APPARATUS AND METHOD FOR COMMUNICATION BETWEEN DOWNHOLE COMPONENTS

• US 20140192621A1
• Filed: 01/07/2013
• Published: 07/10/2014
• Est. Priority Date: 01/07/2013
• Status: Abandoned Application

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Morris, Steven A., Forgang, Stanislav Wilhelm, Ram, Shobha Sundar
• Application Number:
  US13/735,404
• Publication Number:
  US 20140192621A1
• Time in Patent Office: Days
• US Class Current: 367/81
• CPC Class Codes: E21B 47/14 using acoustic waves
• CPC Class Codes: G01V 1/26 Reference-signal-transmitting devices, e.g. indicating moment of firing of shot
• CPC Class Codes: G01V 3/30 operating with electromagnetic waves

Abstract

A method of synchronization between downhole components includes: generating a dual tone synchronization signal by a signal generator in a first downhole component disposed in a borehole in an earth formation, the dual tone signal including a first constituent periodic signal having a first frequency f₁ and a second constituent periodic signal having a second frequency f₂ that is different from the first frequency; transmitting the synchronization signal to a second downhole component disposed in the borehole; receiving the synchronization signal by a signal processor in the second downhole component, calculating a phase difference between the first constituent signal and the second constituent signal, and calculating a transmission delay based on the phase difference; and synchronizing operation of the first and second downhole components based on the delay.

Claims

1. A method of synchronization between downhole components, the method comprising:

generating a dual tone synchronization signal by a signal generator in a first downhole component disposed in a borehole in an earth formation, the dual tone signal including a first constituent periodic signal having a first frequency f₁ and a second constituent periodic signal having a second frequency f₂ that is different from the first frequency;

transmitting the synchronization signal to a second downhole component disposed in the borehole;

receiving the synchronization signal by a signal processor in the second downhole component, calculating a phase difference between the first constituent signal and the second constituent signal, and calculating a transmission delay based on the phase difference; and

synchronizing operation of the first and second downhole components based on the delay.

2. The method of claim 1, wherein the synchronization signal is transmitted directly to the second downhole component over a transmission line connected between the downhole components and a surface unit.

3. The method of claim 2, wherein the transmission line is a single conductor power and telemetry bus.

4. The method of claim 2, wherein the synchronization signal is transmitted in a first frequency band that is different than a second frequency band used to transmit communications between the surface unit and the downhole components.

5. The method of claim 1, further comprising transmitting a trigger signal from the first downhole component to the second downhole component, the trigger signal indicating a time value measured by the first downhole component.

6. The method of claim 5, wherein the time value is a zero crossing point at a selected cycle of the synchronization signal.

7. The method of claim 5, wherein the first downhole component includes a transient electromagnetic (TEM) transmitter, the second downhole component includes a TEM receiver, and the trigger signal indicates a time at which the TEM transmitter commences transmitting TEM signals into the earth formation.

8. The method of claim 1, wherein the first downhole component and the second downhole component are connected via a current loop communication system.

9. The method of claim 8, wherein the first downhole component includes a current loop transmitter configured to convert voltage signals from the first downhole component to current signals and transmit the current signals over a current loop formed by the transmission line.

10. An apparatus for communicating between downhole components, comprising:

an interface coupled to a first downhole component, the interface configured to communicatively couple the first downhole component to a transmission line and transmit signals to a second downhole component over the transmission line, the interface including a current loop transmitter configured to convert voltage signals from the first downhole component to current signals and transmit the current signals on a current loop formed by the transmission line.

11. The apparatus of claim 10, further comprising a second interface coupled to the second downhole component, the second interface including a current loop receiver configured to convert current signals received from the first downhole component over the transmission line to voltage signals.

12. The apparatus of claim 10, wherein the current loop is formed by the transmission line coupled to a surface power source and a return path formed by a borehole string that includes the downhole components.

13. The apparatus of claim 12, wherein the transmission line is a single conductor power and telemetry bus.

14. The apparatus of claim 12, wherein the current loop transmitter is configured to transmit the current signals in a first frequency band that is different than a second frequency band used to transmit communications between the surface unit and the downhole components.

15. The apparatus of claim 14, wherein the current loop transmitter includes a resonant decoupling device configured to prevent coupling of signals in the second frequency band with the current loop transmitter.

16. The apparatus of claim 14, wherein the current loop transmitter includes a band pass filter tuned to frequencies in the first frequency band.

17. The apparatus of claim 11, wherein the first interface and the second interface are configured to both transmit and receive current loop signals.

18. The apparatus of claim 17, wherein the first interface and the second interface are configured as a half-duplex system to allow for two-way communication.

19. The apparatus of claim 17, wherein the first interface and the second interface are configured as a full-duplex system to allow for simultaneous two-way communication.

20. The apparatus of claim 10, wherein the first downhole component includes a signal generator configured to generate a dual tone synchronization signal, the dual tone signal including a first constituent periodic signal having a first frequency f₁ and a second constituent periodic signal having a second frequency f₂ that is different from the first frequency, and the second downhole component includes a processor configured to receive the synchronization signal, calculating a phase difference between the first constituent signal and the second constituent signal, and calculate a transmission delay based on the phase difference.