Abstract

The Campos Basin marine Controlled Source Electromagnetic (mCSEM) data were acquired on a rectangular grid with a line spacing of approximately 5 km. Three component electric fields as well as two component magnetic fields data were recorded. All fields at each receiver location were processed and interpreted using a novel workflow.

The main objective of the survey was to calibrate the mCSEM technology over known reservoirs and quantify the anomalies associated with those reservoirs with the expectation that new prospective location(s) could be found.

We show that the mCSEM response of known reservoirs yields anomalies that, although considered 'marginal, can be imaged by new processing and interpretation procedures and there are evident correlation between the anomalies and the reservoirs.

A further objective was to advance the state of the art in integrated interpretation of mCSEM data and establish an industry standard workflow unavailable at present.

An effective interpretation of mCSEM data requires new developments and new paradigm on how to best integrate EM with seismic, geology and petrophysical data.

We show how the proposed workflow enhances our ability to accurately interpret ‘weak’ anomalies and ensure maximum benefit from the additional mCSEM data.

Introduction

In recent years mCSEM has driven the attention of major oil companies due to its sensitivity to map resistive structures (such as hydrocarbon reservoirs) beneath the ocean bottom, and successful case studies have been reported (Ellingsrud et al., 2002; Eidesmo et al., 2002; Srnka and Carazzone, 2005).

Numerous surveys have been carried out on a variety of prospect scenarios in the marine environments of: North-West Europe, Africa, the Mediterranean, South East Asia and offshore Brazil and many of these have been verified by wells.

The Campos Basin survey was performed as a multiclient survey. Petrobras acquired the raw data and initiated, in collaboration with AGO Schlumberger, an indepth data evaluation, processing and integrated interpretation procedures.

mCSEM

Technology is in its early stage of application to real E&P problems, and a great deal of R&D is needed to improve its efficiency and reliability in: acquisition hardware, accurate survey engineering, data processing, multidimensional modeling and inversion.

Furthermore, the success of mCSEM will depend on integration with seismic, geology and petrophysical data about the area under investigation.

The Campos Basin data set was considered ideal to advance the understanding of mCSEM in the area ofdata processing, interpretation and integration.

Therefore, Petrobras decided to undertake an indepth study to advance the state-of-the-art, develop new insights that would lead to novel and cost effective application of mCSEM and establish an advanced integrated interpretation workflow.

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