Seismic reflection characteristics of fluvial sand and shale interbedded layers

河流相砂泥岩薄互层地震反射特征研究(英文)

A sedimentary geological model is established in order to study the seismic reflection characteristics of channel sand bodies. Synthetic seismic shot gathers are simulated using the acoustic wave equation and then are prestack time migrated. On the imaged data, the reflection characteristics and instantaneous attributes are analyzed and log-constrained impedance inversion is tested. Because of wave field interference, the experimental results show that seismic events do not definitely correspond to the channel sand bodies and that seismic modes of occurrence do not represent the actual ones. The seismic events formed by wave interference may lead to errors and pitfalls in sand body interpretation. The corresponding relations between instantaneous seismic attributes and sedimentary sands are not well established. Log-constrained impedance inversion improves the resolution of channel sands. However, if the inverted resolution is forced to be too high, artifacts related to the initial model may occur.

为考察复杂陆相沉积地层河道砂体在地震剖面上的反射特征,首先建立了河道砂沉积地质模型,然后利用声波波动方程正演得到叠前地震记录,并对模拟的共炮点道集进行叠前时间偏移,最后,对成像数据上的反射特征和瞬时属性特征进行了分析,并对测井约束波阻抗反演方法进行了实验。实验结果表明:由于波场干涉的影响,地震反射同相轴与河道砂体之间不具有明确的对应关系,地震反射同相轴的产状不能代表地下砂体的真实产状,波场干涉形成的同相轴很可能导致砂体解释的误差和陷阱。在利用地震波瞬时属性对沉积砂体进行分析时,未能较好地建立瞬时属性与沉积砂体之间比较明确的对应关系。测井约束反演较好地改善了河道砂体的分辨能力,但是,当对反演结果的分辨率要求过高时,很可能导致与初始模型有关的反演假象。