Seismic attribute analysis of a fault zone in the Thebe field, Northwest shelf, Australia

Abstract

Seismic data are one of the main ways to characterize faults in the subsurface. Faults are 3D entities and their internal structure plays a key role in controlling fluid flow in the subsurface. We have aimed to characterize a geologically sound fault volume that could be used for subsurface model conditioning. We introduce an attribute analysis of a normal fault from a high-resolution seismic data set of the Thebe field, offshore northwest Australia. We merge together a series of common attributes for fault characterization: dip, semblance, and tensor (DST), and we also introduce a new total horizontal derivative (THD) attribute to define the edges of the fault zone. We apply a robust statistical analysis of the attributes and fault damage definition through the analysis of 2D profiles along interpreted horizons. Using the THD attribute, we interpret a smaller width of the fault zone and a more straightforward definition of the boundaries than from the DST cube. Following the extraction of this fault volume, we define two seismic facies that are correlated with lithologies extracted from our conceptual model. We observe a wider fault zone at larger throws, which also corresponds to synrift sequence; hence, more complex internal fault damage. Our method provides volumes at adequate scale for reservoir modeling, and therefore could be used as a proxy for property conditioning.