Sensitivity Analysis of Preserved Amplitude Seismic Images for Reservoir Studies

Jardin, Anne, Hery Rakotoarisoa, Institut Français du Pétrole, Rueil-Malmaison, France

Quantitative evaluation of reservoir parameters is often carried out by pre-stack seismic amplitude analysis for which accurate amplitude preservation during previous seismic pro­cessing steps is essential. That’s why in case of complex subsurface, preserved amplitude migration is the key processing technique to improve the quantitative interpretation of the reservoir. Based on their expertise in preserved amplitude Kirchhoff migration, IFP geo­physicists had developed prototype software for 3D preserved amplitude pre-stack migra­tion. Flexibility and efficiency of the developed algorithm allow taking into account lateral and anisotropic P and S velocity variations. Reservoir oriented seismic gathers in angle or off­set domains are computed and migrated images are provided both in depth and time domains. These software characteristics become essential for advanced seismic reservoir studies like amplitude analysis, stratigraphic inversion and lithoseismic attribute estimation.

The reliability of seismic migrated images depends on the quality of input data, i.e. unmi­grated and unstacked traces and velocity models. Therefore the sensitivity analysis of com­puted preserved amplitude migrated images to these parameters, has been carried out to evaluate the remaining uncertainties for quantitative and qualitative reservoir studies.

By applying migration on realistic synthetic data set, errors in depth estimation of target reservoir have been studied regarding uncertainties due to the approximations present in smooth velocity models used in migration. Real data were used to analyze the influence of seismic pre-processing parameters on qualitative reservoir delineation from interpretation of time and depth migrated images.