Marine controlled source electromagnetic launch system for natural gas hydrate resource exploration

作者:Wang Meng*; Zhang Han Quan; Wu Zhong Liang; Sheng Yan; Luo Xian Hu; Jing Jian En; Chen Kai
来源:Chinese Journal of Geophysics, 2013, 56(11): 3708-3717.
DOI:10.6038/cjg20131112

摘要

Marine Controlled Source Electromagnetic (MCSEM) is one of the effective exploration methods in exploration of natural gas hydrate resources. The launch system is an important part of the MCSEM hardware. In this work, with the seafloor 1D geo-electric model of the gas hydrate as an example, we study the effects of factors on responses of the electric field, including electric dipole source emission frequency, emission dipole lateral drift and source dipole moment value, which provide guidance for launch system design. The self-developed equipment includes the following components: A deck boost control unit, which transfers ship-borne high-power electrical energy through a ten-thousand-meter optical-electric composite cable transported to the submarine transmitter; underwater step-down transformer and rectifier unit, that can convert the high-power AC to high-current DC; the transmitter control circuit hardware and embedded software, that invert underwater transformer output power to high-power rectangular pulse; relying on the emission dipole of the neutral buoyancy, the high-power inverter square waves are sent to the seawater; with the help of the transmitter dynamics design of underwater towed body, used for loading transmitting system of underwater parts and maintain the balance and stability; using the Optical Modem and the fiber in ten-thousand-meter optical-electric composite cable, and remote communication that can be realized between board computer and the submarine transmitter. Marine tests in May 2012 and May 2013 show that the launch system can be used as excitation field source in marine controlled source electromagnetic for exploration of natural gas hydrate resources.