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.