摘要:
地-井瞬变电磁法是利用地表发射、井中接收瞬变场响应来实现查找深部矿产资源的一种方法.在时间域有限差分算法的基础上,以回线源为激发源,采用非均匀网格剖分技术,对均匀半空间和倾斜板状体、含有低阻覆盖层的倾斜板状体进行了数值模拟.通过对比分析表明:均匀半空间中,响应极大值随观测时间延迟而减小;早期主要反映围岩响应特征,异常体响应特征在晚期表现出来;场源位于中心位置激发时,异常体响应可以很好地体现出来,当场源位于右侧位置,则要选取较长的观测时间降低周围围岩的影响,使异常体的响应特征显示出来;低阻覆盖层对异常响应的影响在整个观测时间范围内都存在,削弱了异常体的响应特征.研究工作为定性分析地-井TEM响应特征和资料解释提供了参考.
Abstract:
As one of the effective methods used in geological prospecting,the down-hole transient electromagnetic method is a geophysical survey method in search for mineral resources,which measures the transient electromagnetic field in a borehole by placing the receiving coils in the borehole.In this paper,based on time domain finite difference algorithm,the authors used a loop source and non-uniform gird,developed a 3D simulation program,and simulated the response of the uniform medium half space,inclined conductor,and inclined conductor with overburden.According to the comparative analysis,the maximum value of response decreases with delay time in uniform half space;in the early period of transient electromagnetic survey,it mainly reflects the response of the surrounding rock;in the late period,abnormal response of the conductor can be obviously displayed.When the source is in the central position,the abnormal response conductor can be reflected,and when the source is in the right position,the need to extend the observation time can be observed in response to abnormal conductor.The impact on overburden conductor is reflected in the entire observation time,making the abnormal response of the conductor ambiguously displayed.The authors studied the work and provide the reference for the down-hole TEM abnormal response characteristics and data interpretation.
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