井中板状矿体瞬态异常二次场数值模拟

Numerical Modeling for Transient Anomalous Secondary Electromagnetic of Tabular Orebody in Borehole

通过研究井轴附近矿体瞬态场的响应特征,为井中瞬变电磁场的勘探提供可靠的依据.应用时域有限差分法和Mur吸收边界,对磁偶源产生的瞬变电磁场进行三维数值模拟,建立了全空间内不同埋深、不同大小、不同倾角的低阻矿体和高阻矿体的地电模型.在数据处理过程中,排除导电全空间对二次场的影响,得到反映目标体异常情况的异常二次场.通过分析不同导电模型瞬变场的特征规律,结果表明:不同埋深、大小、倾角和电导率的矿体具有不同的响应特征,且差异较大.该方法对识别井中板状矿体有较为明显的作用.

The transient electromagnetic response of conductive orebody is studied so as to provide a reliable basis for the explo- ration of the transient electromagnetic in borehole. Finite-different time-domain method and Mur absorbing boundary were used to simulate three-dimensional transient electromagnetic field generated by magnetic dipole source, and establishing the geomet- ric model of low resistivity orebody with different depth, different sizes, different dips, as well as high resistivity orebody in the whole space. During the data processing, excluding the impact of conductive whole space to the total response and getting the anomalous secondary field which reflects the target characteristics. The regularity of the geometric model was analyzed, and the result shows that the orebody with different depth, sizes, dips and conductivity have very different response. The method for identification of tabular orbody has a significant effect.