Extended Elastic Impedance – A Time-Efficient Workflow from Prestack Seismic Data, Through Rock Physics, to Reservoir Properties

The use of extended elastic impedance (EEI) as described by Whitcombe et al. (2002) gives promise of a fast and objective way to relate seismic inversion results to different reservoir properties such as, e.g., porosity, fluid content and lithology. This can be a useful tool for exploration, prospect evaluation, and early reservoir characterization. At the same time it is generally less time consuming than other methods such as simultaneous AVO inversion combined with rock physics inversion or lithology/fluid facies classification studies. Two key elements in the EEI workflow are to find the correct chi angles projections used for relating the EEI to different elastic properties and to estimate and select the right wavelet for the inversion of the 0° and 90° EEI. Herein, we will show how rock physics modeling, fluid substitution, and the selection of input data can be crucial to obtain quality results and also in situations where modeling will not be necessary. In addition, we will demonstrate how the EEI inversion workflow can be constructed to be time efficient and to provide quality results. An offshore exploration example will illustrate the possibilities and results with this workflow, where the results were used in prospect evaluation, de-risking, quantitative interpretation, and separation of brine vs. hydrocarbon-saturated sands.