Development of EM Wave Guide Amplifier Potentially used for Sea Bed Logging

Abstract

Seabed logging is a new technology being implemented for deep target exploration. The technology uses electromagnetic (EM) wave where an antenna transmits EM wave into water layer underneath seabed and with resistivity characteristics of hydrocarbon reservoir, the wave is reflected and received by the detectors on the seafloor. However, the roughness of the sea caused by underwater sea current limits the transmission of EM wave. EM wave itself has its own attenuation in seawater that is 102 dBm and the underwater sea current has made it worst. In seabed logging technology, the vessel is towing the transmitter at a very slow speed (1.5 km h-1) with high EM wave energy for transmitting the waves of~1250 A cm-2. Due to this large current more heat is generated. In this project, we propose an EM wave guide amplifier to be used to overcome these problems. The EM wave guide amplifier amplifies the wave without modifying the transmitter (antenna) circuit. Therefore lower energy is required for the transmitter and is sufficient for seabed logging technology. The thermionic cathode and molybdenum (Mo) anode with work function of 1 eV are selected to get higher amplification of EM wave. It is found that potential difference between the cathode and anode improves the electron acceleration in the wave guide amplifier. It has been observed that with the use of wave guide amplifier and with 20 Vpp supply to the transmitter at 5 MHz frequency, the wave received by receiver has been amplified up to 170%. The application of this new method in seabed logging shall reduce the heat generated and overcome the EM wave attenuation problems. © 2011 Asian Network for Scientific Information.