瞬变电磁法在天山山前带表层调查中的应用——以XHBX三维工区为例

天山北麓XHBX三维工区地表起伏剧烈,表层结构复杂,仅靠有限的地震微测井资料难以建立准确的表层结构模型;小折射受地表条件及薄高速夹层等因素影响无法观测到真实的校正界面;野外地震记录中初至前"旁瓣"及背景干扰严重,使基于初至的折射建模方法无法应用。为了获得准确的表层结构,采用瞬变电磁法(TEM)和地震微测井相结合的方法进行表层结构调查。首先通过一维"正演修正法"反演获得表层电性结构,然后利用地震微测井资料标定和非线性高阶多项式拟合将电阻率转换成速度,再经过Kriging网格化插值获得表层结构的速度和厚度平面分布,最终得到完整的三维近地表结构模型。应用该模型计算基准面静校正量并进行后续处理后,XHBX三维工区叠加剖面信噪比得到明显提高,反射同相轴连续性有了较大改善,中、长波长静校正问题也得到部分解决。

Application of transient electromagnetic method on 3D surface structure investigation of mountain front area in Xinjiang

The XHBX3D block in the north of Tianshan is characterized by serious fluctuated surface and complex near-surface structures. The near-surface structure model cannot be accurately established only by using the limited uphole data.Affected by surface conditions and thin high-velocity interbed,accurate actual correction interface cannot be observed by minor refraction.In field seismic record, side lobe before first break and background interference are serious,so the refraction modeling based on first break c...