Detection of Micro Faults in Dipping Layers in 3D Seismic Data by Coherency Attributes

Coherency attribute is a measure of lateral changes in acoustic impedance caused by variations in structure, stratigraphy, lithology, porosity, and fluid content. When coherency attributes are applied to seismic data, they might indicate the continuity between two or more traces within a seismic window. The rate of seismic continuity is an index of geological continuity. Areas of traces that change with a fault or other geological phenomena have lower coherency in contrast with the adjacent traces. There are three solutions to calculate coherency attributes that include cross-correlation, semblance and eigenstructure. To study the ability of coherency attributes in delineating micro faults, we generated several 3-D synthetic seismic cubes including horizontal, dipping, and cross dipping layers with micro faults. We also studied the effect of the dominant frequency and the size of analysis cube in calculating coherency attributes using MATLAB. We applied all three approaches of coherency attributes to 3-D real data. Coherency attributes proved to be very effective in defining micro geological discontinuities even up to 4 ms.