利用叠前CMP资料估计介质品质因子

本文提出了一种利用叠前CMP道集资料估计介质品质因子的方法,同时提出利用地震道间有效信号的相干性估计层位信息的方法.首先采用具有4个待定系数的函数去逼近震源子波,利用黏弹介质中单程波传播理论推导出地震子波包络峰值处的瞬时频率(EPIF)与不同偏移距处走时的关系;其次利用该关系,外推出该同相轴零偏移距处的EPIF,用小波域包络峰值处瞬时频率法(WEPIF)结合层位信息估计Q值.合成数据的结果表明,EPIFVO法(子波包络峰值瞬时频率随偏移距变化)无边界效应,计算精度相对较高;将该方法用于实际资料算例,结果表明,衰减强弱与储层的吸收有较好的对应关系.

Estimation of quality factor Q from pre-stack CMP records

We present a method of estimating quality factor Q from CMP records,and a method of estimating layer positions based on coherent characteristics of traces. First, employing a function with four undetermined parameters to approximate the source wavelet, the relation between the instantaneous frequency (IF) at the envelope peaks of seismic wavelets (EPIF) and traveltime at different offsets is derived based on the theory of one-way wave propagation in a 1D viscoelastic medium; then by using the relationship, we extrapolate the EPIF of zero offset of the event; finally,Q is estimated by combining WEPIF with the reflectivities information. Applied to synthetic pre-stack CMP models and the result indicates that the method has no boundary effect and is more precise; we also apply the method to field record, it produces a Q-curve indicating that the extent of absorption corresponds well to the gas saturation of reservoirs.