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Velocity dispersion: A tool for characterizing reservoir rocks

Geophysics

By:
and

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Abstract

Apparent discrepancies between velocity measurements made with different frequencies in a formation at the Gypsy test site are explained in terms of elastic scattering and intrinsic attenuation. The elastic scattering component of the dispersion (38%) in a marine interval above the Gypsy sandstone is estimated via simple models constructed from well log information. Any dispersion above the predicted value for elastic scattering in this interval is assigned to intrinsic attenuation (62%). Using the vertical measurements in the well, the marine interval directly above the Gypsy sandstone has an estimated intrinsic Q1 = 51 and an effective Q because of the scattering of Qsc = 85. The total Q of the combined mechanisms is 32. The dispersion of the vertical measurements through the heterogeneous sands and shales of the Gypsy formation can be explained using an intrinsic QI = 30 and neglecting the effects of scattering. The horizontal observations require a more detailed modeling effort to unravel the relative roles of path and volume effects, elastic scattering, attenuation, and intrinsic anisotropy. Thin layers barely resolvable on the sonic logs play a significant role in modifying the crosswell response. Potentially, the dispersion can be a key to mapping reservoir properties using crosswell and surface seismic data.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Velocity dispersion: A tool for characterizing reservoir rocks
Series title:
Geophysics
Volume
62
Issue:
2
Year Published:
1997
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysics
First page:
477
Last page:
486