VSP Detection of Fracture-Induced Velocity
Anisotropy
David H. Johnston
A multiple S-wave
polarization VSP survey using gyroscopically oriented
three-component downhole recording documented azimuthal anisotropy associated
with the preferential orientation of fractures within the Austin Chalk. The
anisotropy is manifest in a significant
velocity
contrast between S-waves
polarized parallel to and perpendicular to the dominant fracture orientation as
determined by bore-hole televiewer data. In addition, as discussed by Becker and
Perelberg in another paper, for S-waves polarized 45° to the principal axes of
symmetry, particle motions recorded within the Austin exhibit birefringence or
splitting.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.