| Summary: | This report contains the results of work completed during the eleventh year of the
Borehole Acoustics and Logging Consortium in the Earth Resources Laboratory at
M.LT. We continued our trend toward more general borehole acoustics instead of just
full waveform logging. In this report we have papers related to borehole radiation as
well as reception patterns, as well as more theoretical work on the Green's function of
an anisotropic medium. The borehole reception pattern paper is the continuation of
the work from last year, where we dealt with the receiver pattern in an open borehole.
This year the work is extended to include cased boreholes.
On the subject of borehole radiation, this year we have two papers dealing with the
radiated seismic wavefield away from a borehole. The interest is in the areas of downhole
sources as applied to single hole imaging, measurement while drilling, reverse vertical
seismic profiling, as well as cross borehole tomography. In all these areas how the source energy is coupled into the borehole under different situations is of tremendous interest.
On the more traditional full waveform acoustic logging side, we have a paper dealing
with logging in a randomly heterogeneous formation, and one on the effect of permeability
heterogeneity on the measured Stoneley wave velocity and attenuation. We also have
a paper on the ultrasonic modeling of shear wave logging in an azimuthally anisotropic
formation.
On the numerical side, we have one paper on a fourth-order staggered-grid finite
difference formulation of full waveform logging in a transversely isotropic formation
with vertically varying properties, and one on the formulation of an optimal absorbing
boundary condition for finite difference elastic wave propagation algorithms.
Finally, as a continuation of previous work, we are working to improve our algorithm
to location microearthquakes generated by hydraulic fracturing and thus provide a
better location of the fracture in a three-dimensional space. A more detailed summary
of the papers follows.
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