Survey method, seismic vibrator, and survey system

Patent metadata

Field	Value
Publication number	US-10775523-B2
Application number	US-201715730702-A
Country	US
Kind code	B2
Filing date	Oct 11, 2017
Priority date	Apr 24, 2015
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

A survey method includes generating a first amplitude modulation signal by amplitude-modulating a carrier wave repeating the same pattern at a predetermined cycle in each of a plurality of vibrators with a modulation signal whose cycle is 1/m times the predetermined period and is different for each of the vibrators, transmitting the seismic wave based on the first amplitude modulation signal, generating a second amplitude modulation signal in one or more receivers, the second amplitude modulation signal being identical to the first amplitude modulation signal generated by any one of the seismic vibrators, generating a reception signal in each of the one or more receivers by receiving a synthetic seismic wave in which the seismic waves generated by the seismic vibrators are synthesized, calculating a correlation value between the reception signal and the second amplitude modulation signal, and analyzing characteristics of the medium on the basis of the correlation value.

First claim

What is claimed is:

1. A survey method for surveying a medium using a plurality of seismic vibrators that transmit a plurality of seismic waves to the medium and one or more receivers that receive the plurality of seismic waves generated by the plurality of seismic vibrators, and a signal analyzing apparatus, the survey method comprising the steps of:
generating, in each of the plurality of seismic vibrators that each operates in synchronization, a first amplitude modulation signal by amplitude-modulating a carrier wave that repeats the same pattern at a predetermined cycle with a modulation signal whose cycle is 1/m times (m is a natural number) the predetermined cycle, the first amplitude modulation signal being different for each of the plurality of seismic vibrators;
transmitting a seismic wave based on the first amplitude modulation signal from each of the plurality of seismic vibrators;
generating a reception signal, in each of the one or more receivers, based on a received synthesized seismic wave in which the plurality of seismic waves generated by the plurality of seismic vibrators are synthesized;
generating a second amplitude modulation signal in the signal analyzing apparatus, the second amplitude modulation signal being identical to the first amplitude modulation signal generated by any one of the plurality of the seismic vibrators;
calculating a correlation value between the synthesized seismic wave and the second amplitude modulation signal in the signal analyzing apparatus; and
analyzing characteristics of the medium on the basis of the correlation value in the signal analyzing apparatus.

2. The survey method according to claim 1 , wherein
the transmitting the seismic wave includes the step of:
generating the carrier wave on the basis of a pseudo random code.

3. The survey method according to claim 1 , wherein
the transmitting the seismic wave includes the step of:
generating the carrier wave on the basis of a sweep signal whose amplitude changes with the passage of time.

4. The survey method according to claim 1 , wherein
the predetermined cycle is longer than a propagation delay time from the seismic vibrator to the receiver.

5. The survey method according to claim 1 , wherein
the analyzing characteristics of the medium includes the steps of:
separating the component based on the seismic wave transmitted by the specific seismic vibrator from the reception signal; and
specifying the characteristics of the medium between the specific seismic vibrator and the receiver.

6. The survey method according to claim 1 , wherein
the analyzing characteristics of the medium includes the step of:
specifying the timing at which the correlation value peaks and the magnitude of the correlation value.

7. A survey system comprising:
a plurality of seismic vibrators that transmit a plurality of seismic waves to a medium;
one or more receivers that receive a synthesized seismic wave in which the plurality of seismic waves generated by the plurality of seismic vibrators are synthesized, via the medium; and
a signal analyzing apparatus that analyzes a reception signal based on the synthesized seismic wave received by the one or more receivers, wherein
each of the plurality of seismic vibrators that operates synchronously includes:
a first carrier wave generation part that generates a first carrier wave repeating the same pattern at a predetermined cycle;
a first modulation signal generation part that generates a first modulation signal having a cycle of 1/m times (m is a natural number) the predetermined cycle;
a first modulation part that generates a first amplitude modulation signal obtained by amplitude-modulating the first carrier wave with the first modulation signal; and
a seismic wave generation part that generates a seismic wave on the basis of the first amplitude modulation signal, and wherein

the signal analyzing apparatus includes:
a second carrier wave generation part that generates a second carrier wave identical to the first carrier wave generated by the first carrier wave generation part;
a second modulation signal generation part that generates one or more second modulation signals identical to at least one of the first modulation signals generated by the first modulation signal generation parts of the plurality of seismic vibrators;
a second modulation part that generates one or more second amplitude modulation signals obtained by amplitude-modulating the second carrier wave with the one or more second modulation signals;
a calculation part that calculates a correlation value between the synthesized seismic wave and the one or more second amplitude modulation signals; and
an analyzing part that analyzes characteristics of the medium on the basis of the correlation value calculated by the calculation part.

8. The survey system according to claim 7 , wherein
the second modulation part generates a plurality of second amplitude modulation signals having different cycles,
the signal analyzing apparatus includes a control part that selects the one or more second amplitude modulation signals from the plurality of second amplitude modulation signals generated by the second modulation part, and
the calculation part calculates a correlation value between the synthesized seismic wave and the one or more second amplitude modulation signals selected by the control part.

9. The survey system according to claim 7 , wherein
the signal analyzing apparatus can specify the characteristics of the medium between the specific seismic vibrator and the receiver by separating the component based on the seismic wave transmitted by the specific seismic vibrator from the reception signal.

10. The survey system according to claim 7 , wherein
the signal analyzing apparatus can specify the characteristics of the medium between the specific seismic vibrator and the receiver by specifying the timing at which the correlation value peaks and the magnitude of the correlation value.

Assignees

• Japan Oil Gas & Metals Jogmec

Inventors

• TAKANASHI Mamoru
• Nakamura Yuki
• Kunishi Yosuke

Classifications

• G01V1/005 Primary

  with exploration systems emitting special signals, e.g. frequency swept signals, pulse sequences or slip sweep arrangements · CPC title

• G01V1/48

  Processing data · CPC title

• G01V2210/1295

  Land surface · CPC title

• G01V1/143

  using mechanical driving means {, e.g. motor driven shaft}(G01V1/104, G01V1/133 take precedence) · CPC title

• G01V1/30 Primary

  Analysis (G01V1/50 takes precedence) · CPC title