基于White模型的含气砂岩垂直入射地震响应特征分析

摘要

Based on the White's sphere patchy saturated model and dynamic bulk modulus theory,in this paper we analysis the effect of gas saturation and permeability on seismic phase velocity and inverse quality factor in different sandstone reservoirs,including well consolidated sandstone,medium consolidated sandstone and unconsolidated sandstone.Great attenuation can be observed on phase velocity of P-wave due to the increasing of gas saturation increasing,which can be as high as hundreds of meters per second in seismic frequency band and slightly attenuation can be brought by increasing permeability.And the inverse quality factor is higher when the gas saturation and frequency are both high,which leads to greater attenuation of seismic energy.The simulation results of seismic response for 3 types of sandstome reservoirs based on the phase-shift wave equation shows by phase-shift that “time delay” on the reflection from lower interface can be observed by increasing gas saturation,especially in the unconsolidated and consolidated sandstone reservoir.Furthermore,the main frequency of seismic energy will decline when gas saturation is increased.If containing gas is at a high saturation state,the flow of fluid medium will be enhanced,resulting in greater attenuation of seismic energy by increasing permeability.%基于空间周期排列的球状斑块饱和模型(White模型)和动态体积模量理论,研究了含气饱和度和渗透率对固结良好、中等固结和未固结砂岩储层地震响应特征的影响,结果表明:①当含气饱和度增大时,地震纵波相速度的衰减会更加明显,在地震频段内可达数百m/s,而渗透率增大对其造成的影响则相对较小;②高频情况下,含气饱和度越高,逆品质因子越高,地震波衰减越强;③低频情况下,含气饱和度越高,逆品质因子越低,地震波衰减越弱.利用相移法波动方程正演对三类砂岩储层地震响应特征进行了数值模拟,结果显示:①增大含气饱和度可使储层下界面反射产生时间延迟,且在未固结和中等固结的砂岩储层中十分明显,地震波主频逐渐向低频方向移动;②在含气饱和度较高的状态下,介质中流体的流动性增强,导致渗透率对地震波速度的衰减能力增强.