Abstract

Reservoir characterization is one of the most important components of seismic data interpretation. Conventional practice was to delineate the reservoir using post stack seismic data while pre-stack seismic data was completely ignored. Recently it has been demonstrated that the amplitude characteristics of seismic reflections varies with offset, due to changes in the angle of incidence and is evident in pre-stack CMP gathers. Amplitude Versus Offset (AVO) analysis is based on the dependencies of reflectivity with increasing offset (or angle of incidence in case of AVA analysis) and has proven to be a useful seismic lithology tool and direct hydrocarbon indicator. Seismic Inversion is nothing but the inverse modeling of log from seismic data in order to have log at each trace. Inversion techniques are used to transform seismic volume into P impedance, S impedance and density and many more different attributes, from which we will be able to make predictions about porosity and lithology and will be able to delineate sweet spots. The scope of this paper is confined to AVO analysis and use of seismic inversion (both pre-stack and post-stack) techniques for the differentiation of gas sands from wet sands. The differentiation was remarkably prominent with the aid of AVO and seismic inversion, when applied on a pre-stack CMP gathers of a 3D line of an offshore basin