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在北海Valhall/Hod地区的一条2D地震测线上试验了叠前时间偏移对孔隙度估算的影响。白垩纪白垩剖面中孔隙度的估算分两步。首先,用振幅随偏移距变化(AVO)反演估算出P波和S波的速度及密度。再通过从岩心栓分析得到的岩石物性资料建立起这些参数与孔隙度的联系。孔隙度既可用未偏移的又可用叠前偏移地震资料来估算。对偏移数据集来说,可采用的是标准的叠前基尔霍夫时间偏移,再加上简单的角度和振幅校正。与现代高费用的真振幅偏移方法相比,这种方法既快速又实用。试验测线构造相当简单,最大倾角为5°;但取决于偏移是在反演前还是反演后进行,结果却明显不同。估算的孔隙度的最大误差约为10％(约为相对变化的50％)。从未偏移的数据中估算出的高孔隙度带没有出现在用偏移后的数据估算的孔隙度剖面上。
The effect of prestack time migration on porosity estimation was tested on a 2D seismic line in the Valhall / Hod area of the North Sea. The estimation of porosity in the Cretaceous chalk profile is done in two steps. First, the P-wave and S-wave velocities and densities are estimated using the amplitude versus offset variation (AVO) inversion. The relationship between these parameters and porosity is then established by petrophysical data obtained from core plug analysis. Porosity can be estimated using both undecented and pre-stack offset seismic data. For offset datasets, standard pre-stack Kirchhoff time offsets can be used, along with simple angle and amplitude corrections. This method is fast and practical compared to the modern, high-cost true amplitude migration method. The test line configuration is fairly straightforward with a maximum dip of 5 °; however, the result is significantly different depending on whether the offset was performed before or after inversion. The estimated maximum porosity error is about 10% (about 50% of the relative change). The high-porosity bands estimated from the unshifted data do not appear on the porosity profiles estimated from the offset data.