Analysis of fault damage-zones using 3D seismic coherence in the Anadarko Basin,Oklahoma

Abstract

Fault damage-zones may significantly affect subsurface fluid migration and the development of unconventional resources. Most analyses of fault damage-zones are based on direct field observations, and we expand these analyses to the subsurface by investigating the damage-zone structure of a 32-km (~105 11 ft) long right-lateral strike-slip fault in Oklahoma. We used the 3D seismic attribute of coherence to first define its regional and background levels, and then evaluated the damage-zone dimensions at multiple sites. We found damage-zone thickness of ~1600m (5,300 ft) at a segment that is dominated by subsidiary faults, and it is slightly thicker at a segment with a pull-apart basin. The damage-zone intensity decays exponentially with distance from the fault core, in agreement with field observations and distribution of seismic events. The coherence map displays a strong asymmetry of the damage-zone between the two sides of the 3D fault, which is related to the subsidiary structures of the fault-zone. We discuss the effects of heterogeneous stress field on damage-zone evolution through the detected subsidiary structures. It appears that seismic coherence is an effective tool for subsurface characterization of fault damage-zones.