应用P波振幅的傅里叶系数反演裂缝密度  

Inversion of fracture density by Fourier coefficients of P⁃wave reflection amplitude

作　　者：李荣 薛姣[1] 顾汉明[1] LI Rong;XUE Jiao;GU Hanming(School of Geophysics and Geomatics,China University of Geosciences(Wuhan),Wuhan,Hubei 430074,China)

机构地区：[1]中国地质大学(武汉)地球物理与空间信息学院,湖北武汉430074

出　　处：《石油地球物理勘探》2024年第2期238-249,共12页Oil Geophysical Prospecting

基　　金：国家自然科学基金项目“时频域方位AVO反演方法研究”(41904120)资助。

摘　　要：裂缝预测是非常规储层预测的重要内容。裂缝密度不仅反映了裂缝的发育程度,也是影响裂缝孔隙度和渗透率的重要参数。文中提出了一种应用纵波反射振幅分方位傅里叶系数正、余弦分量加权的裂缝密度反演方法。基于线性滑动裂缝等效介质理论,分别推导了含油和含气条件下HTI介质纵波反射振幅傅里叶系数与裂缝密度的关系,并利用二阶傅里叶系数预测裂缝对称轴方位角;研究了地震数据含噪声时二阶傅里叶系数正、余弦分量信噪比之比随裂缝对称轴方位角的变化规律,并提出应用二阶傅里叶系数正、余弦分量加权的裂缝密度反演方法。模型试算结果表明,所提的裂缝密度反演方法具有较强的抗噪性和稳定性;将其应用于实际地震数据,裂缝密度预测结果与测井信息吻合,验证了方法的有效性。Fracture prediction is a crucial aspect of unconventional reservoir forecasting.The fracture density not only reflects the degree of fracture development but also serves as a significant parameter influencing fracture porosity and permeability.In this study,a fracture density inversion method is proposed,which uses weighted sine and cosine components of Fourier coefficients of P‑wave reflection amplitude.Drawing upon the linear sliding crack equivalent medium theory,relationships between Fourier coefficients of the HTI(Horizontal Transversely Isotropic)medium P‑wave reflection amplitude and fracture density are derived separately for oil‑bearing and gas‑bearing conditions.Additionally,the second‑order Fourier coefficients are employed to predict the azimuthal angle of the fracture symmetry axis.The research investigates the variation patterns of the signal‑to‑noise ratio of the second‑order Fourier coefficients’sine and cosine components with respect to the azimuthal angle of the fracture symmetry axis when seismic data contain noise.An inversion method for fracture density is then proposed using weighted sine and cosine components of second‑order Fourier coefficients.Model simulation results indicate that the proposed fracture density inversion method exhibits strong noise resistance and stability.Application of the method to actual seismic data demonstrates that the predicted fracture density aligns with well log information,thus validating the effectiveness of the approach.

关 键 词：裂缝等效介质 傅里叶系数 裂缝密度 反演 加权 

分 类 号：P631[天文地球—地质矿产勘探]