Abstract: Imaging the Subthrust Structure

Ferraris, O.; Koremblit*, M.; and Lorenzo, D. - YPF

The Subandean thrust belt is one of last places in the world where wells are still located using mainly surface geological data. The reason is simple: seismic lines do not properly image the subthrust structure. The purpose of this paper is to show a generalized methodology for this problem.

First of all it is necessary to define that "not properly imaged structure" means no interpretable image or an interpretable image but with mispositioned structural tops. Both facts strongly relate to the difference between time image and depth image and the custom of interpreting a time image like a depth image. The methodology used can be summarize as follows:

The first step consists of making a data base of geometric data and velocity data.

The second step has two possibilities depending on whether you have enough data quality, in which case the recommendation is PSDM. Otherwise you must do the first geological model with the help of the geometrical data base and calculate the synthetic response in order to compare it with the real seismic data, using this loop as a way to check the geological model.

If PSDM was successful, the model cross section is already done and only a few segments need to be added to accomplish the picture and run the synthetic response as a final double check. The synthetic section also provides information related to field and processing parameters. The case under study is the first PSDM based model in this environment.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil