Strata弹性波阻抗理论和实现方法(中英).ppt

弹性阻抗 介绍 先回顾弹性阻抗反演的原理,然后利用Hampson-Russell 一组软件分析弹性阻抗反演一个实际例子. 弹性阻抗Elastic Impedance (EI) 是由BP 公司Patrick Connolly 提出. 实现弹性阻抗反演可用AVO和STRATA软件自然组合来完成. 在谈论弹性阻抗反演之前, 简单回顾反演方法在地震勘探运用的历史. 地震岩性估算 传统的地震岩性估算是在地震数据叠加偏移后数据(叠后数据)道进行反演. 这只能估算声阻抗, 不足于推测流体成分. AVO分析可能用的属性 但是哪两种(或更多属性)可用来最好地预测流体和岩性这些参数? 目前AVO可提取和使用的一系列不同属性: 偏移距或角度段限(范围限制)叠加 弹性阻抗反演 截距和梯度 提取的纵横波反射系数 RP,RS 由 RP 和 RS 反演到纵横波阻抗 ZP, ZS 纵横波阻抗 ZP, ZS 转换Lambda-Mu-Rho 分析 本讨论先使用前面两个属性的方法. 后面再讨论其它的属性方法. 范围限制叠加 从范围限制叠加到弹性阻抗 弹性阻抗理论 Aki-Richards 等式可写为(三项式) : 然后进行积分和取幂, 可得到以下弹性阻抗 EI等式: 以上等式使用的是Aki-Richards所有三项等式. 对于入射角大于300, 该等式将不是线性的拟合. 对于大角度 (大偏移距), 如果只用等式的前两项,等式可写为: 弹性阻抗 – 实例 下图 显示声阻抗和弹性阻抗(30度角)的曲线比较: 重叠显示更好地区分弹性阻抗和声阻抗在含油砂岩处的差别: EI 反演步骤 Conclusions This has been a overview of the Elastic Impedance (EI) inversion approach, as implemented in the Hampson-Russell AVO and STRATA software packages. By applying the method to the Colony Sand, we were able to note changes at the sand level which were indicative of gas. That is, the Elastic Impedance was much lower on the far angle stack than the near angle stack. On this menu, select Elastic Impedance for both the X and Y axes, and change the Plot Title as shown below. (Note that we will select a different elastic impedance log for each axis on the next menu). Click on Next . On this menu, select EI_Near for the X axis and EI_Far for the Y axis, as shown. Click on Next . On this menu, select Time as the domain, with start and end values of 600 and 675. Click on Ok to get the crossplot. Notice that the axes of the plot are both labeled the same. To change the annotation, click on Edit / Annotations and change the menu as shown on the right: Click on Ok and the plot will appear as shown on the left. Notice the clear separation of the points on the lower left of the plot. Let us now perform zone analysis to see if the anomaly seen on the crossplot really is the gas sand. To do this, first display the well log curves by clicking on the Cross