Coal seismic depth conversion for mine data integration: A case study from the Sandy Creek 3D seismic survey

Abstract

In general, seismic data are presented in two-way reflection times but seismic times are not easily directly scalable to depths due to the variations of seismic velocity in space. Apparent structures in the time domain can be misleading. Conversion of seismic time sections to depth sections removes this ambiguity. In general, seismic depth conversion is a complex process requiring careful use of NMO and migration velocities, the study of well data and the generation of synthetic seismograms. The process is usually iterative, especially when the structures are complex. In this paper, we present a depth conversion algorithm designed for coal seismic data. Our method assumes that the coal seam structures are relatively simple and that there are numerous boreholes available to constrain the process. Once converted to depth, the seismic data can be exported into mine planning software and used to provide seam elevations for tasks such as in-seam drilling and other mine activities. Our method has been implemented into an MS Windows based program SeisWin1 and allows new boreholes to be incorporated without the need to go back to the original seismic processing contractor. A 3D seismic data set from Xstrata?s Sandy Creek mine is used to demonstrate our method. The results show that the depth conversion algorithm can accommodate different seismic processing. The depth-converted seismic data agrees with the geological model based on borehole data and from underground surveys. Given the confidence in the depth conversion, it is possible to look more closely into the data in order to make more detailed interpretations.