--> Joint Seismic-CSEM Imaging Electrifies Deep Water Exploration

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Joint Seismic-CSEM Imaging Electrifies Deep Water Exploration

Abstract

Abstract

Deep water is a complex high-risk environment with no shortcuts to success. While rewards have proven to be huge, the risk involved has also been amplified dramatically. With drilling costs topping $1 million per day, anything that can increase the margin of success is welcomed. Today the quality and accuracy of seismic have improved markedly. Reverse Time Migration, Full Waveform Inversion of full-azimuth surveys are enabling geoscientists to image large volumes of reservoir quality rocks, even in complex geologies. Still, even with all these advances, certain exploration challenges remain.

Today, workflows are being developed to integrate technologies that reduce the exploration risk in demanding deep-water. While all of the seismic advances mentioned above tell a large part of the story, many information gaps may be filled in with deep reading electromagnetic (EM) methods. Seismic may predict the presence of hydrocarbons in a formation, but one of the biggest pre-drill knowledge gaps is formation resistivity. Previously this information has only been available through well logs, but deep reading EM is now providing subsurface resistivity information before drilling.

Controlled Source Electromagnetics (CSEM) is an active deep reading EM technology that images resistive structures beneath the seafloor. Using structural models developed from seismic, CSEM data are used to help prioritize prospects. Applications relevant for the later stages of petroleum operations are being addressed in quantitative reservoir characterization studies on real data and in feasibility studies for reservoir monitoring.

Seismic-CSEM integration has been applied extensively by Petrobras over several distinct geological settings of the deep Brazilian offshore. In this work we present the potential of this integration over selected case histories and demonstrate the value of new ‘hybrid’ and ‘localized’ joint inversions of seismic and CSEM data to locate the most promising prospects, making it an effective tool to minimize timescale and costs.