低阻覆盖层下深部富水区的TEM探测效果

THE EFFECT OF THE TRANSIENT ELECTROMAGNETI METHOD IN DETECTING DEEP WATER-RICH AREA UNDER LOW RESISTIVITY LAYER

浅部低阻层对瞬变电磁法探测信号具有屏蔽效应,特别是在有巨厚低阻覆盖层的地区,要完成较大深度的勘探任务,必须在施工和资料解释过程中采取相应的技术措施。在具有巨厚低阻覆盖层的华北地区,进行了瞬变电磁勘探施工技术和资料解释的试验研究,认为野外施工时需选择合适的回线尺寸和延时,以及采用尽可能大的发射功率以产生较高的信噪比;资料分析和解释过程中,采用拟MT的反演技术,突出异常。据此,在低阻层厚度达300 m的地区完成了深550 m富水区的定位探测工作,其富水性得到了钻探验证。结果说明,该探测方法可以完成受低阻覆盖层影响地区的找水探测任务。

The shallow low resistivity layer has a shielding effect on the detection signal of the transient electromagnetic method ; in are- as with thick low resistivity overburden, in particular, the completion of exploration task at great depth must be based on the choice of proper technology during the construction and interpretation. In thick low resistance covering layer of North China, the authors conduc- ted the transient electromagnetic exploration and the tests on the construction techniques and data interpretation. It is considered that during the field work, we must select the appropriate loop size and sampling time, use launch power as large as possible to produce a higher signal-to-noise ratio, and that during data analysis and interpretation, MT inversion should be used for prominence of the anoma- ly. In the low resistance layer with thickness up to 300 m, the authors completed the locating and detection of the water-rich area at the depth of 550 m, and the rich water resources were proved by drilling. The results show that the methods can be used in the low resist- ance layer water detection in the area affected by low-resistivity overburden.