转换波各向异性叠前时间偏移在喇嘛甸地区的应用

Applications of converted-wave anisotropic prestack time migration in LMD area

介质的各向异性对转换波成像的影响非常大,直接影响到大炮检距道集的成像。本文以转换波各向异性非双曲旅行时方程为基础,提出了一种简单实用的高精度γ0(纵、横波平均速度比)场的建立方法和构造速度扫描方法。应用这两种方法能够得到较准确的γ0场和转换波均方根速度场,并应用各向异性双平方根散射旅行时方程可精确求取偏移旅行时。据大庆长垣喇嘛甸地区的三维三分量的转换波资料三维Kirchhoff叠前时间偏移结果显示,各向异性叠前时间偏移剖面的同相轴连续、断点清楚、断面清晰、归位准确。

Media anisotropy affects greatly converted-wave imaging for large offset gather.Based on non-hyperbolic NMO equations of converted-wave anisotropy,we propose a simple and practical high precision Gamma(Average velocity ratio of P and S wave) field building method and a structure velocity scanning method in this paper.These two methods can obtain accurate Gamma field and converted-wave RMS velocity field.Migration travel time can be calculated by anisotropy double square root scattering travel time equation.The application of the methods on 3D3C data in LMD area,Daqing Changyuan shows good results with clearer breakpoint and section,and more continuous events.