盖层各向异性对时移地震AVO的影响

The effect of caprock anisotropy on timelapse seismic AVO

（中国石油大学资源与信息学院 石油天然气成藏机理教育部重点实验室，北京 102249）

boratory for Hydrocarbon Accumulation Mechanism, Ministry of Education, China University of Petroleum, Beijing 102249, China

摘要:油藏盖层各向异性在油藏开发前后对地震AVO曲线有相同程度的影响，而这种影响能否在2次地震AVO曲线相减后变得很小，可以被忽略？利用某油田数据建立了储层岩石物理模型，根据Gassmann方程获得了该油田储层的纵、横波速度与含油饱和度的关系曲线。设计了双层油藏模型，通过求解横向各向同性 (VTI)介质界面的透射系数与反射系数的线性方程组，计算了油藏盖层存在各向异性时的PP波和PS转换波反射系数，分析了不同Thomsen参数对反射系数及其油藏开发前后反射系数差异的影响，并进行了定量分析。分析结果表明，小入射角情况下进行PP波时移地震AVO分析，可以忽略盖层各向异性的影响；大入射角情况下进行PP波时移地震AVO和多波时移地震AVO分析，盖层各向异性不能忽略。

e and after the reservoir is developed. However, whether this effect of anisotropy of reservoir caprock can be diminished and neglected after subtract the seismic AVO curve from two times. According to the rock physics model in oilfield and Gassmann equations, the relation curve of compresional-to-shear velocity versus oil saturation is gained, and the double reservoir model designed. By the P-P wave and P-S converted wave reflection coefficients can be obtained by solving the linear equations set for reflection and transmission coefficients on the interface of VTI medium. Then how the Thomsen parameters variations affect the P-P wave and P-S converted reflection coefficients and differences have been analyzed quantitatively. Based on the data, the conclusion is followed that the caprock anisotropy can be neglected in P-P wave reflection coefficient difference analysis when incident angle is small, but under other conditions, such as far offset or multiple time-lapse seismic AVO study, they can not be neglected.