oa Investigations on Small Scale Targets with Sputnik, a Two Polarization Transmitter System

Sputnik is a novel CSEM transmitter system, which is used for small scale investigations. The system is special in the sense that it can excite two perpendicular TX polarizations at each TX location. It can be shown that this generally increases the sensitivity of measurements to the resistivity structure of the seafloor. This style of experiment requires new approaches for a first pass data interpretation, for which we have adapted the concept of rotational invariants to the marine case. Rotational invariants allow a display of measured data in terms of apparent resistivity sections. They can also be used in the inversion of data. Additionally - using the skew invariant - a dimensionality analysis of the underlying resistivity structure is possible directly from the measured data. Within the past two years the system has been used in three successful experiments for the investigation of methane hydrates and free gas. First results prove that the system is a useful tool for investigations on small targets.