ABSTRACT: The detection of stress using 3-D seismic data
Evans, Brian J.1, Christopher Walton1, Milovan
Urosevic1, and Kevin Dodds2
(1) Curtin University, Perth, Australia
(2) CSIRO Petroleum, Bentley, Australia
Seismic waves respond to the application of stress. Since high stresses in rocks induce microfracturing, it is not clear whether the seismic response changes as a result of either the stress or the microfractures. This paper presents a case history of where stress is considered the most important factor to have changed the seismic response.
Burton coal mine in Queensland, Australia has very high horizontal stresses. In order to allow the imaging of complex structures which will affect the underground mining of the coal, a land multi-azimuth three dimensional (3-D) seismic survey was recorded over it. The 3-D survey showed an area of normal, thrust and stike-slip faulting, into which the open-pit is currently mining.
Vertical fracturing is not evident in the high wall. However, horizontal fracturing appears evident through seam splitting. The principal stress trend is north-west/south-east, and it appears that many of the faults have absorbed the principal horizontal stresses, rather than fractures develop.
There were two drill holes in the 3-D area which had stress tests performed on them. Both holes appeared to be in separate coal compartments. One hole had the principal stress in the north-west/south-east direction, while the other hole had the stress direction change orthogonally over a distance of 20 m vertically.
The 3-D seismic data were analysed to determine if there was an attribute which could provide an indication of the change in stress direction. Initial work indicates that by the use of special processing of amplitude data, the principal stress direction was predictable.
This research has consequences for the prediction of stress associated with over-pressure, and can asssist with planning multi-laterals in tectonically related stressed zones.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia