Synchronization of seismic data acquisition systems

• US 20070253289A1
• Filed: 05/24/2007
• Published: 11/01/2007
• Est. Priority Date: 10/04/2002
• Status: Active Grant

• Current Assignee: Inova Systems
• Original Assignee: GeoSystems LLC
• Inventors: Chamberlain, Donald, Heidebrecht, Norman
• Granted Patent: US 7,583,560 B2
• Time in Patent Office: Days
• US Class Current: 367/51
• CPC Class Codes: G01V 1/22 Transmitting seismic signals to recording or processing apparatus
• CPC Class Codes: G01V 1/26 Reference-signal-transmitting devices, e.g. indicating moment of firing of shot

Abstract

A network distributed seismic data acquisition system comprises seismic receivers connected to remote acquisition modules, receiver lines, line tap units, base lines, a central recording system and a seismic source event generation unit synchronized to a master clock. One or more high precision clocks is added to the network to correct for timing uncertainty associated with propagation of commands through the network. Seismic receivers and seismic sources are thereby synchronized with greater accuracy than otherwise possible. Timing errors that interfere with the processing of the seismic recordings are greatly reduced, thus enabling an improvement in subsurface geologic imaging.

Claims

1. A method of operating a seismic survey network comprising the steps of:

a. connecting one or more seismic sensors having respective specific identities to a respective data acquisition module for transmission of seismic data to said respective data acquisition module, said data acquisition module being equipped with a first clock;

b. at predetermined time intervals, said data acquisition module being operative to transmit digital data packets comprising the instantaneous amplitude value of seismic data received by said data acquisition module, each data packet being further distinguished by the identity of the seismic sensor source of respective data and a first clock time of the moment said respective data is received by said data acquisition module;

c. transmitting said data packets along a first increment of a data transmission route from a first such data acquisition module to an other data processing module;

d. retransmitting said data packets by said other data processing module along a second increment of said data transmission route to a central data processing unit equipped with a second clock;

e. from said central data processing unit, transmitting a clock synchronization signal at predetermined time intervals to said other data processing modules along said transmission route in a transmission direction opposite to said seismic data packets, said clock synchronization signal corresponding to the time of said second clock; and

,

f. retransmitting said clock synchronization signal by said other data processing module to said first data acquisition module.

2. A method of operating a seismic survey network as described by claim 1 wherein said other data processing module is a second such data acquisition module served respectively, by one or more seismic sensors having respective identities.

3. A method of operating a seismic survey network as described by claim 1 wherein said data acquisition module compares the time of said first clock to the synchronization signal time of said second clock.

4. A method of operating a seismic survey network as described by claim 1 wherein said other data processing module is a communication module.

5. A method of operating a seismic survey network as described by claim 1 wherein said other data processing module is a base line module

6. A method of operating a seismic survey network as described by claim 1 wherein said other data processing module is a line tap unit.

7. A method of operating a seismic survey network as described by claim 1 whereby said first data acquisition module is responsive to said clock synchronization signal to coordinate the time value of said first clock to the time value of said second clock.

8. A method of operating a seismic survey network as described by claim 1 whereby said data acquisition modules, other data processing modules and the central data processing unit are serially linked by data transmission increments, each of said increments having a predetermined data propagation time interval, the data propagation time intervals of data transmission increments adjacent each module and unit being programmed in the respective module and unit as a reference for an expected signal reception time along the respective increment.

10. A method of operating a seismic survey network as described by claim 1 whereby the specific identity of a seismic sensor source of a data packet is implicitly distinguished by the sequential reception order of said data packet by said central data processing unit.

11. A method of operating a seismic survey network as described by claim 1 having one or more global positioning system receivers associated with one or more of said clocks.

12. A method of operating a seismic survey network as described by claim 1 having one or more global, regional or local radio beacon receivers, suitable for receiving timing signals, associated with one or more of said clocks.

13. A method of operating a seismic survey network as described by claim 1 wherein said data acquisition and other data processing modules determine time according to said second clock, create data packets corresponding to said second clock time and annotate the second clock time on the created data packets.

14. A method of operating a seismic survey network as described by claim 1 wherein said second clock is a master clock of greater precision that said first clock.

15. A method of operating a seismic survey network as described by claim 14 wherein said first clock is an instrument of less precision that said master clock.

16. A method of operating a seismic survey network as described by claim 14 wherein said other data processing module comprises a third clock of less precision than said master clock.

17. A method of operating a seismic survey network as described by claim 16 wherein said third clock is an instrument of greater precision than said first clock.

9. A method of operating a seismic survey network as described by claim 9 whereby the time of said first clock is corrected by the value of a difference between said expected signal reception time and the observed signal reception time according to said first clock.

18. A method of acquiring a seismic survey in which a network of seismic acquisition and communication modules is synchronized to a master clock by use of wired and/or wireless communication to one or more high precision clocks at locations in the network are synchronized by linkage to said master clock prior to physical deployment to physical deployment to their network locations and wherein high precision clocks further synchronize other clocks of less precision within the network.

19. A method according to claim 18 wherein the high precision clocks are synchronized to the master clock after their deployment to their network locations by synchronization signal transmission from the master clock.

20. A method according to claim 18 wherein the high precision clocks are synchronized to the master clock after their deployment to their network locations by repeated transmission of synchronization signals from the master clock and in which said synchronization signals are received at the location of a local clock to be synchronized and compared to a predetermined expected statistical distribution of synchronization signals to determine drift of said local clock.

21. A method of acquiring a seismic survey in which a network of seismic acquisition and communication modules includes at least one high precision clock and at least one clock of less precision wherein said clock of less precision is synchronized to said high precision clock by transmission of one or more synchronization signals and in which activation of a seismic source is synchronized to said high precision clock by transmission of one or more synchronization signals.

22. A method of acquiring a seismic survey as described by claim 21 in which said high precision clock is synchronized according to timing signals originating from a global positioning satellite system.

23. A method of acquiring a seismic survey as described by claim 21 in which said high precision clock is synchronized according to timing signals originating from a global, regional or local radio beacon system.