oa From Seismic Impedances to Reservoir Porosities - the Road Is not Always Straight

Seismic data are nowadays commonly used to improve the reservoir image between wells, with techniques for quantitative lithologie interpretation. In particular, when the reservoir is not too heterogeneous, it is standard to use seismic derived acoustic impedances to predict reservoir properties such as average porosities [1, 2], Acoustic impedances are extracted from post-stack seismic amplitudes with inversion techniques. Then, they are turned into porosities with a regression approach (simple regression or eventually cokriging) after a calibration in the vicinities of wells. In this paper, a case study is used to examine some difficulties in this approach and to carry out sensitivity tests for defining critical parameters in the prediction of seismic porosities.