Surface-to-borehole illumination of a high-velocity layer using marine VSP
- British Geological Survey, Edinburgh (United Kingdom)
- Conoco UK Ltd., Aberdeen (United Kingdom)
Two marine walkaway VSP lines are recorded by three-component receivers positioned in a dolomite layer. The layer has a high seismic velocity relative to the surrounding rocks and may be fracture. The recorded wavefield is analyzed to determine whether this acquisition is suitable to image details of the internal structure of the layer. The principal arrivals in the wavefield are a dominant horizontally refracted compressional wave with a smooth unbroken moveout, converted shear-waves from shallow reflectors, and reverberation of these converted shear-waves within the high velocity layer. Anisotropic analyses of the converted shear-waves estimate an overburden birefringence of 3% and a polarization direction consistent with the known NW-SE maximum compressive stress. Full-wave modeling of the recorded wavefield aids identification of the various arrivals and constrains the attenuation and anisotropic properties of the layer, which appears laterally uniform with the most satisfactory model possessing low attenuation but a birefringence of no more than 5%. If the layer is cracked, these results are diagnostic of evenly distributed cracks with a scalelength smaller than a fraction of a wavelength.
- OSTI ID:
- 80183
- Report Number(s):
- CONF-941015-; TRN: IM9532%%310
- Resource Relation:
- Conference: 64. annual meeting of the Society of Exploration Geophysicists and international exposition, Los Angeles, CA (United States), 23-27 Oct 1994; Other Information: PBD: 1994; Related Information: Is Part Of SEG international exposition and sixty-fourth annual meeting -- 1994 Technical program: Expanded abstracts with authors` biographies; PB: 1736 p.
- Country of Publication:
- United States
- Language:
- English
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