利用低频信号提高膏盐区深层成像质量

Application of low frequency signal to imaging anhydrite based on modeling.

膏盐层作为一种很好的烃源岩和极好的盖层与油气储层具有密不可分的关系,但是,膏盐层具有的特殊性质使得其下伏目标地层成像困难。为此,以济阳坳陷HJ复杂膏盐区为目标区,首先通过分析膏盐层的地质和地球物理特征,说明了造成其下伏地层成像困难的主要原因——原位地层条件下处于蠕动状态非均匀分布的膏盐层对地震波场的强烈吸收和散射作用。然后设计了一个简化的膏盐层模型,采用波动方程粘弹介质波场数值模拟技术,分析了单道记录中以膏盐层为界的浅层和深层地震反射信号振幅谱的频率差异,证明了介质对波场的散射和吸收作用与地震信号的频率密切相关,高频信号衰减快,低频信号具有较强的抗散射和抗吸收能力,更易于穿透处于蠕动状态的非均匀膏盐层。最后根据目标区实际地质情况,建立了膏盐层地质模型。模拟数据分频成像处理表明,利用低频信号可以提高深层的成像质量。

Imaging for deep layers is difficulty because of anhydrite in some basins. A case study was performed on imaging HJ anhydrite in Jiyang Basin. Absorbing and scattering effect of anhydrite to seismic wavefield make it difficult to image through analyzing its properties. By wave equation numerical modeling, it is proved that absorbing and scattering effect is related to the frequency of seismic signal, low frequency signal can go through anhydrite easily, so it can be used for imaging for deep layers below anhydrite for its great power to resisted the absorbing and scattering of anhydrite.