基于岩石物理模型的裂缝型储层AVOA反演方法

纵波各向异性裂缝预测方法是目前应用比较广泛、效果较好的一种裂缝预测方法;但传统椭圆拟合方法的准确性受到一系列因素的影响,致使裂缝密度反演结果不准确。本次研究根据Ruger方程精确式推导各向异性介质中储层裂缝密度的计算方法,该方法首先利用入射角、方位角、Thomsen各向异性三参数以及介质弹性参数的函数来计算纵波反射系数,然后根据纵波反射系数计算待测储层中裂缝的切向各向异性系数,最后根据各向异性系数计算待测储层的裂缝密度。利用该方法在四川盆地正坝南地区通过实际纵波AVOA数据反演法向和切向裂隙弱度预测裂缝密度,裂缝参数反演结果与钻井信息吻合;表明该方法能够用于裂缝储层预测,确定研究区裂缝发育情况。

AVOA Inversion Methodof Fractured Reservoir Based on Petrophysical Model

At present, the P-wave anisotropy-based fracture prediction method is widely-used with relatively satisfactory performance. However, the accuracy of the conventional ellipse fitting method is affected by a series of factors, which leads to inaccurate inversion results of fracture density. In this study, the calculation method of reservoir fracture density in anisotropic media is derived according to the exact formula of Ruger equation. Firstly, the reflection coefficient of P-wave is calculated by using the functions of incidence angle, azimuth angle, Thomsen anisotropy and medium elastic parameters; then the tangential anisotropy coefficient of fractures in the reservoir to be measured is calculated according to the reflection coefficient of P-wave; finally, according to the anisotropy coefficient, the fracture density of the reservoir to be measured is calculated. The fracture density of Zhengbanan area in the Sichuan basin was calculated by using the fracture inversion results obtained from the actual P-wave AVOA data, and the results are consistent with the drilling data. It shows that this method can be used to determine the fracture development status and the fractured reservoir identification.