Influense of seismic and velocity uncertainties on reservoir volumetrics

Abstract

Uncertainty is a well-known concept in geology, and can lead to re-evaluation of important development decisions if properly assessed. This thesis describes uncertainty through the set-up of “scenarios”. For each parameter used for the structural model a so-called low case, base case and high case are defined. The combination of the different cases results in many structural models that deliver a distribution of the bulk volume. A generally acknowledged way of handling the large number of models coming from the different combinations of the model parameters is experimental design. This study has shown that the uncertainty in the seismic picks and consequently in the reservoir thickness have a large impact on the gross-volume. The reservoir structural geometry controls the influence of fault uncertainty on the reservoir volume. Well velocities used in this thesis for domain conversion are quite accurate but sparsely sampled and therefore subject to uncertainty. In addition, the geologic complexity may have a dramatic influence on the uncertainty of the depth conversion. A proper assessment of seismic and velocity uncertainties can be applied to risk analysis for field appraisal and development, hydrocarbon volume estimation, accurate well placement, optimal well trajectory and reservoir history matching.