Method and system for estimating the drift of a clock for dating seismic data samples

Patent metadata

Field	Value
Publication number	US-2021263477-A1
Application number	US-201917255373-A
Country	US
Kind code	A1
Filing date	Jun 19, 2019
Priority date	Jun 29, 2018
Publication date	Aug 26, 2021
Grant date	—

Abstract

The method for estimating the drift over time of a physical operating parameter of a clock for dating seismic data samples associated with a seismic data collection node involves measuring (10) at least one quantity associated with the clock, at predetermined instants or during predetermined time periods, and applying (12), to this quantity, a predetermined non-linear law of variation of this quantity that depends on the values collected during the measurement step (10), so as to obtain an estimation of the drift over time of the physical operating parameter.

First claim

1 - 15 . (canceled)

16 . A method for estimating a drift over time of a physical operating parameter of a clock for dating samples of seismic data, associated with a seismic data collection node, wherein:
at least one variable associated with said clock is measured in a measurement step at predetermined instants in time or for predetermined periods of time; and a predetermined non-linear law of variation of said variable, which depends on values of said at least one variable collected in said measurement step, is applied to said variable so as to obtain an estimate of said drift over time of said physical operating parameter, and wherein, in said measurement step: before deploying said node for a seismic data collection mission, an initial instantaneous frequency of said clock is measured and an internal time information signal of said node is synchronized with respect to a reference time information signal; at a predetermined instant in time during said data collection mission, a final instantaneous frequency of said clock and a phase offset between said internal time information signal of said node and said reference time information signal are measured; and wherein, in said step of applying said predetermined non-linear law of variation of said variable, an instantaneous frequency error of said clock is estimated based on said initial instantaneous frequency, said instantaneous frequency at said predetermined instant in time and said phase offset, and wherein, according to said predetermined non-linear law of variation of said variable, said instantaneous frequency varies according to a polynomial equation of order greater than or equal to 2, such that a phase of said clock varies according to a polynomial equation of order greater than or equal to 3.

17 . The method as claimed in claim 16 , wherein, in a preliminary step, an output frequency of said clock is adjusted so as to reduce said instantaneous frequency error of said clock.

18 . The method as claimed in claim 17 , wherein said preliminary step is performed during a phase of manufacturing said clock.

19 . The method as claimed in claim 17 , wherein said preliminary step is performed during a phase of maintaining said clock.

20 . The method as claimed in claim 16 , wherein said reference time information signal is provided by a GPS location system.

21 . The method as claimed in claim 16 , wherein:
before deploying said node for a seismic data collection mission, an evolution of said variable is furthermore measured as a function of a temperature of said clock; during said mission, said temperature of said clock is measured; and said predetermined non-linear law of variation of said variable takes into account said temperature.

22 . The method as claimed in claim 16 , wherein said predetermined instant in time during said mission corresponds to an end of said mission.

23 . The method as claimed in claim 16 , wherein, according to said predetermined non-linear law of variation of said variable, said instantaneous frequency varies according to a 2nd-order polynomial equation, such that said phase of said clock varies according to a 3rd-order polynomial equation.

24 . A method for estimating a drift over time of a physical operating parameter of a clock for dating samples of seismic data, associated with a seismic data collection node, wherein:
at least one variable associated with said clock is measured in a measurement step at predetermined instants in time or for predetermined periods of time; and a predetermined non-linear law of variation of said variable, which depends on values of said at least one variable collected in said measurement step, is applied to said variable so as to obtain an estimate of said drift over time of said physical operating parameter, and wherein, in said measurement step, a phase of said clock is measured for a first predetermined period of time before deploying said node for a seismic data collection mission and for a second predetermined period of time at an end of said mission and, in said step of applying said law, an interpolation method is used so as to obtain an estimate of an accumulated phase error of said clock, and wherein, according to said predetermined non-linear law of variation of said variable, a phase of said clock varies according to a polynomial equation of order greater than or equal to 3.

25 . The method as claimed in claim 24 , wherein, in said measurement step, said accumulated phase error of said clock is measured for a period of time corresponding to a simulated seismic data collection mission.

26 . The method as claimed in claim 24 , wherein said phase of said clock varies according to a 3rd-order polynomial equation.

27 . The method as claimed in claim 25 , wherein:
before deploying said node for a seismic data collection mission, an evolution of said variable is furthermore measured as a function of a temperature of said clock; during said mission, said temperature of said clock is measured.

28 . The method as claimed in claim 16 , wherein said node is designed for use on a seabed.

29 . The method as claimed in claim 24 , wherein said node is designed for use on a seabed.

30 . A system for estimating a drift over time of a physical operating parameter of a clock for dating samples of seismic data, associated with a seismic data collection node, wherein it comprises a module designed to implement steps of a method as claimed in claim 16 .

Assignees

• Sercel Rech Const Elect

Inventors

• L'Her Christophe

Classifications

• G01V1/38

  specially adapted for water-covered areas (G01V1/28 takes precedence) · CPC title

• G04G3/02 Primary

  Circuits for deriving low frequency timing pulses from pulses of higher frequency (pulse frequency dividers in general H03K23/00 - H03K29/00) · CPC title

• G01V2200/12

  Clock synchronization-related issues · CPC title