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为适应海洋可控源电磁法现场数据采集的需求,海底电磁采集站必须解决低噪声、低时漂和低功耗等一系列技术难题。目前,现有的采集站在面向海底浅部水合物探测应用时,其噪声、功耗、时漂等指标仍存在不足。为研制满足这些性能要求的新型采集站,本文首先利用正演数值模拟研究了特定模型的电场异常分布规律,并初步确定了采集站的指标要求,然后对采集站的各个部分进行了详细论述,包括低噪声感应式磁传感器、低噪声Ag/AgCl电极、低噪声斩波放大器、低功耗低漂移数字温补晶振、水声通讯及电腐蚀技术等。最后通过陆地野外试验及海洋试验验证了海底电磁采集站的有效性,证明采集站具有先进的参数指标:典型电场本底噪声:0.12nV/m/rt(Hz)@0.5Hz;动态范围:大于120dB;时漂:小于1ms/day;连续工作时间:至少21天。
In order to meet the needs of on-the-spot data acquisition of marine controlled source electromagnetic method, a series of technical problems such as low noise, low drift and low power consumption must be solved in the subsea electromagnetic collecting station. At present, the indicators of noise, power consumption, time drift and so on are still inadequate when the existing collection station faces the application of shallow sea hydrate detection. In order to develop a new acquisition station that meets these performance requirements, this paper firstly studies the abnormal distribution of electric field in a specific model by using forward numerical simulation, and initially determines the index requirements of the collection station. Then, the various parts of the collection station are discussed in detail. Including low-noise inductive magnetic sensors, low-noise Ag / AgCl electrode, low-noise chopping amplifier, low-power low-drift digital temperature compensated crystal oscillator, underwater acoustic communications and electrical corrosion technology. Finally, the effectiveness of the seabed electromagnetic collection station was verified by field experiments in the field and marine experiments. The results show that the acquisition station has advanced parameters: typical electric field noise floor: 0.12nV / m / rt (Hz) @ 0.5Hz; dynamic range: 120dB; Time drift: less than 1ms / day; continuous working time: at least 21 days.