WO2009097483A1

WO2009097483A1 - Method and apparatus for communication in well environment

Info

Publication number: WO2009097483A1
Application number: PCT/US2009/032537
Authority: WO
Inventors: Bernard G. Juchereau; John R. Lovell; Christian Chouzenoux; Max Kante; Julius Kusuma; Salman Khan
Original assignee: Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Holdings Limited; Schlumberger Technoloogy B.V.; Prad Research And Development Limited
Priority date: 2008-02-01
Filing date: 2009-01-30
Publication date: 2009-08-06
Also published as: BRPI0906355A2; NO20100997L; NO342772B1; GB201011845D0; BRPI0906355B8; GB2470303B; GB2470303A; BRPI0906355B1

Abstract

A technique enables the transfer of signals in subsea well applications. The technique allows a communication signal and a power signal to be transferred through a single penetration disposed through a tubing hanger of a subsea tree. The communication signal and/or the power signal is converted so as to enable communication along a twisted pair for transfer downhole.

Description

METHOD AND APPARATUS FOR COMMUNICATION IN WELL ENVIRONMENT

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present document is based on and claims priority to U.S. Provisional

Application Serial No. 61/025560, filed February 1, 2008, the contents of which are incorporated herein by reference.

BACKGROUND Field of the Invention

[0002] Embodiments of the present invention generally relate to communication systems and more specifically relate to downhole communication of power and signals.

Description of the Related Art

[0003] The following descriptions and examples are not admitted to be prior art by virtue of their inclusion in this section.

[0004] In many well related applications, wellbores are drilled to facilitate recovery of hydrocarbons in subterranean formations. Various systems, methods and downhole tools benefit from the use of electrical wireline to enable transfer of communication signals downhole. For example, precise temperature measurement devices may be deployed along a sandface, and inductive coupling may be used to communicate data from the devices to an upper completion. From there, a downhole communication hub is able to transfer that data to the seabed. Various techniques are used to transfer the data past the subsea tree and to a surface collection location. However, a variety of difficulties arises in passing certain types of signals or combinations of signals to or from a device located in the well beneath the subsea tree. SUMMARY

[0005] In general, the present invention provides a system and methodology for transferring signals in subsea well applications. In one embodiment, a communication signal and a power signal are provided through a single line disposed through a tubing hanger of a subsea tree. At least one of the communication signal and the power signal is converted so as to enable communication along a twisted pair located within a subsea well.

[0006] Other or alternative features will become apparent from the following description, from the drawings, and from the claims,

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Certain embodiments of the invention 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 drawings illustrate only the various implementations described herein and are not meant to limit the scope of various technologies described herein. The drawings are as follows:

FIG. 1 is a schematic view of a subsea well system comprising a signal communication system, according to an embodiment of the present invention;

FIG. 2 is a schematic illustration of a signal conversion system for use with the subsea well system, according to an embodiment of the present invention;

FIG. 3 is another schematic illustration of the signal conversion system, according to an embodiment of the present invention;

FIG. 4 is a schematic illustration of an alternate signal conversion system, according to an embodiment of the present invention;

FIG. 5 is another schematic illustration of an alternate signal conversion system, according to an embodiment of the present invention; and

FIG. 6 is another schematic illustration of an alternate signal conversion system, according to an embodiment of the present invention. DETAILED DESCRIPTION

[0008] In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0009] The present invention generally relates to a system and methodology for use in a subsea well application. The system and methodology utilize a communication system that facilitates communication between devices in a subsea well and devices above the subsea floor, such as devices located at the surface. In applications described herein, the transfer of communication signals and/or power signals is facilitated by a unique signal conversion system. In many applications, signals are transferred via twisted pair telemetry, and various communication protocols can be employed. With twisted pair telemetry, communication across the subsea tree, sometimes referred to as a Christmas tree, utilizes two electrical contacts and can be accomplished either with two penetrations or a single pin penetration using a two-pole connector. As described below, the present system and methodology facilitates use of single pin penetrations. [0010] The system and methodology also enable at least some degree of standardization of subsea trees that can lead to significant cost savings, particularly when deployed across large fields. Sometimes, not all the wells in a given field use twisted pair telemetry, and various solutions can be applied to maintain the same subsea tree topology regardless of the control lines used. For example, suitable wiring can be provided so that two single pins or one dual-pole can be configured such that the subsea tree need not change from twisted-pair to single pair.

[0011] However, another option is described in greater detail below and utilizes an electronic conversion system positioned below the subsea tree/wellhead. The electronic conversion system may communicate up over a single pin penetration and down over a twisted pair. Consequently, all of the subsea trees in a given field can use a single pin, single pole connector. [0012] Twisted pair telemetry is a technology that can be used in many communication systems. The twisted pair communication systems enable a balanced communication protocol in which energy moving down one wire is matched by the corresponding energy moving up the other wire. This is typically referred to as a Differential Mode of transmission. Because the wires are twisted in the twisted pair, any noise entering the system enters identically on both wires and is commonly referred to as a Common Mode signal. Circuits can be constructed to distinguish Common Mode from Differential Mode and generally involve subtracting the signal on one line from the signal on the other line. Consequently, the Common Mode disappears whereas the Differential Mode is doubled.

[0013] A main source of noise in a subsea system is "ground" noise and is due to the change of potential resulting from, for example, activation of large equipment, pumps, boosters, valves, and other devices. Such noise enters directly into the Common Mode and can be difficult to block out, unless the system has two wires. When downhole tools are activated, Common Mode is created and can be transmitted in the same frequency band as the communication telemetry, thus further complicating modulation and demodulation.

[0014] A partial solution to separating out Common Mode is to allow communication only in one direction and to significantly lower the amount of data. For example, the system can be limited to pressure/temperature gauges on a single line. Additionally, downward communication to the gauges may be restricted. In this latter case, a frequency shift keying interface card may be used inside the subsea tree for the demodulation. Communication can be accomplished across a single-pin at the subsea tree. However, even with analog and digital filtering, the communication may be vulnerable to activation of some types of electric submersible pumps. [0015] Twisted pair telemetry also may be used in a temperature array system for not only noise rejection but also to enable bidirectional communication. In this application, minimization of the power budget may be an important parameter in a subsea deployment. Each time a temperature array is deployed, a technician and/or field engineer adjusts the current and voltage settings across the array. The amount of adjustment depends on the length of completion, the components, and even the efficiency of the clamping and protection of the sensors. Often times the amount of adjustment cannot be predicted in advance. In addition, it may be inefficient to fix the power setting at a high level due to potential factors such as poor grounding between two completion components. Moreover, during production to the subsea manifold, the temperature array system may only be operated once every few days in a manner, for example, timed to match when three-phase flow data is available. As a result, bidirectional communication can be useful as a component of a temperature array system. [0016] Furthermore, twisted pair telemetry can be beneficial for power management. Electrical transmission through a well system is not just for providing communication, but the electrical signals also may be used to power tools and other devices. In this latter application, Common Mode is an advantage because both wires may be used to carry the power in Common Mode so the electrical resistance is halved. [0017] In various illustrative communication applications discussed below, twisted pair telemetry is employed in subsea communication systems. The communication may be accomplished through the subsea tree via a single pin penetration/connector that has two separate conductors. In one example, the single pin connector comprises two separate conductors located on a single concentric pin, such as the Diamould Seawell-02 single pin connector. Single pin connectors can be designed so as to render it unnecessary to provide rotational alignment prior to mating of the plug and receptacle portions of the single pin connector. Additionally, the plug and receptacle portions of the connector may have seal barriers, such as dual seal barriers, between the connector and the surrounding housing in the subsea tree.

[0018] As described below, various devices may be employed for transferring signals, e.g. power and communication signals, through a tubing hanger and subsea tree in a subsea well application. In one example, an interface card, a communication network, and a single pin connector are employed to carry the desired signals, Communication from a subsea electronics module to the interface card can be conducted through, for example, a 96 pin DIN. In some cases, the subsea electronics module is powered via a 24 V power supply, and the power can be provided locally or through, for example, an umbilical. Modbus communication may utilize a 2-wire or a 4-wire design. [0019] Both a power signal and a communication signal may be passed through the single pin penetration at the subsea tree. Conceivably, noise can occur over any frequency band, but the power signal may be sent in a frequency different than the frequency of the communication signal. The interface card may be designed to transmit power as, for example, 175V DC power. Additionally, the frequency range of the communication network protocol may be selected to optimize data transmission over long distances. In general, a high frequency transmission can be used to send substantial amounts of data over short distances, and a low frequency transmission can be used to send less data over much longer distances.

[0020] Referring generally to FIG. 1, one example of a subsea system and communication application is illustrated schematically. In this embodiment, a well system 20 comprises a subsea tree 22 and a communication system 24 that enables communication across the subsea tree 22. The subsea tree 22 is positioned at a subsea floor 26 above a well 28 having a wellbore 30 that extends down into a subterranean formation 32. The subsea tree 22 may comprise a variety of components, including a tubing hanger 34 having a penetration 36. The penetration 36 may be designed to accommodate a single pin penetration 38 that can be employed, for example, to transfer both communication signals and power singles to and/or from a twisted-pair located in well 28. By way of illustrative example, the subsea tree 22 may be a vertical tree. [0021] In addition to single pin penetration 38, communication system 24 comprises a signal conversion system 40 having an upper conversion system 42, located generally above single pin penetration 38, and a lower conversion system 44, located generally below single pin penetration 38. For example, upper and lower conversion systems 42, 44 can be positioned on opposite sides of tubing hanger 34. The communication system 24 also may comprise communication lines 46, 48 that can be used for carrying signals, e.g. communication and power signals, to and/or from surface locations and downhole locations, respectively. In the embodiment illustrated, communication line 48 comprises at least in part a twisted pair communication line to enable twisted pair communication/telemetry. Although a twisted pair communication line is shown in this illustrative example, embodiments may not be limited to this configuration. Other types of communication lines may be used, such as a multi-core cable among others.

[0022] The communication system 24 can be used to deliver communication signals and/or power signals to and from a variety of devices 50 located downhole. The devices 50 may vary from one application to another and may include valves, pumps, sensors, gauges, tools, and other devices. Furthermore, the one or more downhole devices 50 may be used in cooperation with, or form part of, a variety of completions 51. [0023] Referring generally to FIG. 2, one embodiment of signal conversion system 40 is illustrated. In this embodiment, single pin penetration 38 extends through tubing hanger 34 to connect upper conversion system 42 with lower conversion system 44. The lower conversion system 44 is connected to a twisted pair 52 which may be grounded via a suitable ground 54. The twisted pair 52 may be connected to, or formed as part of, a downhole bus or network 56, such as a Wellnet communication network available from Schlumberger Corporation.

[0024] Although signal conversion system 40 may comprise a variety of components, the illustrated embodiment utilizes an interface card 58 and a subsea electronics module 60 to form upper conversion system 42. By way of example, the subsea electronics module 60 may be connected to interface card 58 through a 96-pin DIN or other suitable technique. Communication signals may be delivered from subsea electronics module 60 to interface card 58 via Modbus communication or another suitable communication method. Additionally, power may be delivered through subsea electronics module 60 to interface card 58. In FIG. 2, power is illustrated as supplied from a 24V source in subsea electronics module 60, however many applications supply electrical power via an umbilical or other suitable power supply line. [0025] Interface card 58 may comprise a converter module 62 which receives communication signals from subsea electronics module 60 and converts them to an appropriate protocol for use in the subsea communication system. For example, the communication signals can be converted to Wellnet compatible communication signals. The interface card 58 further comprises a frequency module 64 coupled to converter module 62 and used to increase the frequency of the communication signal before it is combined with the power signal. The power signal supplied through subsea electronics module 60 also is converted by a power converter module 66 which may be part of interface card 58. By way of example, the power converter module 66 converts the power signal to a direct current signal, such as a 175V direct current signal or other appropriate signal. Other embodiments may not be limited to the 175V direct current signal described for this example.

[0026] The converted communication signal and power signal are delivered to a combination module 68 which is used to combine the signals before the interface card 58 transfers the combined signals through single pin penetration 38 to lower conversion system 44. It should be noted that interface card 58 also can be designed to separate signals that are transferred up through single pin penetration 38 from downhole. Additionally, appropriate grounds may be provided for the components of upper conversion system 42, lower conversion system 44, and downhole network 56, as necessary.

[0027] In this particular embodiment, lower conversion system 44 comprises a frequency enhanced bridge 70 which is located below tubing hanger 34. The frequency enhanced bridge 70 receives the outgoing interface card communication which, as described above, has been raised to a higher frequency before being combined with the direct current power signal. Because of the higher frequency, analog components can be used inside the frequency enhanced bridge 70 to separate the power signal and the communication signal from the combined signal. Following signal separation, the frequency enhanced bridge 70 is used to convert the interface card signal back to communication network frequencies. The power signal is recombined back with the communication signal and the combination is delivered to twisted-pair 52 for transfer downhole.

[0028] Frequency enhanced bridge 70 may have a variety of forms and components, but one embodiment is illustrated schematically in FIG. 3. In this embodiment, frequency enhanced bridge 70 comprises a signal separation module 72 designed to separate the power signal from the communication signal after receiving the combined signal from interface card 58 via single pin penetration 38. In this embodiment, the separated communication signal is delivered to a digital converter module 74 that converts the communication signal to a digital signal. The digital signal is delivered to a subsequent converter module 76 that is designed to convert the digital signal to an appropriate network signal, such as a Wellnet communication signal. [0029] The separated power signal is delivered to a power signal converter 78 which is used to convert the power signal back to a direct current signal, such as a 175V direct current signal. The power signal and the communication signal are then delivered to a combination module 80 which is used to recombine the power signal and the communication signal for transfer to twisted pair 52 and downhole network 56. It should be noted that frequency enhanced bridge 70 also can be designed to separate signals that are received from downhole, and those signals can be recombined for transfer to upper conversion system 42 through single pin penetration 38. [0030] Various alternatives exist with respect to efficient ways to shift communication network frequencies up and down. One approach is to convert the signals from analog to digital and then back again, hi effect, the communication system must demodulate and then immediately modulate again. Accordingly, an appropriate and capable communication protocol is used. In some embodiments, the frequency enhanced bridge 70 is effectively used for "catching" data from the interface card 58 and then "throwing" the data back to the communications network 56, while the frequency enhanced bridge 70 is simultaneously "catching" data from the network 56 and passing it up to the interface card 58.

[0031] Several variations of the signal conversion system 40 also can be employed. In one embodiment, as illustrated in FIG. 4, the upper conversion system 42 is simplified by modifying the interface card 58 to avoid shorting communication to ground. According to one embodiment, the modification to avoid shorting can be accomplished by utilizing one or more passive components 82 in an alternate combination module 84 used to combine the separate communication signal and power signal.

[0032] In another variation of the conversion system, further simplification is achieved with a simplified frequency enhanced bridge, as illustrated in FIG. 5. In this example, the frequency enhanced bridge 70 utilizes a power module 86 designed to use an incoming direct current at a desirable voltage, such as 175V. Additionally, the conversion to digital is achieved at communication network frequencies. Schematically, the system is similar to the frequency enhanced bridge illustrated in FIG. 3, except for accomplishing the conversion to digital at communication network frequencies. Effectively, two communication network stations are provided back to back. The first communication network communicates to the interface card 58, and it communicates digitally to the second communication network in the simplified frequency enhanced bridge, and that second communication network passes the communication downhole to, for example, downhole device or devices 50 (see FIG. 1).

[0033] In some embodiments, modifications can be made to the circuitry to ensure that communication does not get shorted to ground. For example, passive components can be used in frequency enhanced bridge 70. As illustrated in FIG. 6, the simplified frequency enhanced bridge 70 may be modified by using cooperating communication network stations 88, 90, respectively.

[0034] By way of example, the modified network stations 88, 90 can be formed at least in part with software. Power consumption and other operational parameters can be estimated from the existing devices/tools and thus when the communication network stations are upgraded, similar upgrades can be applied to the software on frequency enhanced bridge 70. Whether use of the software-based components is suitable often depends on the specific environment and application in which the communication system is employed.

[0035] Well system 20 and communication system 24 may be formed with a variety of components for use with many types of well systems. Furthermore, the selection of components for constructing the signal conversion system may vary depending on environmental factors to which the system is subjected in a given application. Furthermore, numerous types of subsea trees, e.g. vertical Christmas trees and other subsea trees, can be employed with different types of tubing hangers. In many embodiments, the tubing hanger is designed with a single penetration to accommodate passage of a single communication line. However, the communication line may comprise one or more electrical wires, optical fibers, and other media for carrying power and/or communication signals. [0036] Furthermore, the location of the upper conversion system and the lower conversion system can vary. Also, the control boards and cooperating components can be constructed as stand-alone components or in combination with other well components. The signal conversion system components also may comprise digital components, analog components and/or mixtures of digital and analog components. In some applications, one or more of the modules within the signal conversion system may achieve the desired functionality via software, either alone or in combination with hard components. [0037] Accordingly, although only a few embodiments of the present invention 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 invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.

Claims

CLAIMSWhat is claimed is:

1. A system, comprising: a subsea well communication system comprising: a tubing hanger having a single penetration for both a communication signal and a power signal; an interface card positioned above the single penetration to transfer the communication signal and the power signal through the single penetration: and a lower conversion system to convert the communication signal and the power signal for transfer through a twisted pair.

2. The system as recited in claim 1, wherein the tubing hanger is positioned in a vertical tree located on a subsea floor.

3. The system as recited in claim 1, further comprising a subsea electronics module couple to the interface card above the tubing hanger.

4. The system as recited in claim 1, wherein the lower conversion system comprises a frequency enhanced bridge.

5. The system as recited in claim 4, wherein the frequency enhanced bridge separates the communication signal from the power signal.

6. The system as recited in claim 5, wherein the frequency enhanced bridge converts the power signal to a 175 volt signal.

7. The system as recited in claim 5, wherein the frequency enhanced bridge converts the communication signal to a digital signal.

8. The system as recited in claim 5, wherein the frequency enhanced bridge converts the digital signal to a Wellnet communication signal.

9. The system as recited in claim 5, wherein the frequency enhanced bridge combines the power signal and the communication signal for transfer along the twisted pair.

10. The system as recited in claim 1, wherein the single penetration comprises a single pin penetration.

11. A method for use in a subsea well application, comprising: providing a communication signal and a power signal through a single line disposed through a tubing hanger; and converting at least the communication signal to a twisted pair communication for transfer downhole.

12. The method as recited in claim 11, wherein providing comprises using an interface card positioned above the tubing hanger.

13. The method as recited in claim 12, wherein providing comprises using a frequency enhanced bridge positioned below the tubing hanger.

14. The method as recited in claim 13, further comprising coupling a subsea electronics module to the interface card above the tubing hanger.

15. The method as recited in claim 11, further comprising using the frequency enhanced bridge to separate the communication signal from the power signal.

16. The method as recited in claim 15, further comprising using the frequency enhanced bridge to recombine the communication signal and the power signal for transfer along the twisted pair.

17. A method, comprising: combining a communication signal and a power signal above a tubing hanger of a subsea tree; transferring the combined signal through the tubing hanger; separating the combined signals into a separate communication signal and a separate power signal below the tubing hanger; and recombining the separate communication signal and the separate power signal for transfer via a twisted pair.

18. The method as recited in claim 17, wherein combining comprises using an interface card to combine the communication signal and the power signal.

19. The method as recited in claim 17, wherein transferring comprises transferring the combined signals via a single pin penetration through the tubing hanger.

20. The method as recited in claim 17, wherein separating comprises employing a frequency enhanced bridge to separate the combined signals.

21. The method as recited in claim 20, wherein recombining comprises using the frequency enhanced bridge to recombine the separate communication signal and the separate power signal for transfer along the twisted pair.

22. A communication system for use in a subsea application, comprising: a tubing hanger positioned in a subsea tree, the tubing hanger having a penetration through which signals are communicated; an upper conversion system having electronics to combine a power signal and a communication signal into a combined signal, the upper conversion system being positioned above the penetration: a lower conversion system positioned below the penetration, the lower conversion system having electronics to receive the combined signal upon transfer through the penetration and to separate the combined signal into the power signal and the communication signal; and a twisted pair, wherein the lower conversion system is able to transmit at least the communication signal via the twisted pair.

23. The communication system as recited in claim 22. wherein the lower conversion system further recombines the power signal and the communication signal for transfer via the twisted pair.

24. The communication system as recited in claim 22. wherein the upper conversion system comprises a subsea electronics module and an interface card.

25. The communication system as recited in claim 22. wherein the lower communication system comprises a frequency enhanced bridge