The separation of P- and S-wave components from three-component crosswell
, Xiangzhi Zeng
, Jianghai Xia
, Mao Mao
Institute of Geophysics and Geomatics, The China University of Geosciences, 388 Rumo Rd., Wuhan 430074, China
Subsurface Imaging and Sensing Laboratory, Institute of Geophysics and Geomatics, The China University of Geosciences, 388 Rumo Rd., Wuhan 430074, China
Received 9 January 2012
Accepted 12 March 2012
Available online 23 March 2012
3C crosswell data
P- and S- wave separation
We present a method of separation of P- and S-wave components from three-component (3C) crosswell
seismic data. Based on differences between P and S waves in polarization and apparent velocity, this method
separates P and S waves in a common source gather without estimating emergence angles and by means of
data processing techniques including band-pass ﬁlter for preprocessing, high-resolution τ–p transform for
removing tube waves and separating up-going and down-going waves, and covariance polarization analysis
for correcting the direction of geophone and separating polarization. To separate P- and S-wave data, this
method requires only the input of original 3C crosswell data and the ﬁrst arrivals of P waves. We verify
and demonstrate effectiveness and practicability of this method using 2C modeling tests as well as real 3C
© 2012 Elsevier B.V. All rights reserved.
Along with the continued progressing in geophysical exploration
techniques, hydrocarbon reservoirs with thin layers, a small
extension scale, volcanic rocks and mud rock cracks have become
new exploration targets. As a high-resolution exploration method,
the crosswell seismic technique plays a critical role in oil-gas explora-
tion and production. Crosswell seismic data in seismic exploration
contain nearly all types of waves such as direct waves, transmitted
waves, refracted waves, converted waves, diffracted waves, tube
waves, and guided waves. The recorded waveﬁelds include valuable
information on the subsurface, so multi-component borehole
exploration has become a hotspot in research and practice.
Multicomponent processing possesses obvious advantages compared
to P waves. For example, S waves have higher spatial resolution than
P waves; and the combined P-wave and S-wave exploration is
successfully used in determining medium properties like Poisson's
ratio and anisotropy, etc. A bottleneck problem in multi-component
crosswell data processing is separation of P-wave and S-wave data.
If P-wave and S-wave data are separated successfully, it will be
possible to not only increase quality of P-wave imaging, but also
obtain S-wave velocity proﬁles from crosswell data.
Techniques of separation of P-wave and S-wave data have been
studied and developed by numerous researchers, among which
methods based on wave equation are perfect in theory. Dankbaar
(1985) brought forward a P- and S-wave separation equation in the
FK domain, which used elastic wave equation and free surface
condition. Devaney and Oristaglio (1986) made use of plane wave
to decompose P- and S-wave data, and introduced the equation for
P- and S-wave separation in the frequency domain. Wapenaar et al.
(1990) decomposed multi-component data into primary P- and
S-wave responses. Zhang and Zhou (1995) put forward the 45°
equation to obtain an equation for separation of P-wave and S-wave
data in the time-space domain, and made the separation of P and S
waves suitable for the velocities varying horizontally. Sun et al.
(2004) extrapolated the waveﬁeld downward to a proper depth,
determined its divergence and vorticity, and ﬁnally extrapolated it
upward to the surface. Sun's method was proved to have worked
well in modeling test. All of the methods mentioned previously are
designed for reﬂected seismic data, but with some modiﬁcations,
they can also be applied in crosswell seismic waveﬁelds.
Although methods based on wave-equation could obtain decent
results from synthetic data, their practical applications are not so
good due to the limited signal-to-noise ratio of real records, different
gains among traces, and the inaccurate wave-velocity measurement
of near surface around the receiver wells. Compared with wave-
equation-based methods, methods based on the relationship between
polarization and wave velocity are attractive in practice. Zhu et al.
(1990) brought forward a method for VSP wave-ﬁeld separation
using apparent velocity and polarization information, which required
estimating the emergence angle by means of ray tracing. Wei et al.
(1993) presented wave ﬁeld separation using apparent variable
slowness, which was adapted to transverse wave velocity change
Journal of Applied Geophysics 82 (2012) 163–170
⁎ Corresponding author. Tel.: + 86 27 6788 3485.
E-mail addresses: email@example.com, firstname.lastname@example.org (J. Xia).
Formerly at Kansas Geological Survey, The University of Kansas, 1930 Constant
Avenue, Lawrence, Kansas 66047, USA.
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