Application of Seismic Coherency Attributes For Characterization of Reservoir Faults and Fractures

It is very important to recognize faults and fractures in order to enhance oil recovery and to develop oil fields. Seismic coherency attribute is one of the common techniques in discontinuity characterization. Seismic coherency defines continuity of seismic events using the measurement of lateral changes in seismic responses. The rate of seismic continuity is a sign of geological continuity. In areas where are changed by faults and fractures، seismic traces have a low similarity with their neighboring traces. In this study، coherency attributes were determined using two algorithms based on cross correlation and semblance. These algorithms applied on a 3D seismic data cube from one of the Iranian oil fields in Persian Gulf. The performance of algorithms was evaluated to detect faults and fractures at lower member of Fahliyan reservoir. The results show that the semblance based algorithm provides a better coherency cube than the cross-correlation algorithm. The quality of the recognized discontinuities، especially fractures، was further increased by applying appropriate filters on stacked data cube and using reflectors dip and azimuth information. According to the results، the main orientation of faults and fractures at Fahliyan reservoir is NW-SE. This orientation is in accordance with the orientation detected by FMI log at the same depth from nearby well.