, preferably for at least one month, more preferably for at least one month least for one year or more than five years.

Claims (25)

1. A downhole electrical power collection module, configured to be electrically connected between two spaced sections in a downhole installation and containing an electrical circuit configured to collect electrical energy from direct currents, when used, from the potential difference between said spaced sections, acting as an input voltage, wherein the electrical circuit comprises a DC-DC converter comprising self-starting means to enable the energy harvest to be started when the available input voltage is below 0.5 V. 2. The module of claim 1, comprising control means for changing the input impedance of the electrical loop to match the source impedance of the electrical loop to optimize power conversion efficiency. 3. The module according to claim 1 or 2, wherein the DC-DC converter includes a step-up transformer. 4. The module according to claim 3, in which the self-starting means comprises a field-effect transistor assembled together with a step-up transformer to form a resonant step-up oscillator. 5. The module as claimed in any one of the preceding claims, wherein the dc-dc converter comprises an H-bridge of transistors controlled by the control means to provide an input signal to the step-up transformer, wherein the self-starting means comprises an auxiliary power supply for the control means to enable launch. 6. The module according to any one of claims 3 to 5, wherein the collection module includes control means configured to control the turns ratio of the step-up transformer to change the load generated by the DC-DC converter. 7. The module of claim 6, wherein the secondary winding of the step-up transformer comprises a plurality of taps and/or the step-up transformer comprises a plurality of secondary windings, wherein the control means is configured to select the windings and/or taps to provide the required turns ratio. 8. A module as claimed in any one of the preceding claims, wherein the self-starting means comprises a battery to enable starting. 9. A module according to any of the previous paragraphs, comprising at least a pair of terminals from which a connection can be formed to two spaced sections. 10. The module of claim 9, wherein the collection module has more than two terminals, each of the terminals being configured to be capable of forming a connection to a corresponding portion, the collection module also comprising switching means for selectively electrically connecting two of said terminals to the electrical circuit. to allow a choice between which of the respective sections to connect the electrical circuit. 11. A module as claimed in any one of the preceding claims, comprising an energy storage device for storing the collected energy. 12. The module of claim 11, wherein the energy storage device comprises a charge storage device, which may include at least one capacitor and/or a rechargeable battery. 13. The module as claimed in any one of the preceding claims, wherein the collection module comprises variable impedance means for varying the load between said two connections. 14. The module according to claim 13, which provides control of the variable impedance means using a microprocessor. 15. The module of claim 13 or 14, wherein the harvesting module is configured to use variable impedance means to vary the load to optimize energy harvesting. - 34 043424 16. The module according to any one of claims 13 to 15, wherein the acquisition module is configured to use variable impedance means to modulate the load to transmit data from the acquisition module. 17. A module as claimed in any of the preceding claims, comprising a primary battery such that, when in use, it is capable of selectively drawing power collected by the circuit from the primary battery. 18. A downhole apparatus containing a collection module according to any of the previous paragraphs, and a downhole device for receiving power from the collection module. 19. The apparatus of claim 18, comprising charge storage means and power control means for controlling power supplied to the downhole device when sufficient power is available to supply power to said device. 20. The apparatus of claim 18 or 19, comprising impedance modulation means for changing the input impedance of the collection module to modulate the load to transmit data from at least one of the electrical power collection unit and the downhole device. 21. The apparatus of any one of claims 18 to 20, comprising modulation means for supplying a modulated voltage across said spaced data connections. 22. The apparatus according to any one of claims 18 to 21, comprising a primary battery such that, during use, it is possible to selectively take off the collected power from the primary battery. 23. The device according to any one of claims 18-22, in which the downhole device contains at least one of the following elements: downhole sensor; downhole actuator; an annular sealing device, such as a packer or packer element; valve; downhole communication module, such as a transceiver or repeater. 24. The apparatus according to claim 23, wherein said valve comprises at least one of the following elements: underground safety valve; wellbore flow control valve; valve wellbore - annulus; valve annulus - annulus; wellbore valve - pressure compensation chamber; valve annulus - pressure compensation chamber; valve through the packer or bypassing the packer. 25. Downhole installation having a metal structure that allows electric current to flow in it, containing: collection module according to any one of claims 1 to 17, electrically connected to a metal structure in the first section and to a second section spaced from the first section, wherein the first and second sections are selected so that, when used, there is a potential difference between them due to the flow of electrical power in the structure current; wherein the collection module is configured to collect electrical energy from said electrical current.