Seismic source array calibration and synchronization method, apparatus and system

1. A method for quality control of a first source array for a seismic survey, the method comprising:

towing the first source array in water, wherein the first source array includes plural individual sources;

shooting at least one of the individual sources of the first source array;

receiving a time-break signal associated with a given individual source;

recording a near-field signal associated with the given individual source; and

calculating a time delay between (1) a time-break point of the time-break signal and (2) a point of the near-field signal for the given individual source,

wherein the point on the near-field signal is a start of slope or a best maximum point.

2. The method of claim 1 , wherein the time delay for the given individual source is calculated as a difference in time between the time-break point and the start of slope of the near-field signal recorded with a hydrophone located next to the given individual source.

3. The method of claim 1 , wherein the step of calculating the time delay further comprises:

computing the best maximum point from the near-field signal recorded with a hydrophone located next to the given individual source,

wherein the time delay of the given individual source is a difference in time between the time-break point and the best maximum point of the near-field signal.

4. The method of claim 3 , wherein the best maximum is a sum of a start of slope of the near-field signal and an offset function that depends on a gun volume and a gun type for the given individual source.

5. The method of claim 3 , wherein the best maximum is a sum of a start of slope of the near-field signal and an offset function determined during a bubble test during which the given individual source has been shooting alone.

6. The method of claim 1 , wherein a first time delay of a first source element in a cluster belonging to the first source array is calculated as a difference in time between the time break point of the first source element in the cluster and a start of slope of a near-field signal recorded with a hydrophone located next to the first source element.

7. The method of claim 6 , wherein a second time delay of a second source element in the cluster is calculated as a difference in time between the time break point of the second source element and a start of slope of a residual near-field signal recorded with a hydrophone located next to the second source element, wherein the residual near-field signal is computed by removing a reference signal from a mean near-field signal of the cluster.

8. The method of claim 7 , further comprising:

firing the cluster for a number of times;

correlating first and second time delays variations with a time-break variation to determine which source element of the cluster has fired first; and

determining a delay of each source element in the cluster.

9. The method of claim 1 , wherein the time delay is corrected with a travel time of an acoustic wave that propagates from (i) the given individual source to (ii) a corresponding near-field sensor.

10. A method for quality control of a first source array for a seismic survey, the method comprising:

towing the first source array in water, wherein the first source array includes plural individual sources;

shooting at least one of the individual sources of the first source array;

receiving a time-break signal associated with a given individual source;

recording a near-field signal associated with the given individual source; and

calculating a time delay between the time-break signal and the near-field signal for the given individual source,

wherein the step of calculating the time delay further comprises:

computing a best maximum point of the near-field signal recorded with a hydrophone located next to the given individual source,

wherein the time delay of the given individual source is a difference in time between the time-break signal and the best maximum point of the near-field signal, and

wherein the best maximum is a sum of a start of slope of the near-field signal and an offset function that depends on a gun volume and a gun type for the given individual source.

11. The method of claim 10 , wherein a first time delay of a first source element in a cluster belonging to the first source array is calculated as a difference in time between the time break signal of the first source element in the cluster and a start of slope of a near-field signal recorded with a hydrophone located next to the first source element.

12. The method of claim 11 , wherein a second time delay of a second source element in the cluster is calculated as a difference in time between the time break signal of the second source element and a start of slope of a residual near-field signal recorded with a hydrophone located next to the second source element, wherein the residual near-field signal is computed by removing a reference signal from a mean near-field signal of the cluster.

13. The method of claim 12 , further comprising:

firing the cluster for a number of times;

correlating first and second time delays variations with a time-break variation to determine which source element of the cluster has fired first; and

determining a delay of each source element in the cluster.

14. The method of claim 10 , wherein the time delay is corrected with a travel time of an acoustic wave that propagates from (i) the given individual source to (ii) a corresponding near-field sensor.

15. A method for quality control of a first source array for a seismic survey, the method comprising:

towing the first source array in water, wherein the first source array includes plural individual sources;

shooting at least one of the individual sources of the first source array;

receiving a time-break signal associated with a given individual source;

recording a near-field signal associated with the given individual source; and

calculating a time delay between the time-break signal and the near-field signal for the given individual source,

wherein the step of calculating the time delay further comprises:

computing a best maximum point of the near-field signal recorded with a hydrophone located next to the given individual source,

wherein the time delay of the given individual source is a difference in time between the time-break signal and the best maximum point of the near-field signal, and

wherein the best maximum is a sum of a start of slope of the near-field signal and an offset function determined during a bubble test during which the given individual source has been shooting alone.

16. The method of claim 15 , wherein a first time delay of a first source element in a cluster belonging to the first source array is calculated as a difference in time between the time break signal of the first source element in the cluster and a start of slope of a near-field signal recorded with a hydrophone located next to the first source element.

17. The method of claim 16 , wherein a second time delay of a second source element in the cluster is calculated as a difference in time between the time break signal of the second source element and a start of slope of a residual near-field signal recorded with a hydrophone located next to the second source element, wherein the residual near-field signal is computed by removing a reference signal from a mean near-field signal of the cluster.

18. The method of claim 17 , further comprising:

firing the cluster for a number of times;

correlating first and second time delays variations with a time-break variation to determine which source element of the cluster has fired first; and

determining a delay of each source element in the cluster.

19. The method of claim 15 , wherein the time delay is corrected with a travel time of an acoustic wave that propagates from (i) the given individual source to (ii) a corresponding near-field sensor.