Identifying minor faults on top of coalfield Ordovician limestone stratum using seismic attributes derived from azimuthally stacked data

Abstract

Identifying geologic faults has always been the primary aim of geophysical prospecting work in coalfields. However, identifying minor faults of the top Ordovician limestone stratum (in coalfield areas) remains a significant challenge. As parts of the work described herein, we build a geologic model with a fault located on top of the Ordovician limestone stratum in a coalfield. We use a 2D seismic profile obtained by means of forward modeling in a numerical simulation (by azimuth) process, to fit seismic attributes to a general ellipse equation. The seismic attributes derived from these azimuthally stacked data sets have found that, at the fault locations, the maximum amplitude decreases, whereas the minimum amplitude increases. Fitting the seismic attributes according to the least-squares method for the maximum and minimum amplitudes by azimuth produces ellipses that fitted well to the fault plane and could be used to determine fault plane characteristics. Specifically, the major axis of the ellipses runs parallel to the faults’ strike. At a given fault dip angle, eccentricity ( e) can be used to qualitatively determine fault throw and fault dip. The larger the value of eccentricity ( e), the greater the fault throw and fault dip. Finally, the validity of this azimuth analysis method is verified by application to actual seismic data.