Downhole energy harvesting

Abstract

Downhole electrical energy collection and communication in systems of well facilities having metallic structures carrying current (e.g., CP current). In some cases, there is a collection module (4) electrically connected to the metal structure (2) at a first location and to a second location spaced apart from the first location, the first and second locations being selected such that, in use, the collection module (4) is electrically connected to the metal structure (2) due to a current flowing in the structure (2). A potential difference exists between the first position and the second position; and the collection module (4) is arranged to collect electrical energy from the current. In addition or alternatively, there is a communication device (4, 5, 6) that communicates by modulating the current (e.g., CP current) in the metal structure (2).

Description

[0001] This application is a divisional application of the application for patent filed on December 30, 2016, application number 201680092122.5, entitled "Downhole energy harvesting". TECHNICAL FIELD

[0002] The present invention relates to downhole energy harvesting. In particular cases, the invention relates to methods and systems for powering downhole equipment in a well installation having a metal structure provided with cathodic protection. The invention also relates to methods and systems incorporating the energy harvesting methods and systems and instruments used in such methods and systems. BACKGROUND

[0003] It is generally desirable to be able to extract data from oil and / or gas wells and from control equipment in oil and / or gas wells, such as valves, for example sub-surface safety valves.

[0004] However, powering such downhole equipment presents challenges. There are some cases where power can be provided directly from the surface via an electrical cable or where the equipment can be powered directly from the surface using hydraulic power. However, in other cases, these power delivery methods are not appropriate. In some cases, the use of batteries becomes an option. However, this in itself presents challenges, particularly in downhole environments where the relatively high temperatures tend to result in shortened battery life. SUMMARY

[0005] It is therefore desirable to provide an alternative source of power for downhole equipment that can be used in cases where it is difficult, impossible or undesirable to deliver power directly from the surface via an electrical cable or hydraulically, while avoiding the limitations that would be encountered in relying on battery power. It is also desirable to provide an alternative method for communicating between downhole locations and other downhole locations and / or surface locations.

[0006] In this specification, the expression "surface" includes the land surface where the wellhead in a land well would be located, the sea bed / mud line in a sub-sea well and the wellhead deck on a platform. Where appropriate, it also includes locations above these. In general, "surface" is used to refer to any convenient location, for example for applying and / or picking up power / signals, that is external to the borehole of the well.

[0007] According to a first aspect of the invention, there is provided a downhole electrical energy harvesting system for harvesting electrical energy in a well installation having a metal structure carrying an electrical current, the system comprising:

[0008] a collection module electrically connected to the metallic structure at a first location and electrically connected to a second location spaced apart from the first location, the first and second locations being selected so that, in use, there is a potential difference between the first and second locations due to current flowing in the structure; and the collection module being arranged to collect electrical energy from the current.

[0009] The well facility can be a well facility with cathodic protection, so that the current is a cathodic protection current. Although the present technology can be used in systems where current is specifically applied to the downhole structure for power delivery, it has been recognised that power can be collected from cathodic protection systems, and it is particularly preferred if power can be collected from already existing currents.

[0010] The second location will typically be a downhole location.

[0011] In some cases, the connection to the second location can be a connection via an electrode to the formation. However, most typically the collection module will be connected to the metallic structure at spaced apart first and second locations.

[0012] Such systems and methods are advantageous because power can be provided to downhole equipment without having to set up a separate power supply. Furthermore, power can be supplied without having to rely on local batteries which can tend to have a limited lifetime, and power can be supplied without having to set up cables which penetrate the wellhead. Similarly, these techniques can be implemented without using toroidal coils to inject or extract signals. This reduces the complexity and technical problems which can arise when implementing the system.

[0013] The collection module can be arranged to collect electrical energy from a dc current.

[0014] Preferably, the flow of current within the plurality of portions of the metallic structure in the region between the first and second locations is in the same longitudinal direction.

[0015] Preferably, there is an uninterrupted current flow path between the first and second locations, at least partially via the metallic structure.

[0016] These represented features will typically be present in the facility unless the set up is modified. The present idea does not typically require modification of the standard set up of the well facility as a whole, that is to say they are intended to work with standard facilities.

[0017] The collection module can be electrically connected to the metallic structure at the second location.

[0018] The or each connection to the metallic structure can be formed to a length of metallic elongate member / a length of metallic tubing.

[0019] In one set of embodiments, the spaced apart locations can be axially spaced apart. The connections can be formed to a common length of metal elongate member, for example a common length of metal tubing that is part of the metal structure. The uppermost of the two spaced apart locations can be proximate a location of a liner hanger disposed in the well. Typically, this will represent the highest practical location for the uppermost location. In some cases, the upper connection can be formed to a riser.

[0020] Thus, for example, both of the connections can be formed to production tubing disposed in the well, or both can be formed to a first length of casing that is separate from the production tubing by a first "A" annulus, or both can be formed to a second length of casing that is separate from the first length of casing by a second "B" annulus, or the like.

[0021] In other cases, the axially spaced apart connections can be formed to different lengths of metal elongate member, for example different lengths of metal tubing with similar results, but typically it is more convenient to form the connections to the same length of metal elongate member / metal tubing if there is no reason to change.

[0022] Where the spaced apart locations are axially spaced apart and there is a potential difference between them, the spacing between the locations can be quite large, typically 100 m or more. More preferably 300 m to 500 m.

[0023] The electrical connection to the metal structure at the first location can be a current connection.

[0024] The electrical connection to the metal structure at the second location can be a current connection.

[0025] The collection module can be positioned in one or more of: outside the well elongate member, in an annulus of the well, and in the bore of the well.

[0026] The connection to at least one of the first and second locations can be via a cable extending alongside the metal structure.

[0027] Preferably, if the second spaced apart contact is formed to at least one length of metal elongate member, the current flowing in the at least one length of metal elongate member at the location where the first contact is formed flows in the same longitudinal direction as the current flowing in the at least one length of metal elongate member at the location where the second contact is formed.

[0028] Preferably, if both the first and second spaced apart contacts are formed to the same length of metal elongate member, the length of metal elongate member is continuously electrically conductive between the first and second locations.

[0029] At least one of the electrical contacts can be provided by an insulated electrical cable.

[0030] The cable can be selected to have a conductor of relatively large cross sectional area. When selecting the cable, the aim is to pick a cross sectional area large enough to allow the desired level of collection, which provides a low enough electrical resistance in the cable.

[0031] 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.

[0032] The cable can be an oil pipe encapsulated conductor.

[0033] One of the connections can be formed without an external cable. One of the connections can be formed via a conductive housing of the collection module or a conductive housing surrounding the conductive module.

[0034] Typically, there will be an optimum spacing between the connections. The greater the spacing, the greater the change in potential between the contact locations, but also the greater the electrical resistance of the cable. The method can comprise determining the optimum spacing between the spaced apart locations. This can be determined by modelling for a particular installation.

[0035] The spacing between the locations can be at least 100 m.

[0036] In another set of embodiments, the spaced apart locations can be radially spaced apart. A first of the connections can be formed to a first section of metal elongate member, for example a first section of metal pipe that is part of the metal structure, and a second of the connections can be formed to a different second section of metal elongate member, for example a different second section of metal pipe that is part of the metal structure. Thus, the connections can span an annulus defined by the two sections of metal pipe.

[0037] For example, one connection can be formed to a production tubing string disposed in the well and one connection is formed to a first section of casing that is separate from the production tubing string by a first "A" annulus, or one connection can be formed to a first section of casing disposed in the well and one connection is formed to a second section of casing that is separate from the first section of casing by a second "B" annulus, and so on.

[0038] In some cases, the spaced apart locations can be both axially spaced apart and radially spaced apart.

[0039] The connections can be formed to a common section of metal elongate member that is part of the metal structure.

[0040] In some embodiments, a first one of the connections is formed to a first section of metal elongate member that is part of the metal structure, and a second one of the connections is formed to a second, different section of metal elongate member that is part of the metal structure.

[0041] Insulation means can be provided for electrically insulating the first section of metal elongate member from the second section of metal elongate member in the region of the connection.

[0042] Insulation means can be provided for electrically insulating the first section of elongate member / metal pipe from the second section of elongate member / metal pipe in the region of at least one of the connections. This can help to ensure that there is a potential difference between the sections of elongate member / metal pipe at the location where the connection is formed. This is due to the different paths to ground that exist from each section of member / pipe.

[0043] Note that in the present technology, current (from which energy is harvested) will generally flow in the same direction in the first and second sections of metal elongate member / pipe. Thus, rather than providing a separate return path, the insulation is provided to alter the path to ground for one of the sections relative to the other.

[0044] The insulation means can comprise an insulating layer or coating provided on at least one of the sections of elongate member / metal pipe. The insulation means can comprise at least one insulating centraliser for keeping the sections of elongate member / metal pipe apart from each other.

[0045] The insulation means can be provided to avoid electrical contact between the sections of elongate member / metal pipe over a distance of at least 100m, preferably at least 300m.

[0046] At least one of the connections can be positioned within an insulated region. Both of the connections can be positioned within an insulated region. At least one of the connections can be positioned towards a midpoint of an insulated region. The position of at least one of the connections can be determined by modelling a particular installation to determine an optimum position that is then selected.

[0047] The harvesting module can be provided in a bore of a central section of tubing, in an annulus, or outside a casing - between the casing and the formation. Thus, among other possible locations, the harvesting module can be provided in an "A" annulus, a "B" annulus, a "C" annulus, a "D" annulus, or any other annulus.

[0048] This creates the possibility of providing power in locations where it would normally not be possible and / or not be desirable to set up a cable from the surface. This is particularly useful for subsea wells. Furthermore, this is possible without relying on the use of primary batteries or another local power source, so there is the possibility of providing "well life" power in such locations.

[0049] The harvesting module can comprise a variable impedance device for varying the load present between the two connections. The variable impedance device can be microprocessor controlled.

[0050] The variable impedance device can be used to vary the load in order to optimise energy harvesting.

[0051] The variable impedance device can be used to modulate the load in order to communicate data from the harvesting module towards the surface.

[0052] Downhole communication means can be provided for transmitting data from downhole towards the surface. The downhole communication means can also be arranged for receiving data, for example from the surface.

[0053] The harvesting module can comprise downhole communication means. In other cases, the downhole communication means can be provided separately. Downhole equipment powered by the harvesting module can comprise the downhole communication means.

[0054] The downhole communication means can comprise the variable impedance device.

[0055] The upper communication means can be provided at a location outside the borehole, comprising a detector for detecting a change in current flowing in the metal structure (e.g. cathodic protection current), thus allowing data encoded by modulation of the load at the harvesting module to be extracted. For example, the detector can be arranged to detect the potential of the metal structure relative to a reference, or to detect the potential present across a power supply used to apply an impressed cathodic protection current to the metal structure, or to detect the current present through a power supply used to apply an impressed cathodic protection current to the metal structure.

[0056] In other embodiments, rather than communicating towards the surface by modulating the load, other communication techniques can be used. Typically, for example, acoustic signal transmission and / or EM (electromagnetic) signal transmission can be used. Modulating the load is one embodiment of EM signal transmission, but other more direct ways of EM signal transmission can be used.

[0057] The downhole communication means can be arranged to apply acoustic data carrying signals to the metal structure, and the upper communication means can be arranged to receive acoustic data carrying signals.

[0058] The downhole communication device can be arranged to apply EM (electromagnetic) data carrying signals to the metal structure, and the uphole communication device can be arranged to receive EM data carrying signals.

[0059] The uphole communication device can be arranged to apply acoustic data and / or EM (electromagnetic) data carrying signals to the metal structure, and the downhole communication device can be arranged to receive acoustic data and / or EM data carrying signals.

[0060] In some cases, the uphole communication device and the downhole communication device can be arranged to communicate using both acoustic signals and EM signals. This creates useful redundancy, since if one communication channel fails, the other communication channel can remain operational.

[0061] The collection module can be arranged at a selected downhole location for collecting power, and a cable can be provided for further supplying electrical power downhole to downhole equipment. The cross-sectional area of the cable for further supplying electrical power downhole will typically be smaller than the cross-sectional area of any cable used for collecting power, and typically, power will be further supplied downhole at a higher voltage than the voltage created across the spaced apart contacts due to current flowing in the metal structure (e.g. due to cathodic protection current).

[0062] In some embodiments, the current flowing in the elongate member is supplied from the surface of the well.

[0063] In some embodiments, the current flowing in the elongate member is supplied from one or more sacrificial anodes.

[0064] In some embodiments, the current flowing in the elongate member is an impressed current from an external power supply.

[0065] In some embodiments, the voltage at the surface of the well is limited in use to the range of -0.7 volts to -2 volts relative to a silver / silver chloride reference cell.

[0066] Preferably, the potential difference between the spaced apart contacts is less than 1 volt, preferably less than 0.5 volts, more preferably less than 0.1 volts.

[0067] Optionally, the electrical resistance of the well structure between the contacts is less than 0.1 ohms, preferably less than 0.01 ohms.

[0068] The optimal location for collecting power will typically be close to the location at which current (e.g. cathodic protection current) is injected into the metal structure.

[0069] In the case where the spaced apart locations are axially spaced apart, preferably the upper location is proximate to a location where current (e.g. cathodic protection current) is injected into the metal structure. Note that in the presence of a platform structure, current (e.g. cathodic protection current) can reach the downhole metal structure via a current connection with the platform structure. In some cases, the present technology can include controlling the location of the connection.

[0070] The optimal location for collecting power will often be close to the wellhead, where there is the largest rate of change of potential as one proceeds further down the well. On the other hand, the downhole equipment to be powered can be further down the well. Thus, the collection module and the downhole equipment can be at different locations in the well, in particular at different depths.

[0071] In other cases, the collection module and the downhole equipment can be positioned together. The system can include a downhole unit that includes the collection module and the downhole equipment.

[0072] The upper spaced apart contact can be:

[0073] In the case where the well is a land well, within 100m of the land surface, preferably within 50m of the land surface; and

[0074] In the case where the well is a subsea well, within 100m of the mudline, preferably within 50m of the mudline.

[0075] The upper spaced apart contact can be positioned proximate to a location corresponding to a maximum in the magnitude of potential caused by current flowing in the structure.

[0076] The system can further include a downhole communication device for transmitting and / or receiving data.

[0077] The downhole communication device can be arranged for transmitting data by varying a load existing between the connections at the spaced apart locations.

[0078] According to another aspect of the present invention, there is provided a downhole equipment operating system including a downhole electrical energy collection system as defined above and a downhole equipment, the collection module being electrically connected to the downhole equipment and arranged for providing power to the downhole equipment.

[0079] The downhole equipment can include a downhole sensor, for example a pressure sensor and / or a temperature sensor. The sensor can be installed in, for example, an "A" annulus, a "B" annulus, a "C" annulus or a "D" annulus.

[0080] A sensor arranged in an annulus or borehole can be arranged to monitor a parameter in an adjacent annulus or borehole, and / or to monitor a parameter in the annulus or borehole in which it is located. A port can be provided through a length of metal structure to allow sensing in an adjacent annulus or borehole.

[0081] The sensor can be arranged to detect a leak in an annulus being cemented.

[0082] The sensor can comprise an array of sensors.

[0083] The downhole apparatus can comprise at least one of:

[0084] A downhole sensor;

[0085] A downhole actuator;

[0086] An annular sealing apparatus, such as a packer or packer element;

[0087] A valve;

[0088] A downhole communication module, such as a transceiver or transponder.

[0089] The communication module can comprise a downhole communication transponder. This downhole communication transponder can be a transponder, for acoustic communication, or EM communication including wireless EM communication and cable-borne EM communication, or for a hybrid communication system. For example, the transponder can receive acoustic signals from further downhole and transmit signals towards the surface using EM communication, or vice versa. Similarly, both acoustic communication and EM communication can be used in one or both directions. EM signal transmission can be achieved by applying an electrical signal downhole or modulating the load in the collection module as described above. EM signal transmission can be at least partially along a cable, as mentioned above.

[0090] In the case that the downhole apparatus is a transponder or transceiver, the system can be pre-installed in a well installation to make the well "wireless-ready". That is, the system can be installed even if the communication capability can not initially be used, thereby providing a wireless communication backbone. Here again, wireless refers to the presence of at least one wireless leg in the communication channel, the other leg(s) can be via a cable.

[0091] In other cases, the system can be retro-fitted.

[0092] The valve can comprise at least one of:

[0093] A subsurface safety valve;

[0094] A borehole flow control valve;

[0095] A borehole-to-annulus valve;

[0096] annulus-to-annulus valve;

[0097] hole-to-pressure-compensated-chamber valve;

[0098] annulus-to-pressure-compensated-chamber valve;

[0099] through-the-packer or packer bypass valve.

[0100] Note that each device can be a remotely controlled device, which can be a wireless controlled device, for example in the sense that there is at least one wireless branch in the communication channel in the case of control from the surface. Other branches can be via a cable, for example between the sensor location and the collection location.

[0101] The EM signal transmission can use a dc signal or an ac signal and an appropriate modulation scheme. The collection module can comprise a dc-dc converter for collecting power from the cathodic protection current or other existing current. The collection module can comprise an energy storage device for storing the collected power. The energy storage device can comprise a charge storage device, which can comprise at least one capacitor and / or at least one rechargeable battery. In the presence of an energy storage device, the collection module can be arranged to selectively supply power from the storage device or directly from the collected energy. This selection can be made based on predetermined conditions. Alternatively, there can be no energy storage device, and the collection module can be arranged to supply power continuously when required.

[0102] A primary battery can also be provided at the collection module for selective use.

[0103] The dc-dc converter can comprise one field effect transistor arranged to form a resonant boost oscillator. The dc-dc converter can comprise a boost transformer, and can comprise a coupling capacitor.

[0104] The collection module can be arranged to control the turns ratio of the boost transformer to modify the load generated by the dc-dc converter. The secondary winding of the boost transformer can comprise a plurality of taps and / or the boost transformer can comprise a plurality of secondary windings, and the collection module can be arranged to select the winding and / or the taps to provide a desired turns ratio. Microprocessor controlled switches can be used to select the taps and / or windings.

[0105] According to another aspect, there is provided a downhole unit comprising one collection module as defined above and at least one device arranged to be powered by the collection module.

[0106] One or more of the sensor module, the communication module and the collection module can be provided in the annulus, e.g. the "B" annulus or the "C" annulus or another annulus. The sensor module and the collection module can be provided as part of a common downhole unit, however more typically they will be separate, such that the sensor can be located deeper than the collection module.

[0107] The downhole equipment can be provided at a different location in the well than the collection module.

[0108] The collection module can be arranged at a selected downhole location for collecting power, and a cable can be provided for further supplying electrical power downhole to downhole equipment at different locations in the well.

[0109] The cross-sectional area of one or more electrically conductive cores of the cable for further supplying electrical power downhole can be smaller than the cross-sectional area of one or more electrically conductive cores of the cable for connecting the collection module to the downhole structure for collecting power.

[0110] According to another aspect of the application, there is provided a downhole well monitoring system for monitoring at least one parameter in a well installation having a current-carrying metal structure, the system comprising:

[0111] a power collection system as defined above;

[0112] a sensor module for sensing at least one parameter; and

[0113] a communication module for transmitting data encoding readings from the sensor module towards the surface,

[0114] the power collection system being arranged to supply electrical power to at least one of the sensor module and the communication module.

[0115] According to another aspect of the application, there is provided a downhole well monitoring system for monitoring at least one parameter in a well installation having a current-carrying metal structure, the system comprising:

[0116] a sensor module for sensing at least one parameter;

[0117] a communication module for transmitting data encoding readings from the sensor module towards the surface; and

[0118] An electrical energy harvesting system, the electrical energy harvesting system comprising a harvesting module electrically connected to the metallic structure at a first location and electrically connected to a second location spaced apart from the first location, the first and second locations being selected so that, in use, there is a potential difference between the first and second locations due to an electrical current flowing in the structure; and the harvesting module being arranged to harvest electrical energy from the current, the electrical energy harvesting system being arranged to supply electrical power to at least one of the sensor module and the communication module.

[0119] The system can comprise at least one first length of electrical cable for connecting the harvesting module to one of the spaced apart locations.

[0120] The system can comprise at least one second length of electrical cable for supplying power from the harvesting module to the sensor module.

[0121] A cross-sectional area of a conductive portion of the first length of electrical cable can be greater than a cross-sectional area of a conductive portion of the second length of electrical cable.

[0122] The communication module can be arranged for modulating the current flowing in the metallic structure at a signal transmission location in order to encode data, allowing the data at a receiving location remote from the signal transmission location to be extracted by detecting an effect of said modulation on the current at said receiving location.

[0123] The well monitoring system can comprise a detector for detecting the effect of said modulation on the current at said receiving location, thereby extracting the encoded data.

[0124] The communication module can be arranged for controlling a load generated by the harvesting module to produce said modulation of the current in the metallic structure at the signal transmission location.

[0125] The sensor module can comprise a pressure sensor.

[0126] The pressure sensor can be arranged for monitoring a reservoir pressure of the well.

[0127] The pressure sensor can be arranged for monitoring a pressure in an annulus of the well.

[0128] The pressure sensor can be arranged for monitoring a pressure in a closed annulus of the well.

[0129] According to another aspect of the application, there is provided a downhole communication repeater system for use in a well installation having a metallic structure carrying an electrical current, the system comprising:

[0130] an electrical energy harvesting system as defined above; and

[0131] A communication repeater arranged in and down a well and arranged to communicate with a first device beyond a wellhead using a wireless communication channel at least through the wellhead and arranged to communicate with a second device positioned in the well so as to be below the wellhead such that the communication repeater can act as a repeater between the first device and the second device, the electrical energy harvesting system arranged to supply electrical power to the communication repeater.

[0132] According to another aspect of the present invention there is provided a downhole communication repeater system for use in a well installation having a metal structure carrying an electrical current, the system comprising:

[0133] A communication repeater arranged in and down a well and arranged to communicate with a first device beyond a wellhead using a wireless communication channel at least through the wellhead and arranged to communicate with a second device positioned in the well so as to be below the wellhead such that the communication repeater can act as a repeater between the first device and the second device; and

[0134] An electrical energy harvesting system comprising a harvesting module electrically connected to the metal structure at a first location and electrically connected to a second location spaced apart from the first location, the first and second locations being selected such that, in use, there is a potential difference between the first and second locations due to the electrical current flowing in the structure; and the harvesting module being arranged to harvest electrical energy from the electrical current, the electrical energy harvesting system arranged to supply electrical power to the communication repeater.

[0135] It should be understood that reference herein to a first device beyond a wellhead refers to a device on the other side of the wellhead from the second device in the well such that communication across the wellhead is desired. Ultimately, the first device can be positioned in almost any location, which can be close to the wellhead or at a remote location, as long as appropriate communication is provided.

[0136] The communication repeater can be arranged to modulate the electrical current flowing in the metal structure at a signal transmission location in order to encode data, allowing the data at a receiving location remote from the signal transmission location to be extracted by detecting the effect on the current at said receiving location of said modulation.

[0137] The communication repeater and / or the harvesting module can be provided in an annulus, for example a "B" annulus or a "C" annulus or another annulus.

[0138] The communication repeater and the harvesting module can be provided as part of a common downhole unit.

[0139] The system can comprise at least one first length of electrical cable for connecting the collection module to one of the spaced apart locations.

[0140] The system can comprise at least one second length of electrical cable for supplying power from the collection module to the communication transponder.

[0141] The cross-sectional area of the electrically conductive portion of the first length of cable can be greater than the cross-sectional area of the electrically conductive portion of the second length of cable.

[0142] The downhole communication transponder system can comprise a detector for detecting the effect of said modulation on the current at said receiving location to extract the encoded data.

[0143] The communication transponder can be arranged to control a load generated by the collection module to cause said modulation of the current in the metal structure at the signal transmission location.

[0144] According to another aspect of the application, there is provided a downhole equipment operating system for operating downhole equipment in a well installation having a metal structure carrying an electric current, the system comprising:

[0145] a downhole equipment;

[0146] an electrical energy collection system comprising a collection module electrically connected to the metal structure at a first location and electrically connected to a second location spaced apart from the first location, the first and second locations being selected so that, in use, there is a potential difference between the first and second locations due to the current flowing in the structure; and the collection module being arranged to collect electrical energy from the current, the electrical energy collection system being arranged to supply electrical power to the downhole equipment.

[0147] The downhole equipment can comprise at least one of:

[0148] a downhole sensor;

[0149] a downhole actuator;

[0150] an annular sealing device, such as a packer or a packer element;

[0151] a valve;

[0152] a downhole communication module, such as a transceiver or a transponder.

[0153] The valve can comprise at least one of:

[0154] a subsurface safety valve;

[0155] a bore flow control valve;

[0156] orifice to annular valve;

[0157] Annular space to annular space valve;

[0158] Orifice to pressure compensation chamber valve;

[0159] Annular space to pressure compensation chamber valve;

[0160] Through packer or packer bypass valve.

[0161] Power can be supplied to control the valve, wherein the power for moving the valve comes from another source (e.g., spring loading, differential pressure), or is supplied for moving the valve or for controlling and moving the valve. The valve may include a triggering mechanism, such as a pilot valve that uses power from a power delivery system to operate it.

[0162] The operating system of this device can be configured to supply variable power levels. Therefore, a first power level can be provided, except when a second, higher power level is required. When a higher power level is required, the applied current can be increased by connecting more anodes or applying a higher applied current, such as a cathodic protection current. This may be at a level that is undesirable in the long term but acceptable in the short term due to the potential damaging effects of excessively high potential differences caused by the cathodic protection current—hydrogen embrittlement. Therefore, the system, apparatus, and method can be arranged to temporarily increase the applied current, such as 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 level is used at other times, such as for monitoring and / or control signals.

[0163] The downhole equipment can be installed at a different location in the well than the collection module.

[0164] The collection module can be positioned at a selected location downhole for collecting power, and a cable is configured to further supply power downhole to the downhole equipment at different locations within the well.

[0165] The cross-sectional area of ​​one or more conductive cores of the cable used to further supply electrical power to the downhole may be smaller than the cross-sectional area of ​​one or more conductive cores of the cable used to connect the collection module to the downhole structure for power collection.

[0166] In addition to the electrical power supplied by the power harvesting module, another power source can be available from the downhole equipment.

[0167] In each of the devices described above, the collection module may include a variable impedance device for varying the load between the two connections. This variable impedance device may be microprocessor controlled.

[0168] This variable impedance device can be used to change the load in order to optimize energy harvesting.

[0169] The variable impedance device can be used to modulate the load so that data can be transmitted from the collection module toward the ground.

[0170] Impedance modulation can also be used in communication from the upper position toward the collection module to modulate the applied (e.g., cathodic protection) current. One possibility is to operate the anode connection and disconnect the slave operation, which modulates the potential present downhole. Therefore, data can be encoded by operating the anode connection and disconnecting the slave operation. For example, the connection between the anode and the structure can be selectively formed and disconnected by a switching device. Therefore, the upper communication unit can include a switching device for disconnecting the anode connection and slave operation. In an impressed current system, the applied signal can be modulated to encode data.

[0171] According to another aspect of the present invention, a method for supplying power to downhole equipment in a well facility having a current-carrying metal structure is provided, the method comprising the following steps:

[0172] A collection unit is electrically connected to the metal structure at a first position and electrically connected to a second position spaced apart from the first position. The first and second positions are selected such that a potential difference exists between the first and second positions due to the current flowing in the structure, and the collection unit is arranged to collect electrical energy from the current when connected between the positions having the potential difference.

[0173] Electric power is collected from the current at the collection unit; and

[0174] The collection unit supplies electrical power to the downhole equipment.

[0175] The method may include the following steps: determining the location where a maximum value of the potential caused by the current flowing in the structure exists; and selecting, based on the location of the maximum value, the first location to which the collection unit is connected to the metal structure.

[0176] According to another aspect of the invention, a downhole power harvesting system is provided for use in a well facility having a metal structure including at least one elongated metal member carrying current. The harvesting system includes: an energy harvesting module comprising a circuit connected between spaced-apart contacts to harvest energy from a potential difference between the spaced-apart contacts, wherein a first contact of the spaced-apart contacts is formed at a first location to the at least one elongated metal member, and a second contact of the spaced-apart contacts is formed at a second location to the at least one elongated metal member, and the potential difference is caused by a current flowing in the at least one elongated metal member and at least partially by the impedance of the at least one elongated metal member.

[0177] The current flowing in the at least one elongated metal member at the location where the first contact portion is formed can flow in the same longitudinal direction as the current flowing in the at least one elongated metal member at the location where the second contact portion is formed.

[0178] Preferably, if both the first spaced-apart contact portion and the second spaced-apart contact portion are formed on the same segment of elongated metal member, then the segment of elongated metal member is continuously conductive between the first and second positions.

[0179] Preferably, the metal structure provides an uninterrupted current flow path between the first position and the second position.

[0180] Preferably, the current flow within the multiple portions of the metal structure in the region between the first and second positions is in the same longitudinal direction.

[0181] Preferably, the collection module is arranged to collect electrical energy from DC current.

[0182] The electrical connection to the metal structure at this first position can be a current connection.

[0183] The electrical connection to the metal structure at this second location can be a current connection.

[0184] The electrical connection to the metal structure at the first location can be formed to one of the following: casing, tailpipe, tubing, coiled tubing, or sucker rod.

[0185] The electrical connection to the metal structure at the second location can be formed to one of the following: casing, tailpipe, tubing, coiled tubing, or sucker rod.

[0186] The spaced-out positions can be spaced out axially.

[0187] The spaces between the points can be spaced radially apart.

[0188] At least one of the electrical contacts and at least one connection between the circuit can be provided by an insulated cable.

[0189] Preferably, the insulated cable has a conductive area of ​​at least 10 mm², more preferably at least 20 mm², and more preferably at least 80 mm².

[0190] The cable can be a tubing-encapsulated conductor.

[0191] The interval between the locations can be at least 100m.

[0192] The connection can be formed into a common elongated metal member that is part of the metal structure.

[0193] In some embodiments, the first connecting portion of the connection is formed to a first elongated metal member that is part of the metal structure, and the second connecting portion of the connection is formed to a different second elongated metal member that is part of the metal structure.

[0194] The insulating device can be configured to electrically insulate the first elongated metal member from the second elongated metal member in the region of the connection.

[0195] The insulation device may include an insulating layer or coating disposed on at least one of the elongated metal segments.

[0196] The insulation device may include at least one insulating straightener for keeping the elongated metal segments separated from each other.

[0197] The insulation device can be configured to prevent electrical contact between two slender metal components over a distance of at least 100m.

[0198] The current flowing in the elongated member can be supplied from the surface of the well.

[0199] Current flowing in the elongated member can be supplied from one or more sacrificial anodes.

[0200] The current flowing in the elongated member can be an applied current from an external power supply.

[0201] Compared to the silver / silver chloride reference cell, the voltage at the well surface can be limited to a range of -0.7 volts to -2 volts during use.

[0202] The potential difference between the spaced-apart contacts can be less than 1 volt, preferably less than 0.5 volts, and more preferably less than 0.1 volts.

[0203] The resistance between the contact portions of the well structure can be less than 0.1 ohms, preferably less than 0.01 ohms.

[0204] The spaced-out contact portions at the top can be:

[0205] When the well is a land-based well, it should be within 100m of the land surface, preferably within 50m of the land surface; and

[0206] In the case of a subsea well, the well should be within 100m of the mudline, preferably within 50m of the mudline.

[0207] The spaced-out contact portions at the top can be positioned near the location corresponding to the maximum value of the potential caused by the current flowing in the structure.

[0208] The system may include downhole communication devices for transmitting and / or receiving data.

[0209] The downhole communication device can be arranged to transmit data by causing load changes detected between the connections at the spaced-out locations.

[0210] According to another aspect of the invention, a downhole device operating system is provided, which includes a downhole power harvesting system as defined above and a downhole device, wherein the harvesting module is electrically connected to the downhole device and is arranged to provide power to the downhole device.

[0211] The downhole equipment may include at least one of the following:

[0212] Downhole sensors;

[0213] Downhole actuators;

[0214] Annular sealing devices, such as packers or packer elements;

[0215] valve;

[0216] Downhole communication modules, such as transceivers or repeaters.

[0217] The valve may include at least one of the following:

[0218] Underground safety valve;

[0219] Orifice flow control valve;

[0220] orifice to annular valve;

[0221] Annular space to annular space valve;

[0222] Orifice to pressure compensation chamber valve;

[0223] Annular space to pressure compensation chamber valve;

[0224] Through packer or packer bypass valve.

[0225] The downhole equipment can be installed at a different location in the well than the collection module.

[0226] The collection module can be positioned at a selected location downhole for collecting power, and a cable can be configured to further supply power downhole to the downhole equipment at different locations in the well.

[0227] The cross-sectional area of ​​one or more conductive cores of the cable used to further supply electrical power to the downhole may be smaller than the cross-sectional area of ​​one or more conductive cores of the cable used to connect the collection module to the downhole structure for collecting electrical power.

[0228] According to another aspect of the present invention, a method for supplying power to downhole equipment in a well facility having a current-carrying metal structure is provided, the method comprising the following steps:

[0229] A collection unit is electrically connected to the metal structure at a first position and at a second position spaced apart from the first position. The first and second positions are selected such that a potential difference exists between the first and second positions due to the current flowing in the structure, and the collection unit is arranged to collect electrical energy from the current when connected between the positions with the potential difference.

[0230] Electric power is collected from the current at the collection unit; and

[0231] The collection unit supplies electrical power to the downhole equipment.

[0232] The method may include the following steps: determining the location where a maximum value of the potential caused by the current flowing in the structure exists; and selecting, based on the location of the maximum value, the first location to which the collection unit is connected to the metal structure.

[0233] According to another aspect of the present invention, a downhole power harvesting system is provided, which harvests electrical energy in a well facility having a metal structure provided with cathodic protection, the system comprising:

[0234] A collection module is electrically connected at a first position to the metal structure and electrically connected to a second position spaced apart from the first position. The first and second positions are selected such that, during use, a potential difference exists between the first and second positions due to the cathodic protection current flowing within the structure.

[0235] The collection module is arranged to collect electrical energy from the cathodic protection current.

[0236] The collection module can be arranged to collect electrical energy from DC current.

[0237] The current flow within multiple sections of the metal structure in the region between the first and second positions can be in the same longitudinal direction.

[0238] An uninterrupted current flow path may exist between the first position and the second position, and the uninterrupted current flow path passes at least partially through the metal structure.

[0239] The collection module can be electrically connected to the metal structure at the second location.

[0240] The spaced-out positions can be spaced out axially.

[0241] The spaces between the points can be spaced radially apart.

[0242] At least one of the electrical contacts and at least one connection between the collection module can be provided by an insulated cable.

[0243] The insulated cable has a conductive area of ​​at least 10 mm², preferably at least 20 mm², and more preferably at least 80 mm².

[0244] The cable can be a tubing-encapsulated conductor.

[0245] The interval between the locations can be at least 100m.

[0246] The connection can be formed into a common elongated metal member that is part of the metal structure.

[0247] The first connecting portion of the connecting portion can be formed to a first elongated metal member that is part of the metal structure, and the second connecting portion of the connecting portion can be formed to a different second elongated metal member that is part of the metal structure.

[0248] The insulating device can be configured to electrically insulate the first elongated metal member from the second elongated metal member in the region of the connection.

[0249] The insulation device may include an insulating layer or coating disposed on at least one of the elongated metal segments.

[0250] The insulation device may include at least one insulating straightener for keeping the elongated metal segments separated from each other.

[0251] The insulation device can be configured to prevent electrical contact between two slender metal components over a distance of at least 100m.

[0252] The current flowing in the elongated member can be supplied from the surface of the well.

[0253] Current flowing in the elongated member can be supplied from one or more sacrificial anodes.

[0254] The current flowing in the elongated member can be an applied current from an external power supply.

[0255] Compared to the silver / silver chloride reference cell, the voltage at the well surface can be limited to a range of -0.7 volts to -2 volts during use.

[0256] The potential difference between the spaced-apart contacts can be less than 1 volt, preferably less than 0.5 volts, and more preferably less than 0.1 volts.

[0257] The resistance between the contact portions of the well structure can be less than 0.1 ohms, preferably less than 0.01 ohms.

[0258] The spaced-out contact portions at the top can be:

[0259] When the well is a land-based well, it should be within 100m of the land surface, preferably within 50m of the land surface; and

[0260] In the case of a subsea well, the well should be within 100m of the mudline, preferably within 50m of the mudline.

[0261] The spaced-out contact portions at the top can be positioned near the location corresponding to the maximum value of the potential caused by the current flowing in the structure.

[0262] The system may also include downhole communication devices for transmitting and / or receiving data.

[0263] The downhole communication device can be arranged to transmit data by causing changes in the load present between the connections at the spaced-out locations.

[0264] According to another aspect of the invention, a downhole device operating system is provided, which includes a downhole power harvesting system as defined above and a downhole device, wherein the harvesting module is electrically connected to the downhole device and is arranged to provide power to the downhole device.

[0265] The downhole equipment may include at least one of the following:

[0266] Downhole sensors;

[0267] Downhole actuators;

[0268] Annular sealing devices, such as packers or packer elements;

[0269] valve;

[0270] Downhole communication modules, such as transceivers or repeaters.

[0271] The valve may include at least one of the following:

[0272] Underground safety valve;

[0273] Orifice flow control valve;

[0274] orifice to annular valve;

[0275] Annular space to annular space valve;

[0276] Orifice to pressure compensation chamber valve;

[0277] Annular space to pressure compensation chamber valve;

[0278] Through packer or packer bypass valve.

[0279] The downhole equipment can be installed at a different location in the well than the collection module.

[0280] The collection module can be positioned at a selected location downhole for collecting power, and a cable can be configured to further supply power downhole to the downhole equipment at different locations in the well.

[0281] The cross-sectional area of ​​one or more conductive cores of the cable used to further supply electrical power to the downhole may be smaller than the cross-sectional area of ​​one or more conductive cores of the cable used to connect the collection module to the downhole structure for collecting electrical power.

[0282] According to another aspect of the invention, a downhole data communication device is provided for use in a well facility having a metal structure equipped with a cathodic protection system, such that a circuit including the metal structure and a ground return are provided, and current flows around the ground return due to the cathodic protection system. The downhole data communication device includes:

[0283] A first communication module, positioned at a first location, includes a modulation device for modulating a current at the first location to encode data; and

[0284] The second communication module is configured to be positioned at a second location spaced apart from the first location, and includes a detector for detecting the effect of modulating the current at the first location in order to extract the data.

[0285] The modulation device can be arranged in at least one of the following ways:

[0286] i) In the case that the cathodic protection system is an external cathodic protection system, control the signal source of the external cathodic protection system to directly modulate the cathodic protection current applied to the metal structure;

[0287] ii) Modify the connection between at least one anode of the cathodic protection system and the metal structure; and

[0288] iii) Change the impedance of the circuit.

[0289] The first communication module can be deployed for positioning downhole.

[0290] The second communication module can be deployed for positioning downhole.

[0291] The device may include a sensor module for sensing at least one parameter, wherein the first communication module is arranged to transmit data encoding readings from the sensor module toward the second communication module.

[0292] The sensor module may include a pressure sensor.

[0293] The second communication module can be configured to provide data to downhole equipment based on data received from the first communication module via the second communication module.

[0294] The downhole equipment may include at least one of the following:

[0295] Downhole sensors;

[0296] Downhole actuators;

[0297] Annular sealing devices, such as packers or packer elements;

[0298] valve;

[0299] Downhole communication modules, such as transceivers or repeaters.

[0300] The valve may include at least one of the following:

[0301] Underground safety valve;

[0302] Orifice flow control valve;

[0303] orifice to annular valve;

[0304] Annular space to annular space valve;

[0305] Orifice to pressure compensation chamber valve;

[0306] Annular space to pressure compensation chamber valve;

[0307] Through packer or packer bypass valve.

[0308] At least one of the first and second communication modules may include a communication repeater positioned in the well below the wellhead and arranged to communicate with a first device extending beyond the wellhead using a wireless communication channel that passes at least through the wellhead, and to communicate with a second device positioned in the well and thus below the wellhead, such that the communication repeater can act as a repeater between the first and second devices.

[0309] The device may include a downhole power harvesting module arranged for electrical connection between two spaced-apart locations in a well facility, and includes a circuit arranged for harvesting electrical energy from a potential difference between the spaced-apart locations during use, the potential difference serving as an input voltage, and the harvesting module arranged for powering at least one component of the communication device.

[0310] The first communication module can be arranged to control the load generated by the collection module to produce the modulation of the current in the metal structure at the signal transmission location.

[0311] The collection module can be arranged to collect electrical energy from DC current.

[0312] According to another aspect of the invention, a downhole data communication system is provided, which includes a downhole data communication device as defined above, the downhole data communication device being positioned in a well facility having a metal structure provided with cathodic protection.

[0313] According to another aspect of the invention, a downhole data communication system for use in a well facility having a metal structure provided with a cathodic protection system, such that a circuit including the metal structure and a ground return are provided, and current flows around the ground return due to the cathodic protection system, the system including a downhole data communication device comprising:

[0314] A first communication module, positioned at a first location, includes a modulation device for modulating a current at the first location to encode data; and

[0315] A second communication module is positioned at a second location spaced apart from the first location and includes a detector for detecting the effect of modulating the current at the first location in order to extract the data.

[0316] The device may include a downhole power harvesting module electrically connected between two spaced-apart locations in the well facility and includes a circuit arranged to harvest electrical energy from a potential difference between the spaced-apart locations during use, the potential difference serving as an input voltage, and the harvesting module being arranged to power at least one component of the communication device.

[0317] The current flow within multiple sections of the metal structure in the region between spaced-out locations used for collection can be in the same longitudinal direction.

[0318] An uninterrupted current flow path can exist between the spaced-out locations used for collection, and this uninterrupted current flow path passes at least partially through the metal structure.

[0319] At least one of the first communication module and the second communication module can be positioned in the closed annulus of the well.

[0320] The system or apparatus may include a pressure sensor arranged to monitor reservoir pressure in the well.

[0321] The system or apparatus may include a pressure sensor arranged to monitor the pressure in the annulus of the well.

[0322] The system or apparatus may include a pressure sensor arranged to monitor the pressure in the closed annulus of the well.

[0323] According to another aspect of the invention, a downhole power harvesting module is provided, which is arranged for electrical connection between two spaced-apart locations in a well facility, and includes a circuit arranged for harvesting electrical energy from a potential difference between the spaced-apart locations during use, the potential difference serving as an input voltage.

[0324] The collection module can be arranged to collect electrical energy from DC current.

[0325] The collection module may include a control device for modifying the input impedance of the circuit to match the source impedance of the circuit, thereby optimizing the power conversion efficiency.

[0326] This circuit may include a DC-DC converter.

[0327] The DC-DC converter can be arranged to operate with an input voltage above a minimum threshold, wherein the minimum threshold is no greater than 0.5 volts, preferably no greater than 0.25 volts, and more preferably no greater than 0.05 volts.

[0328] The DC-DC converter may include a self-starting device to allow energy harvesting to be initiated when the available input voltage is below the semiconductor bandgap voltage of the components in the DC-DC converter.

[0329] The DC-DC converter may include a self-starting device to allow energy harvesting to begin when the available input voltage is below 0.5 volts.

[0330] The DC-DC converter may include a step-up transformer.

[0331] The self-starting device may include a field-effect transistor arranged together with the boost transformer to form a resonant boost oscillator.

[0332] The DC-DC converter may include an H-bridge of transistors arranged to provide input to the step-up transformer under the control of a control device, and the self-starting device may include an auxiliary power source for the control device to allow startup.

[0333] The collection module may include a control device arranged to control the turns ratio of the step-up transformer to modify the load generated by the DC-DC converter.

[0334] The secondary winding of the step-up transformer may include multiple taps and / or the step-up transformer may include multiple secondary windings, and the control device may be arranged to select windings and / or taps to provide a desired turns ratio. The collection module may include at least one pair of terminals, from which connections may be formed to two spaced-apart locations.

[0335] The collection module may have more than two terminals, each of which is used to allow connection to a corresponding location, and the collection module may also include a switching device for selectively electrically connecting two of the terminals to both ends of the circuit, thereby allowing selection of which locations the circuit is connected to in the corresponding locations.

[0336] This allows for a setup that can form multiple contacts with the metal structure both during and after installation, with a choice made regarding which contacts should be used. Thus, for example, the setup could include a lower connector and two upper connectors located at different positions. Once installed, it can be determined that if the first upper connector is used, a larger amount of power can be collected, and therefore this first connector can be used. In another scenario, a second upper connector might be preferable.

[0337] The switch can also be used dynamically during operation to switch between connections.

[0338] In another case, there may be two lower connecting parts and / or two upper connecting parts instead, or there may be other numbers of upper connecting parts and / or lower connecting parts.

[0339] The collection module may include an energy storage device for storing the collected power. 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 a variable impedance device for varying the load present between the two connections.

[0340] This variable impedance device can be microprocessor controlled.

[0341] The collection module can be configured to use the variable impedance device to vary the load in order to optimize energy collection.

[0342] The collection module can be arranged to use the variable impedance device to modulate the load so that data can be transmitted away from the collection module.

[0343] The collection module may include a primary battery, enabling power to be selectively drawn from the primary battery and from the power collected through the circuit during use.

[0344] According to another aspect of the invention, a downhole device is provided, comprising a collection module as defined above and a downhole device that receives power from the collection module.

[0345] The downhole device may include a charge storage device and a power control device to control the power supplied to the downhole device when sufficient energy is available to power the device.

[0346] The downhole device may include an impedance modulation device for varying the input impedance of the collection module to modulate the load, thereby transmitting data from at least one of the power collection unit and the downhole device.

[0347] The downhole instrument may include a modulation device for applying a modulated voltage via the spaced-out connection to transmit data.

[0348] The downhole device may include a primary battery, allowing power to be selectively drawn from the collected power and the primary battery during use.

[0349] The downhole equipment of the downhole instrument may include at least one of the following:

[0350] Downhole sensors;

[0351] Downhole actuators;

[0352] Annular sealing devices, such as packers or packer elements;

[0353] valve;

[0354] Downhole communication modules, such as transceivers or repeaters.

[0355] The valve may include at least one of the following:

[0356] Underground safety valve;

[0357] Orifice flow control valve;

[0358] orifice to annular valve;

[0359] Annular space to annular space valve;

[0360] Orifice to pressure compensation chamber valve;

[0361] Annular space to pressure compensation chamber valve;

[0362] Through packer or packer bypass valve.

[0363] According to another aspect of the present invention, a downhole power harvesting system is provided for harvesting electrical energy in a well facility having a current-carrying metallic structure, the system comprising:

[0364] A collection module as defined above, electrically connected at a first position to the metal structure and electrically connected to a second position spaced apart from the first position, wherein the first and second positions are selected such that, during use, a potential difference exists between the first and second positions due to the current flowing in the structure; and

[0365] The collection module is arranged to collect electrical energy from the current.

[0366] According to another aspect of the present invention, a downhole power delivery system is provided for supplying power to downhole equipment in a well facility having a current-carrying metallic structure, the system comprising:

[0367] A collection module as defined above, electrically connected at a first position to the metal structure and electrically connected to a second position spaced apart from the first position, wherein the first and second positions are selected such that, during use, a potential difference exists between the first and second positions due to the current flowing in the structure; and

[0368] The collection module is arranged to collect electrical power from the current and supply electrical power to the downhole equipment.

[0369] According to another aspect of the present invention, a downhole power delivery system is provided for supplying power to downhole equipment in a well facility having a metal structure provided with cathodic protection, the system comprising:

[0370] A collection module as defined above is electrically connected to the metal structure at two spaced-apart locations, the two spaced-apart locations being chosen such that, during use, a potential difference exists between the two spaced-apart locations due to the cathodic protection current flowing in the structure; and

[0371] The collection module is arranged to collect electrical power from the cathodic protection current and supply electrical power to the downhole equipment.

[0372] According to another aspect of the invention, a method for data communication in a well facility having a metal structure equipped with a cathodic protection system is provided, such that there is a circuit including the metal structure and a ground return, and current flows around the ground return due to the cathodic protection system. The method includes the following steps:

[0373] Modulate the current at the first position to encode the data; and

[0374] At a second position spaced apart from the first position, the effect of modulating the current at the first position is detected in order to extract the data.

[0375] One of the locations can be an external location of the wellbore, such as on the surface, while the other location can be underground.

[0376] The steps of modulating the current may, among other things, include, and the modulation device may, among other things, be arranged as follows:

[0377] i) In the case that the cathodic protection system is an external cathodic protection system, control the signal source of the external cathodic protection system to directly modulate the cathodic protection signal applied to the metal structure;

[0378] ii) Modify the connection between at least one anode and the metal structure, thereby enabling, for example, switching at least one anode to be connected to or disconnected from the metal structure to modulate an electrical signal or to change the impedance between the anode and the structure; or

[0379] iii) Change the impedance of the circuit, which can be achieved, for example, by using a variable impedance device, or by switching a component to be connected to or disconnected from the circuit.

[0380] Techniques i) and ii) may be available only at one upper location, while technique iii) may be available at both downhole and upper locations.

[0381] Communication using this general idea can be used for, for example, one-way communication from the surface to the well, one-way communication from the well to the surface, and two-way communication.

[0382] These technologies enable communication as part of a hybrid communication system, where some parts of the signal channel are provided by modulating cathodic protection signals, while other parts are provided by other technologies, such as other wireless technologies including other EM technologies and acoustic technologies.

[0383] In each of the above cases, cathodic protection (where applicable) can be provided by a passive cathodic protection system or by an external cathodic protection system. In a passive cathodic protection system, the sacrificial anode is connected to the metal structure of the well facility. In an external cathodic protection system, a protective current is applied to the metal structure of the well facility.

[0384] In this method and system, the aim is to utilize existing cathodic protection systems (or, if available, other current sources), particularly existing anodes in subsea facilities (where applicable) without requiring modification. Therefore, the anodes (where applicable) will typically be located outside the wellbore (i.e., above the wellbore) and positioned in the water. Furthermore, the anodes will typically be located away from locations requiring power and / or signal transmission.

[0385] Therefore, any system described above may include one or more of the following: at least one existing anode; at least one anode disposed in water, such as the water body in which a subsea well facility is disposed; at least one anode located away from a location where power and / or signal transmission will be achieved using the current generated by the anode.

[0386] Furthermore, any of the systems described above can be arranged such that power can be transferred from the location where a current (e.g., a CP current) is applied to the structure to the collection location and / or signal transmission location. This is true regardless of whether the current is a passive CP current, an applied CP current, or any other applied current. That is, typically, the source of the CP current or other current is located away from the collection location and / or signal transmission location.

[0387] Furthermore, the metal structure can be continuous in the area of ​​at least one anode and / or the area of ​​the collection module.

[0388] In the context of optimization through modeling, such as the spacing of connections, the use of insulation, the selection of radial or axial spacing only, and the selection of preset collection loads mentioned above, at least one of the following parameters can be used in the model:

[0389] 1. The attenuation rate at the top of the well, derived from the casing and fitting dimensions, weight, material type (resistivity), and resistivity of the overlying rock formation (the medium surrounding the well).

[0390] 2. Location of the upper connecting part.

[0391] 3. Location of the lower connecting part.

[0392] 4. The cross-sectional area and material (resistivity) type of the upper cable used at the collector input.

[0393] 5. The number, location, material (potential), and surface area of ​​the wellhead anodes.

[0394] 6. The effective resistance of the well, as examined from the seabed / wellhead, is again derived from the resistivity of the casing and fitting dimensions, weight and material type (resistivity) and the overlying rock (the medium surrounding the well), but this time for all.

[0395] In each of the above scenarios, the system may include a primary battery for supplying power independently of the collected power. The collection module may include this primary battery. When a primary battery is provided, it can be used preferentially while it is maintaining power. For example, it might be used to enable a higher data rate in the early stages, allowing that data rate to decrease when only the collected power is available.

[0396] According to another aspect of the invention, a well facility is provided comprising a current-carrying metal structure and any one of the systems or devices described above, such as at least one of: a downhole power harvesting device or system; a downhole equipment operating device or system; a downhole communication repeater device or system; a power transfer device or system; or a harvesting module; or a downhole well monitoring device or system; or a downhole communication device or system as defined above. Such a facility may also have a cathodic protection system for protecting the metal structure.

[0397] Note that, generally, each of the optional features following each of the various aspects of the invention described above also applies to optional features for each of the other aspects of the invention, and may be rewritten after each aspect with any necessary wording changes. For the sake of brevity, not all such optional features are rewritten after each aspect.

[0398] For example, it should be understood that any of the systems, methods, apparatuses and facilities mentioned above may utilize collection modules, etc., having any combination or sub-combination of the features defined above.

[0399] The well mentioned in any of the methods, systems, apparatus or facilities described above may be a subsea well.

[0400] The object of the present invention is achieved by the following items 1-68.

[0401] 1. A downhole power harvesting system for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged to carry cathodic protection current during use, the system comprising:

[0402] A collection module is electrically connected at a first position to at least one section of downhole metal pipe of the metal structure and at a second position spaced apart from the first position. The first and second positions are selected such that, during use, a cathodic protection current flows in at least one section of downhole metal pipe between the first and second positions, resulting in a potential difference between the first and second positions due to the cathodic protection current flowing in the at least one section of downhole metal pipe.

[0403] The collection module is connected between the first position and the second position and is arranged to collect electrical energy from the potential difference existing between the first position and the second position due to the cathodic protection current, wherein the collection module includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe.

[0404] 2. The downhole power harvesting system according to item 1 above, wherein the electrical connection between the harvesting module and the at least one section of the downhole metal pipe of the metal structure at at least one of the first and second positions is provided by an insulated cable, wherein the insulated cable has a conductive area of ​​at least 10 mm², and further wherein the interval between the first and second positions is at least 100 m.

[0405] 3. The downhole power harvesting system according to item 1 or 2 above, wherein:

[0406] In the case of a land-based well, the upper, spaced-out contact portions are within 100m of the land surface; and

[0407] In the case of a subsea well, the upper spaced-out contact portions are within 100m of the mudline.

[0408] 4. The downhole power harvesting system according to item 1 or 2 above, wherein the harvesting module includes a variable impedance device for varying the load between two connections, and the harvesting module is arranged to use the variable impedance device to vary the load in order to optimize energy harvesting.

[0409] 5. The downhole power harvesting system according to item 1 or 2 above, wherein the current flow in the multiple portions of the metal structure in the region between the first position and the second position is in the same longitudinal direction.

[0410] 6. The downhole power harvesting system according to item 1 or 2 above, wherein there is an uninterrupted current flow path between the first location and the second location, the uninterrupted current flow path passing at least partially through the metal structure.

[0411] 7. The downhole power harvesting system according to item 1 or 2 above, wherein the spaced-out positions are axially spaced.

[0412] 8. The downhole power harvesting system according to item 1 or 2 above, wherein the spaced-out positions are radially spaced.

[0413] 9. The downhole power harvesting system according to item 1 above, wherein at least one of the electrical contacts and at least one connection between the harvesting module is provided by an insulated cable.

[0414] 10. The downhole power harvesting system according to item 9 above, wherein the insulated cable has a conductive area of ​​at least 10 mm².

[0415] 11. The downhole power harvesting system according to item 9 above, wherein the cable is a tubing-encapsulated conductor.

[0416] 12. The downhole power harvesting system according to item 1 or 2 above, wherein the interval between the locations is at least 100m.

[0417] 13. The downhole power harvesting system according to item 1 above, wherein the connection is formed to a common elongated metal member that is part of the metal structure.

[0418] 14. The downhole power harvesting system according to item 1 above, wherein a first connecting portion in the connecting portion is formed to a first elongated metal member that is part of the metal structure, and a second connecting portion in the connecting portion is formed to a different second elongated metal member that is part of the metal structure.

[0419] 15. The downhole power harvesting system according to item 14 above, wherein the insulating device is configured to electrically insulate the first elongated metal member from the second elongated metal member in the region of the connection.

[0420] 16. The downhole power harvesting system according to item 15 above, wherein the insulating device includes an insulating layer or coating disposed on at least one of the elongated metal members.

[0421] 17. The downhole power harvesting system according to item 15 above, wherein the insulation device includes at least one insulating centralizer for keeping the elongated metal segments separated from each other.

[0422] 18. The downhole power harvesting system according to item 15 above, wherein the insulation device is configured to prevent electrical contact between two slender metal components over a distance of at least 100 m.

[0423] 19. The downhole power harvesting system according to item 13 or 14 above, wherein the current flowing in the elongated member is supplied from the surface of the well.

[0424] 20. The downhole power harvesting system according to item 13 or 14 above, wherein the current flowing in the elongated member is supplied from one or more sacrificial anodes.

[0425] 21. The downhole power harvesting system according to item 19 above, wherein the current flowing in the elongated member is an applied current from an external power supply.

[0426] 22. The downhole power harvesting system according to item 1 or 2 above, wherein the surface voltage of the well is limited to a range of -0.7 volts to -2 volts relative to the silver / silver chloride reference cell during use.

[0427] 23. The downhole power harvesting system according to item 1 or 2 above, wherein the potential difference between the spaced-apart contacts is less than 1 volt.

[0428] 24. The downhole power harvesting system according to item 1 or 2 above, wherein the resistance between the contact parts of the well structure is less than 0.1 ohms.

[0429] 25. The downhole power harvesting system according to item 1 or 2 above, wherein the spaced-apart upper contact portion is located near the position corresponding to the maximum value of the potential caused by the current flowing in the structure.

[0430] 26. The downhole power harvesting system according to item 1 or 2 above further includes a downhole communication device for transmitting and / or receiving data.

[0431] 27. The downhole power harvesting system according to item 26 above, wherein the downhole communication device is arranged to transmit data by causing load variations between connections at spaced locations.

[0432] 28. The downhole power harvesting system according to item 9 above, wherein the insulated cable has a conductive area of ​​at least 20 mm².

[0433] 29. The downhole power harvesting system according to item 9 above, wherein the insulated cable has a conductive area of ​​at least 80 mm².

[0434] 30. The downhole power harvesting system according to item 1 or 2 above, wherein the potential difference between the spaced-apart contacts is less than 0.5 volts.

[0435] 31. The downhole power harvesting system according to item 1 or 2 above, wherein the potential difference between the spaced-apart contacts is less than 0.1 volts.

[0436] 32. The downhole power harvesting system according to item 1 or 2 above, wherein the resistance between the contact parts of the well structure is less than 0.01 ohms.

[0437] 33. The downhole power harvesting system according to item 3 above, wherein:

[0438] In the case of a land-based well, the upper spaced-out contact portions are within 50m of the land surface.

[0439] 34. The downhole power harvesting system according to item 3 above, wherein:

[0440] In the case of a subsea well, the upper spaced-out contact portions are within 50m of the mudline.

[0441] 35. A downhole device operating system comprising a downhole power harvesting system according to any of the preceding claims and a downhole device, the harvesting module being electrically connected to the downhole device and arranged to provide power to the downhole device.

[0442] 36. The downhole equipment operating system according to item 35 above, wherein the downhole equipment includes at least one of the following:

[0443] Downhole sensors;

[0444] Downhole actuators;

[0445] Annular sealing equipment;

[0446] valve;

[0447] Downhole communication module.

[0448] 37. The downhole equipment operating system according to item 36 above, wherein the valve includes at least one of the following:

[0449] Underground safety valve;

[0450] Orifice flow control valve;

[0451] orifice to annular valve;

[0452] Annular space to annular space valve;

[0453] Orifice to pressure compensation chamber valve;

[0454] Annular space to pressure compensation chamber valve;

[0455] Through packer or packer bypass valve.

[0456] 38. The downhole equipment operating system according to items 35 to 37 above, wherein the downhole equipment is located in the well at a different location from the collection module.

[0457] 39. The downhole equipment operating system according to item 38 above, wherein the collection module is arranged at a selected location downhole for collecting power, and a cable is configured to further supply electrical power downhole to the downhole equipment located at different locations in the well.

[0458] 40. The downhole equipment operating system according to item 39 above, wherein the cross-sectional area of ​​one or more conductive cores of the cable used to further supply electrical power to the downhole is smaller than the cross-sectional area of ​​one or more conductive cores of the cable used to connect the collection module to the downhole structure for collecting power.

[0459] 41. The downhole equipment operating system according to item 36 above, wherein the annular sealing device is a packer or a packer element.

[0460] 42. The downhole equipment operating system according to item 36 above, wherein the downhole communication module is a transceiver or a repeater.

[0461] 43. A downhole monitoring system for monitoring at least one parameter in a well facility with a current-carrying metallic structure, the system comprising:

[0462] An energy harvesting system according to any one of items 1 to 35 above;

[0463] A sensor module for sensing at least one parameter; and

[0464] A communication module is used to transmit data encoded from the readings of the sensor module toward the ground.

[0465] The energy harvesting system is arranged to supply electrical power to at least one of the sensor module and the communication module.

[0466] 44. A downhole monitoring system for monitoring at least one parameter in a well facility with a current-carrying metallic structure, the system comprising:

[0467] A sensor module for sensing at least one parameter;

[0468] A communication module for transmitting data encoded from readings received from the sensor module toward the ground; and

[0469] An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being cathodic protection and including at least one section of downhole metal tubing. The metal structure is arranged such that it carries a cathodic protection current during use. The energy harvesting system includes a harvesting module electrically connected at a first position to the at least one section of downhole metal tubing of the metal structure and at a second position spaced apart from the first position. The first and second positions are selected such that, during use, the cathodic protection current is carried at the first and second positions. A current flows through at least one section of downhole metal pipe between the two positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing through the at least one section of downhole metal pipe; and a collection module is connected between the first and second positions and arranged to collect electrical energy from the potential difference between the first and second positions caused by the cathodic protection current, wherein the collection module includes a DC-DC converter for collecting electrical energy from the DC current flowing through the at least one section of downhole metal pipe, and the energy collection system is arranged to supply electrical power to at least one of the sensor module and the communication module.

[0470] 45. The downhole monitoring system according to item 43 or 44 above, wherein the communication module is arranged to modulate the current flowing in the metal structure at the signal transmission location in order to encode the data, thereby allowing the data at the receiving location to be extracted by detecting the effect of the modulation on the current at a receiving location remote from the signal transmission location.

[0471] 46. ​​The downhole monitoring system according to item 45 above, comprising a detector for detecting the effect of the modulation on the current at the receiving location to extract encoded data.

[0472] 47. The downhole monitoring system according to item 45 above, wherein the communication module is arranged to control the load generated by the collection module, thereby generating the modulation of the current in the metal structure at the signal transmission location.

[0473] 48. The downhole monitoring system according to item 43 or 44 above, wherein the sensor module includes a pressure sensor.

[0474] 49. The downhole monitoring system according to item 48 above, wherein the pressure sensor is arranged to monitor the reservoir pressure of the well.

[0475] 50. The downhole monitoring system according to item 48 above, wherein the pressure sensor is arranged to monitor the pressure in the annulus of the well.

[0476] 51. The downhole monitoring system according to item 48 above, wherein the pressure sensor is arranged to monitor the pressure in the closed annulus of the well.

[0477] 52. A downhole communication repeater system for use in well facilities with current-carrying metallic structures, the system comprising:

[0478] An energy harvesting system according to any one of items 1 to 34 above; and

[0479] A communication repeater is disposed in and located below the wellhead, and is configured to communicate with a first device extending beyond the wellhead using a wireless communication channel that passes at least through the wellhead, and is also configured to communicate with a second device located in and below the wellhead, such that the communication repeater can act as a relay between the first and second devices.

[0480] The power harvesting system is configured to supply electrical power to the communication repeater.

[0481] 53. A downhole communication repeater system for use in well facilities with current-carrying metallic structures, the system comprising:

[0482] A communication repeater, disposed in and located below the wellhead, and configured to communicate with a first device extending beyond the wellhead using a wireless communication channel passing at least through the wellhead, and configured to communicate with a second device located in the well and thus below the wellhead, such that the communication repeater can act as a repeater between the first and second devices; and

[0483] An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being cathodic protection and including at least one section of downhole metal tubing. The metal structure is arranged to carry a cathodic protection current during use. The energy harvesting system includes a harvesting module electrically connected at a first position to the at least one section of downhole metal tubing of the metal structure and at a second position spaced apart from the first position. The first and second positions are selected such that, during use, the cathodic protection current is carried by the at least one section of downhole metal tubing in the first position. A current flows through at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing through the at least one section of downhole metal pipe; and a collection module is connected between the first and second positions and arranged to collect electrical energy from the potential difference between the first and second positions caused by the cathodic protection current, wherein the collection module includes a DC-DC converter for collecting electrical energy from the DC current flowing through the at least one section of downhole metal pipe, and the energy collection system is arranged to supply electrical power to a communication repeater.

[0484] 54. The downhole communication repeater system according to item 52 or 53 above, wherein the repeater is arranged to modulate the current flowing in the metal structure at the signal transmission location in order to encode data, thereby allowing data at the receiving location to be extracted by detecting the effect of the modulation on the current at a receiving location remote from the signal transmission location.

[0485] 55. The downhole communication repeater system according to item 54 above, comprising a detector for detecting the effect of the modulation on the current at the receiving location to extract encoded data.

[0486] 56. The downhole communication repeater system according to item 54 above, wherein the repeater is arranged to control the load generated by the collection module to produce the modulation of the current in the metal structure at the signal transmission location.

[0487] 57. A downhole equipment operating system for operating downhole equipment in a well facility with a current-carrying metallic structure, the system comprising:

[0488] A downhole device;

[0489] An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being cathodic protection and including at least one section of downhole metal tubing. The metal structure is arranged to carry a cathodic protection current during use. The energy harvesting system includes a harvesting module electrically connected at a first position to the at least one section of downhole metal tubing of the metal structure and at a second position spaced apart from the first position. The first and second positions are selected such that, during use, the cathodic protection current is carried by the at least one section of downhole metal tubing in the first position. A current flows through at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing through the at least one section of downhole metal pipe; and a collection module is connected between the first and second positions and arranged to collect electrical energy from the potential difference between the first and second positions caused by the cathodic protection current, wherein the collection module includes a DC-DC converter for collecting electrical energy from the DC current flowing through the at least one section of downhole metal pipe, and the energy collection system is arranged to supply electrical power to the downhole equipment.

[0490] 58. The downhole equipment operating system according to item 57 above, wherein the downhole equipment includes at least one of the following:

[0491] Downhole sensors;

[0492] Annular sealing equipment;

[0493] valve;

[0494] Downhole communication module.

[0495] 59. The downhole equipment operating system according to item 58 above, wherein the valve includes at least one of the following:

[0496] Underground safety valve;

[0497] Orifice flow control valve;

[0498] orifice to annular valve;

[0499] Annular space to annular space valve;

[0500] Orifice to pressure compensation chamber valve;

[0501] Annular space to pressure compensation chamber valve;

[0502] Through packer or packer bypass valve.

[0503] 60. The downhole equipment operating system according to any one of items 57 to 59 above, wherein the downhole equipment is located in the well at a different location from the collection module.

[0504] 61. The downhole equipment operating system according to item 60 above, wherein the collection module is arranged at a selected location downhole for collecting power, and a cable is configured to further supply electrical power downhole to the downhole equipment at different locations in the well.

[0505] 62. The downhole equipment operating system according to item 61 above, wherein the cross-sectional area of ​​one or more conductive cores of the cable used to further supply electrical power to the downhole is smaller than the cross-sectional area of ​​one or more conductive cores of the cable used to connect the collecting module to the downhole structure for collecting power.

[0506] 63. The downhole equipment operating system according to any one of items 57 to 59 above, wherein in addition to the electrical power supplied by the power harvesting module, another power source is available to the downhole equipment.

[0507] 64. The system according to item 1 or 2 above, wherein the well is a subsea well.

[0508] 65. The downhole equipment operating system according to item 58 above, wherein the annular sealing device is a packer or a packer element.

[0509] 66. The downhole equipment operating system according to item 58 above, wherein the downhole communication module is a transceiver or a repeater.

[0510] 67. A method for harvesting electrical energy from DC current to power downhole equipment in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged such that it carries cathodic protection current during use, the method comprising the steps of:

[0511] A collection unit is electrically connected at a first position to at least one section of downhole metal pipe of the metal structure and at a second position spaced apart from the first position to at least one section of downhole metal pipe of the metal structure. The first and second positions are selected such that a potential difference exists between the first and second positions due to a cathodic protection current flowing in the at least one section of downhole metal pipe between the first and second positions. The collection unit is arranged to collect electrical energy from the potential difference between the first and second positions due to the cathodic protection current when connected between the positions with the potential difference. The collection unit includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe.

[0512] At the collection unit, electrical power is collected from the cathode protection current; and

[0513] The collection unit supplies electrical power to the downhole equipment.

[0514] 68. The method according to item 67 above includes the steps of: determining a location where a maximum value of the potential caused by the current flowing in the structure exists; and selecting a first location for connecting the collection unit to the metal structure based on the location of the maximum value. Attached Figure Description

[0515] Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0516] Figure 1 A well facility including a well monitoring device, which includes a downhole power delivery system, is schematically shown.

[0517] Figure 2A schematically shown Figure 1 The collection module of the power delivery system, and Figure 2B An alternative downhole unit is shown;

[0518] Figure 2C It is a schematic circuit diagram of a DC-DC converter that can be used in the collection module;

[0519] Figure 2D It is a schematic circuit diagram of a DC-DC converter that can be used in the collection module;

[0520] Figure 3 A well facility including a downhole communication device is schematically shown, the downhole communication device including a downhole communication repeater and a downhole power delivery system for supplying power to the downhole communication repeater;

[0521] Figure 4 A well facility including a valve operating device is schematically shown, the valve operating device comprising a remotely controlled downhole valve and a power delivery system for supplying power to the remotely controlled downhole valve;

[0522] Figure 5 A well facility including an alternative well monitoring system is schematically shown, which includes a downhole meter and a downhole power delivery system for powering the downhole meter;

[0523] Figure 6 The alternative well facility is shown schematically;

[0524] Figure 7 It shows that for Figure 1 A graph showing the optimal collectable power of the type of arrangement shown relative to the depth of the lower connector;

[0525] Figure 8A flowchart of energy harvesting optimization is shown;

[0526] Figure 9 A flowchart illustrating the operation of the downhole unit is shown; and

[0527] Figure 10 The diagram schematically illustrates a well facility including a platform. Detailed Implementation

[0528] Figure 1 A well facility for an oil well and / or gas well is shown. As is well known, such oil wells and / or gas wells can be onshore wells or subsea wells (meaning wells located beneath any body of water), in which the wellhead is underwater and on the seabed, riverbed, lakebed, etc., or on a platform. Typically, the well facility is equipped with a cathodic protection system. In the case of onshore wells, this cathodic protection system is most likely in the form of an impressed current cathodic protection system, in which a protective current is applied to the metal structure of the well. On the other hand, for subsea wells, the cathodic protection is most likely a passive cathodic protection system, in which multiple anodes of a relatively active metal (such as a magnesium alloy) are connected to the metal structure and exposed to the water in which the well facility is located.

[0529] Note that this technology also relates to water injection wells, which are wells used in the art to inject water into a reservoir to aid in the extraction of oil and / or gas from other wells. Therefore, a “well facility” in this specification can refer to a water injection well. Such a well will have a similar construction to the facility shown in more detail in this application. Similarly, this technology can be used concurrently with drilling, during production, and after abandonment. Thus, a well facility can be a partially completed facility in which drilling is underway. More generally, this technology can be used at any stage of the well facility's lifespan.

[0530] Furthermore, although this specific description is written with regard to facilities in which cathodic protection is present and which is particularly preferred, many of the systems and techniques of the present invention also work in other cases where current flows through a metal structure and power can be harvested from that metal structure.

[0531] Figure 1 The well facility shown includes a wellhead 1 and a downhole metal structure 2 extending downwards from the surface S into the wellbore. The well facility is equipped with cathodic protection systems 3A and 3B. As mentioned above, this cathodic protection system is either an impressed current cathodic protection system 3A or a passive cathodic protection system 3B comprising multiple anodes connected to the metal structure of the well facility (i.e., connected to the wellhead 1 or other metal components connected to the wellhead 1).

[0532] The downhole metal structure 2 includes a first section of metal tubing 21 extending downward into the wellbore, namely, the production tubing. Surrounding this production tubing is a first casing 22. Outside this layer is a second casing 23, followed by a third casing 24. As will be understood, there are corresponding annexes between each section of metal tubing. Thus, there is a first annulus between the production tubing 21 and the first casing 22, which is commonly referred to in the oil and gas industry as the "A" annulus and is indicated by reference numeral A in the accompanying drawings. There is a second annulus between the first casing 22 and the second casing 23, which is commonly referred to as the "B" annulus and is so indicated in the accompanying drawings, and a third annulus between the second casing 23 and the third casing 24, which is commonly referred to as the "C" annulus and is so indicated in the accompanying drawings. The well may also typically have another "D" annulus, and sometimes even more annexes.

[0533] In other cases, the metal structure may include other elongated members, specifically one or more of casing, liner, tubing, coiled tubing, and sucker rod.

[0534] The monitoring equipment installed in the well facility includes an electrical power harvesting module 4, which, in this embodiment, is located in the A-annulus. The harvesting module 4 is electrically connected via cable 41 to a pair of spaced-apart locations 41a, 41b on the production tubing 21. Alternatively, the harvesting module 4 may be electrically connected to one of the locations via cable, but may be electrically connected to the other location without a cable. The harvesting module 4 may be electrically connected to one of the locations via its conductive housing (or the housing surrounding it). Therefore, only one such cable needs to exit the housing.

[0535] Note that there are current connections at spaced-out locations 41a and 41b, and between the harvesting module 4 and the metal structure 21. Specifically, there is a current connection to the metal structure 21, rather than, for example, inductive coupling. This simplifies the construction and eliminates engineering difficulties. In the present case, there is a constant current connection from the metal structure to the inputs of the circuitry included in the harvesting module for energy harvesting.

[0536] Furthermore, it should be noted that the well's metal structure is generally unaffected by the installation of this system. No insulating joints are introduced into any of the multiple metal sections to make the system effective, and the normal flow of cathodic protection current in the structure remains unchanged, except, of course, for ongoing collection. Thus, for example, between the spaced-out locations, the metal structure formed by the joints is continuous; more generally, all the multiple metal sections are continuous in these areas. This is not necessary for operation, but it is possible and normal practice in well facilities, i.e., the standard metal structure of the facility remains unchanged. Similarly, the current can and does flow in the same direction in the areas of the joints and between the joints and in the metal structure. Again, this is normal practice in well facilities, avoiding modifications to the well facility. Current flow may occur in a single metal section formed by the joints, or jump from one section to another, or flow in parallel in several sections. Crucially, it is not necessary to artificially arrange the metal structure in the well to allow the system to operate, and thus, there is an uninterrupted current flow path provided by the metal structure, and the current flow in the metal structure is in the same longitudinal direction.

[0537] Note that the “A” annulus is typically accessible via cable through wellhead 1. However, using this arrangement remains advantageous because it minimizes the number of penetrators in the wellhead, reducing risk and cost and / or freeing up penetrators for other uses.

[0538] The monitoring device also includes a downhole meter 5, which is positioned deeper in the well than the collection module 4 and connected to the collection module 4 via a cable 42. In this embodiment, the downhole meter 5 is positioned directly above the packer P. Typically, the cable 41 connecting the collection module 4 to the production unit 21 is a tubing closed conductor (TEC), as is typically used in the oil and gas industry, and the cable 42 connecting the collection module 4 to the downhole meter 5 is also a tubing closed conductor (TEC). Furthermore, typically, the cross-sectional area of ​​the conductors in the multiple segments of cable 41 connecting the collection module 4 to the production tubing 21 is larger than the cross-sectional area of ​​the cable 42 connecting the collection module 4 to the downhole meter 5.

[0539] When cathodic protection is installed in the well facility, the potential of the well's metal structure acquires a sufficiently negative potential at the injection point (e.g., wellhead 1) to suppress corrosion at the wellhead and at other points along the downhole metal structure 2 as it descends into the well. However, the magnitude of this negative potential decreases due to losses in the system as the downhole metal structure advances further into the well. Therefore, the potential of the metal structure 2 near the wellhead is more negative than at deeper locations in the well. Consequently, when the cathodic protection current is flowing in the well facility, a potential difference exists between positions 41a and 41b, where a first cable in cable 41 connects from the collection module to the production tubing 21, and another cable in cable 41 connects from the collection module 4 to the production tubing 21 at position 41b. The collection module 4 thus observes the potential difference across its terminals and can extract energy from the cathodic protection current.

[0540] It should be noted that the extracted energy will utilize power from the cathodic protection system; however, the impact on the effectiveness of the cathodic protection system or any acceleration of anode corrosion will be negligible. Typically, the cathodic protection current will be approximately 10 amps, while this system can extract, for example, 10 mA to 100 mA. Therefore, the amount of current extracted is well within the tolerances typically allowed when developing cathodic protection systems. If desired, increased levels of impressed current can be provided, or the number of anodes can be increased beyond the standard. This will increase the cathodic protection current, thereby improving collection.

[0541] Electrical power can be collected from the system at the downhole location of the collection module 4, and the collected power can be used for other purposes.

[0542] exist Figure 1 In this arrangement, the collected power is used to power the downhole meter 5 and allows readings to be extracted from the downhole meter 5 and communicated to the surface S.

[0543] In this embodiment, the upper communication unit 6 is configured to communicate with the collection module 4 and the downhole meter 5. In this case, the upper communication unit 6 is located at the ground surface S (in this case, the land surface).

[0544] It should be understood that arrangements such as this one can be used instead of conventionally installed permanent downhole gauges (PDGs), with the advantage of avoiding the use of penetrators through the wellhead, while the lifespan of well monitoring will be feasible in many cases. Monitoring can be the monitoring of reservoir pressure as desired or, similarly, the monitoring of pressure in the closed annulus, to help detect, for example, any leaks, problems, or malfunctions in the system. In such cases, sensors and collection modules can be positioned in the closed annulus.

[0545] All of these options are possible in, for example, subsea well facilities, where there is typically a ready source of current to be collected (i.e., CP current) generated by a sacrificial anode located in the water where the subsea facility is located, and other power and signal transmission options are more problematic in subsea well facilities.

[0546] In wells with subsea wellheads, it is typically not (practically / cost-effectively) possible to provide hydraulic or electrical connections to the outer annulus (B, C, etc.). Particularly useful when these annulus are sealed at their base, it is beneficial to monitor and optionally control the pressure within these annulus, for example, to reduce the risk of casing collapse due to high pressure. Specifically, flow or borehole drilling increases the temperature of the sealed outer annulus, thereby increasing the pressure within it. In such cases, the ability to monitor the pressure and optionally control it (e.g., by having vent valves between the annulus, as mentioned elsewhere) is advantageous. In particular, monitoring the pressure within the closed annulus allows for higher production rates compared to rates achievable solely by modeling the expected pressure rise, as the use of the modeled pressure would require a greater safety margin and potentially a correspondingly lower production rate. It should be understood that this technique can facilitate such monitoring and / or control.

[0547] Another specific embodiment of this technology will include a sensor module located at the same location most commonly found in conventional permanent downhole meters, and configured for the same purpose as conventional permanent downhole meters.

[0548] Therefore, the sensor module can be arranged in the A-ring and configured to monitor reservoir pressure by sensing pressure in the tubing via a pressure connection port passing through the tubing, thereby allowing reservoir pressure to be inferred based on the sensed pressure, taking into account static pressure and flow effects. As with conventional PDGs, reservoir pressure is typically inferred rather than measured directly (directly positioning the sensor in the reservoir is generally not feasible), and as should also be understood, "monitoring reservoir pressure" encompasses the use of such measurement techniques.

[0549] The collection module can also be located at the same position as the sensor module.

[0550] Different technologies can be used to allow data to be extracted from the downhole meter 5 toward the surface.

[0551] In this embodiment, the collection module 4 is arranged to receive signals from a downhole meter indicating the parameter to be measured, such as pressure and / or temperature, and transmits this data toward the surface by modulating the load generated between the spaced-out connections 41a and 41b of the collection module 4. This load change, in turn, alters the amount of current drawn from the cathodic protection current applied to the system. This is thus detectable at the surface or other convenient location due to a change in the potential of the metal structure at the surface or other convenient location. It can be detected, for example, by detecting a change in potential at the wellhead 1 or by detecting the voltage across the power supply used in the external cathodic protection system 3A or the current detected by the power supply used in the external cathodic protection system 3A. In this embodiment, the effect of this modulation is detected by the upper communication unit 6 monitoring the potential of the wellhead relative to a reference ground to extract pressure and / or temperature measurement data.

[0552] Preferably, the spacing between the spaced-out connections 41a and 41b is at least 100 meters, and more likely in the range of 300 to 500 meters. The optimal spacing for the spaced-out connections 41a and 41b can be determined by modeling a given facility. As the distance between these connections increases, this tends to increase the potential difference between the connections (although the rate of increase in potential difference decreases as the depth of the lower connection increases). On the other hand, as the spacing increases, the total length of the cable 41, and thus the resistance of the cable 41, increases. Therefore, in most systems, there will be an optimal spacing.

[0553] Figure 2A Showing more details Figure 1 The device shown includes a collection module 4. In this embodiment, the collection module 4 has a pair of terminals 43a and 43b, to which a corresponding cable 41 is connected. A current connection exists between the metal structure and the terminals 43a and 43b. Connected between these terminals 43a and 43b is a low-voltage DC-DC converter used to collect electrical energy when a potential difference exists across the terminals 43a and 43b. The DC-DC converter 44 is connected to a charge storage device 45, which includes at least one low-leakage capacitor and is connected to and controlled by a microprocessor-driven central unit 46. The charge storage device 45 and the central unit 46 are also connected via a corresponding terminal 43c to the section of cable 42 leading to the downhole meter 5. In an alternative, the charge storage device 45 can be omitted, allowing sufficient power to be collected as needed or when required to permit continuous operation.

[0554] In operation, the central unit 46 controls the operation of the DC-DC converter 44 to optimize the load (which presents a current due to the cathodic protection current to the current supplied by the collection module 4) to maximize the energy that can be collected and used or stored in the charge storage device 45. Note that the central unit can be arranged to directly and selectively use and / or deliver the collected energy when appropriate, and to store and extract the stored energy when appropriate.

[0555] Note that in one alternative, the microprocessor-driven central unit 46 can be replaced by alternative electronics, such as analog feedback circuits or state machines, or even based on a fixed collection load modeled for a particular facility.

[0556] When the stored energy is to be used, power from the charge storage device 45 is fed to the downhole meter 5 via cable 42, and the reading from the downhole meter 5 is acquired by the central unit 46 via cable 42. The central unit 46 also controls the operation of the DC-DC converter 44 to modulate the load introduced between terminals 43a and 43b, thereby sending the signal carrying the reading from the downhole meter 5 back to the surface, as described above.

[0557] Note that in this embodiment, since the central unit 46 controls the operation of the DC-DC converter 44 to introduce a variable impedance between terminals 43a and 43b, the DC-DC converter 44 and the central unit 46 together act as a variable impedance device.

[0558] Note that, in an alternative, a suitable sensor can be placed in the same location as the collection module 4, instead of in a separate downhole meter 5.

[0559] Specifically, it is possible to set, for example Figure 2B The downhole unit 4a shown includes both a collection module 4 and at least one downhole device to be powered. In this case, the downhole unit 4a includes a pressure sensor 47 and a communication unit 48.

[0560] In such a case, the secondary cable 42 leading from the downhole unit 4a may not be necessary. On the other hand, in some other cases, the downhole unit 4a may still be used to power external equipment, even including its own sensors 47 and / or communication units 48, thus potentially requiring the presence of a secondary cable 42.

[0561] In an alternative, downhole unit 4a may use its own communication unit 48 for back-to-surface communication instead of using the load modulation technique described above. Such communication may take the form of an EM communication signal, which may be applied back to the downhole metal structure 21 via cable 41. Alternatively, the communication unit 48 in downhole unit 4a may be an acoustic communication unit for applying acoustic signals to the metal structure 21 for back-to-surface transmission. In this case, the upper communication unit would be arranged to receive the acoustic signals. It should be understood that bidirectional communication may be provided throughout any or all parts of the communication channel, depending on preference or when desired. Both communication techniques may be used in parallel in either branch of the communication channel, thus allowing EM signals and acoustic signals to be used side-by-side.

[0562] In another alternative, the harvesting module 4 or downhole unit 4a may include at least one power converter for controlling the harvested power to provide a voltage for delivery to the charge storage device 45 and / or other components (such as the central unit 46). It may be desirable to store energy at a voltage different from the voltage at which energy is harvested and / or at a voltage different from the voltage at which the central unit 46 or other components use energy. For example, it may be desirable to store power at a higher voltage than the voltage at which power is harvested and / or consumed. This may be useful, for example, if there is a large drawdown of the stored power during events such as transmission.

[0563] One possible implementation for a DC-DC converter is to use commercially available integrated circuits. An alternative is to use discrete components to create a similar circuit. For effective performance, it is desirable to be able to handle low input voltage DC-DC converters. One way to achieve this is to use field-effect transistors, such as JFET switches, to form a resonant boost oscillator using a boost transformer and coupling capacitors. To help optimize energy harvesting, the turns ratio on the transformer can be selected, preferably dynamically during operation. Multiple taps can be provided on the secondary side of the transformer, which can be selectively used to provide the appropriate turns ratio.

[0564] Processors (such as processors in the central unit) can be arranged to control switches, thereby dynamically selecting appropriate taps and thus controlling the load generated by the DC-DC converter.

[0565] Figure 2CA schematic circuit diagram of one possible implementation of a resonant boost oscillator of the type described above is shown. An available input potential difference can be connected across the input terminals as Vin, and an output Vout exists across the output terminals. The circuit includes a field-effect transistor 201, a boost transformer 202, and a rectified output arrangement 203, which together act as the oscillator, including a crossover diode pair 206 and corresponding coupling capacitors 205. The primary winding 202a of the transformer 202 is connected in series with the FET 201, and the input Vin is applied across these terminals. The gate of the FET 201 is connected to the secondary winding 202b of the transformer 202. The output Vout exists across the coupling capacitors 205, each connected across the secondary winding 202b via a corresponding diode 204.

[0566] The secondary winding 202b of transformer 202 includes multiple taps 202c, which can be selected using switch 206, thereby allowing adjustment of the turns ratio. Switch 206 can be controlled by a microprocessor, in this case, central unit 4b.

[0567] This type of DC-DC converter arrangement can function even when the potential difference (input voltage) across the terminals is low (i.e., 0.5V or less). In practical embodiments, this input voltage can be less than 0.25V and possibly even less than 0.05V. Since this is very low compared to the semiconductor bandgap voltage (e.g., 0.7V), many types of DC-DC converters would not function, thus allowing energy harvesting at such input voltages. However, a DC-DC converter based on the above principle can function even at such low voltages. Such a DC-DC converter can be considered to include a startup mechanism arranged to allow operation at input voltages of 0.5V or less, as well as at higher voltages.

[0568] An alternative approach is to provide a circuit with discrete power sources, thus acting as part of the starting mechanism. Therefore, for example, a primary battery can be configured to start the system after installation. Furthermore, if energy harvesting temporarily ceases, the energy stored in the energy storage device can be used to restart the system.

[0569] Figure 2D A schematic circuit diagram of one possible implementation of a DC-DC converter for operation on such a basis is shown. Figure 2DThe DC-DC converter includes an H-bridge 207 with transistor 207a, across which the input voltage is connected. The gate of transistor 207a is connected to a control unit 208, which is configured to control the switching of transistor 207a to generate an AC output. The AC output of the H-bridge 207 is connected across the primary winding 202a of a step-up transformer 202. The secondary winding 202b of the transformer 202 is connected to a rectifier 209. One output of the rectifier 209 is connected to the input of a power supply unit 210 via a diode 204, and the other output is connected to ground. A battery 211 is also connected to the input of the power supply unit 210 via another diode 204.

[0570] Power supply unit 210 is arranged to power control unit 208. For startup, power supply unit 210 can use power from battery 211. When energy is being harvested via a DC-DC converter, power supply unit 210 can use power received from rectifier 209, i.e., the harvested power.

[0571] While in this embodiment the power is used directly upon being harvested, alternatively, the harvested energy may also be stored in and used from a storage device. As described elsewhere in this application, the storage device may, for example, include at least one low-leakage capacitor and / or at least one rechargeable battery. In the case of stored energy, this allows the system to be restarted if harvesting stops at any point after battery 211 has discharged.

[0572] Battery 211 can be a primary (disposable) battery or a rechargeable battery, as long as it is charged during installation. In the case of a rechargeable battery, in some embodiments, power supply unit 210 can be arranged to store energy therein when available; alternatively, it may be more convenient to provide a discrete energy storage device (which may include the rechargeable battery).

[0573] Also note that in another alternative, Figure 2D The type of DC-DC converter shown can be arranged to allow control of the load generated by the DC-DC converter. Therefore, for example, it can be used with... Figure 2C The arrangement shown is similar to that in which the secondary winding 202b has multiple taps and a switch is provided to allow tap selection. This switch can be located between the winding and the input of the rectifier 209. Alternatively, a discrete secondary winding can be provided instead of multiple taps to achieve a similar result. Figure 2C In this configuration, the switch can be controlled by a control unit.

[0574] It should also be noted that in other embodiments, the collection module 4 and the downhole meter 5 (or downhole unit 4a) may be located in other annulus within the well facility, rather than in annulus A. Furthermore, the meter may be arranged to sense parameters in annulus different from the one in which it is located.

[0575] For example, these components can be positioned in the B or C annulus, and meters located, for example, in the B annulus can be arranged to sense one or more parameters in the A, B, C annulus, or any combination thereof. It should be noted that these are locations where providing direct cable connections from the surface is generally impossible or at least undesirable. Therefore, the technology of this invention creates the possibility of monitoring pressure in, for example, the B or C annulus throughout the life of the well facility, where conventional power delivery methods would be difficult and / or expensive. The technology of this invention avoids the use of penetrators through the wellhead, which reduces risk and cost. They also provide a relatively simple, flexible, and easy-to-install solution.

[0576] Figure 3 It shows the relationship with Figure 1 The well facility is similar but includes a downhole communication repeater 7 instead of a downhole meter. Repeater 7 is related to the one mentioned above. Figure 1 , Figure 2A to Figure 2D The same type of collection module 4 described herein is arranged together in the B-ring. Here, again, collection module 4 collects power from the cathodic protection current in the metal structure 2 and provides this power to the downhole communication repeater 7.

[0577] Figure 3 Structure and operation of well facilities, cathodic protection systems and power delivery systems in the layout and reference Figure 1 , Figure 2A to Figure 2D The structures and operations of the described systems are largely the same. The only difference is that the downhole component that delivers power through the power delivery system is the communication repeater 7 instead of the downhole meter 5.

[0578] Therefore, for the sake of brevity, a detailed description of the well facilities and power delivery system is omitted here. (The following is a separate section regarding this implementation plan.) Figure 1 and Figure 2A to Figure 2D In the case of identical parts, the same reference numerals are used.

[0579] A downhole communication repeater 7 is arranged to pick up signals from the downhole metal structure 2 in the area of ​​the repeater 7 and transmit the relevant data forward toward the surface. In this embodiment, the signal is applied as an EM signal to the downhole metal structure 2 by a transmission tool 71 further positioned downward in the well (e.g., in the production tubing 21). Correspondingly, the repeater 7 is arranged to pick up the EM signal.

[0580] In an alternative approach, different types of transmission tools can be configured to transmit signals picked up by the transponder. Such tools can, for example, be positioned outside the pipeline.

[0581] In an alternative, the communication repeater 7 can be arranged to pick up the acoustic signals that have already been applied further downhole from the downhole metal structure 2.

[0582] Similarly, the downhole communication repeater 7 can be arranged to apply acoustic signals to the downhole structure 2 for transmission toward the surface, or it can be arranged to apply EM signals to the downhole metal structure 2 for transmission to the surface, or it can be arranged to utilize the impedance modulation signal transmission technique described above.

[0583] Therefore, for example, the communication repeater 7 can pick up signals at its location and transmit these signals along the cable 42 to the collection module 4 by applying a signal to the collection module 4 or by modulating the load it applies to the power supply in the collection module 4. Similarly, the collection module 4 can be arranged to apply a signal to the metal structure 2 for transmission toward the ground, or it can be arranged to modulate the load it generates between the spaced-apart connections 41a, 41b for detection at the ground via the upper communication unit 6.

[0584] Note that when the downhole communication repeater 7 is installed, the EM signal can be picked up and / or applied, for example, by using spaced-out contacts or inductive couplings formed into the metal structure, and the inductive couplings comprising loop coils or signal transmissions at both ends of an insulating joint (if present). Similarly, conventional acoustic signal pickup and application techniques can be used.

[0585] In an alternative approach, communication can exist from the surface down to the underground location, and is typically bidirectional. Therefore, repeater 7 can act as a repeater in both directions. Furthermore, two communication technologies can be used in parallel on at least one branch of the channel to provide redundancy.

[0586] Also note that the downhole communication repeater 7 can be positioned in a location that is not in the product flow while allowing for the lifespan of well operations.

[0587] and Figure 3 The two specific embodiments are as follows:

[0588] 1. The repeater 7 includes a continuously powered EM receiver located at a depth of 3m-500m, which receives and decodes messages, or continuously retransmits the original data / signals at a higher frequency using only load impedance modulation for decoding at the ground.

[0589] 2. The repeater 7 includes a continuously powered acoustic receiver located at a depth of 3m-500m, which receives and decodes messages and then uses load impedance modulation to retransmit the data to the ground.

[0590] Note that in both cases, the repeater 7 can be installed together with the collection module in the downhole unit, or it can be separate from the collection module. Furthermore, the repeater can also be a bidirectional repeater.

[0591] In any of the systems described in this specification, the device can be arranged to manage the power budget by using the intermittent operation of components such as EM or acoustic receivers and / or transmitters, i.e., using less overall energy.

[0592] Figure 4 A well facility is schematically shown, which includes remotely controlled valves and a power delivery system of the same general type as described above.

[0593] The overall structure and operation of the well facility and the power delivery system are again consistent with the above description. Figure 1 , Figure 2A to Figure 2D The arrangement shown describes a well facility and a power delivery system whose overall structure and operation are largely the same. Therefore, for the sake of brevity, detailed descriptions of these common elements are omitted here, and the same reference numerals are used to indicate those features common to both embodiments.

[0594] In this embodiment, the well facility includes a first hydraulically operated underground safety valve SSSV, as conventionally installed in the production tubing 21.

[0595] However, an additional underground safety valve 8 is also installed within the production tubing 21, but further down into the well. Therefore, in the current configuration, the second underground safety valve 8 is installed as an additional safety measure or fallback measure. However, in an alternative, the hydraulically operated underground safety valve SSSV could be omitted.

[0596] The second underground safety valve 8 is powered and operated using a power delivery system. Specifically, a collection module 4 is connected to the second underground safety valve 8 via cable 42, and the collection module is arranged to send power and control signals to the second underground safety valve 8 via cable 42. Therefore, energy is harvested from the cathodic protection current traveling in the downhole structure 2, and this energy is used to control and operate the second underground safety valve 8.

[0597] Compared to traditional hydraulically operated underground safety valves (SSSVs), this underground safety valve 8 can be positioned deeper in the well. This is because it is not limited by the same range as hydraulically driven systems and does not require the driving hydraulic fluid to be directed towards it. It should be noted that the control signal for the second underground safety valve 8 can be transmitted from the upper communication unit 6 via the metal structure of wells 1 and 2, detected by the collection module 4, and transmitted forward to the underground safety valve 8. In some cases, valve 8 can be operated in fail-safe mode, meaning the valve will close in the absence of power and / or control signals. Note that, of course, in an alternative, valve 8 and the collection module may be configured as part of a common downhole tool 4a. Furthermore, in some cases, the power for closing the valve can come from another source, where a downhole power delivery system supplies power for control operation and / or operation triggering mechanisms.

[0598] Figure 5 Alternative well facilities, including well monitoring equipment, are shown. Here, again, in conjunction with the reference... Figure 1 , Figure 2A to Figure 2D The arrangement shown and described are similar. Again, there is a collection module 4 located within and connected to the downhole metal structure 2 at a spaced-apart position, and a downhole meter 5 connected to the collection module 4. In this case, both the collection module 4 and the downhole meter 5 are located in the B annulus to provide monitoring of the conditions in this annulus. The downhole meter 5 may include, for example, a pressure sensor and / or a temperature sensor.

[0599] In this configuration, spaced-apart positions 41a and 41b are positioned on different sections of the downhole metal structure 2. Specifically, in this embodiment, the first connection 41a is formed to the second casing 23, while the other connection 41b is formed to the first casing 22. The system operates on a principle similar to that discussed above, and therefore relies on the potential difference existing between the two connections 41a and 41b. In this embodiment, this potential difference is achieved by insulating the two metal structures 22 and 23 from each other, at least in the regions of these connections. This means that for cathodic protection currents from the two metal structures 22 and 23, there are different paths to ground. In this embodiment, the means of insulating the two metal structures 22 and 23 from each other include an insulating coating 91 disposed on the outer surface of the first casing 22 and a plurality of insulating centering devices 92 disposed on the first casing 22 to maintain the separation of the first casing and the second casing 23.

[0600] Preferably, the insulation 91 and these centering devices 92 will be installed over a length of at least 100 meters, and more likely 300 to 500 meters, of the first bushing 22. Where desired and practical, the insulating spacers can be mounted on the metal structure forming the annulus. Thus, for example, in the embodiment described above, they are mounted on the second bushing 23. Note that the insulation does not need to be completely continuous to provide a useful effect. The purpose is to create different paths to ground. Therefore, while insulation may be provided, for example, over 100 meters, it may not be continuous, or it may be continuous insulation over this distance.

[0601] Figure 5 The advantage of the arrangement shown is that it eliminates the need for Figure 1 The arrangement shown requires a long cable 41 located between the collection module 4 and the metal structure 2. This means the system can be installed more easily. For example, the system can be deployed by mounting the housing of the collection module 4 onto a metal pipe and providing a sliding contact that crosses the annulus to contact another pipe. To further simplify the location, the downhole meter 5 can be omitted, and the sensor can be placed together with the collection module 4 in the downhole unit 4a. Such an arrangement can reduce the rig time required for installation.

[0602] Therefore, in some cases, installing insulation devices 91, 92 is preferred over installing cable 41. Which system is preferred for a given facility can be determined by external factors related to the facility or possibly by modeling the specific facility.

[0603] However, in typical cases, where it is feasible to use the system, Figure 1 The arrangement may give a better result than Figure 5 The layout provides better performance.

[0604] exist Figure 5 In the type of arrangement shown, a relatively high current but a relatively low potential difference can be detected by the collection module. Therefore, in Figure 5 In this arrangement, the potential difference can be, for example, 10mV-20mV, and the current can be, for example, 1A. On the other hand, in Figure 1 In this arrangement, the potential difference can be, for example, 100mV-200mV, and the current can be, for example, 100mA-150mA. Higher potential differences are achieved through... Figure 1 The larger spacing provided by the cables 41 in the arrangement is achieved, but the lower current is caused by the resistance of the cables.

[0605] Besides the differences in how the connection is formed and the potential difference is achieved, as well as the accompanying advantages and disadvantages, such as Figure 5 The structure and operation of the system shown are similar to those of,Figure 1 The structure and operation are shown. Therefore, the above text about Figure 1 to Figure 4 The different alternatives explained also apply to the use of, for example Figure 5 The system shown is a system configuration.

[0606] In other words, such as Figure 5 The insulation and connection arrangement shown can be Figure 1 , Figure 3 and Figure 4 In each of the embodiments shown, the collection module 4 and downhole unit 4a of the different forms discussed above are used, and similarly, they can be used in, for example... Figure 5 The arrangement shown is used in the layout.

[0607] Note that in some cases, even if wireless functionality is not intended for use during the initial installation of the well, it may be desirable to use this power delivery system to provide a wireless-ready well facility.

[0608] Therefore, when installing a well for the first time to make it wirelessly ready, it can be set up. Figure 3 The arrangement shown includes a communication repeater 7 and an associated power delivery system enclosed in the B-ring. This would facilitate communication with the surface, for example, the downhole wireless signal transmission tool 71 sending signals to the surface, should a later decision be made to use it. Here, it is noted again that we are referring to "wireless" communication between the downhole and the outside, meaning there are no cables / wires running through the wellhead.

[0609] In other cases, this system can be refurbished. For example, when replacing production tubing, systems such as... Figure 1 The system shown is installed in the A-annulus. In another case, the system can be installed in the master bore of the production tubing. Note, importantly, that each of the arrangements and techniques described in this specification avoids the need for cable penetration into the wellhead 1. Therefore, these systems can be used when no penetrator is available or when using a penetrator is undesirable.

[0610] Although Figure 4 The arrangement shown depicts the installation of an additional underground safety valve 8; however, in other cases, different types of valves or components (potentially remotely operated) may be installed. For example, Figure 4The arrangement of the type shown can be used with an annulus venting valve located in the well to allow controlled fluid communication or venting between one annulus and another, or between an annulus and a borehole. The valve may include a gas lift valve to allow gas to enter the borehole of the production tubing from annulus A. Similarly, the valve may be a packer, a through-packer valve, or a packer bypass valve. Again, it is used to allow controlled venting of a specific annulus from the surface. In another embodiment, the valve may include a flow control valve to control contributions from a region, or to provide means for improved pressure establishment data capture by eliminating the effects of borehole storage. Note that in each case, the valve may be a flow control device that does not allow complete shut-off of flow but, for example, acts as a variable choke.

[0611] In each case, the valve or component can be a wirelessly controlled valve or component.

[0612] In another alternative, this technology can be used to communicate with and / or control tools that are supported or attached to the continuous tubing in production tubing 21 by wireline / slip-line. That is, such tools can be arranged to apply signals to and / or pick up signals from the tubing, the signal transmission being via repeater 7.

[0613] With this type of system, one might be able to extract power at a level of perhaps 50mW. Therefore, the amount of power that can be extracted is not particularly large, but the interesting fact is that this power can be available for the entire life of the well and is sufficient to perform useful functions (such as controlling downhole equipment, making important measurements, and allowing these measurements to be transmitted to the surface).

[0614] Note that usually in Figure 1 to Figure 4 In the general type of implementation shown, the collection efficiency will be dominated by the cross-sectional area of ​​cable 41, and the source impedance provided by connectors 41a and 41b is very low. This means that if multiple collection systems are included in a well facility, there is little degradation in the performance of any one collection module 4. Note that typically any additional collection system will have its own cable 41 where appropriate. This is because losses in the cable mean that by having more than one collection system share a single cable, very little loss will typically be achieved.

[0615] Typically, multiple collection modules of any of the types described above can be installed in a single well facility. Thus, for example, meters can be installed to monitor conditions in the production tubing, meters can be installed to monitor the annulus, and valves can be installed, all powered from separate, respective collection modules. Similarly, any one collection module can be used to power multiple devices. In some cases, each device may have a dedicated cable from the collection module. In other cases, a multi-drop system may be present, where a single cable from the collection module is used to connect to multiple downhole devices. This multi-drop system can be arranged to allow power delivery and communication with multiple downhole devices. Thus, the cable can carry power signals, communication data, and addressing data. Correspondingly, the collection module can be arranged to manage this multi-drop system.

[0616] Note that although in the above-described embodiments, cables 41 and 42 extend within an unobstructed annulus, in other cases, one or more of cables 41 and 42 may pass through a packer (including an expansion packer), cement, or other annular sealing device.

[0617] It should also be understood that, in at least some cases, the features of this system and apparatus may be distributed. Thus, for example, a collection module may be disposed in multiple separate parts, components, or sub-modules that will be located distinctly.

[0618] Figure 6 Alternative well facilities are shown, which are related to Figure 1 The facilities shown are similar, and the same reference numerals are used to indicate the same features. Figure 1 The implementation schemes share common features, but detailed descriptions of these common features are omitted.

[0619] Figure 6 The well facilities shown in the illustrations help to illustrate the references above in more detail. Figure 1 to Figure 5 Some of the described alternatives for each of the well facilities shown and described.

[0620] The well facility is in conjunction with Figure 1The same approach includes monitoring devices. Therefore, there is a collection module 4 connected via cable 41 to a pair of spaced-apart locations 41a and 41b. However, in this case, the first location 41a is located on the production tubing 21, so that the first cable 41 is connected to the production tubing, while the second location 41b is located on the casing 22. Therefore, in this embodiment, there are axial and radial spacings between the connections 41a and 41b, so that the collection module 4 is connected across the “A” annulus. Furthermore, an insulation portion 91 is provided on the production tubing 21 and in the region of the second connection 41b, extending axially on either side of this production tubing. Note that in another alternative, one connection might be connected to the formation rather than to a metal structure. In some cases, all the devices of the power delivery system can be located outside the casing, i.e., between the casing and the formation. From the perspective of installation risk / difficulty, this is generally undesirable, but possible.

[0621] Furthermore, in this embodiment, there are a second collection module 4' and a third collection module 4" (which are part of the corresponding downhole unit) located in the "A" annulus. In this embodiment, each of these other collection modules 4', 4" utilizes the same first cable 41, and thus, one terminal of each collection module 4', 4" is connected to the first connection point 41a. Note that in other embodiments, discrete cables may be used to form these connections to the first connection point, and this would be preferred, resulting in improved performance. A single top cable (as shown), while possible, is unlikely to be used, but it helps to simplify the figures. In some cases, multiple collection modules may be provided, distributed across different annulus sections.

[0622] In this implementation scheme, similar to Figure 1 In the illustrated embodiment, the first collection module 4 is connected to the downhole meter 5 via a secondary cable 42. However, here, the downhole meter 5 is positioned below the packer P, and the cable 42 passes through the packer P. In this case, the meter 5 is arranged to measure the pressure and / or temperature of the interior of the production tubing 21 through a port 21a located in the wall of the production tubing 21. That is, although the downhole meter 5 is located in the "A" annulus, it is arranged to measure parameters within the production tubing 21.

[0623] Furthermore, in this embodiment, a second downhole meter 5' and a third downhole meter 5" are provided. In this embodiment, each of the downhole meters 5, 5', and 5" is connected to the collection module 4 via the same secondary cable 42. Therefore, this is a multi-branch system, and the cable 42 is used to carry power signals, control signals, parameter data, and addressing data to allow power to be supplied to each of the meters 5, 5', and 5" and to retrieve readings from them.

[0624] Note that in alternative embodiments, multiple downhole meters or other downhole devices can be powered from a single collection module 4 via individual dedicated cables 42, instead of a single cable as in this embodiment. Furthermore, as mentioned above, while multiple meters extend from a single collection module in this embodiment, in other embodiments, a single collection module can be used to power different types of downhole devices. Thus, a single collection module can, for example, be used to power downhole meters, downhole repeaters, and downhole valves.

[0625] In this embodiment, the second collection module 4' is part of a downhole tool that includes a collection module and a sensor. In this case, the sensor is arranged to measure parameters in the annulus "B" via a port 22a provided in the first casing 22. Thus, for example, the sensor in the second collection module 4' can be arranged to measure pressure and / or temperature in the annulus "B".

[0626] Furthermore, in this embodiment, the third collection module 4” is again part of a downhole tool, which in this case includes a collection module and a communication unit for communicating with sensors 605 disposed in the “B” and “C” annulus. Here, communication between the sensors 605 and the second collection module 4” is wireless. Therefore, for example, there may be inductive signal transmission or acoustic signal transmission between the sensors 605 and the collection module 4”. The sensors 605 can be placed as physically as possible close to the collection module 4”.

[0627] It should be understood that once the data is at the upper communication unit 6, it can be transmitted forward to any desired location, such as the desktop location D, using standard communication technologies (e.g., mobile communication technologies, the Internet, etc.), for further processing and / or retrieval. Of course, a wired connection can also be established between the desktop location and the upper communication unit 6.

[0628] Furthermore, data can be transmitted from the desktop position D to the upper communication unit 6 for downhole transmission. Therefore, for example, control signals can be transmitted from the desktop position D to the downhole via the upper communication unit 6 to control the operation of collection modules, sensors, downhole valves, or repeaters, and similarly, any desired data can be transmitted downhole in this manner.

[0629] In another alternative, the insulation can be located in the outermost sleeve (e.g., in...). Figure 6 In the illustrated embodiment, the third casing 24 is located on the outside of the casing and in the region near the wellhead 1. This helps to drive the maximum negative potential caused by the cathodic protection current further down into the well. This is due to minimizing leakage in this region near the wellhead. Therefore, providing insulation on the outermost casing helps to allow the uppermost connection 41a to be positioned lower in the well without significantly reducing the effectiveness of the system. If one considers the potential decay curve, by providing insulation on the outermost casing 24, the negative potential will decay very slowly in the insulated region near the wellhead, and then begin to decay more rapidly once it reaches the non-insulated region.

[0630] Figure 7 This is a graph illustrating one embodiment of how the optimal power that can be collected in a well facility varies with the depth of the well. As mentioned above, due to the increase in the available potential difference caused by the increased spacing between the connectors on the one hand and the increased resistance of the cable on the other hand, there tends to be an optimal depth for the lower connector 41b, or in other words, there tends to be an optimal spacing between the two connectors 41a and 41b. Figure 7 The graph shown relates to the location of the upper connection 41a approximately 5 meters below the wellhead, thus within the area of ​​the tailpipe hanger. In this embodiment, it can be seen that the optimal depth of the lower connection is approximately 550 meters downwards in the well. However, it can also be seen that a considerable proportion of the optimal power can be collected at depths, for example, between 300 meters and 950 meters. Generally, it is desirable to minimize the cable length while achieving optimal power collection, which implies minimizing the depth of the second connection. However, there may be cases where the advantage of the collection module being able to be placed deeper in the well can be taken advantage of.

[0631] The optimal location for the upper connection may depend on the location where the injected CP current (or other current) is greatest and the location where the current is greatest or the potential caused by the current is greatest. This method and system may include the following steps: first determining the location where the applied current (or potential) has the greatest magnitude, and selecting the location of the upper connection accordingly.

[0632] When the well is a land-based well, the upper connection can be within 100 meters, preferably within 50 meters, of the ground.

[0633] In the case of a subsea well, the upper connection can be within 100 meters of the mud line, preferably within 50 meters.

[0634] As mentioned above, although the description above involves collecting current from the cathodic protection current, which is preferred, other currents can be used in the same way if they are present in the metal structure.

[0635] It should be understood that although specific embodiments have been given above, in general any of the components of the system can be set in any available annulus.

[0636] In the context of optimizing aspects such as the spacing of connections, the use of insulation, the choice between radial or axial spacing, and the selection of pre-loaded loads, as mentioned above, at least one of the following parameters can be used in the model:

[0637] 1. The attenuation rate at the top of the well, derived from the casing and fitting dimensions, weight, material type (resistivity), and resistivity of the overlying rock formation (the medium surrounding the well).

[0638] 2. Location of the upper connecting part.

[0639] 3. Location of the lower connecting part.

[0640] 4. The cross-sectional area and material (resistivity) type of the upper cable used at the collector input.

[0641] 5. The number, location, material (potential), and surface area of ​​the wellhead anodes.

[0642] 6. The effective resistance of the well as seen from the seabed / wellhead, which is again derived from the resistivity of the casing and fittings dimensions, weight and material type (resistivity) and the overlying rock (the medium surrounding the well), but this time for all.

[0643] In a specific embodiment of the system described above, one or more cables 41 used to connect the collection module to the structure / surrounding environment may have, for example, a 10mm diameter. 2 Up to 140mm 2 The cross-sectional area. 10mm 2 This could be considered the lower end of the desired operating cable size. Normally, a larger cross-sectional area would be preferred. 140mm² 2 The cable is likely a Kerite(RTM) LTF3 flat type cable. This represents the top end of currently commercially available cables; however, larger sizes may be used if available.

[0644] Figure 8 This is a flowchart illustrating the process for optimizing energy harvesting of the type of harvesting module described above.

[0645] In step 801, the DC-DC converter 44 is started using initial setup / configuration and delivers available energy to the charge storage device 45.

[0646] In step 802, it is determined whether there is sufficient voltage to power the microprocessor in the central unit 46. If not, step 802 is repeated until the answer is yes, and when the answer is yes, the process proceeds to step 803, where the microprocessor in the central unit 46 is powered.

[0647] Then, in step 804, the microprocessor measures the power output from the energy harvester, and in step 805, the microprocessor modifies the DC-DC converter 44 settings to slightly increase the load. Subsequently, in step 806, it is determined whether this results in an increase in the harvester output. If the answer is yes, the process returns to before step 805 so that the DC-DC converter 44 settings can be changed again to slightly increase the load.

[0648] On the other hand, if it is determined in step 806 that the output has not increased, the process proceeds to step 807, in which the microprocessor modifies the settings of the DC-DC converter 44 to slightly reduce the load, and the process returns to before step 806, so it can be determined whether this has caused the output to increase.

[0649] Subsequently, steps 805, 806, and 807 are iteratively repeated during energy harvesting, such that the load is continuously increased and decreased based on the results in step 806. This results in dynamic optimization of power harvesting.

[0650] As mentioned above, in the case of DC-DC converter 44 utilizing field-effect transistors and an accompanying transformer, the steps of changing the DC-DC converter settings in steps 805 and 807 may include changing the taps used on the secondary transformer to appropriately modify the load. This is as follows in such a variable transformer setup: Figure 2D The same applies to the H-bridge shown. Alternatively, in such a case, the duty cycle of the transistors in the H-bridge can be adjusted to vary the load.

[0651] Figure 9 A flowchart illustrating the operation of downhole unit 4a of the type described above is shown.

[0652] In step 901, it is determined whether there is sufficient power to power the processor in the central unit 46. If not, the process stops at this step until sufficient power is available.

[0653] When sufficient power is available, the process proceeds to step 902, where it is determined whether a command has been received or whether there is a request to send a predetermined dataset. If not, the process remains in the state of determining whether any action is required until an action is requested.

[0654] When an action is required, the process proceeds to step 903, in which data is recovered from the sensor or from the memory as required, and the load presented by the energy harvester module between the connection parts 41a is modulated to encode the data.

[0655] Discretely at the wellhead, in step 904, the voltage potential at the wellhead is monitored and the data is decoded in a second microprocessor. Then, in step 905, the extracted data can be exported or retransmitted to the client, for example, via a seawater acoustic link or an umbilical link.

[0656] Figure 10 The diagram illustrates a well facility including a platform 1000. A wellhead 1 is located on a deck 1001 of the platform 1000. In this case, the metal structure includes a riser 1002 located between the mudline and the deck 1001. A production tubing 21 extends within the riser 1002 and downhole. Casings 22 and 23 are installed downhole. The innermost casing 22 is a continuation of the riser 1002. A cathodic protection anode 3B is installed on the platform structure 1000. An electrical connection will exist between the platform and the downhole structure 2 (casing and production tubing). This can be via the drill base 1003 and / or via the wellhead, riser, and other components such as riser guides. In such a case, it may be difficult to know the formation... Figure 1 , Figure 3 , Figure 4 or Figure 6 The illustrated type of upper connection is positioned for optimal performance. The location where the cathodic protection current will be injected into the conductive conduit (multiple slender segments) extending downwards into the well will not always be known. As mentioned above, it may be desirable to form the upper connection near the location where the CP current is injected. If optimization is sought, one option is to control this injection point, i.e., ensure current connection at a known point. Another option is to provide the system with multiple alternative upper connection points for the collection module, allowing the most efficient connection point to be selected after installation. Typically, in such cases, the power delivery system will be equipped with multiple upper cable connections to the metal structure, and the best-performing one will be selected by operating a switch, for example, under the control of a central unit.

[0657] Signal, device and sensor options

[0658] The foregoing has described a variety of specific signal transmission techniques. For the avoidance of doubt, it should be noted that in current types of systems, many different signal transmission techniques can be used individually or in combination in multiple parts of the signal channel. Therefore, wireless signals can be transmitted in at least one of the following forms: electromagnetic, acoustic, inductively coupled, and coded pressure pulses, and unless otherwise stated, references to “wireless” herein refer to these forms.

[0659] Unless otherwise stated, signals may include control signals and data signals. Control signals can control downhole equipment, including sensors. Data from sensors can be transmitted in response to control signals. Furthermore, suitable control signals can be used to vary data acquisition and / or transmission parameters (such as acquisition and / or transmission rate or resolution).

[0660] Pressure pulses include a method of communicating at least one of the following: from / to inside the well / bore, from / to another location inside the well / bore, and to the surface of the well / bore, using changes in positive and / or negative pressure and / or changes in the flow rate of fluid in a tubular or annular space.

[0661] Encoded pressure pulses are pressure pulses in which a modulation scheme has been used to encode commands and / or data within pressure or flow rate changes, and a transducer is used within the well / wellbore to detect and / or generate said changes, and / or an electronic system is used within the well / wellbore to encode and / or decode the commands and / or data. Therefore, pressure pulses used with electronic interfaces within the well / wellbore are defined herein as coded pressure pulses. The advantage of coded pressure pulses as defined herein is that they can be sent to electronic interfaces and can provide a greater transmission rate and / or bandwidth than pressure pulses sent to mechanical interfaces.

[0662] When using coded pressure pulses to transmit control signals, various modulation schemes can be used to encode the control signals, such as pressure changes or the rate of pressure change. Combinations of modulation schemes, such as OOK, Pulse Position Modulation (PPM), Pulse Width Modulation (PWM), Frequency Shift Keying (FSK), Pressure Shift Keying (PSK), Amplitude Shift Keying (ASK), and others, such as OOK-PPM-PWM, can be used. The transmission rate used for coded pressure modulation schemes is typically low, usually less than 10 bps, and can be less than 0.1 bps. The coded pressure pulses can be sensed in static or flowing fluids and can be detected by directly or indirectly measuring changes in pressure and / or flow rate. Fluids include liquids, gases, and multiphase fluids, and can be static control fluids and / or fluids produced from or injected into the well.

[0663] Wireless signals can be transmitted through an obstacle (such as a plug or the aforementioned annular sealing device) while it is fixed in place. Therefore, wireless signals can be transmitted in at least one of the following forms: electromagnetic, acoustic, and inductively coupled pipes.

[0664] EM pulses / acoustic pulses and coded pressure pulses use a well, wellbore, or formation as the transmission medium. EM signals / acoustic signals or pressure signals can be transmitted from the well or from the surface. If placed in a well, the EM signal / acoustic signal can travel through any annular seal device; however, in some implementations, it can travel indirectly, such as around any annular seal device.

[0665] Electromagnetic and acoustic signals are useful because they can be transmitted through / through annular sealing devices without special inductive coupling pipework infrastructure, and for data transmission, the amount of information that can be transmitted is normally much higher than that of coded pressure pulses, especially when receiving data from a well.

[0666] In the use of inductively coupled tubing, there are typically at least ten, and usually more, individual lengths of inductively coupled tubing, which are connected together in use to form a series of inductively coupled tubing. They have integral conductors and can be formed into tubing such as tubing, drill pipe, or casing. Inductive coupling exists at each connection between adjacent lengths. Inductively coupled tubing that can be used may be branded Intellipipe and supplied by NOV.

[0667] Therefore, EM signals / acoustic signals or pressure wireless signals can be transmitted over relatively long distances as wireless signals, reaching at least 200m, optionally greater than 400m or longer, which is a significant advantage over other short-range signals. Inductively coupled tubing provides this advantage / effect through a combination of an integrated conductor and an inductive coupler. The travel distance can be even longer, depending on the length of the well.

[0668] Data and commands within a signal can be relayed or transmitted in other ways. Therefore, wireless signals can be converted into other types of wireless or wired signals and optionally relayed in the same way or in other ways (such as hydraulic lines, electrical lines, and fiber optic lines). For example, a signal can be transmitted over a first distance, such as more than 400 meters, via cable, and then over a shorter distance, such as 200 meters, via acoustic or EM communication. In another embodiment, they can be transmitted over 500 meters using coded pressure pulses, and then over 1000 meters using hydraulic lines.

[0669] In addition to wireless methods, non-wireless methods can also be used to transmit signals. The distance the signal travels depends on the depth of the well, and is often a wireless signal, including repeaters but excluding any non-wireless transmissions, traveling greater than 1000 meters or greater than 2000 meters.

[0670] Different wireless signals can be used in the same well for communication from the well toward the surface, and for communication from the surface to the well.

[0671] Wireless signals can be transmitted directly or indirectly to communication devices, such as using in-well repeaters above and / or below any annular sealing device. Wireless signals can optionally be transmitted from the surface or from a probe section of cable / coiled tubing (tractor) above any annular sealing device at any point in the well.

[0672] Acoustic signals and communications can include vibration transmission through the well's structure, including fittings, casing, tailpipe, drill pipe, drill collars, tubing, coiled tubing, sucker rod, and downhole tools; transmission via fluids (including gas), including fluid transmission within the casing-free section of the well, within fittings, and in the annulus; transmission via static or flowing fluids; mechanical transmission via cables, conductors, or coiled rods; transmission via grounding; and transmission via wellhead equipment. Communication via structure and / or fluids is preferred.

[0673] Acoustic transmission can be at subsonic (<20Hz), sound (20Hz-20kHz), and supersonic frequencies (20kHz-2MHz). Preferably, acoustic transmission is sound wave (20Hz-20kHz).

[0674] Acoustic signals and communications may include frequency shift keying (FSK) and / or phase shift keying (PSK) modulation methods, and / or more advanced derivatives of these methods, such as quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM), and preferably incorporate spread spectrum techniques. Typically, they are adapted to automatically tune the acoustic signal transmission frequencies and methods to suit well conditions.

[0675] Acoustic signals and communications can be unidirectional or bidirectional. Piezoelectric transducers, moving-coil transducers, or magnetostrictive transducers can be used to transmit and / or receive signals.

[0676] Electromagnetic (EM) (sometimes referred to as quasi-static (QS)) wireless communication normally operates in the following frequency bands: (selected based on propagation characteristics)

[0677] sub-ELF (extremely low frequency) <3Hz (normal is above 0.01Hz);

[0678] ELF 3Hz to 30Hz;

[0679] SLF (Extra Low Frequency) 30Hz to 300Hz;

[0680] ULF (Extra Low Frequency) 300Hz to 3kHz; and,

[0681] VLF (Very Low Frequency) 3kHz to 30kHz.

[0682] An exception to the frequencies mentioned above is EM communication using tubes as waveguides, particularly, but not only, when the tube is filled with gas. In this case, frequencies typically ranging from 30 kHz to 30 GHz can be used, depending on the tube size, the fluid in the tube, and the communication range. The fluid in the tube is preferably non-conductive. US 5,831,549 describes a telemetry system relating to gigahertz transmission in a gas-filled tubular waveguide.

[0683] Sub-ELFs and / or ELFs are useful for well-to-surface communication (e.g., over distances of 100 meters or more). For more local communication, such as less than 10 meters, VLFs are useful. The nomenclature used for these ranges is defined by the International Telecommunication Union (ITU). EM communication may include transmitting communication via one or more of the following: imposing a modulated current on an elongated member and using ground as a return path; transmitting current in a pipe fitting and providing a return path in a second pipe fitting; using a second well as part of the current path; near-field or far-field transmission; creating a current loop within a portion of the well metalwork to create a potential difference between the metalwork and ground; using spaced-out contacts to create an electric dipole transmitter; imposing current in the well metalwork using a toroidal transformer; using an insulator (insulating sub); a coil antenna to create a modulated time-varying magnetic field for local transmission or transmission through the formation; transmission within the well casing; using an elongated member and ground as a coaxial transmission line; using a pipe fitting as a waveguide; and transmission to the outside of the well casing.

[0684] Particularly useful are the application of modulated current to a slender member and the use of ground as a return path; the creation of a current loop within a portion of a well metalwork to create a potential difference between the metalwork and ground; the use of spaced-out contacts to create an electric dipole emitter; and the use of a toroidal transformer to apply current to a well metalwork.

[0685] To advantageously control and guide current, many different techniques can be used. For example, one or more of the following: using an insulating coating or spacer on the well fitting; selecting well control fluid or cement inside or outside the well fitting to conduct electricity or insulate it from the fitting; using a high-permeability helical tube to create inductance, thereby generating impedance; using insulated wires, cables, or insulated slender conductors for the transmission path or part of an antenna; using the fitting as a circular waveguide, using the SHF (3 GHz to 30 GHz) band and the UHF (300 MHz to 3 GHz) band.

[0686] Various devices can be used to receive the transmitted signal, including: detecting current flow; detecting potential difference; using a dipole antenna; using a coil antenna; using a toroidal transformer; using a Hall effect or similar magnetic field detector; and using a section of well metal as part of a dipole antenna.

[0687] When using the phrase "slender member," for the purposes of EM transmission, it can also refer to any slender electrical conductor, including: tailpipe; casing; tubing or fittings; coiled tubing; sucker rod; steel cable; borehole pipe; conductor rail or continuous rod.

[0688] The meter may include one or more of a variety of different types of sensors. The sensor, or each sensor, may be coupled (physically or wirelessly) to a wireless transmitter, and data may be transmitted from the wireless transmitter to above the annular sealing device or toward the ground. Data may be transmitted in at least one of the following forms: electromagnetic, acoustic, and inductively coupled, particularly acoustic and / or electromagnetic as described above herein.

[0689] Such short-range wireless coupling can be facilitated through EM communication within the VLF range.

[0690] The sensors can sense any parameter and therefore can be of any type, including but not limited to, such as temperature, acceleration, vibration, torque, movement, motion, cement integrity, pressure, direction and tilt, load, various fitting / casing angles, corrosion and erosion, radiation, noise, magnetic force, seismic movement, stress and strain on fittings / casing, including torsion, shear, compression, expansion, buckling, and any form of deformation; detection of chemical or radioactive tracers; fluid identification (such as gas detection); water detection, carbon dioxide detection, hydrate, wax, and sand production; and fluid properties such as (but not limited to) flow, density, water cutting, resistivity, pH, viscosity, bubble point, gas / oil ratio, hydrocarbon composition, fluid color, or fluorescence. Sensors can be imaging devices, mapping devices, and / or scanning devices, such as, but not limited to, cameras, video, infrared, magnetic resonance, acoustic, ultrasonic, electrical, optical, impedance, and capacitance. Sensors can also monitor equipment in the well, such as valve position or motor rotation. Furthermore, sensors can be adapted to induce signals or parameters detected by incorporating suitable transmitters and mechanisms.

[0691] The device (especially the sensor) may include a storage device that can store data for retrieval at a later time. In some cases, the storage device can also be retrieved and the data restored after retrieval. The storage device may be configured to store information for at least one minute, optionally at least one hour, more preferably at least one week, preferably at least one month, more preferably at least one year or more than five years.

Claims

1. A downhole power harvesting system for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged to carry cathodic protection current during use, the system comprising: A collection module is electrically connected at a first position to at least one section of downhole metal pipe of the metal structure and at a second position spaced apart from the first position to at least one section of downhole metal pipe of the metal structure. The first and second positions are selected such that, in use, a cathodic protection current flows in at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing in the at least one section of downhole metal pipe. and The collection module is connected between the first position and the second position and is arranged to collect electrical energy from the potential difference existing between the first position and the second position due to the cathodic protection current, wherein the collection module includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe.

2. The downhole power harvesting system according to claim 1, wherein the electrical connection between the harvesting module and the at least one section of the downhole metal pipe of the metal structure at at least one of the first and second positions is provided by an insulated cable, wherein the insulated cable has a conductive area of ​​at least 10 mm², and further wherein the interval between the first and second positions is at least 100 m.

3. The downhole power harvesting system according to claim 1 or 2, wherein: In the case of a land-based well, the upper, spaced-out contact portions are within 100m of the land surface; and In the case of a subsea well, the upper spaced-out contact portions are within 100m of the mudline.

4. A downhole equipment operating system comprising a downhole power harvesting system according to any of the preceding claims and a downhole device, the harvesting module being electrically connected to the downhole device and arranged to provide power to the downhole device.

5. A downhole monitoring system for monitoring at least one parameter in a well facility with a current-carrying metallic structure, the system comprising: An energy harvesting system according to any one of claims 1 to 3; A sensor module for sensing at least one parameter; as well as A communication module is used to transmit data encoded from the readings of the sensor module toward the ground. The energy harvesting system is arranged to supply electrical power to at least one of the sensor module and the communication module.

6. A downhole monitoring system for monitoring at least one parameter in a well facility with a current-carrying metallic structure, the system comprising: A sensor module for sensing at least one parameter; A communication module for transmitting data encoded from readings received from the sensor module toward the ground; as well as An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged such that it carries a cathodic protection current in use, the energy harvesting system including a harvesting module electrically connected at a first position to the at least one section of downhole metal pipe of the metal structure and electrically connected at a second position spaced apart from the first position, the first and second positions being selected such that, in use, a cathodic protection current flows in at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing in the at least one section of downhole metal pipe; The collection module is connected between the first position and the second position and is arranged to collect electrical energy from the potential difference between the first position and the second position caused by the cathodic protection current. The collection module includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe. The energy collection system is arranged to supply electrical power to at least one of the sensor module and the communication module.

7. A downhole communication repeater system for use in well facilities with current-carrying metallic structures, the system comprising: An energy harvesting system according to any one of claims 1 to 3; as well as A communication repeater is disposed in and located below the wellhead, and is configured to communicate with a first device extending beyond the wellhead using a wireless communication channel that passes at least through the wellhead, and is also configured to communicate with a second device located in and below the wellhead, such that the communication repeater can act as a relay between the first and second devices. The power harvesting system is configured to supply electrical power to the communication repeater.

8. A downhole communication repeater system for use in well facilities with current-carrying metallic structures, the system comprising: A communication repeater is arranged in and below a well and is configured to communicate with a first device beyond the wellhead using a wireless communication channel that passes at least through the wellhead and to communicate with a second device located in the well and thus below the wellhead, such that the communication repeater can act as a repeater between the first device and the second device. as well as An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged such that it carries a cathodic protection current in use, the energy harvesting system including a harvesting module electrically connected at a first position to the at least one section of downhole metal pipe of the metal structure and electrically connected at a second position spaced apart from the first position, the first and second positions being selected such that, in use, a cathodic protection current flows in at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing in the at least one section of downhole metal pipe; The collection module is connected between the first position and the second position and is arranged to collect electrical energy from the potential difference between the first position and the second position caused by the cathodic protection current. The collection module includes a DC-DC converter for collecting electrical energy from DC current flowing in at least one section of downhole metal pipe. The energy collection system is arranged to supply electrical power to the communication repeater.

9. A downhole equipment operating system for operating downhole equipment in a well facility with a current-carrying metallic structure, the system comprising: A downhole device; An energy harvesting system is provided for harvesting electrical energy from DC current in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged such that it carries a cathodic protection current in use, the energy harvesting system including a harvesting module electrically connected at a first position to the at least one section of downhole metal pipe of the metal structure and electrically connected at a second position spaced apart from the first position, the first and second positions being selected such that, in use, a cathodic protection current flows in at least one section of downhole metal pipe between the first and second positions, such that a potential difference exists between the first and second positions due to the cathodic protection current flowing in the at least one section of downhole metal pipe; The collection module is connected between the first position and the second position and is arranged to collect electrical energy from the potential difference between the first position and the second position caused by the cathodic protection current. The collection module includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe. The energy collection system is arranged to supply electrical power to the downhole equipment.

10. A method for harvesting electrical energy from DC current to power downhole equipment in a well facility having a metal structure, the metal structure being provided with cathodic protection and including at least one section of downhole metal pipe, the metal structure being arranged to carry cathodic protection current during use, the method comprising the steps of: A collection unit is electrically connected at a first position to at least one section of downhole metal pipe of the metal structure and at a second position spaced apart from the first position to at least one section of downhole metal pipe of the metal structure. The first and second positions are selected such that a potential difference exists between the first and second positions due to a cathodic protection current flowing in the at least one section of downhole metal pipe between the first and second positions. The collection unit is arranged to collect electrical energy from the potential difference between the first and second positions due to the cathodic protection current when connected between the positions with the potential difference. The collection unit includes a DC-DC converter for collecting electrical energy from DC current flowing in the at least one section of downhole metal pipe. Electric power is collected from the cathodic protection current at the collection unit; as well as The collection unit supplies electrical power to the downhole equipment.

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