裂缝性储层AVO模型研究

预测储层中的有利裂缝发育带及裂缝发育的主方位在油气勘探开发中具有重要的意义。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。AVO分析方法所表现的方向性，可从三维道集的地震资料中分析出不同方向上的地震属性参数变化，这些参数与地层的各向异性具有一定的对应关系。当储层存在一定方位的裂缝时，其弹性参数会表现出方向性差异，这种差异能被AVO方法有效地检测。通过对不同方位角裂缝储层AVO模型研究得出：当地震波传播方向与裂缝走向的夹角逐渐增大时，反射系数随入射角的增大而减小；含水平裂缝地层的曲线斜率逐渐减小，地层的AVO截距逐渐减小，斜率逐渐增大；垂直裂缝地层的曲线斜率逐渐增大，地层的AVO截距逐渐增大，斜率逐渐减小。

AVO MODELING STUDY ON THE FRACTURED RESERVOIRS

Prediction of fractured zones in reservoirs and the main azimuth of fracture are very important in petroleum exploration and development.When fractures occur in reservoirs,the significant contrast of physical properties between fluid and tight rock can create a physical interface of a certain scale,resulting in changes of seismic reflectance signatures of the reservoirs.These changes are important information on seismic section that can indicate the existence of fractures.As AVO analysis has vectorial property,it can be used to analyze the change of attribute parameters in different directions from 3D seismic data.These attribute parameters correlate with anisotropy of strata.When fractures with a certain azimuthal angle occur in strata,the elastic parameters of the strata will show directional variations,which can be effectively detected through AVO analysis.Study on AVO models of fractured strata with different azimuthal angles shows that when the included angle between the direction of seismic wave propagation and the fracture orientation increases gradually,reflection coefficient will decrease with increasing incident angle,strata with horizontal fractures will show a decreasing rate of curve,a declining AVO intercept,and an increasing AVO slope;while strata with vertical fractures will show an increasing rate of curve,an increasing AVO intercept,and a decreasing AVO slope.