Near-surface noise prediction and removal for data recorded with simultaneous seismic sources

Patent metadata

Field	Value
Publication number	US-9348050-B2
Application number	US-201313886761-A
Country	US
Kind code	B2
Filing date	May 3, 2013
Priority date	May 23, 2012
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A seismic data processing method for predicting and removing unwanted near-surface noise, e.g. refracted waves and surface waves, from composite seismograms acquired with multiple, encoded seismic sources in which the time records from the different sources overlap or interfere. Surface-consistent properties are determined ( 403 ) for the near-surface noise and used to predict the noise waveforms ( 404 ) for the composite simultaneous-source seismograms, and the waveforms are then subtracted or adaptively subtracted ( 406 ) from the seismograms.

First claim

The invention claimed is:

1. A method for predicting and removing near-surface noise from seismic data, comprising:
acquiring the seismic data by exciting a plurality of encoded sources operating simultaneously so as to produce time-overlapping records that are recorded at a plurality of seismic receivers;
using locations of the sources and their respective encoding information to characterize near-surface properties affecting propagation of seismic energy along the surface from each source to each receiver;
using a computer to predict time-overlapping noise recorded by a selected receiver; and
subtracting or adaptively subtracting, with a computer, the predicted noise from the seismic data measured by the selected receiver to yield data with reduced near-surface noise,
wherein the characterizing of near-surface properties comprises using waveform tomography using an iterative model optimization method.

2. The method of claim 1 , further comprising repeating the method for at least one additional selected receiver.

3. The method of claim 1 , wherein the source encoding information comprises at least one of a group consisting of time shifts, phase shifts, different sweep rates, and other encoding functions.

4. The method of claim 1 , wherein the sources are seismic vibrators.

5. The method of claim 1 , wherein at least two different modes of near-surface noise are characterized, modeled, and subtracted.

6. The method of claim 5 , wherein the at least two different modes comprise at least two of a group consisting of surface waves, refracted waves, and guided waves.

7. The method of claim 1 , wherein the characterizing near-surface properties and the predicting of the time-overlapping noise comprise:
for each seismic data trace in the seismic data and a selected time window, identifying simultaneous contributing sources, their locations, and their encoding functions;
determining raypaths along the surface connecting each receiver to each contributing source;
determining the surface-consistent properties of one or more of modes of propagation of seismic energy along the raypaths; and
for each of the contributing sources and for each mode, predicting a waveform for the near-surface noise by integrating effects of the surface-consistent properties over a raypath connecting the contributing source to the selected receiver and down-scaling seismic amplitudes to account for wave-spreading changes as distance from the source increases.

8. The method of claim 7 , wherein the determining of the surface-consistent properties comprises using an iterative optimization scheme, to minimize differences between predicted or modeled waveforms of near-surface noise and waveforms extracted from the acquired seismic data.

9. The method of claim 7 , further comprising repeating said method for one or more additional seismic data traces and time windows.

10. The method of claim 9 , wherein full data redundancy is utilized by considering all contributing sources in the optimization of a predicted waveform corresponding to a given measured seismic data trace.

11. The method of claim 7 , further comprising summing all of the predicted waveforms for each of the contributing sources and for each mode, and using that sum as the modeled noise which is subtracted or adaptively subtracted from the seismic data measured by the receiver.

12. The method of claim 7 , wherein the down-scaling of the seismic amplitudes to account for wave-spreading changes with distance traveled from the source comprises scaling the amplitudes in proportion to the inverse square root of the distance traveled.

13. The method of claim 7 , wherein the predicted waveforms are made to match actual waveforms in both amplitude and phase.

14. The method of claim 7 , wherein the predicted waveform for the near-surface noise is a plane wave, and the surface-consistent properties are coefficients or terms in a mathematical expression for the plane wave.

15. The method of claim 14 , wherein the coefficients or terms in the mathematical expression for the plane wave include at least one of a group consisting of:
a receiver coupling term for the receiver, which is a complex quantity, a function of frequency, and includes both amplitude and phase effects associated with the receiver's location;
a source encoding term for each window and contributing source; and
a source coupling term for each source location, which is a complex quantity, a function of frequency, and includes both amplitude and phase effects associated with the source's location.

16. The method of claim 14 , wherein the mathematical expression for the plane wave takes into account a plurality of different modes of near-surface wave propagation, and interference effects between the different modes.

17. The method of claim 7 , wherein the surface-consistent properties over a raypath are determined bin-by-bin, for each bin crossed by the raypath, the surface having been subdivided into regular or irregular bins.

18. A non-transitory computer readable medium encoded with instructions which when executed by a computer causes the computer to implement a method for predicting and removing near-surface noise from seismic data acquired using a plurality of encoded sources operating simultaneously so as to produce time-overlapping records at each of a plurality of seismic receivers, said method comprising:
using locations of the sources and their respective encoding information to characterize near-surface properties affecting propagation of seismic energy along the surface from each source to each seismic receiver;
predicting time-overlapping noise recorded by a selected receiver; and
converting the time-overlapping noise and the seismic data into a subsurface image with reduced noise by subtracting or adaptively subtracting the predicted noise from the seismic data measured by the selected receiver to yield data with reduced near-surface noise,
wherein the characterizing of near-surface properties comprises using waveform tomography using an iterative model optimization method.

19. A method for predicting and removing near-surface noise from seismic data, comprising:
acquiring the seismic data by exciting a plurality of encoded sources operating simultaneously so as to produce time-overlapping records that are recorded at a plurality of seismic receivers;
using locations of the sources and their respective encoding information to characterize near-surface properties affecting propagation of seismic energy along the surface from each source to each receiver;
using a computer to predict time-overlapping noise recorded by a selected receiver; and
subtracting or adaptively subtracting, with a computer, the predicted noise from the seismic data measured by the selected receiver to yield data with reduced near-surface noise,
wherein at least two different modes of near-surface noise are characterized, modeled, and subtracted, and
wherein the at least two different modes comprise at least two of a group consisting of surface waves, refracted waves, and guided waves.

20. A method for predicting and removing near-surface noise from seismic data, comprising:
acquiring the seismic data by exciting a plurality of encoded sources operating simultaneously so as to produce time-overlapping records that are recorded at a plurality of seismic receivers;
using locations of the sources and their respective encoding information to characterize near-surface properties affecting propagation of seismic energy along the surface fr

Assignees

• Krohn Christine E
• Exxonmobil Upstream Res Co

Inventors

• Krohn Christine E

Classifications

• G01V1/364 Primary

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

• G01V2210/324

  Filtering · CPC title