Subterranean formation monitoring using frequency domain weighted analysis

Patent metadata

Field	Value
Publication number	US-9921326-B2
Application number	US-201515120366-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Feb 25, 2014
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The disclosed method includes receiving resulting signals emanating from a subterranean formation, wherein the resulting signals are caused by signals emitted from seismic sources. The method further includes dividing the resulting signals into a plurality of sub-samples. The method includes determining a frequency content of one or more of the sub-samples and assigning a weight to or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample, wherein the assigned weight is based, at least in part, on an estimate of the amount of noise present in the frequency content of the sub-sample. The method further includes combining the weighted frequency contents of the sub-samples to produce a weighted sample. The method further includes determining one or more properties of the subsurface formation based, at least in part, on the weighted sample.

First claim

The invention claimed is:

1. A method of seismic monitoring of a subterranean formation comprising:
receiving resulting signals emanating from the subterranean formation, wherein the resulting signals are caused, at least in part, by incident signals emitted from a plurality of seismic sources located above the subsurface formation and wherein the resulting signals are received for a predetermined emission length of time;
dividing a total time length of at least a part of the resulting signals into a plurality of sub-samples such that each sub-sample has a time length smaller than the total time length;
for one or more of the sub-samples:
determining a frequency content of the sub-sample in a frequency domain; and
assigning a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample, wherein the assigned weight is based, at least in part, on a comparison of (1) the frequency components of the sub-sample to (2) frequency components of received signals from previous times;

combining the weighted frequency contents of the sub-samples to produce a weighted sample; and
determining one or more properties of the subsurface formation based, at least in part, on the weighted sample.

2. The method of claim 1 , wherein the step of assigning a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample is based, at least in part, on an estimate of the amount of noise present in the frequency content of the sub-sample and further comprises:
determining one or more amplitudes of frequency components of the sub-sample that are adjacent to one or more frequencies of the incident signals.

3. The method of claim 2 , further comprising:
determining a set of median value for frequency components that are adjacent to one or more frequencies of the incident signals; and
wherein assigning a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample further comprises determining if the amplitude a frequency component of the sub-sample is above a corresponding median value for the frequency component and, if so, removing the frequency component from the sub-sample.

4. The method of claim 1 , wherein determining one or more properties of the subsurface formation based, at least in part, on the weighted sample further comprises:
combining a plurality of weighted samples, wherein the weights samples correspond to a plurality of received resulting signals based on monofrequency incident signals with different frequencies; and
determining one or more properties of the subsurface formation based, at least in part, on the combined plurality of weighted samples.

5. The method of claim 1 , further comprising:
controlling the plurality of seismic sources to each emit an incident signal having a selected frequency for a predetermined emission length of time.

6. The method of claim 5 , wherein the selected frequency for two or more of the seismic sources is the same.

7. The method of claim 1 , wherein determining one more properties of the subsurface formation based, at least in part, on the frequency content of the sub-samples, as weighted by the weight of the sub-sample comprises:
monitoring fluid production from the subsurface formation.

8. The method of claim 1 , wherein determining one more properties of the subsurface formation based, at least in part, on the frequency content of the sub-samples, as weighted by the weight of the sub-sample comprises:
monitoring a steam injection operation in the subsurface formation.

9. The method of claim 1 , wherein the sub-samples have equal lengths.

10. A seismic monitoring system, comprising:
one or more seismic sources to emit incident signals into a subterranean formation for a predetermined emission length of time;
one or more seismic receivers to receive resulting signals emanating from the subsurface formation;
at least one processor; and
a memory including non-transitory executable instructions that, when, executed cause the at least one processor to:
divide a total time length of at least a part of the resulting signals into a plurality of sub-samples such that each sub-sample has a time length smaller than the total time length;
for one or more of the sub-samples:
determine a frequency content of the sub-sample in a frequency domain; and
assign a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample, wherein the assigned weight is based, at least in part, on a comparison of (1) the frequency components of the sub-sample to (2) frequency components of received signals from previous times;

combine the weighted frequency contents of the sub-samples to produce a weighted sample; and
determine one or more properties of the subsurface formation based, at least in part, on the weighted sample.

11. The seismic monitoring system of claim 10 , wherein the executable instructions that cause the at least one processor to assigning a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample, wherein the assigned weight is based, at least in part, on an estimate of the amount of noise present in the frequency content of the sub-sample comprises further causes the at least one processor to:
determine one or more amplitudes of frequency components of the sub-sample that are adjacent to one or more frequencies of the incident signals.

12. The seismic monitoring system of claim 10 , wherein the executable instructions further cause the at least one processor to:
determine a set of median value for frequency components that are adjacent to one or more frequencies of the incident signals; and
wherein the executable instructions that case the at least one processor to assign a weight to one or more components of the frequency content of the sub-sample to produce a weighted frequency content of the sub-sample further cause the at least one processor to:
determine if the amplitude a frequency component of the sub-sample is above a corresponding median value for the frequency component and, if so, removing the frequency component from the sub-sample.

13. The seismic monitoring system of claim 10 , wherein the executable instructions further cause the at least one processor to:
combine a plurality of weighted samples, wherein the weights samples correspond to a plurality of received resulting signals based on monofrequency incident signals with different frequencies; and
determine one or more properties of the subsurface formation based, at least in part, on the combined plurality of weighted samples.

14. The seismic monitoring system of claim 10 , wherein the executable instructions that cause the at least one processor to determine a frequency content of the sub-sample further causes the at least one processor to:
determine whether the sub-sample includes frequency components that are indicative of impulsive signals or noise.

15. The seismic monitoring system of claim 10 , wherein the executable instructions further cause the at least one processor to:
control the plurality of seismic sources to each emit an incident signal having a selected frequency for a predetermined emission length of time.

16. A non-transitory computer-readable medium, comprising instructions that, when executed by a processor, cause the processor to:
receive resulting signals emanating from the subterranea

Assignees

• Cgg Services Sa
• Cgg Services Sas

Inventors

• Forgues Eric
• Beilles Michael
• Berron Cécile

Classifications

• G01V1/306

  for determining physical properties of the subsurface, e.g. impedance, porosity or attenuation profiles · CPC title

• G01V1/364 Primary

  Seismic filtering (G01V1/37 takes precedence) · CPC title

• G01V2210/21

  Frequency-domain filtering, e.g. band pass · CPC title

• G01V2210/324

  Filtering · CPC title

• G01V1/003

  Seismic data acquisition in general, e.g. survey design (G01V1/3808, G01V1/42 take precedence) · CPC title