Azimuthal offset‐dependent attributes applied to fracture detection in a carbonate reservoir

Abstract

Offset‐dependent attributes—amplitude versus offset (AVO) and frequency versus offset—are extracted from 2‐D P‐wave seismic data using the multiple signal classification technique. These attributes are used to detect fracture orientation in a carbonate reservoir located in the Maporal field in the Barinas basin of southwestern Venezuela. In the fracture normal direction, P‐wave reflectivity is characterized by a large increase of amplitude with offset (large positive AVO gradient) and a large decrease of frequency with offset (large negative frequency versus offset gradient). In the fracture strike direction, P‐wave reflectivity shows a scattered variation in AVO but a small variation in frequency with offset. Our results also show that the reservoir heterogeneity can lead to large variations of AVO signatures and that using azimuthal offset‐dependent frequency attributes can help lessen the ambiguity when detecting fracture orientation.