用相关分析法寻找AVO异常

AVO anomaly detection using correlation analysis

AVO技术在油气储层横向预测中具有独特的优点,但由于受信噪比和薄层效应的影响,给AVO技术的应用带来了很大的困难。为此,本文用相关分析法提取AVO信息,较好地克服了信噪比低的影响,弥补了AVO技术的不足之处。其方法为:设F(θ_i)是井附近的CDP道集经动校正后某一时刻反射振幅随入射角变化的函数,这样便可根据测井资料建立的地质模型计算井处含气砂岩顶面反射的理论CMP道集,对其反射振幅进行分析,求出一条用于AVO分析的R(θ_i)曲线(也可用反演法求取);用该曲线与F(θ_i)进行相关,则得到AVO相关系数剖面。通过分析剖面中最大相关值的分布范围可实现储层横向预测的目的。文中以中原油田323测线文17井处含气砂岩为例,说明了该方法的实现步骤及应用效果。

AVO technique has unique advantage in lateral prediction of hydrocarbon reservoir. However,low signal-to-noise ratio and thin-bed effect make very difficult the application of AVO technique in this field. AVO information extraction using correlation analysis removes quite well the unfavourable factor caused by low signal-to-noise ratio, avoiding the shortcoming of AVO technique. The method recommended here includes the following steps. ·If F(θ_i) is the function which shows that the reflection amplitudes of NMO-corrected CDP gather near a well vary With incident angles,, the theoretical CMP gather of reflection wave from gas-bearing sandstone bed near the well can be calculated in the light of the geological model which was constructed from logging data. ·R(θ_i) curve for AVO analysis can be plotted by analysing its reflection amplitudes (or by inverion method). ·AVO correlation coefficient section can be produced by correlating R(θ_i) curve with F(θ_i) curve of NMO-corrected CDP gather. ·Lateral reservoir prediction can be achieved by analysing the distribution of highest correlation coefficients in the section. The example of gas-bearing sandstone at well No.wen-17 on seismic line No. 323 in Zhongyuan oil field is taken to show the performance steps and application effect of this method.