基于VSP数据的任意弱各向异性参数反演方法  

An inversion method for arbitrary weak anisotropy parameters based on VSP data

作　　者：陈占国[1] 曾昭翰 杨心超 CHEN Zhanguo;ZENG Zhaohan;YANG Xinchao(Geophysical Research Institute,SINOPEC,Nanjing,Jiangsu 211103,China)

机构地区：[1]中国石化石油物探技术研究院,江苏南京211103

出　　处：《石油地球物理勘探》2022年第2期311-319,I0003,共10页Oil Geophysical Prospecting

基　　金：国家自然基金联合基金项目“海相深层油气富集机理与关键工程技术基础研究”(U19B6003)资助。

摘　　要：VSP数据具有较高的信噪比和准确的深度信息,基于它的旅行时等信息可反演地层VTI、TTI各向异性参数,但较难获得任意各向异性参数。极化和慢度矢量是表征Christoffel方程中弹性矩阵的直接参数,VSP能够测量到不受上覆地层影响的慢度和极化信息,且具有准确深度信息的优势,可用于反演介质的任意弱各向异性参数。文中首先介绍基于扰动理论的Christoffel方程求解方法,引入qP波的慢度和极化矢量正、反演公式,然后给出基于Walkaway VSP测量的高精度慢度和极化矢量获取方法,最后提出适用于任意弱各向异性参数的加权迭代反演算法。应用模型数据反演了最多15个弱各向异性参数,结果与理论值高度吻合;实际资料应用进一步表明,该方法有较高的精度,适用于高精度的地震各向异性参数提取。Vertical seismic profile(VSP)data boast a high signal-to-noise ratio and accurate depth information.Information such as traveltime in VSP data can be used to obtain vertical transversely isotropic(VTI)and tilted transversely isotropic(TTI)anisotropy parameters of the formation through inversion.However,it is difficult to determine arbitrary anisotropy parameters in this way.Polarization and slowness vectors are direct parameters that characterize the elastic matrix in the Christoffel equation and can be measured by VSP without being influenced by overlying strata.VSP also enjoys an advantage in accurate depth information.Therefore,it is available for obtaining arbitrary weak anisotropy parameters of a medium through inversion.To start with,we present a solution method for the Christoffel equation based on the perturbation theory and introduce forward and inversion formulas for slowness and polarization vectors of the qP wave.Then,we provide a highprecision acquisition method for slowness and polarization vectors based on Walkaway VSP measurement.Finally,a weighted iterative inversion algorithm for arbitrary weak anisotropy parameters is proposed.A maximum of 15 weak anisotropy parameters are worked out with model data,and the results are highly consistent with the theoretical values.Application on field data further shows that the proposed method,with high precision,applies to extraction of seismic anisotropy parameters.

关 键 词：VSP 各向异性参数 慢度 极化 

分 类 号：P631[天文地球—地质矿产勘探]