钻孔瞬变电磁法研究现状综述

Present study situation review of borehole transient electromagnetic method

与航空、地面瞬变电磁法不同,钻孔瞬变电磁法将接收探头置于钻孔之中,由于距离探测目标更近且远离地表,不仅可以观测到更强的响应信号,还可有效削弱孔外各类电磁信号的干扰,能够满足大埋深、精细化探测需求,尤其是深部盲矿和水害探测。通过回顾各类钻孔瞬变电磁法(回线源地.井、电性源地.井和隧(巷)道钻孔瞬变电磁法)的研究历史,总结各类方法在正演模拟、反演成像、仪器装备和应用案例等方面的研究现状。研究结果表明:回线源地.井瞬变电磁法研究基础丰厚,发展较为全面,已在生产中取得较多成功应用;而电性源地.井和隧(巷)道钻孔瞬变电磁法研究基础薄弱,由于理论方法、探测装备、反演技术等方面的限制,目前尚未得到广泛推广与应用,整体仍处在初步研究阶段,相关技术仍有待进一步提升。未来发展方向可以从以下几个方面入手,如带地形三维反演、快速地形校正方法、伪随机发射、多辐射源发射、套管干扰消除和多参数地球物理方法联合解释等,形成完善的钻孔瞬变电磁法理论和解译方法,为深部矿体探测、煤矿和隧道含水构造探测提供理论依据。

In the borehole transient electromagnetic method(TEM),the receiving probe is placed in the borehole,which is different from either aerial or ground TEM.In such methods,as the probe will be closer to the detection target and far away from surface,not only stronger response signals can be observed,but also the interference of various electromagnetic signals outside the borehole can be attenuated effectively.It can meet the demand of meticulous detection with large burial,especially the detection demand of deep blind ore and water hazard.The present situation of using various methods in the study in forward modeling,inversion imaging,instrument and equipment as well as application cases was summarized,by reviewing the study history of various borehole TEMs(return line source surface-to-borehole TEM,electric source surface-to-borehole TEM,and tunnel borehole TEM).According to the study results,the study of the return line source surface-to-borehole TEM,with solid foundation and comprehensive development,has been applied frequently and successfully in production.Both the study of electric source surface-to-borehole TEM and that of the tunnel borehole TEM have not been widely promoted or applied currently due to their weak foundation and the limitations in terms of theoretical methods,detection equipment,inversion techniques,etc.The study of the both TEMs is still at the preliminary stage,and the related technologies still require further improvement.For the future development direction,the implementation can be commenced in terms including the three-dimension(3D)inversion with topography,rapid to-pographic correction,pseudo-random emission,emission with multiple radiation sources,interference elimination for casings and the combined interpretation using the multi-parameter geophysical method,so as to form the complete bore-hole TEM theory and interpretation method,and to provide theoretical basis for the detection of deep ores and the detec-tion of the water-bearing structures in coal and tunnels.