7. Time Domain Controlled Source Electromagnetics for Hydrocarbon Applications

During the past 10 years, marine electromagnetics has developed from infancy into a sizable geophysical industry. While this is feasible in the time and the frequency domains, most of the commercial marine hydrocarbon applications operate in frequency domain, i.e. Controlled-Source Electromagnetic (fCSEM). Until 5 years ago, it was generally assumed that time domain (tCSEM^TM) methods would not be of any use in oil exploration. Since then, however, many such measurements have been recorded with several independent tCSEM^TM systems that already exist or under development. Time domain measurements can be used everywhere and more suitable for shallow water. They have large anomalous responses than those in fCSEM. From the physical viewpoint, time domain measurements are complementary to frequency domain measurements, as they focus on different spatial regions. With recent advances in electronics time-domain CSEM data can reliably be acquired in an offshore environment. Multiple surveys using autonomous receiver nodes have successfully acquired marine time domain CSEM data. Our work takes the technology a step further, by developing a high-density marine cabled system with novel 5-component sensor package.