浅层瞬变反演电阻率资料在表层速度成像中的应用

Near surface velocity imaging with the resistivity inverted from shallow transient electromagnetic sounding data

(1. 长江大学地球物理与石油资源学院，湖北荆州 434023;2.新疆正通诚信科技发展有限公司，新疆乌鲁木齐 830016)

(1.Jianghan Petroleum University, Jingzhou 434023,China; 2. Zhentong Chenxin science and development Ltd., Urumchi 830016,China)

通过浅层瞬变电磁测深反演的电阻率剖面与同一测线的微测井速度深度曲线的对比研究认为，表层速度结构与电阻率分层有较好的对应关系，这种关系表现为非线性。提出了对弗斯特公式的修改方法，即在对数域中以电阻与深度的高阶多项式来近似表示地层速度，通过利用剖面上微测井速度资料及其该测点上瞬变反演的电阻率资料，用共轭梯度法反演求取多项式系数，给出了速度与电阻率及深度的经验关系式，并利用该关系式对瞬变电磁测深反演的电阻率剖面进行速度成像。试验剖面的速度成像结果对认识表层速度结构和划分低、降速带有参考价值，对地震资料的静校正的速度建模有指导作用。

The comparison of resistivity inverted from shallow transient electromagnetic sounding data and formation velocity observed by microlog at the same line revealed that there is a close correlation between near surface velocity structure and resistivity zonation, and this correlation is nonlinear. This paper put forward a modified Faust formula in which the formation velocity was represented by a high order polynomial of resistivity and depth in logarithm domain. The coefficients of the polynomial were calculated from microlog velocity data and inverted resistivity data. Velocity imaging was then carried out on the inverted resistivity profile based on the polynomial. The resulted velocity can be used to build velocity model for seismic static correction.