LOTEM视电阻率曲线对一维层状介质的分辨能力

摘要

Based on the one-dimensional forward modeling of the long-offset transient electromagnetic method,the mod-el response is calculated in this paper.The parameter variations of the layer and the offset,law of the resistivity curve and the resolution coefficient are compared and analyzed.The results show that the distinguishing ability of the low resistance target layer is mainly determined by the longitudinal conductance.The larger the longitudinal conductivity and the higher the ratio the longitudinal conductivity of the low resistance target layer to the cover layer will be easier to distinguish the low resistance lay-er.When V2>1,distinguishing ability to the high resistance layer increases with increasing thickness,and the resistivity va-ries within a certain range to almost no effect on it.WhenV21,the apparent resistivity curve exists T equivalence principle. The distinguishing ability of method is better than the high resistance layer for the low resistance layer.The change of the off-set distance has little effect on the distinguishing ability.%基于长偏移距瞬变电磁法一维正演研究,计算层参数和偏移距变化时的模型响应,对比分析视电阻率曲线变化规律和分辨系数.结果表明,对低阻目标层的分辨能力主要由纵向电导所决定,纵向电导越大越易分辨,低阻目标层纵向电导与覆盖层纵向电导比值越高,越易对低阻层分辨;在高阻层厚/覆盖层厚(V2)>1时,对高阻层的分辨能力随厚度的增大而提高,而电阻率在一定范围内变化对其几乎无影响,在V21时,视电阻率曲线在一定范围内存在T 等值原理.该方法对低阻层的分辨能力要远大于高阻层,偏移距的变化对分辨能力影响甚微.