Geophysical Anomaly: A Novel Contribution to Integrated Geophysical Interpretation

Abstract

In different geophysical methods, the physical responses derived from a specific type of geological target show very distinct characteristics. Such responses represent different rock properties with specific physical units, which in most of the times differ within several orders of magnitude. Therefore, geophysical data combination and integrated interpretation are not simple straightforward processes and cannot be satisfactorily performed by visual inspection only. The proposed Geophysical Anomaly is a data fusion solution for multiphysics data that is under development by Petrobras’ Multiphysics Team. It consists in a spatial representation of the correlation between anomalous regions detected by different geophysical methods, designed to improve the integrated interpretation of multimodal geophysical data. In the geophysical anomaly approach, maps from several types of seismic attributes as well as gravity, magnetics and resistivity anomaly maps are mathematically treated to allow reliable combination. Anomalous regions interpreted from each geophysical methodology, as resulting from the same geological source, are mathematically highlighted because they represent areas with great probability for target occurrence. Resulting highlighted anomaly maps are mathematically combined in such a way that anomalies showing spatial superposition will be stressed while remaining anomalies tend to be diminished. The final result is a new anomaly map named Geophysical Anomaly Map. This novel solution bounds regions where individual interpretations of different geophysical methods correlate, bringing confidence to the interpretation. We illustrate the effectiveness of the geophysical anomaly approach by showing results from the application of the proposed methodology to three real data examples from Brazil: offshore Campos Basin where the results correlate with volcanic rocks thickness; offshore Sergipe-Alagoas Basin where we were able to identify a oil-bearing channel; and onshore Reconcavo Basin where the results were related to the thickness of a sand channel. The variety of results describes in these examples make clear the flexibility of the geophysical anomaly as a qualitative interpretation tool for a wide range of geological problems.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018