用VSP初至半周期脉冲谱分析法求取吸收参数

Absorption rate calculation using half-period pulse spectrum of VSP first break.

在实际资料处理中发现,以线性吸收理论为基础建立的各种处理方法,其效果并不十分理想。究其原因主要是选用的处理对象不符合处理方法的要求。具体地说,就是一个完整地震子波的对数谱不遵循线性衰减规律。如果选用半周期地震脉冲作为处理对象,就能与这些处理方法取得较好的协调与匹配。VSP 和井间地震资料恰好具有一个非常有利的特点,即它们的初至波不仅清晰可辨,而且振幅最强、信噪比最高,因此,可以有效地利用半周期法求取地层吸收参数。实际 VSP 数据的试算表明,用该方法求得的吸收参数与以往文献中提供的数据吻合较好,说明该方法是可行的。

It is practically found that the effect of processing methods based on absorption theory are usually not very desirable.The reason is that the data to be processed of ten don't satisfy the requirements of these methods.To speak exactly,the logarith- mic spectrum of a complete seismic wavelet does not follow linear attenuation law. However,half-period seismic pulses can well harmonize these processing methods. VSP and interborehole seismic data just have such favourable property,name- ly,their distinct first breaks having top amplitudes and summit signal/noise ratio; therefore,half-period pulse spectrum can be well used to derive absorption rate of a formation.Real VSP data processing says that the absorption rates obtained using this method coincide with those in literatures.This method is feasible.