Using CSEM in frontier exploration settings: a unique tool for stratigraphic trap detection and evaluation

Abstract

The Atlantic Margin poses an extremely challenging exploration problem. The stratigraphic nature of the entrapments added to the high drilling costs, the large minimum economic field sizes needed, and the scarcity of information, turn this region into an extremely high risk-high reward exploration environment. Many companies are faced with the challenge of exploring extremely large areas with very little information and a high chance of failure. CSEM can help mitigating this problem by reducing several of the main uncertainties involved.

3D CSEM is a proven technology that can improve the understanding of several key uncertainties in this environment. The fluid distribution and hydrocarbon volume are two of the main ones, hence having a potentially large impact in the reduction of the probability of success assessment uncertainty, and volume estimation uncertainty. CSEM can also have a large influence on the choice of well placement, which is a key problem when exploring very large areas, especially in the absence of a structural component in the entrapment.

Many explorationists are wary of using 3D CSEM in the absence of well calibration, but it has been shown that 3D CSEM has performed extremely well in this kind of environment. In this paper we explain the reasons why CSEM can be used in the absence of well calibration and the data processing approaches used. We also discuss how 3D CSEM data can be used in conjunction with seismic to reduce the uncertainties related to reservoir HC extent and content to optimize well placement. The remaining uncertainties and 3D CSEM limitations are also analyzed in these type of applications.

These points will be illustrated with application examples from several parts of the world, with emphasis on those coming from the Atlantic margin (e.g., Brazil).

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015