A new method for shear‐wave logging

Geophysics ◽  
1980 ◽  
Vol 45 (10) ◽  
pp. 1489-1506 ◽  
Author(s):  
Chōrō Kitsunezaki
Keyword(s):  
Shear Wave ◽  
Single Point ◽  
External Pressure ◽  
Borehole Wall ◽  
S Wave ◽  
Neutral Buoyancy ◽  
Wave Characteristics ◽  
Sonic Log ◽  
Receiver System ◽  
Filter Tube

Reliable evaluation of shear (S) wave characteristics in boreholes may be facilitated by the system proposed here, in a wide variety of geologic conditions and depths. The measurements can be done with a sonde, suspended freely in water contained in a borehole. The main part of the sonde consists of a source, a filter tube, and receivers. In this system, the wave field is treated approximately as that in an infinite homogeneous solid medium, because the wavelength is sufficiently longer than the borehole diameter. The source behaves as a single point force. The direct S‐wave is detected on a line (borehole axis) perpendicular to the force axis, in which pre‐dominant radiation of shear wave is expected. This fact is completely different from some modified systems of sonic log, in which (shear wave) is the converted‐refracted wave propagating as the shear wave along a borehole wall. The proposed source system is the (indirect‐excitation type), wherein the force is applied to a borehole wall indirectly through a pressure distribution of doublet‐type excited in the water. Based on its principle, this source system eliminates generation of dilatational noise waves and also assures operation at greater depths because no work is done against the external pressure, as a whole, at the source. The proposed receiver system is the suspension type, wherein horizontal motion of the borehole wall (ground motion of S‐wave) is detected through corresponding water motion by a detector of neutral buoyancy. The fundamental applicability of this logging system was confirmed by experiments at shallow depths.

FROM THE BOREHOLE WALL INTO THE FORMATION – COMBINING BOREHOLE IMAGES WITH DEEP SHEAR WAVE IMAGING TECHNOLOGY

2019 ◽  
Author(s):  
Stefan Schimschal ◽  
Stephen Fayers ◽  
Nicklas Ritzmann ◽  
Martin Cox ◽  
Iain Whyte
Keyword(s):  
Shear Wave ◽  
Borehole Wall ◽  
Imaging Technology ◽  
Shear Wave Imaging ◽  
Wave Imaging

Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

2022 ◽  
Vol 41 (1) ◽  
pp. 47-53
Author(s):  
Zhiwen Deng ◽  
Rui Zhang ◽  
Liang Gou ◽  
Shaohua Zhang ◽  
Yuanyuan Yue ◽  
...  
Keyword(s):  
Shear Wave ◽  
Reservoir Characterization ◽  
Qaidam Basin ◽  
P Wave ◽  
Data Sets ◽  
Direct Shear ◽  
Subsurface Structure ◽  
S Wave ◽  
West China ◽  
Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

scholarly journals Rapid assessment of S-wave profiles from the inversion of multichannel

1998 ◽  
Vol 41 (1) ◽  
Author(s):  
G. A. Tselentis ◽  
G. Delis
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Structure ◽  
Rapid Assessment ◽  
Detailed Knowledge ◽  
S Wave ◽  
Surface Wave Dispersion ◽  
Wave Profiles ◽  
Shear Wave Velocity Structure

The importance of detailed knowledge of the shear-wave velocity structure of the upper geological layers was recently stressed in strong motion studies. In this work we describe an algorithm which we have developed to infer the 1D shear wave velocity structure from the inversion of multichannel surface wave dispersion data (ground-roll). Phase velocities are derived from wavenumber-frequency stacks while the inversion process is speeded up by the use of Householder transformations. Using synthetic and experimental data, we examined the applicability of the technique in deducing S-wave profiles. The comparison of the obtained results with those derived from cross-hole measurements and synthesized wave fields proved the reliability of the technique for the rapid assessment of shear wave profiles during microzonation investigations.

On the ratio of P-wave to S-wave corner frequencies for shallow earthquake sources

1974 ◽  
Vol 64 (4) ◽  
pp. 1159-1180 ◽  
Author(s):  
F. A. Dahlen
Keyword(s):  
Single Point ◽  
Three Dimensional ◽  
P Wave ◽  
Corner Frequency ◽  
S Wave ◽  
Earthquake Sources ◽  
Kinematical Model ◽  
Self Similar ◽  
Smooth Deceleration ◽  
Shallow Focus

abstract We construct a theoretical three-dimensional kinematical model of shallow-focus earthquake faulting in order to investigate the ratio of the P- and S-wave corner frequencies of the far-field elastic radiation. We attempt to incorporate in this model all of the important gross kinematical features which would arise if ordinary mechanical friction should be the dominant traction resisting fault motion. These features include a self-similar nucleation at a single point, a subsonic spreading of rupture away from that point, and a termination of faulting by smooth deceleration. We show that the ratio of the P-wave corner frequency to the S-wave corner frequency for any model which has these features will be less than unity at all points on the focal sphere.

Wave characteristics in elliptical orthorhombic media

Geophysics ◽  
2021 ◽  
pp. 1-52
Author(s):  
Alexey Stovas ◽  
Yuriy Roganov ◽  
Vyacheslav Roganov
Keyword(s):  
Anisotropic Medium ◽  
Wave Equations ◽  
Reference Model ◽  
Relative Magnitude ◽  
P Wave ◽  
S Wave ◽  
Wave Characteristics ◽  
Singularity Point ◽  
Wave Properties ◽  
Wave Modes

An elliptical anisotropic medium is defined as a simplified representation of anisotropy in which the anelliptic parameters are set to zero in all symmetry planes. Despite of the fact that this model is rather seldom observed for real rocks, it is often used as a reference model. The P-wave equations for an elliptical anisotropic medium is well known. However, the S-wave equations have not been derived. Thus, we define all wave modes in elliptical orthorhombic models focusing mostly on the S-wave properties. We show that all wave modes in elliptical orthorhombic model are generally coupled and analyze the effect of additive coupling term. As the result, there is an S wave fundamental singularity point located in one of the symmetry planes depending on the relative magnitude of S wave stiffness coefficients.

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