大偏移距地震资料各向异性动校正方法研究及效果分析

由于介质的非均匀性,反射层的弯曲性,以及介质的各向异性,使得反射波旅行时不再是双曲线的形式,从而使常规动校正产生较大误差。这里从理论上分析了大偏移距处出现动校不平的原因,指出了介质的各向异性是影响地震资料大偏移距处速度分析精度的主要因素,并对Hake、Castle和Alkhalifah三种各向异性动校正理论及其应用效果做了细致研究。结果表明,在偏移距～深度比小于"1"时,几种动校正方法与常规动校正差别不大:在大偏移距处,Hake方法具有较大的误差;Castle能够得到较好的效果;Alkhalifah方法在大炮检距任意各向异性强度下都可以得到比较精确的校正结果。对应用效果最好的Alkhalifah各向异性动校正进行了算法实现,并基于Java语言的开发环境,编制了各向异性速度分析和非双曲动校正的软件,在模型测试和实际资料的应用中取得了良好的效果。

RESEARCH OF ANISOTROPIC NMO METHODS AND EFFECT ANALYSIS OF LONG OFFSET SEISMIC DATA

Conventional method has a certain degree of un-flatness after NMO,this is because the non-homogeneity of the medium,curved reflector and anisotropy,which make the travel time curve of reflection wave no more a hyperbolic form.This paper analyzes the reasons of un-flatness after NMO in the long offset,and indicates that anisotropy is the main factor of affecting the accuracy of velocity analysis in the long offset.We discussed three kind of anisotropic NMO theories,Hake,Castle and Alkhalifah methods.It turns out that,when the ratio of offset to depth is less than one,there are little differences between conventional NMO and these three methods.While at the long offset,Hake method shows a larger error,Castle method can get a better result,and Alkhalifah method presents exact result in the long offset under arbitrary anisotropy.We accomplish the algorithm of anisotropic NMO,and develop the processing software of anisotropic velocity analysis and non-hyperbolic NMO based on Java language environment.The good results are obtained both in the model test and real data application.