裂缝介质中多方位AVO特征分析技术及应用举例

有利裂缝发育带及裂缝发育的主方位在储层预测中具有重要的意义。当储层中存在裂缝时，流体与致密岩石的巨大物理性质差异形成一定规模的物理界面，引起储层地震波反射特征的改变，成为地震剖面上反映裂缝存在的重要信息。地层中分布的裂缝，特别是在构造应力作用下形成的具有一定方位性分布的裂缝，其特征可以采用多方位AVO 方法进行检测。理论上讲，裂缝对地震属性参数的影响在垂直裂缝走向的方向上表现为最强，在水平裂缝走向的方向上表现为最弱，对AVO 属性参数的影响也是如此。因此，对于发育裂缝的储层采用多方位AVO方法进行矢量差异分析可以确定储层中裂缝发育的强度和密度。从理论公式入手讨论了不同入射角、方位角以及不同裂缝倾角情况下裂缝性储层的方位AVO响应，研究了裂缝性储层多方位AVO的变化特征与裂缝走向和倾向的关系，尤其是具有一定倾斜角度的裂缝对地震波方位AVO的响应特征，并用这一方法分析了新疆某油区的有利裂缝发育带，取得了较为理想的效果。

MULTI-AZIMUTHAL AVO ANALYSIS OF FRACTURED RESERVOIRS

It is important to predict a favorable fractured reservoir and its main azimuth of fractures during the exploration and exploitation of petroleum. When fractures occur in the reservoir, a nature interface can be formed by the huge difference of physical properties between fluids and compacted rocks, and it changes the characteristics of seismic reflection waves of the reservoir. These are the important information of the fractures existence in the seismic sections. AVO can detect fractures in formation, especially those distributed in certain orientation under structural stress. Theoretically, the influence of fractures to seismic attributes may reach maximum in its dip direction, and may reach minimum in its strike direction. And the influence is the same to AVO parameters. Therefore, applying the multi-azimuthal AVO method to fractured reservoirs and its vector difference analysis can determine the fracture intensity and density of the reservoirs. The authors discuss in detail various azimuthal AVO responses of fractured carbonate reservoirs to various incidence angles, azimuth and fracture dips through theoretical formula, and find the relation between the AVO characteristics of seismic wave and the fracture strike and dip, especially for the tilt fractures, which provides the foundation for the prediction of favorable fractured reservoirs. The theory is successfully applied to the analyzation of the favorable fractured zone of Tarim.