裂缝介质的纵波方位AVO反演研究

Azimuthal AVO inversion of P-wave in fractured medium

1. 同济大学海洋与地球科学学院,上海 200092;2. 中国石化胜利油田物探研究院,山东东营 257022

Ocean & Earth Science School of Tongji University, Shanghai 200092, China

基于Zoeppritz方程的地震波反射系数解析式是非线性的,而利用地震波反射系数公式来反演介质的弹性参数,或是直接利用非线性反演方法,或是对复杂的反射系数公式进行线性化近似。首先,从理论上讨论了各向异性介质中的反射和透射系数方程,给出了裂缝介质的线性近似反射系数公式;然后,利用ISO/HTI模型对Vavrycuk和Ruger的近似反射系数与真实反射系数进行了对比,得出在大角度情况下Vavrycuk近似比Ruger近似更逼近真实值的结论。因此,选择Vavrycuk纵波近似反射系数公式对纵波方位AvI线性反演公式进行了推导;最后,用模型对反演公式进行了验证,反演结果能满足精度要求。

Due to the complexity of Zoeppritz equation, the analytic formula of seismic wave reflection is nonlinear. Two ways may be chosen to inverse elastic properties through seismic wave reflection formula,and one is nonlinear inversion, and other is to approximate linearly reflection coefficient formula. There are two approximate reflection coefficients applied generally, and their differences are compared in order to attain the linear formula of azimuthal AVO inversion of P-wave. The PP wave approximation reflection coefficient of Vavrycuk is nearer to the real reflection coefficient in the case of bigger incident angle,so it is chosen to derive the formula of azimuthal AVO inversion.Finally, full elastic properties of a model are attained through this method, which meet the certain precision and prove the validity of inversion formula.