煤田电法勘探中的TEM地形校正方法

在煤田瞬变电磁勘探中,由于煤层埋藏较浅,地形影响程度较大.从煤田TEM勘探中较常用的深度计算公式出发,分别计算出地形变化对感应电动势以及衰减时间的影响程度,把这两个影响因子代入到参数中,重新计算出视电阻率,再根据新的视电阻率计算深度,得到了一套较实用的煤系地层情况下的地形校正方法;编制了相应的软件,可实时显示校正前后削面对比.经理论模型与实际资料检验,证明了该方法及软件的有效性.

TEM TOPOGRAPHIC CORRECTION IN COAL FIELD ELECTRICAL EXPLORATION

It is usually considered that TEM detection which uses the signal of secondary induction field is influenced little by the topography.Based on many years’ production practice,however,the authors have found that the influence of topography should not be neglected.Due to the relatively shallow burial of the coal seam,TEM detection in the coal field is influenced considerably by the topography.Using the commonly used depth calculation formula in the coal field,the authors calculated the influence extent of topographic variation on induced electromotive force and on attenuation time separately.Then,the two influencing factors substituted for parameters so as to recalculate the apparent resistivity.According to the new apparent resistivity calculation depth,a set of practical topographic correction methods for the coal measure strata could be obtained.Lastly,by designing the corresponding software,the comparative profiles before and after correction can be displayed in real-time.The theoretical model and actual data have proved the effectiveness of this method and the software.