基于叠前地震道集的FVO分析方法

FVO analysis using pre-stack seismic data

本文首先讨论了地层吸收和薄层滤波对地震波频率的影响,分析表明地层吸收和薄层时间厚度的变化都会引起中心频率向低频方向移动。然后从叠前地震资料出发,采用S变换时频分析法提出了FVO相对梯度属性的概念,推导了地震波在吸收介质中中心频率与炮检距的近似关系式;通过分析不同吸收分布模型可知,所有吸收模型的中心频率随着炮检距增大向低频方向移动;最后建立四种理论模型,基于单程波动方程数值模拟的方法得到相应的叠前CMP道集,利用频率随炮检距的变化关系提取FVO梯度属性。数值算例分析结果表明了该法能有效区分较厚的吸收介质与薄互层介质。

We discuss in the paper frequency change caused by stratum absorption and thin-layer filter,and find that both of them can cause the center frequency shifted to the lower direction.Using prestack seismic data,a new conception called FVO relative gradient is proposed based on a time-frequency S transform analysis method.And then,approximate relationship between the center frequency and offset in the absorbing media is derived.With different distribution model analysis,we have found that the center frequency of the absorption model moves toward lower frequency with offset increase.Finally,four models are built to estimate the FVO relative gradient,which is estimated from synthesis CMP gathers numerically simulated by nonzero-offset one-way wave equation.The numerical result indicates that FVO relative gradient can distinguish thick absorption medium with thin inter-bedded medium.