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.