An Integrated Approach to 3-D Seismic and Electromagnetic Interpretation for Reducing Risks in Hydrocarbon Exploration

Mikhail Boulaenko, Roy Davies, Jonny Hesthammer, and John Howell
University of Bergen, Bergen, Norway

Hydrocarbon exploration is a challenging and expensive business. The chances of discovering producible reserves using conventional methods such as 2D and 3D seismic are relatively slim – less than 20%, on the whole. This is partly due to the fact that gas-saturation levels as low as 5–10% can produce seismic features such as bright spots and flat spots.

Recent developments in electromagnetic imaging (EM) technology have shown the potential to increase the chances of success by providing a means of identifying hydrocarbon and water filled reservoirs prior to drilling wells. However, there are still many challenges related to optimized use of the technology, including integration with seismic and well data, use in production, and differentiating between the responses of hydrocarbon reservoirs and other resistive bodies such as carbonates and salt.

In this paper we present an integrated workflow for interpretation of 3D seismic and EM data using examples from real fields and forward-modelled synthetic studies. Advanced inversion algorithms were used to process data collected by towing an electromagnetic source over lines of sea bed receivers in order to produce 2D and 3D “resistivity maps” of the subsurface. These were then combined with 3D seismic data in order to understand the sources of resistive anomalies. This has important implications for predicting the location and volume of potential hydrocarbon reservoirs. Where the seismic character of anomalies indicates that they are caused by salt or shallow gas pockets, further “joint inversion” can be run in order to remove them from the processing results.