slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Does It Matter What Kind of PowerPoint Presentation
Download Presentation
Does It Matter What Kind of

Loading in 2 Seconds...

play fullscreen
1 / 37

Does It Matter What Kind of - PowerPoint PPT Presentation


  • 278 Views
  • Uploaded on

Does It Matter What Kind of. Vibroseis Deconvolution is Used?. Larry Mewhort* Husky Energy. Sandor Bezdan Geo-X Systems. Mike Jones Schlumberger. Outline. Introduction Description of Pikes Peak 141/15-06-50-23W5M VSP Filtering elements of the Vibroseis system

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Does It Matter What Kind of' - Faraday


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Does It Matter What Kind of

Vibroseis Deconvolution is Used?

Larry Mewhort* Husky Energy

Sandor Bezdan Geo-X Systems

Mike Jones Schlumberger

outline
Outline
  • Introduction
  • Description of Pikes Peak 141/15-06-50-23W5M VSP
  • Filtering elements of the Vibroseis system
  • Down hole wavelets before and after deconvolutions
  • Conclusions
  • Acknowledgements
introduction i
Introduction I
  • Effective stratigraphic seismic interpretation is aided by having a constant and known phase in the final section.
  • Removal of the transfer function between the vibrator pilot sweep and the far-field velocity signature is needed to achieve such high quality seismic.
  • The downgoing wavefield extracted from a Vertical Seismic Profile (VSP) represents the far-field signature at the discrete depths sampled by the geophones.
introduction ii
Introduction II
  • Vibroseis deconvolution attempts to remove the transfer function knowing only the pilot sweep; the impulse responses of the geophones and the recording instruments; and usually assuming white reflectivity in the Earth.
  • The VSP is an ideal tool to test the effectiveness of deconvolutions.
pikes peak vsp experiment
Pikes Peak VSP Experiment
  • A 3C, five-level ASI tool was used to acquire data from 66 depths 27.0 to 514.5 meters (depth increment of 7.5 meters).
  • A Mertz HD18 Vibrator located 23 meters from the well head generated an 8 to 200 Hz linear sweep.
  • The weighted-sum estimate of the ground force (WSEGF) was used as the phase lock signal.
  • The WSEGF was maintained in phase with the pilot sweep as per the SEG standard.
filters that deconvolution must remove to recover the reflectivity of the earth
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

If these were all minimum phase then perhaps all that would be needed would be conventional spiking deconvolution?

slide7

Convert the Klauder wavelet into its minimum phase equivalent with the Vibop operator

Klauder Wavelet

Minimum phase equivalent of the Klauder wavelet

Vibop

filters that deconvolution must remove to recover the reflectivity of the earth8
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

slide9

The recorded weighted-sum ground force estimates

Wavelets

200 ms

Amplitude

200 Hz

0 Hz

200 degrees

Phase

-200 degrees

filters that deconvolution must remove to recover the reflectivity of the earth10
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

slide11

50

Phase (degrees)

0

-50

filters that deconvolution must remove to recover the reflectivity of the earth12
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

standard vibroseis theory
Standard Vibroseis Theory
  • The P-wave far-field particle displacement is proportional to the applied force.
  • Equivalently, the far-field particle velocity is the time derivative of the true ground force.
  • In the frequency domain the derivative filter boosts the amplitude spectrum 6 dB/octave and applies a +90 degree phase shift.
slide15

Test of whether a differential filter is minimum phase

Input Wavelets

Derivative Wavelet

Wavelet

After Wiener Deconvolution

Derivative Wavelet

Wavelet

filters that deconvolution must remove to recover the reflectivity of the earth16
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

slide17

Inverse Geophone Filter

Filter

Phase

Amplitude

filters that deconvolution must remove to recover the reflectivity of the earth18
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

filters that deconvolution must remove to recover the reflectivity of the earth20
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

slide21

Q from VSP

Q - Spectral Ratios (blue) and Centroid Frequency (red)

Q

slide22

Theoretical effect of a constant Q of 50

Wavelet at 102 meters depth

Wavelet at 514.5 meters depth

102 meter wavelet after applying a Q of 50 over a distance of 400 meters

filters that deconvolution must remove to recover the reflectivity of the earth23
Filters that Deconvolution must remove to recover the reflectivity of the Earth

Klauder Wavelet

Vibrator Electronic and

Hydraulic Distortions

Baseplate Flexing

Differential Filter

Geophone Impulse

Response

Instrument Impulse

Response

Attenuation of the

Earth ‘Q’

Reflectivity Scattering

Attenuation

slide25

Downgoing Wavelets

10 ms

+200 degrees

90 degrees

0 Hz

-200 degrees

200 Hz

  • wavelets have been compensated for the amplitude and phase effects of the geophone
slide26

Finding the best fit Constant phase Wavelet

Correlation Coefficient versus Constant Phase

Blue is the best fit constant phase wavelet

Red is the actual wavelet

Green is the zero phase equivalent wavelet

slide27

Downgoing Wavelets

Average constant phase is 49 degrees

10 ms

+200 degrees

0 Hz

-200 degrees

200 Hz

90%

100%

  • wavelets have been compensated for the amplitude and phase effects of the geophone
slide28

Spectra for the Downgoing Wavelets before and after Deconvolutions

Geophone at 394.5 meters

Amplitude (dB)

slide29

Wavelets after zero phase deconvolution and geophone phase removal (80 ms operator 0.1% PW)

Downgoing multiple

10 ms

Average constant phase is 46 degrees

Precursor

+200 degrees

-200 degrees

0 Hz

200 Hz

Deconvolution operator designed on wavelets averaged over 400 meters

90%

100%

slide30

Low Frequency Adjustments when computing the phase of the T5 Deconvolution Operator

22 dB

Amplitude (dB)

48 dB/octave

Applied to reduce the effect of low frequency estimation problems on the phase of the output

slide31

Wavelets after T5 deconvolution (4 Hz frequency smoothing 0.01% PW) with geophone phase and amplitude removal

Average constant phase is -75 degrees

10 ms

+200 degrees

-200 degrees

200 Hz

0 Hz

Deconvolution operator designed on wavelets averaged over 400 meters

90%

100%

slide32

Wavelets after T5 deconvolution (4 Hz Frequency smoothing 0.01% PW), low frequency filtering and Vibop

Average constant phase is 41 degrees

10 ms

+200 degrees

Deconvolution operator designed on wavelets averaged over 400 meters

-200 degrees

200 Hz

0 Hz

90%

100%

slide33

Wavelets after T5 deconvolution (4 Hz frequency smoothing 0.01% PW) and spectral replacement

Average constant phase is 3 degrees

10 ms

+200 degrees

0 Hz

-200 degrees

200 Hz

Deconvolution operator designed on wavelets averaged over 400 meters

90%

100%

slide34

Wavelets after T5 deconvolution (4 Hz frequency smoothing 0.01% PW) and low frequency filtering

Average constant phase is -27 degrees

10 ms

+200 degrees

0 Hz

-200 degrees

200 Hz

Deconvolution operator designed on wavelets averaged over 400 meters

90%

100%

conclusions i
Conclusions I
  • T5 deconvolution gave the most consistent constant phase results.
  • Adjusting the Klauder wavelet to minimum phase resulted in wavelets that were less constant phase or compressed (but they appeared to be close to minimum phase).
  • Spectral replacement of the low frequencies resulted in the wavelets being less consistent than using low frequency filtering.
conclusions ii
Conclusions II
  • The amount of low frequency filtering changed the slope of the low frequency phase curve.
  • Zero phase deconvolution of course did not change the phase of the original data and did not remove the down-going multiple.
  • Removing the geophone impulse response was not desirable.
acknowledgements
Acknowledgements
  • Husky Energy
  • Geo-X (Xi-Shuo Wang and Mike Perz)
  • Schlumberger
  • Dr. Gary Margrave
  • Guillaume Cambois
  • AOSTRA and the CREWES sponsors