Downhole seismic imaging of a massive sulfide orebody with mode‐converted waves, Halfmile lake, New Brunswick, Canada

Geophysics ◽  
2004 ◽  
Vol 69 (2) ◽  
pp. 318-329 ◽  
Author(s):  
Gilles Bellefleur ◽  
Christof Müller ◽  
David Snyder ◽  
Larry Matthews
Keyword(s):  
New Brunswick ◽  
Seismic Data ◽  
Massive Sulfide ◽  
Data Migration ◽  
P Waves ◽  
S Waves ◽  
Additional Imaging ◽  
Mineralized Zone ◽  
Converted Waves ◽  
Host Rocks

Multioffset, multiazimuth downhole seismic data were acquired at Halfmile lake, New Brunswick, to image known massive sulfide lenses and to investigate the potential existence of a steeply dipping mineralized zone connecting them. The massive sulfide lenses, which have significantly higher elastic impedances than host rocks, produce strong scattering. The downhole seismic data show prominent scattered (P‐P and S‐S) and mode‐converted (P‐S and S‐P) waves originating from the deposit. Such complex scattering from massive sulfide ore was not observed previously in vertical seismic profiling data. Migration of the scattered and mode‐converted waves from several shot points imaged different parts of the deepest lens. The scattered S‐waves and mode‐converted waves provide additional imaging capabilities that should be considered when selecting downhole seismic methods for mining exploration.

Transformation to zero offset for mode‐converted waves

Geophysics ◽  
1992 ◽  
Vol 57 (3) ◽  
pp. 474-477 ◽  
Author(s):  
Mohammed Alfaraj ◽  
Ken Larner
Keyword(s):  
Seismic Data ◽  
Constant Velocity ◽  
Reflection Point ◽  
P Waves ◽  
S Waves ◽  
Nmo Correction ◽  
Converted Waves ◽  
Zero Offset ◽  
Correct Data

The transformation to zero offset (TZO) of prestack seismic data for a constant‐velocity medium is well understood and is readily implemented when dealing with either P‐waves or S‐waves. TZO is achieved by inserting a dip moveout (DMO) process to correct data for the influence of dip, either before or after normal moveout (NMO) correction (Hale, 1984; Forel and Gardner, 1988). The TZO process transforms prestack seismic data in such a way that common‐midpoint (CMP) gathers are closer to being common reflection point gathers after the transformation.

scholarly journals Three-component amplitude versus offset analysis

1989 ◽  
Vol 20 (2) ◽  
pp. 257
Author(s):  
D.R. Miles ◽  
G. Gassaway ◽  
L. Bennett ◽  
R. Brown
Keyword(s):  
Seismic Data ◽  
P Wave ◽  
S Wave ◽  
Converted Wave ◽  
P Waves ◽  
S Waves ◽  
Avo Analysis ◽  
Avo Inversion ◽  
Amplitude Versus Offset ◽  
Converted Waves

Three-component (3-C) amplitude versus offset (AVO) inversion is the AVO analysis of the three major energies in the seismic data, P-waves, S-waves and converted waves. For each type of energy the reflection coefficients at the boundary are a function of the contrast across the boundary in velocity, density and Poisson's ratio, and of the angle of incidence of the incoming wave. 3-C AVO analysis exploits these relationships to analyse the AVO changes in the P, S, and converted waves. 3-C AVO analysis is generally done on P, S, and converted wave data collected from a single source on 3-C geophones. Since most seismic sources generate both P and S-waves, it follows that most 3-C seismic data may be used in 3-C AVO inversion. Processing of the P-wave, S-wave and converted wave gathers is nearly the same as for single-component P-wave gathers. In split-spread shooting, the P-wave and S-wave energy on the radial component is one polarity on the forward shot and the opposite polarity on the back shot. Therefore to use both sides of the shot, the back shot must be rotated 180 degrees before it can be stacked with the forward shot. The amplitude of the returning energy is a function of all three components, not just the vertical or radial, so all three components must be stacked for P-waves, then for S-waves, and finally for converted waves. After the gathers are processed, reflectors are picked and the amplitudes are corrected for free-surface effects, spherical divergence and the shot and geophone array geometries. Next the P and S-wave interval velocities are calculated from the P and S-wave moveouts. Then the amplitude response of the P and S-wave reflections are analysed to give Poisson's ratio. The two solutions are then compared and adjusted until they match each other and the data. Three-component AVO inversion not only yields information about the lithologies and pore-fluids at a specific location; it also provides the interpreter with good correlations between the P-waves and the S-waves, and between the P and converted waves, thus greatly expanding the value of 3-C seismic data.

A plane‐wave decomposition for elastic wave fields applied to the separation of P‐waves and S‐waves in vector seismic data

Geophysics ◽  
1986 ◽  
Vol 51 (2) ◽  
pp. 419-423 ◽  
Author(s):  
A. J. Devaney ◽  
M. L. Oristaglio
Keyword(s):  
Plane Wave ◽  
Elastic Wave ◽  
Seismic Data ◽  
Seismic Profile ◽  
P Waves ◽  
Wave Fields ◽  
S Waves ◽  
Plane Wave Decomposition ◽  
Wave Decomposition ◽  
Seismic Measurements

We describe a method to decompose a two‐dimensional (2-D) elastic wave field recorded along a line into its longitudinal and transverse parts, that is, into compressional (P) waves and shear (S) waves. Separation of the data into P-waves and S-waves is useful when analyzing vector seismic measurements along surface lines or in boreholes. The method described is based on a plane‐wave expansion for elastic wave fields and is illustrated with a synthetic example of an offset vertical seismic profile (VSP) in a layered elastic medium.

Shear waves, multiple reflections, and converted waves found by a deep vertical wave test (vertical seismic profiling)

Geophysics ◽  
1980 ◽  
Vol 45 (9) ◽  
pp. 1373-1411 ◽  
Author(s):  
C. C. Lash
Keyword(s):  
Traveling Waves ◽  
Wave Energy ◽  
S Wave ◽  
Multiple Reflections ◽  
P Waves ◽  
S Waves ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Converted Waves ◽  
Set Up

Evidence that shear (S) waves are much more important in seismic surveys than currently believed was found in each of two deep well tests conducted some time ago. Wave tests were recorded along vertical lines, following procedures which are now designated “vertical seismic profiling.” The results may be divided into (1) evidence that shear (S) waves are produced by in‐hole dynamite charges and by the resulting compressional (P) waves, and (2) evidence that the S‐waves subsequently produce P‐waves. The proof of S‐wave production is quite conclusive. Even if we say that only P‐waves are set up in the immediate vicinity of the shot, some S‐waves are then generated within a radius of 10 to 100 ft to form what we will call a direct or “source S wave.” Other S‐waves are set up by conversion of P‐wave energy to S‐wave energy at interfaces hundreds and thousands of feet from the dynamite charge. In contrast to the P to S conversion, the evidence for S to P conversion is less conclusive. The source S‐wave generated near the shot was found to have a long‐period character, with many cycles which are believed to be controlled by the layering near the shot. The PS converted waves, which appear later, resemble the P‐waves that produce them. The interference to primary reflections by multiple reflections and/or converted waves produces complex signals at points deep in the well which require directional discrimination to separate up‐traveling waves from down‐traveling waves.

Real data results of Kirchhoff elastic wave migration

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 1006-1011 ◽  
Author(s):  
Ting‐Fan Dai ◽  
John T. Kuo
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Horizontal Layer ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Surface Data ◽  
And Migration ◽  
Wave Migration ◽  
Kirchhoff Integral

Although Kirchhoff integral migration has attracted considerable attention for seismic data processing since the early 1970s, it, like all other seismic migration methods, is only applicable to compressional (P) waves. Because of a recent surge of interest in shear (S) waves, Kuo and Dai (1984) developed the Kirchhoff elastic (P and S) wave migration (KEWM) formulation and migration principle for the case of source and receiver noncoincidence. They obtained encouraging results using two‐dimensional (2-D) synthetic surface data from various geometric elastic models, including a dipping layer, a composite dipping and horizontal layer, and two layers over a half‐space.

Separation of P-waves and S-waves in borehole seismic data

1985 ◽  
Author(s):  
M. L. Oristaglio ◽  
A. J. Devaney ◽  
A. Track
Keyword(s):  
Seismic Data ◽  
P Waves ◽  
S Waves ◽  
Borehole Seismic

Separating P‐ and S‐waves in prestack 3D elastic seismograms using divergence and curl

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 286-297 ◽  
Author(s):  
Robert Sun ◽  
George A. McMechan ◽  
Hsu‐Hong Hsiao ◽  
Jinder Chow
Keyword(s):  
Wave Equation ◽  
Computational Model ◽  
Seismic Data ◽  
Velocity Model ◽  
Scalar Wave ◽  
Elastic Wave Equation ◽  
Seismic Section ◽  
P Waves ◽  
Scalar Wave Equation ◽  
S Waves

The reflected P‐ and S‐waves in a prestack 3D, three‐component elastic seismic section can be separated by taking the divergence and curl during finite‐difference extrapolation. The elastic seismic data are downward extrapolated from the receiver locations into a homogeneous elastic computational model using the 3D elastic wave equation. During downward extrapolation, divergence (a scalar) and curl (a three‐component vector) of the wavefield are computed and recorded independently, at a fixed depth, as a one‐component seismogram and a three‐component seismogram, respectively. The P‐ and S‐velocities in the elastic computational model are then split into two independent models. The divergence seismogram (containing P‐waves only) is then upward extrapolated (using the scalar wave equation) through the P‐velocity model to the original receiver locations at the surface to obtain the separated P‐waves. The x‐component, y‐component, and z‐component seismograms of the curl (containing S‐waves only) are upward extrapolated independently (using the scalar wave equation) through the S‐velocity model to the original receiver locations at the surface to obtain the separated S‐waves. Tests are successful on synthetic seismograms computed for simple laterally heterogeneous 2D models with a 3D recording geometry even if the velocities used in the extrapolations are not accurate.

Downhole seismic scattered and mode‐converted waves from the Halfmile Lake massive sulfide orebody, New Brunswick

2002 ◽  
Author(s):  
Gilles Bellefleur ◽  
Christof Müller ◽  
Dave Snyder ◽  
Larry Matthews
Keyword(s):  
New Brunswick ◽  
Massive Sulfide ◽  
Converted Waves
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