多道瞬变电磁法(MTEM)技术分析

Technical Analysis of Multi-transient Electromagnetic Method

多道瞬变电磁法(MTEM)具有深度大且探测精度高的特点,是目前电磁法领域研究热点之一。为推进多道瞬变电磁法深部探测系统的研发,对多道瞬变电磁法的技术特点及地球物理机制进行了分析。首先,对多道瞬变电磁法的关键技术进行总结,其特点包括:采用大功率接地源形式;编码发射;多道观测;类地震资料处理。然后,指出多道瞬变电磁法的地球物理实质:多道瞬变电磁法属于近源测深,即通过改变偏移距达到测深目的;接收信号包括系统响应和大地脉冲响应(即含有一次场与二次场的混合场)信号,采用反卷积方法获取大地脉冲响应。最后,针对中国复杂环境下的深部探测,对现有的多道瞬变电磁法提出改进思路:1把二维观测系统改进成三维观测系统,即三维数据采集系统,使其应用性更强且更方便,探测深度大,精度高;2把常规一维拟地震资料简单处理改进成三维拟地震成像解释;3从油气勘探领域拓展到复杂的深部矿产资源领域。

Multi-transient electromagnetic method（MTEM）has the merit of detecting deeper target with higher resolution,and becomes one of hot topics.In order to develop MTEM instrument system, Technical characteristics and geophysical mechanics of MTEM were discussed.Firstly,the key technology of MTEM includes that superpower grounded-wire is the source of MTEM;transmitter signal is generated by pseudo random binary sequence（PRBS）form;multi-channel receivers are employed for signal collection;seismic method is adopted in data processing.Secondly,the geophysical mechanics of MTEM include that because of the array layout,MTEM belongs to near-source sounding or geometric sounding,which means that changing the offset distance can finish the deep target;the receiver signals include system and impulse responses,which is an information mixed with primary field and secondary field,and the impulse response can be collected by deconvolution method.Finally,for the deeper buried targetdetection with complexity condition in China,the new modified MTEM is proposed that twodimensional data collection system is modified into three-dimensional,so as to make the method more applicable and convenient for exploration and obtain a greater detection depth with higher detection accuracy;traditional one-dimensional pseudo-seismic interpretation is improved into three-dimensional data imaging system;the application scope is enlarge from petroleum exploration to ore deposit investigation.