Sea to Borehole Application of Marine Controlled Source EM Method

The marine controlled source electromagnetic (CSEM) method, also referred to as Seabed logging, is established as a new method in oil & gas exploration. EM signals are measured along the seafloor in response to a powerful electric dipole towed by a vessel. We explore here the potential for further developments of the technique by extending the measurements to the borehole environment. The advantage of borehole measurements is that EM signals are measured closer to the oil or gas reservoir and enables detection of smaller targets and in shallower water than traditional marine CSEM. The challenge is that measurements in the borehole are affected by the steel casing. We will present simulations performed by COMSOL Multiphysics finite element code and explore sensitivities on target size, shape and properties together with simulations on effect of borehole casing on EM signals.