WO2016089398A1

WO2016089398A1 - System and method for isolating capacitor bank

Info

Publication number: WO2016089398A1
Application number: PCT/US2014/068418
Authority: WO
Inventors: Qing Zhang; Christian Robert Keppeler; Peter R. SWINBURNE
Original assignee: Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Holdings Limited; Schlumberger Technology B.V.; Prad Research And Development Limited; Schlumberger Technology Corporation
Priority date: 2014-12-03
Filing date: 2014-12-03
Publication date: 2016-06-09
Also published as: AR102875A1

Abstract

A technique facilitates the use of capacitors in a subterranean environment. A well tool is constructed for deployment in a borehole and comprises a capacitor bank. The capacitor bank is prepared by electrically linking capacitors in series and in parallel. Additionally, the capacitor bank is electrically coupled with a circuit board which may be mounted to a body of the well tool. The capacitor bank is mounted in a shock isolating relationship with respect to the body of the well tool so as to protect the capacitor bank during deployment and operation in a subterranean, e.g. wellbore, environment.

Description

SYSTEM AND METHOD FOR ISOLATING CAPACITOR BANK

BACKGROUND

[0001] Many types of downhole tools are powered tools supplied with electrical power from the surface or from a storage device, e.g. a battery and/or capacitors, located downhole. In certain perforating operations, for example, power is supplied to a downhole perforating gun by a battery. The electrical power may be used to control and trigger detonators which initiate detonation of shaped charges oriented to create perforations into the surrounding formation. However, the power sources and circuitry associated with the power sources can be susceptible to the harsh subterranean conditions and to shock loading which can occur during a perforating operation or other downhole related operation.

SUMMARY

[0002] In general, the present disclosure provides a system and method for using capacitors in a subterranean environment. A well tool is constructed for deployment in a borehole and comprises a capacitor bank. The capacitor bank is prepared by electrically linking capacitors in series and in parallel. Additionally, the capacitor bank is electrically coupled with a circuit board which may be mounted to a body of the well tool. The capacitor bank is mounted in a shock isolating relationship with respect to the body of the well tool so as to protect the capacitor bank during deployment and operation in a subterranean, e.g. wellbore, environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0004] Figure 1 is a schematic illustration of an example of a well system having a well tool with a capacitor bank isolated from shock loads, according to an embodiment of the disclosure;

[0005] Figure 2 is a schematic illustration of another example of a well system in which the well tool comprises a perforating assembly utilizing an isolated capacitor bank, according to an embodiment of the disclosure;

[0006] Figure 3 is an illustration of an example of a perforating assembly, according to an embodiment of the disclosure;

[0007] Figure 4 is a schematic illustration of an example of a capacitor bank which may be used with a well tool or other suitable tool, according to an embodiment of the disclosure;

[0008] Figure 5 is an illustration of a capacitor in a capacitor bank having a floating mount with respect to a circuit board and thus with respect to a body of the well tool, according to an embodiment of the disclosure;

[0009] Figure 6 is an illustration of a capacitor bank assembled onto a circuit board with a floating mount formed of a potting material, according to an embodiment of the disclosure; and

[0010] Figure 7 is a bottom view of the circuit board illustrated in Figure 6, according to an embodiment of the disclosure.

DETAILED DESCRIPTION [0011] In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or

methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0012] The disclosure herein generally relates to a technique for using capacitors in a subterranean environment. In well applications, for example, a well tool is constructed for deployment in a borehole and comprises a capacitor bank which is used to supply electrical power and/or to provide general-purpose filtering of electric signals. The capacitor bank also may be used in cooperation with a battery to store a voltage that has been stepped up from the voltage supplied by the battery. Additionally, the capacitor bank may be mounted to a body of the tool in a manner which isolates the capacitor bank from shock loads incurred during movement downhole into a wellbore and/or during operation of the well tool.

[0013] According to an embodiment, the capacitor bank is prepared by electrically linking capacitors in series and in parallel. The series coupling may be used to extend a direct current (DC) working voltage, and the parallel coupling may be used to achieve a desired level of capacitance. In an embodiment, the capacitor bank also may be electrically coupled with a circuit board mounted to the body of the tool, e.g. well tool. In this example, the capacitor bank is mounted in a shock isolating relationship with respect to the body of the tool so as to protect the capacitor bank from shock loads. The shock isolating mounting may be achieved by coupling the capacitor bank to the circuit board and/or tool body with a floating mount which may be provided by mounting the capacitor bank in a potting material. The potting material also may be used to protect the capacitor bank from a potentially harsh surrounding environment. To further isolate the capacitor bank from shock loads, the plurality of capacitors may be soft leaded to the circuit board, e.g. printed circuit board. By way of example, flexible wires may be used to electrically couple the plurality of capacitors to corresponding pads on the circuit board. [0014] Referring generally to Figure 1, an example of a well system 20 is illustrated as comprising a tool 22, e.g. a well tool. The well tool 22 is deployed to a subterranean location 24 to perform a desired operation, such as a perforating operation. In the example illustrated, the well tool 22 is deployed downhole in a wellbore 26 via a conveyance 28 which may be in the form of coiled tubing or a wireline. The conveyance 28 is deployed downhole from surface equipment 30 which may be positioned at a surface location 32, e.g. an Earth surface or seabed. It should be noted that tool 22 may comprise a variety of well tools or non-well related tools depending on the application.

[0015] In the embodiment illustrated, tool 22 is in the form of a well tool having an electrically operated device 34. By way of example, the electrically operated device 34 may be a perforating gun with electrically controlled detonators. However, device 34 also may comprise a variety of electrically operated valves, sensors, gauges, triggers, and/or other devices. The electrically operated device 34 is controlled via a local or downhole control system 36 which comprises a plurality of capacitors in the form of a capacitor bank 38 mounted to a body 40 of the tool 22. The downhole control system 36 may be coupled with a surface control 42 via a suitable communication line 44.

Depending on the application, the communication line 44 may be a hardwired communication line, wireless communication line, or a combination of wired and wireless communication lines depending on the telemetry system employed in well system 20.

[0016] The capacitor bank 38 may be used in a variety of downhole operations such as, but not limited to, wireline operations, coiled tubing operations, and/or drilling operations For example, the capacitor bank 38 may be used to provide electrical energy storage for downhole perforating tools deployed by wireline or coiled tubing. In some applications, however, the capacitor bank 38 may be used as a general-purpose filtering capacitor bank for downhole tools that perform in high temperature, high- voltage, and high shock environments. As described in greater detail below, the structure of capacitor bank 38 and downhole control system 36 isolates the capacitors in capacitor bank 38 from shock and/or vibration loads that could otherwise have a detrimental impact on the functional longevity of the control system 36.

[0017] Referring generally to Figure 2, a specific example of well system 20 is illustrated. In this embodiment, the well tool 22 comprises a perforating gun assembly 46 deployed downhole into wellbore 26 via conveyance 28 in the form of coiled tubing 48. The coiled tubing 48 is deployed downhole through a wellhead 50 of surface equipment 30 via a coiled tubing injector 52. The coiled tubing 48 is delivered through coiled tubing injector 52 from a coiled tubing reel 54 which may be unspooled and spooled to convey well tool 22 downhole and to retrieve to well tool 22, respectively. In this example, the communication line 44 may be routed along and/or within coiled tubing 48, such as within the internal flow path defined by the coiled tubing 48.

[0018] Control over the coiled tubing reel 54 and/or control over signals sent to or received from well tool 22 may be controlled by surface control 42. In this example, the surface control 42 is a computer-based control system which may comprise a control computer 56 and supporting equipment 58. Additionally, a coiled tubing controller 60 may be coupled with surface control 42 and positioned to control operation of coiled tubing reel 54. Power may be provided to controller 60 via a suitable battery 62. A pressure bulkhead 64 also may be coupled with the coiled tubing 48 and with the controller 60 to control pressure within the coiled tubing 48. In a specific example, the controller 60, battery 62, and pressure bulkhead 64 may be used in an intelligent perforating platform, such as a combined perforating tool and ACTive™ coiled tubing downhole platform available from Schlumberger Corporation.

[0019] When tool 22 comprises a perforating gun assembly 46, a variety of components may be employed in the perforating gun assembly 46 according to the parameters of a given perforating application. By way of example, the capacitor bank 38 may be mounted to a perforating head 66 of the perforating gun assembly 46, as illustrated in Figure 3. Examples of other components of perforating gun assembly 46 comprise a coiled tubing head 68 by which the tool 22/assembly 46 is coupled with coiled tubing 48. Additionally, the perforating gun assembly 46 may comprise an optical motor head assembly 70, a pressure-temperature collar 72, a casing collar locator 74, and an exit port 76.

[0020] In some embodiments, the capacitor bank 38 works in cooperation with a battery 78 of a battery module 80. For example, the capacitor bank 38 may be used to store a voltage that has been stepped up from the battery supplied voltage from battery 78. The stored voltage is at a level suitable for actuating the electrically operated device 34. In the example illustrated, the electrically actuated device 34 may comprise a gun string 82 having a plurality of electrically actuated detonators 84 associated with corresponding shaped charges. The gun string 82 may be connected to perforating head 66 by a suitable adapter 86.

[0021] Referring generally to Figure 4, an example of the capacitor bank 38 is illustrated schematically. In this example, the capacitor bank 38 comprises a plurality of capacitors 88. At least some of the capacitors 88 may be operated in series to extend a direct current working voltage. An example of the capacitors 88 connected in series is illustrated by the encircled group 90 of capacitors 88. Additionally, at least some of the capacitors 88 may be operated in parallel to achieve a capacitance desired for a specific application. An example of the capacitors 88 connected in parallel is illustrated by the encircled group 92 of capacitors 88. A variety of capacitors 88 may be used to create the capacitor bank 38, however, an example of a suitable capacitor is the Wet Tantalum Capacitor™ available from VISHAY™ Corporation. For example, a plurality of the Wet Tantalum Capacitors™ may be coupled together in series and in parallel as illustrated in Figure 4 to extend the capacitance and to provide the desired direct current working voltage. This type of capacitor also has demonstrated a good tolerance for high temperature, high shock load environments although the capacitor bank 38 is further isolated from shock loads, as described in greater detail below.

[0022] According to an embodiment, a plurality of balance resistors 94 is coupled with the capacitor bank 38 to ensure the voltage is evenly distributed for series operation of the capacitors 88, for example by ensuring that the current flow during discharge of the capacitors 88 does not cause an imbalance of voltage across any one parallel set of capacitors. The balance resistors 94 also ensure that the capacitor bank 38 is self- discharging. In the example illustrated, six balance resistors 94 are electrically coupled with the plurality of capacitors 88. However, the number and arrangement of balance resistors 94 may be changed according to the number of capacitors 88 employed in capacitor bank 38 and according to the parameters of a given application.

[0023] To enable operation of the capacitor bank 38 in high shock load environments, the capacitor bank 38 and the individual capacitors 88 are further isolated from shock loading. For example, the isolation protects capacitors 88 against shock loading that can be incurred by the well tool 22 during deployment and/or operation in wellbore 26. According to an embodiment, the capacitor bank 38 is mounted to body 40 of tool 22 by a floating mount 96, as illustrated in Figure 5.

[0024] In some embodiments, the capacitor bank 38 and its capacitors 88 are mounted to a circuit board 98, e.g. a printed circuit board, by floating mount 96. In turn, the circuit board 98 is mounted to body 40 of tool 22, e.g. to perforating head 66 of perforating gun assembly 46. In an embodiment, the floating mount 96 is formed by a potting material 100. For example, the plurality of capacitors 88 may be potted in potting material 100 which holds them in a floating relationship, i.e. floating mount 96, with respect to the corresponding circuit board 98.

[0025] To further ensure floating isolation of the capacitors 88 from the circuit board 98 and tool body 40, the plurality of capacitors may be soft leaded to a plurality of conductive pads 102 on circuit board 98. For example, lead wires 104 may be coupled between the capacitor bank 38 and the conductive pads 102 to electrically couple the capacitor bank 38 with circuit board 98. The lead wires 104 are provided with sufficient slack to ensure the floating isolation. The lead wires 104 may be electrically connected to conductive pads 102 by soldering or by other suitable coupling techniques. In some applications, the soft lead wires 104 also may be formed with service loops 106 which may be located between the capacitors 88 of capacitor bank 38 and the circuit board 98. In an embodiment, the lead wires 104 are formed from a multi-strand wire gauge that allows for adequate movement of the lead wires 104 during, for example, shock load conditions. The lead wires 104 are selected to have insulators to provide adequate insulation during high voltage conditions, such as about 600 volts. The electrical connection between the lead wires 104 and the conductive pads ensures that there is no wicking of solder in the connection.

[0026] According to a specific application, the capacitors 88, capacitor bank 38, lead wires 104, and other circuit board components 108 may be potted with potting material 100, as illustrated in Figure 6. An example of a suitable potting material 100 is Nusil™ R2188, although other potting compounds may be used depending on the characteristics of the application and the environment in which tool 22 is operated. The potting material 100 may be used to cover the entire body of each capacitor 88 so that the capacitors are fully encapsulated. By using the soft lead wires 104, the service loops 106, and the potting material 100 between the capacitors 88 and the corresponding circuit board 98, the capacitor bank 38 is provided with a floating, shock isolating relationship with the corresponding tool body 40. The components and structure effectively establish the floating mount 96 between capacitor bank 38 and tool 22. Although Fig. 6 shows ten capacitors 88 disposed on the circuit board 98, in an embodiment or embodiments, the capacitor bank 38 may comprise more or fewer capacitors 88 as part of the capacitor bank, as will be appreciated by those skilled in the art.

[0027] Additionally, both the floating mount 96 and the shock absorbing characteristics of the potting material 100 cooperate to further isolate the capacitor bank 38 and to protect the capacitors 88 against shock loads during deployment and operation of tool 22. This structure provides a suitable coupling between the capacitor bank 38 and the corresponding circuit board 98 and tool body 40 while also protecting the components from the harsh downhole environment. Floating the capacitors 88 in the potting material 100 also reduces the mass coupling, thus further improving shock tolerance of the capacitor bank 38. [0028] In many applications, the capacitors 88 are not laced, e.g. tied, to the circuit board 98 so as to ensure the floating relationship between the capacitor bank 38 and the circuit board 98 is maintained during operation. To further protect both the capacitor bank 38 and the circuit board 98, the wiring, e.g. lead wires 104 and other appropriate wiring, may be maintained on one side of the circuit board 98 such that traces or vias are not exposed on the opposite side of the circuit board. An example is illustrated in Figure 7 which shows the vacant opposed side of circuit board 98.

[0029] As described above, the tool 22 may be used with capacitor bank 38 in a variety of systems such as perforating gun systems or other well related systems. Various tools and capacitor banks also may be combined for use in non-well applications in which capacitors of the capacitor bank benefit from shock load protection. The various components of the tool 22 and overall system 20 also may be changed to accommodate the parameters of a given application. In well related applications, for example, various conveyances may be used to convey the gun string assembly or other type of well tool into a variety of wellbores. Additionally, many types of downhole control systems and surface control systems may be used to control the operation of the downhole tool as well as the deployment of that tool. The capacitor bank 38 may be coupled with many types of electrically actuated devices 34, e.g. electrically actuated perforating gun detonators 84, depending on the specifics of the application. Additionally, the type of capacitors, potting materials, circuit boards, and other components and materials associated with the capacitor bank may be adjusted according to environmental and/or operational considerations. In a given example, the capacitors 88 may comprise VISHAY™ capacitors rated 27 μΡ and 125 V, however many other types of capacitors and capacitors with other ratings to be used to form the capacitor bank 38.

[0030] Although a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

CLAIMS What is claimed is:

1. A system for storing and providing electric power, comprising: a well tool for deployment in a wellbore, the well tool comprising:

a plurality of capacitors, at least some of the plurality of capacitors being electrically coupled in series to extend a direct current working voltage and at least some of the plurality of capacitors being coupled in parallel to achieve a desired level of capacitance; and

a printed circuit board having a plurality of pads, the plurality of capacitors being soft leaded to the plurality of pads, the plurality of capacitors being mounted with a floating mount with respect to the printed circuit board.

2. The system as recited in claim 1, wherein the plurality of capacitors is potted in a potting material such that the plurality of capacitors is floating in the potting material.

3. The system as recited in claim 1, wherein the plurality of capacitors is not laced to the printed circuit board.

4. The system as recited in claim 1, wherein the well tool further comprises a

plurality of balance resistors electrically coupled to the plurality of capacitors to ensure voltage is evenly distributed for series operation.

5. The system as recited in claim 1, wherein the plurality of capacitors stores a

voltage that has been stepped up from a battery supplied voltage.

6. The system as recited in claim 1, where in the well tool comprises a perforating tool.

7. The system as recited in claim 1, further comprising a coiled tubing coupled to the well tool to convey the well tool into the wellbore.

8. The system as recited in claim 1, further comprising a wireline coupled to the well tool to convey the well tool into the wellbore.

9. The system as recited in claim 6, wherein the printed circuit board is mounted in a perforating head of the perforating tool.

10. A method for using capacitors in a downhole environment, comprising: preparing a capacitor bank by electrically linking capacitors in series and in parallel;

electrically coupling the capacitor bank with a circuit board and maintaining the capacitor bank in a floating relationship with respect to the circuit board; and

mounting the capacitor bank to a body of a well tool via the circuit board, the well tool being of the type used in a downhole environment.

11. The method as recited in claim 10, wherein electrically coupling comprises

connecting soft lead wires between the capacitor bank and the circuit board.

12. The method as recited in claim 11, further comprising arranging the soft lead wires with service loops located between the capacitor bank and the circuit board.

13. The method as recited in claim 10, wherein mounting comprises mounting the capacitor bank to a perforating tool.

14. The method as recited in claim 13, wherein mounting comprises mounting the capacitor bank to a perforating head of the perforating tool.

15. The method as recited in claim 10, further comprising conveying the well tool downhole into a wellbore.

16. The method as recited in claim 10, further comprising using the capacitor bank for electrical energy storage.

17. The method as recited in claim 10, further comprising using the capacitor bank for general-purpose filtering of an electrical signal in the downhole environment.

18. The method as recited in claim 10, further comprising electrically coupling

balance resistors to the capacitor bank; and using the balance resistors to ensure voltage is evenly distributed in the capacitor bank for series operation.

19. A system, comprising : a well tool deployed downhole on a conveyance, the well tool comprising an electrically operated device and a capacitor bank coupled with the electrically operated device, the capacitor bank having capacitors connected in series and in parallel to store electrical energy for selective operation of the electrically operated device, the capacitor bank having a floating mount with respect to a body of the well tool to isolate the capacitor bank from shock loads.

20. The system as recited in claim 19, further comprising a potting material used to encapsulate the capacitor bank and to provide the floating mount.