Autonomous Seismic Data Acquisition Unit

• US 20080049550A1
• Filed: 08/22/2006
• Published: 02/28/2008
• Est. Priority Date: 08/22/2006
• Status: Active Grant

• Current Assignee: Geophysical Technology, Inc.
• Original Assignee: Global Geophysical Services Incorporated
• Inventors: Walker, Larry, Fleure, Thomas J.
• Granted Patent: US 7,660,201 B2
• Time in Patent Office: Days
• US Class Current: 367/14
• CPC Class Codes: G01V 1/24 Recording seismic data
• CPC Class Codes: G01V 2200/12 Clock synchronization-related issues

Abstract

A method, apparatus and system for acquiring land seismic data includes acquiring seismic data with a first autonomous seismic data acquisition unit and a second autonomous seismic data acquisition unit wherein each acquisition unit comprises a plurality of digitally controlled temperature-compensated crystal oscillators. Oscillator-based timing signals are acquired that are associated with the plurality of digitally controlled temperature-compensated crystal oscillators and a time correction is determined to apply to the seismic data acquired with the first autonomous seismic data acquisition unit. The time correction is determined using the oscillator-based timing signals from the first and second autonomous seismic data acquisition units.

Claims

1. A seismic data acquisition apparatus comprising:

a) a memory;

b) a seismic sensor;

c) a temperature sensor;

d) a processor;

e) a plurality of digitally controlled temperature-compensated crystal oscillator (DC-TCXO) associated with a real-time clock; and

f) a data input/output interface.

2. The apparatus of claim 1 further comprising an application program for determining a time delay between the real time clock and an external reference timing signal.

3. The apparatus of claim 1 further comprising an application program to determine a time correction value based on continuous clock count accumulations.

4. The apparatus of claim 1 further comprising a removable memory module.

5. The apparatus of claim 1 further comprising an analog to digital converter.

6. A method for acquiring seismic data comprising:

a) acquiring seismic data with a first autonomous seismic data acquisition unit and a second autonomous seismic data acquisition unit wherein each acquisition unit comprises a plurality of digitally controlled temperature-compensated crystal oscillators;

b) acquiring oscillator-based timing signals associated with the plurality of digitally controlled temperature-compensated crystal oscillators; and

c) determining a time correction to apply to the seismic data acquired with the first autonomous seismic data acquisition unit, the correction determined using the oscillator-based timing signals from the first and second autonomous seismic data acquisition units.

7. The method of claim 6 further comprising determining the time correction as a function of the relative time difference between a selected plurality of the oscillator-based timing signals from the first and second autonomous seismic data acquisition units.

8. The method of claim 6 further comprising applying the determined time correction value to the recorded seismic data.

9. The method of claim 8 further comprising merging corrected data from the first autonomous seismic data acquisition unit with data collected from a telemetry-based seismic data acquisition system.

10. The method of claim 6 further determining a relative time difference between the first autonomous seismic data acquisition unit and a telemetry-based seismic data acquisition system.

11. The method of claim 6 further comprising recording a reference timing signal from a reference clock on at least one of the autonomous seismic data acquisition units.

12. The method of claim 6 further comprising determining a time correction associated with the first autonomous seismic data acquisition units that is a function of one of:

i) the relative time difference between the plurality of digitally controlled temperature compensated crystal oscillators, ii) a long term time history of the plurality of digitally controlled temperature compensated crystal oscillators; and

iii) a temperature history of at least one of the plurality of digitally controlled temperature compensated crystal oscillators.

13. The method of claim 6 wherein the first autonomous seismic data acquisition unit further comprises removable media storage.

14. A method for recording seismic data comprising:

a) deploying a first and second autonomous seismic data acquisition unit for acquiring seismic signals;

b) deploying a plurality of digitally controlled temperature-compensated crystal oscillators with the first and second autonomous seismic data acquisition unit to generate oscillator-based timing signals;

c) using the oscillator-based timing signal to determine a time correction to apply to the seismic data acquired with the first autonomous seismic data acquisition unit based on the oscillator-based timing signals from the first and second autonomous seismic data acquisition units; and

d) applying the determined time correction to the seismic data.

15. The method of claim 14, further comprising:

a) recording the temperature in the first autonomous seismic data acquisition unit;

b) computing the determined time correction as a function of at least one of;

i) the recorded temperature, ii) the oscillator-based timing signals, and iii) a synchronizing-time signal from a master clock.

16. The method of claim 14, further comprising the steps of:

a) accessing a database of the long term historical performance of the digitally controlled temperature compensated crystal oscillators;

b) computing the determined time correction as a function of at least one of;

i) the recording temperature, ii) the oscillator-based timing signals, iii) values from the historical database of digitally controlled temperature compensated crystal oscillator performance, and iv) a synchronizing-time signal from a master clock.

17. The method of claim 14 further comprising recording a synchronizing-time signal from a master clock on the first autonomous seismic data acquisition unit at relatively sparse intervals in time.

18. The method of claim 14 further comprising recording a synchronizing-time signal from a master clock on the first autonomous seismic data acquisition unit prior to deployment.

19. The method of claim 14 further comprising merging the corrected seismic data with seismic data acquired with a telemetry-based seismic system.

20. The method of claim 14 further comprising downloading the seismic data and the oscillator-based timing signals from the first autonomous seismic data acquisition unit to a data depository.