| dc.description.abstract | This report contains the results of work completed during the twelfth year of the Borehole Acoustics and Logging Consortium in the Earth Resources Laboratory at M.LT.
This year we have achieved one of our major goals in numerical modelling. We have
completed a code for modelling elastic wave propagation in a borehole in a generally
anisotropic and heterogeneous formation in three dimensions. This opens up a lot of
possibilities in terms of modelling full waveform and shear wave logging.
Along the same trend, we have continued to develop our numerical modelling of permeable
zones. We are able to simulate Stoneley wave propagation in zones with varying
vertical permeability. This allows us to match the field observations better. Another
application of numerical flow modelling is to model tracer transport in heterogeneous
media. This has applications in environmental as well as enhanced oil recovery areas.
Another area we have addressed is the influence of borehole geometry on the full
waveform and dipole wavefield. We have looked at the effects of a borehole with an
irregular cross-section on the full waveform, and we have also effectively modelled a
borehole with a vertically varying radius, such as in the case of washouts. We can
model the scattered Stoneley waves from these washouts and the results compare well
with data.
On the field data Side, we have a paper dealing with the estimation of permeability
from Stoneley waves. This case study was done in a water well. We have processed a
number of other data sets during the past year, and some of the results will be discussed
at the Annual Meeting.
On the more theoretical side, we have a paper on the radiation of a borehole source
into a layered or transversely isotropic medium. This work is done using the Boundary
Element method. We also have a paper addressing the possibility of using non-linear
semblance to better process the full waveform array data. The idea is to estimate
velocity changes (increases) away from the borehole.
In the laboratory we have examined the effects of fractures (vertical, horizontal, and
inclined) on flexural wave propagation. We have also begun to investigate the electroseismic coupling in porous rocks, with an eye on the possibility of coupling acoustic and electric logs to better delineate permeability/fluid changes in the field.
More detailed descriptions of the papers follow. | en_US |
