Marine controlled-source electromagnetics (CSEM) has recently become a significant business tool for upstream applications due to the convergence of many technologies. CSEM provides valuable information on subsurface lithology and fluids independently from seismic data; however, its spatial resolution is much lower. Uptake has been dramatic, with more than 200 industry marine CSEM surveys acquired worldwide since late 2000.

This presentation discusses some results that demonstrate both the promise and the challenges that lie ahead. CSEM can detect and map offshore reservoir hydrocarbon resistivity at depths exceeding 2000 meters. But resistivity determination is hardly a fool-proof method for hydrocarbon identification, since many geologic facies are electrically resistive relative to their surroundings. As marine CSEM matures, it may prove to be the most important geophysical technology for probing below the seafloor since the emergence of 3D reflection seismology 30 years ago. The key determinant of commercial success will be whether the value of CSEM information is worth the money spent, relative to what other data can provide.