Underground » Geology
The objectives of this project were to develop seismic methods to detect and image complex structure such as faults, fracture systems and dykes, which will benefit underground mine operations. The project proposed to work in the two dimensional (2-D) and three component (3-C) areas, but expanded to include single borehole imaging and three dimensional (3-D) seismic.
Project Results
This highly successful project shows for the first time that sub-vertical structure such as dykes, can be imaged if the seismic technique and processing sequence is performed correctly. Furthermore, we show that the tops of weathered dykes can be observed in the basic field data without the need for seismic processing.
The 2-D data showed how a sub-vertical dyke was imaged using surface seismic methods, whereas the use of single borehole imaging methods in which both shot and receiver a placed in a borehole, can image dykes at depth, and in great detail. The technology can also be extended to fracture swarms.
We also show, by using 2-D 3-C seismic data, that we can use seismic waves to indicate both the presence of a sheet-line dyke, and its direction. The 3-D data showed that where 2-D seismic lines allowed partial interpretation of normal and thrust faulting in coal seams, 3-D seismic data provides the total geological picture without further drilling. In particular, the 3-D data provided the correct data base upon which underground mining plans could be developed, and this was the only solution where complex geology provided anomalous results.
Conclusions
This research has shown that sub-vertical dykes can be detected using seismic methods. It shows that fracture swarms and dykes can be sensed, as well as their orientation. It also shows the impact which 3-D seismic has on resource assessment, and 3-D seismic must be the development tool to be used prior to underground mining.