摘要
页岩气储层具有明显的层理结构,其弹性性质呈现典型的VTI介质各向异性特征。为了实现面向页岩气储层的叠前多参数稳定、可靠反演,提出了一种稳健的基于VTI等效介质AVA反演的储层弹性模量与裂缝弱度参数评价方法。该方法以新构建的四项模型参数表征的VTI等效介质反射系数方程为基础,基于贝叶斯反演理论以及属性之间的数学关系,获得储层的纵波模量、剪切模量、密度和裂缝弱度等4个参数,以表征页岩气储层的弹性特征和裂缝发育特征。测井和实际资料的测试与应用表明,反演结果与测井解释结果一致,且反演结果稳定性好。该方法能够合理可靠地从叠前地震数据中反演得到储层弹性模量和裂缝弱度参数,以实现页岩气储层特征的精细描述与刻画。
Shale gas reservoirs have clear bedding structures,and their elastic properties exhibit vertical transversely isotropic(VTI)medium anisotropy.Anisotropy is a key challenge in shale gas reservoir characterization.Most amplitude variation with angle(AVA)inversion methods based on approximate VTI formulas are ill-suited to address anisotropy because of more than five unknown model parameters.This affects the precision and reliability of estimating elastic and fracture weakness parameters.Thus,the purpose of this study was to develop a robust AVA inversion method to estimate elastic and fracture weakness parameters in the VTI medium.Firstly,by combining changes in weak-anisotropy elastic stiffness components in the VTI medium and scattering theory,we derived a linearized PP-wave reflection coefficient from five variables:isotropic elastic properties(P-and S-wave moduli and density)and two fracture weakness parameters.Secondly,to improve the stability of the inverse problem,we modified approximation formulas to include four model attributes.Following Bayesian theory,we established an AVA inversion method to estimate these new attributes.Finally,we predicted elastic and fracture weakness parameters based on the relationship between these attributes.This method was successfully evaluated using synthetic and real data.Results show that the AVA inversion method can effectively estimate elastic and fracture weakness properties and has great potential for application in shale gas reservoirs.
作者
陈勇
孙振涛
许凯
CHEN Yong;SUN Zhentao;XU Kai(Sinopec Geophysical Research Institute Co.Ltd.,Nanjing 211103,China)
出处
《石油物探》
CSCD
北大核心
2022年第6期1016-1027,共12页
Geophysical Prospecting For Petroleum
基金
国家自然科学基金企业创新发展联合基金项目(U19B6003)
中国石化科技部重点项目(P20046)共同资助。
