厚黄土覆盖地区有利激发层位选取方法

摘要

合理选取激发层位可有效提高巨厚黄土覆盖地区原始地震数据信噪比及分辨率,而单一的浅层折射、瞬态面波、微测井等手段常因复杂的浅表层地质条件,难以分出黄土层中的高速小层或薄层.利用微测井约束的瑞雷波反演方法,可以准确的划分浅表层速度界面的深度,进而确定激发层位的位置.以山西万荣、洪洞二项目为例,介绍了该方法的地质效果:其中万荣勘探区解释速度界面深度分别为27m、37m与45m,确定激发层位为37m深的高速粘土层,地震资料解释成果经3口钻孔验证,钻遇煤层最大相对误差约3%;洪洞勘探区以2、3层的粘土(15～18m)作为激发层位,其资料解释成果经1口钻孔验证,钻遇煤层相对误差约5%.%Reasonable shotpoint horizon selection can improve initial seismic data S/N ratio adn resolution in very thick loess covered regions effectively. While single means of shallow seismic refraction, transient ground roll and micrologging cannot distinguish high velocity minor or thin beds often because of complex near-surface geological condition. Using micrologging constrained Rayleigh wave inversion can separate out depth of near-surface velocity interface, and then proceed to determine shotpoint position. Taking two projects in Wanrong and Hongtong, Shanxi Province as examples, introduced geologic effect of the method: in the Wanrong exploration area, depths of interpreting velocity interface are 27m, 37m and 45m respectively, determined shotpoint horizon is depth 37m high velocity clay bed, 3 boreholes have verified interpretation results, maximum relative error of intersected coal seam is about 3％. In the Hongtong exploration area, 2 or 3 beds of clay (15-18m) as the shotpoint horizon, one borehole has verified the interpretation results, intersected coal seam relative error is about 5％