Analysis and application of low frequency shadows based on the asymptotic theory for porous media
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View abstract on PubMed
Summary
This summary is machine-generated.Low-frequency shadows beneath gas reservoirs are caused by slow P-waves converting from fast P-waves in porous media. This study confirms slow P-waves are key to dispersion and attenuation, explaining these seismic anomalies.
Area Of Science
- Geophysics
- Seismic Exploration
- Porous Media Physics
Background
- Low-frequency shadows beneath gas reservoirs are not fully explained by conventional P-wave attenuation or dispersion.
- Existing theories fail to account for the observed time delays and energy loss.
Purpose Of The Study
- To investigate the cause of low-frequency shadows using a new asymptotic theory for porous media.
- To analyze the dispersion and attenuation characteristics of seismic P-waves in layered permeable reservoirs.
- To validate a method for calculating and analyzing low-frequency shadows in 3D seismic data.
Main Methods
- Forward analysis of fast and slow P-wave dispersion and attenuation based on asymptotic theory for porous media.
- Analysis of methods for calculating low-frequency shadow occurrence frequencies.
- Application of S-transform time-frequency analysis to 3D seismic data from Sichuan work area M.
Main Results
- Fast P-waves show no significant dispersion or attenuation within the seismic frequency band.
- Slow P-waves are identified as the primary cause of dispersion and attenuation, leading to low-frequency shadows.
- S-transform analysis of seismic data revealed low-frequency shadow anomalies consistent with well data.
Conclusions
- The new asymptotic theory effectively explains low-frequency shadows through P-wave mode conversions in porous media.
- Slow P-waves are critical for understanding seismic wave behavior in gas reservoirs.
- The S-transform method demonstrates strong applicability for identifying low-frequency shadows in practical seismic exploration.
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