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Results
Results of systematic laboratory study involving shear wave propagation in anisotropic rocks demonstrate a number of features which are, without exception, in excellent agreement with theory. For a fixed propagation direction, shear wave splitting takes place whenever the polarization direction does not coincide with a principal anisotropic direction. The two shear waves have constant but distinct velocities as a function of the polarization angle. The slower shear mode exhibits a higher attenuation compared to the faster mode. Finally, and most importantly, this study unarguably demonstrates that principal anisotropic directions of a medium can be determined by mathematical rotation of a properly acquired data set as proposed by Alford (1986); this is based on demonstration of equivalence between physical and mathematical rotation in laboratory samples.
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
Shear-wave splitting diagnostic of some 3) What are the exact effects of cracks form of effective anisotropy is seen along on seismic waves? Perfecting formulations almost all raypaths in the crust, whether for propagation through perfectly parallel in shear-wave reflection surveys, shearwave flat penny-shaped cracks is not the answer. VSPs, above hydraulic-fracture induced The earth is not like that. I suggest the events, or above small earthquakes. My understanding has come from of compression (thrust faults), sedimentary numerical experiments, and sophisticated basins, in ancient rocks, in young rocks.
The darkened region in each figure represents the zone Resistivity soundings may be conducted in of low relative resistivity as predicted areas where subsurface conditions do not from a filtering method used in this study.
This clay layer is underlain by southeast of Saskatoon.
- Geophysics > Magnetic Surveying (1.00)
- Geophysics > Gravity Surveying (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.48)
Magnetic source bodies sometimes inversion procedures designed to estimate have a remanent magnetic field that the direction of remanent magnetization is very different from the current and existing have a major drawback. Estimation of direction of the present-day earth's field remanent magnetization has required knowledge for a given locality. Magnetic sources can be of the horizontal dimensions, depth classified as remanent, induced, or a combination of source, and strength of magnetization of of both remanent and induced magnetization. the magnetic source body. Often, magnetic In the case of magnetic induction, source bodies are buried'in the subsurface.
Wojcik, K.M., Bsrendsen, P., and Knapp, R.W., 1987, Seismic reflection study of a lamproite I would like to thank R.W. Kuapp for his help intrusion, Silver City Dome, Woodson Co. KS.: in processing the data, M.E.
- North America > United States > Texas > Meramec Formation > Meramec Formation > Mississippi Chat > Mississippi Lime > St. Louis Formation (0.89)
- North America > United States > Texas > Meramec Formation > Meramec Formation > Mississippi Chat > Meramec Formation > St. Louis Formation (0.89)
- North America > United States > Texas > Meramec Formation > Meramec Formation > Meramec Formation > Mississippi Lime > St. Louis Formation (0.89)
- (21 more...)
The convolution which replaces points by circles can be Three dimensional migration of zero offset data can be expressed in the frequency domain by a multiplication with a performed using Fourier transforms of time slices.
At the 53rd Annual SEG Meeting in Las Vegas, observations of anisotropy on surface reflection data and in downhole, clamped 3-component geophones near Cotulla, Texas were reported. For the first 5000 ft of sediment, the dominant effect, as discussed, was that of transverse isotropy with a vertical symmetry axis. Recent published reports on observations of azimuthal anisotropy prompted a reexamination of the downhole data for an estimate of azimuthal effects at this location. Upon careful editing and evaluation of data, the following conclusions were reached. This is evident from the linearly polarized downhole signals obtained on walkaway Sh and Sv checkshot surveys in these directions.
There has been much recent interest in field observations of shear-wave velocity variation with azimuth, e.g., the velocity difference between vertically propagating shear waves with orthogonal directions of horizontal particle motion. Some discussion of seismic surface and VSP data demonstrating these phenomena have tended to ignore the effects of the very commonly observed variation of seismic P-and S-wave velocities with polar angle, e.g., as evidenced by the difference between vertical S-wave velocity and "apparent" horizontal velocity measured from reflection normal moveout and walkaway VSP observations. A striking example of such data was described in the 1983 SEG Annual Meeting (Sriram et al., 1983), and some of the consequences were discussed at the 1984 Annual Meeting (Seriff, 1984). The fact that both azimuthal and polar anisotropy can exist simultaneously will be exemplified by data presented in this workshop (Sriram, 1987). The observations and significances of the polar anisotropy will be reviewed in this present at ion. References Seriff, A.J., 1984, Anisotropy, shear waves and shales: Presented at the 54th Annual International SEG Meeting, Atlanta.
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Near-well and vertical seismic profiles (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Three-component seismic data recorded in the Silo field, Wyoming, indicate shear-wave polarization and splitting caused by azimuthal anisotropy. Measurements in traveltime delays between split shear waves are used to determine the location and orientation of fractured zones in a carbonate reservoir level at 8000 ft (2400 m). Research is cant inuing to determine whether converted wave data and amplitude offset studies from compressional wave data will give similar results. The 3-component data enable lithology determination at a elastic reservoir level at 9000 ft (2700 m) in a stratigraphic interval in which sandstone reservoirs cannot be differentiated from shales on ordinary compressional wave data. Considerable potential exists in using 3-component seismic data for reservoir characterization.
- North America > United States > Wyoming > Laramie County (0.74)
- North America > United States > Texas > Montague County (0.47)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.68)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.31)
- North America > United States > Wyoming > Silo Field (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin (0.99)
- North America > United States > Nebraska > DJ (Denver-Julesburg) Basin (0.99)
- (2 more...)