DAMAGE ZONE CHARACTERIZATION USING COHERENCE & REJECTED NOISE DERIVED FROM STRUCTURE ORIENTED FILTERING

Abstract

As seismic attributes were first incorporated into academic and industry workflows, fault detection and visualization became a primary objective. Faults and their associated damage zones exert significant control on subsurface fluid flow, seal integrity, and reservoir compartmentalization. While attributes such as coherence have proven effective for delineating fault geometries, quantitative workflows for constraining fault damage zone widths from seismic data remain underdeveloped.This study investigates the use of coherence and rejected noise derived from structure-oriented filtering (SOF) to characterize fault damage zones within the Bacalhau 3D seismic dataset in the post-salt interval of the Santos Basin. Coherence consistently delineated fault geometries and produced damage zone width estimates comparable to field-based outcrop measurements, reproducing the near 1:1 linear scaling relationship between fault slip and damage zone width documented in field studies. Rejected noise frequently mimicked seismic stratigraphy, reducing its reliability for estimating fault zone widths. However, noise aligned with interpreted faults was morphologically distinct and enhanced continuity along small-offset faults that do not register a coherence anomaly. At times, rejected noise also modeled a substantially wider damage zone than coherence. In the pre-salt carbonates of the Bacalhau field, well data indicated that coherence primarily responds to the most intensely fractured intervals, whereas rejected noise is more sensitive to mechanical and petrophysical transitions, capturing shifts from tight rock to porous and/or fractured rock not resolved by coherence. These results demonstrate that coherence and SOF-derived noise are complementary attributes, and when integrated with well data, can provide a more robust framework for seismic characterization of fault damage zones.