Seismic diffraction imaging for improved coal structure detection in complex geological environments

Abstract

To provide a “no major surprises” guarantee of coal seam conditions, reflection seismic surveying is often used for delineation of faults and dykes that have the potential to disrupt underground coal mining operations. Although reflection seismic methods are usually effective for locating faults with throws greater than 5-10 m for 2D and 2-5 m for 3D seismic data, detection of faults with smaller throws, shears and dykes with widths of a few metres remains a challenge to seismic methods. Instead of ignoring or suppressing diffractions by conventional seismic data processing, it has been demonstrated that diffractions contain valuable information, which can be used for identification of subtle coal seam structures. In this paper, we describe a moving average error filter (MAEF) applied in the neighbouring traces to extract diffractions from post-stack reflection seismic data. The filter estimates the reflections with the average values of the neighbouring traces along the reflection direction or dip, which can be computed by the gradients of seismic data. The difference (or error) between the original data and the estimated reflections, yields the diffractions. By identifying diffractions, small faults and other minor features that are difficult to detect using conventional seismic reflection processing can be detected. Numerical and real data examples are used to illustrate the effectiveness of the proposed method in coal seam structure detection by extracting diffractions from reflection seismic data in a relatively complex geological environment.