论文部分内容阅读
当我们打算重现潜在油气臧的AVO响应时,在射线追踪模拟中时常忽略局部转换横波。常用的方式是在射线追踪模拟中仅用一次波,其中Zoeppritz方程描述反射振幅。然而,局部转换横波对地震响应时常具有重要影响。这一事实似乎要么未能广泛认识,要么就是其本质未被透彻理解。仅用一次波的Zoeppritz模拟很容易使人误入歧途。来自于岩层底部的转换波和一次反射之间的干涉随着岩层厚度的减小而增强。这种干涉时常使产生的地震记录与仅有一次波的Zoeppritz假设产生的记录有很大的不同。对于薄层一次波模拟,利用Zoeppritz方程的线性近似公式来描述反射系数得到的合成地震记录,要比用精确的Zoeppritz反射系数得到的更准确。最近,有文献讨论了薄互层组合的一个实例。由于仅有一次波假设不可靠,故用预测的振幅随炮检距变化对真正地层特征等作出的推断是错误的。有这么一个模型,仅有一次波模拟预测出振幅从近道到远道增加了二倍,而反射率模拟的振幅随炮检距增大而减小。 O’Doherty-Anstey效应认为,对于法向入射合成地震记录,如果不包括短周期混响,则一次反射波透射损失也不应包括在内。对叠前模拟,这一原则也成立。同样,如果不包含局部转换横波,那末Zoeppritz方程也不能用来做合成地震记录。
When we intend to reproduce the AVO response of a potential oil and gas, the locally converted shear waves are often overlooked in ray tracing simulations. A common approach is to use only the primary wave in the ray-tracing simulation, where the Zoeppritz equation describes the reflected amplitude. However, the locally converted shear waves often have an important impact on the seismic response. This fact seems to have either not been widely understood or that its essence has not been thoroughly understood. Zoeppritz simulations that use only a single wave can easily be misleading. The interference between the converted wave and the primary reflection from the bottom of the rock formation increases as the thickness of the rock formation decreases. This type of interference often makes the difference between the resulting seismogram and the one produced by the Zoeppritz hypothesis, which has only one primary wave. For the first-order wave simulation, using the linear approximation of the Zoeppritz equation to describe the synthetic seismograms obtained from the reflection coefficients is more accurate than using the accurate Zoeppritz reflection coefficient. Recently, there is literature to discuss an example of a thin interlaminar combination. Since only one-time wave assumptions are unreliable, it is wrong to make inferences about true stratigraphic features, etc., from predicted variations in amplitudes with offset. With such a model, only a single wave simulation predicts a three-fold increase in amplitude from near-to-far, while the amplitude of the reflectivity simulation decreases with increasing offset. The O’Doherty-Anstey effect considers that, for normal incident synthetic seismograms, the loss of primary reflected transmission should also not be included if short-period reverberations are not included. The pre-stack simulation, this principle also holds. Similarly, the Zoeppritz equation can not be used to make synthetic seismograms without including locally converted shear waves.