分频技术在气层识别中的应用

Application of frequency division technology in the detection of gas reservoir.

拟合追逐分解(MPD,Matching Pursuit Decomposition)法能提高地震数据谱分解的分辨率,使时间分辨率和频率分辨率保持一致,该方法避免了傅氏变换谱分解方法的时窗大小选择和分析时间点不准确的问题。含气地层对纵波资料产生较大的频率衰减,在储层下方可能出现低频强振幅的阴影区。而转换波资料受气藏影响小,在转换波剖面中不会出现同纵波类似的低频阴影区。因此,综合2种资料在分频剖面上的表现,可以进行储层含气性预测。对已知气藏的实际多波地震资料进行MPD分频处理,在不同波场的分频剖面上分析气层响应特征,可以找出含气地层在纵波和转换波分频剖面上的识别标志。

Spectral decomposition of PP-and PS-wave data using matching pursuit decomposition(MPD)has better resolution on both time and frequency,and maintains consistency across the entire time-frequency plane.Comparing to Fourier transform method,the MPD algorithm avoids choosing the size of window and dose not show temporal smearing of frequencies.PP-waves attenuate more than PS-waves when going through a gas reservoir,which gives rise to a noticeable low-frequency amplitude shadow on the PP-wave common frequency section beneath the gas reservoir.There exists no such a shadow on the PS-wave common frequency section.Thus we can predict gas-bearing potentials by investigating the behaviors of seismic waves on the both kinds of common frequency sections.The proposed method was verified on a real multi-component data set from northeaster China.