基于广义S变换的叠前Q值反演方法研究

准确估计地震波衰减对提高地震成像分辨率和储层预测及裂缝检测的可靠性具有重要作用。针对利用叠后地震资料估算Q值精度较低、适用性差的问题,提出了一种基于广义S变换的叠前Q值估算方法。首先利用时频分辨率可调的广义S变换,对叠前CMP道集进行时频分析,减小薄层空间谱干扰的影响,从而得到精度较高的时频谱;其次,通过构建并求解时频域反演方程得到谱比斜率,由Q值与偏移距的关系(Q versus offset,QVO)经线性回归估算出零偏移距处的射线平均品质因子;最后,应用层剥离法估算层品质因子。模型数据测试结果证明了方法的可行性;实际地震资料含气砂岩储层段Q值反演预测结果验证了方法的有效性。

The accurate estimation of seismic wave attenuation is crucial for the enhancement of imaging resolution,reservoir discrimination and fracture prediction.In order to overcome the inaccuracy and poor applicability of Q estimation from poststack seismic records,we developed a method for estimating Q from surface seismic data,usually prestack CMP gathers,based on generalized S transform.Firstly,the generalized S transform is utilized with adjustable time-frequency resolution,to carry out time-frequency analysis on prestack CMP gathers,reduce the spatial spectral interference of thinbed to achieve higher-accuracy time-frequenly spectrum.Then by constructing and solving inversion equation in time-frequency domain, the slope of spectral ratio is obtained,meanwhile,the variation of apparent Q versus offset (QVO) is extrapolated to obtain zero-offset spectral ratio slope and the average source-to-reflector Q by linear regression.Finally,the layer stripping procedure is used to calculate the interval Q.Model data testing demonstrates the feasibility of the method.Actual data application result on gas-bearing sandstone reservoir indicates the effectiveness of the prestack Q-inversion.