摘要
利用拖曳式海洋可控源电磁发射系统在探测埋藏较浅的天然气水合物资源时,会遇到一些新问题.如拖曳式轴向发射偶极源不能贴紧海底,发射偶极源和海底间海水的电磁衰减,使得10 Hz以上的相对高频能量难以导入至海底以下介质;发射偶极源有可能出现水平或垂向摆动;拖曳式发射时,时间窗口内叠加的数据有限;拖曳路线可能与海底构造走向平行,不利于揭示探测目标体的异常形态.新型坐底式发射系统有望解决上述问题.坐底式发射系统的硬件部分包括甲板端供电和监控单元、长距离电力和数据通信单元,以及水下发射机主体.新型坐底式发射系统的发射电极紧贴海底,没有海水层衰减,有利于相对高频的人工源电磁信号经过海底以下介质传输至接收端;通过超短基线信标更容易精确定位发射机拖体,利用姿态方位参考系统确定发射电极的供电方向,可以精确校正电偶源水平偏角的影响;增加单点供电时间,提高接收信号信噪比;提供两对电偶极源,从两个相互垂直的方向对异常体进行人工源激发.2015年海洋试验的结果表明,坐底式与拖曳式发射系统联合作业,可从多角度对海底异常体进行宽频带电磁激发,为数据采集提供丰富的场源信息.
There are some problems when using the deep tow Marine Controlled Source Electromagnetic （MCSEM） transmitter system to detect some shallow resources like gas hydrate. For example, the transmitter electrodes could not be towed along the seafloor, which will lead to the electromagnetic attenuation of the seawater layer, so the relatively high-frequency over 10 Hz cannot be transmitted beneath the seafloor. The number of data in the time window is limited in the towing process. The towing route may be parallel with the strike of the submarine structure. A new type of deployed MCSEM transmitter system probably could solve the above problems. The deployed transmitter system includes on-board power supply and monitoring control unit, long distance electrical power and data transformation unit, and underwater transmitter main body. The deployed transmitter electrodes are close to the bottom of the seafloor, which is a benefit for the relatively high-frequency long distance transmission below the seafloor. The location and the transmission direction are easy to confirm by using the ultra-short baseline beacon and Attitude and Heading Reference System, respectively. The signal to noise ratio could be promoted by adding the transmitting time in one site. The abnormal target can be detected in two orthogonal directions by using the transmitter electrodes. The test result in 2015 showed that the deployed transmitter and deep tow transmitter can be used jointly to excite the beneath seafloor abnormal body in a wide band and different directions and provide more useful source information for the receivers.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第11期4253-4261,共9页
Chinese Journal of Geophysics
基金
国家自然科学基金(41504138
61531001)
国家重点研发计划(2016YFC0303100)
中国地质调查局项目(201100307)
中央高校基本科研业务费专项(2652015407)等联合资助
