Structural model uncertainty of a prospect - a geostatistical approach

The structural geometry of a Prospect is usually defined using some Time to Depth migration technique, as a function of the time map and of the corresponding seismic velocity map . For time migrated data, a simpte Time to Depth conversion is needed, with an adjustment of the depth surtace to Well data, if necessary . Depth reconstructions are always affected by quality and spatial frequency of vetocity information; if, as in the study presented, the structures are very gentle, a special precision would be necessary for a good prospect reconstruction and evaluation. For the study presented, two seismic markers were interpreted and mapped, corresponding to the top (level B ) and the bottom (level C ) of a sequence of finely stratified sand and clay layers, structured in a gentle anticline, which bears gas in correspondence of Well A1. The targets of the study were the reconstruction of their depth maps, the evaluation of the trap potentiality and the estimation of the result reliability . To reach these targets we put our main effort in improving the estimation of the velocity maps and to establish a method for providing results in term of probability .