Instantaneous frequency modulation acquisition scheme for seismic sources

Patent metadata

Field	Value
Publication number	US-9778385-B2
Application number	US-201414894560-A
Country	US
Kind code	B2
Filing date	Jun 25, 2014
Priority date	Jun 27, 2013
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Computing device, computer software and methods for generating sweep signals corresponding to plural sources that generate seismic waves. The method includes selecting a nominal sweep signal (S 0 ); applying a perturbation (P) to the nominal sweep signal (S 0 ); and calculating the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source.

First claim

What is claimed is:

1. A method for generating sweep signals corresponding to plural sources that generate seismic waves, the method comprising:
selecting a nominal sweep signal (S 0 ) whose phase φ(t) is characterized by an instantaneous frequency

F
⁡

(
t
)

=

1

2
⁢
π

⁢

∂

φ
⁡

(
t
)

∂
t

;

applying a perturbation (P) to the nominal sweep signal (S 0 ); and
calculating the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source,
wherein the perturbation causes a frequency rate change,

d
dt

⁢

P
⁡

(
t
)

,

that is less than a predetermined fraction, γ, of a nominal sweep's frequency rate

d
dt

⁢

F
⁡

(
t
)

.

2. The method of claim 1 , wherein the predetermined fraction is less than 0.5.

3. The method of claim 1 , wherein the perturbation (P) is a polynomial function of time.

4. The method of claim 3 , further comprising:
selecting coefficients of the polynomial function.

5. The method of claim 4 , further comprising:
applying constraints to the coefficients, the constraints including at least one of:
maintaining perturbed sweep frequency within a predetermined range; and
having the instantaneous frequency monotonically increasing.

6. The method of claim 5 , further comprising:
calculating candidate sweep signals;
calculating auto- and cross-correlations of the candidate sweep signals;
computing performance statistics associated with the auto- and cross-correlations of the candidate sweep signals;
comparing the performance statistics with reference performing statistics; and
selecting the candidate sweep signals to be the sweep signals (Sn) if a result of the comparing step is positive.

7. The method of claim 1 , wherein the perturbation (P) is a non-linear function of time.

8. The method of claim 1 , wherein the perturbation (P) includes a sine term.

9. The method of claim 1 , further comprising:
downloading in each source a corresponding sweep signal; and
acquiring seismic data with the sweep signals.

10. The method of claim 1 , wherein each one of the sweep signals is unique and when the plural sources operate simultaneously, a cross-correlation among the plural sources is minimized.

11. A computing device for generating sweep signals corresponding to plural sources that generate seismic waves, the computing device comprising:
a processor configured to,
select a nominal sweep signal (S 0 ) whose phase φ(t) is characterized by an instantaneous frequency

F
⁡

(
t
)

=

1

2
⁢
π

⁢

∂

φ
⁡

(
t
)

∂
t

;

apply a perturbation (P) to the nominal sweep signal (S 0 ); and

calculate the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source,
the perturbation causes a frequency rate change,

d
dt

⁢

P
⁡

(
t
)

,

that is less than a predetermined fraction, γ, of a nominal sweep's frequency rate

d
dt

⁢

F
⁡

(
t
)

.

12. The computing device of claim 11 , wherein the predetermined fraction is 0.5.

13. The computing device of claim 11 , wherein the perturbation (P) is a polynomial function of time.

14. The computing device of claim 13 , wherein the processor is further configured to:
select coefficients of the polynomial function.

15. The computing device of claim 14 , wherein the processor is further configured to:
apply constraints to the coefficients, the constraints including at least one of:
maintaining perturbed sweep frequency within a predetermined range; and
having the instantaneous frequency monotonically increasing.

16. The computing device of claim 15 , wherein the processor is further configured to:
calculate candidate sweep signals;
calculate auto- and cross-correlations of the candidate sweep signals;
compute performance statistics associated with the auto- and cross-correlations of the candidate sweep signals;
compare the performance statistics with reference performing statistics; and
select the candidate sweep signals to be t

Assignees

• Cgg Services Sa
• Cgg Services Sas

Inventors

• Castor Kaelig
• Bianchi Thomas
• Sallas John

Classifications

• G01V2210/127

  Cooperating multiple sources · CPC title

• G01V1/005 Primary

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

• G01V2210/1214

  Continuous · CPC title