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基于横纵波速度比值迭代的纵横波联合反演方法

杜启振1 霍国栋1 陈刚2

(1.中国石油大学(华东)地球科学与技术学院, 山东青岛 266580)
(2.中国石油新疆油田公司, 新疆克拉玛依 834000)

【摘要】在利用弹性阻抗EI反演纵、横波速度和密度时,若无速度信息,通常设定横纵波速度比k为常数,从而与真实的k值存在误差,将导致反演结果不准确。进一步研究发现,当缺乏大入射角信息时单独基于EI反演纵、横波速度和密度,反演结果易受噪声影响而很不稳定。为此,利用参数分辨矩阵分析了k值对反演结果的影响,发现纵波速度和密度几乎不受k值误差的影响,横波速度对k值的变化十分敏感。基于此提出了非线性k值迭代方法,通过逐次迭代求取准确的k值,相应得到准确的横波速度,进而基于Aki-Richards转换横波反射系数近似方程推导了转换横波弹性阻抗(SEI)方程,提出了基于k值迭代的纵横波联合反演方法。利用层状模型和Marmous 2的部分模型测试了上述方法,结果表明该方法能使k值较快地收敛到真实值,可更加稳定地反演纵、横波速度和密度。

【关键词】 弹性阻抗;参数分辨矩阵;横波速度;k值迭代;联合反演;

【DOI】

【基金资助】 国家自然科学基金(41174100、41074087); 国家科技重大专项(2011ZX05019-008-08、2011ZX05014-004-003HZ); 中国石油天然气集团公司项目(2014A-3609)联合资助;

Joint inversion of PP- and PS-waves based on the iteration of ratio of S-wave velocity and P-wave velocity

Du Qizhen1 Huo Guodong1 Chen Gang2

(1.School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong, China 266580)
(2.Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang, China 834000)

【Abstract】If we do not have velocity information when extracting P-wave velocity, S-wave velocity, and density from EI (elastic impedance), k (ratio of S-wave velocity and P-wave velocity) is set to a constant, which is always different from real k. This assumption leads to errors in the inversion results. It is found that inversion of P-wave velocity, S-wave velocity, and density based on EI is unstable due to noise (lack of information of big incident angles). We analyze influences of k on inversion results by the parameter resolution matrix, and have found that P-wave velocity and density are hardly affected by k, and that S-wave velocity is very sensitive to k. Based on this point, we design a nonlinear k value iteration method to obtain first accurate k value, and then accurate S-wave velocity. Then we derive P-SV wave elastic impedance accurate (SEI) formula based on Aki-Richards P-SV wave reflection coefficient approximation formula. Finally we propose a joint iteration of k value to extract P-wave velocity, S-wave velocity, and density from EI and SEI. The proposed join inversion is tested on a four-layer model and Marmousi 2 model. The tests results show that k value can rapidly converge to its real value and inversed P-wave velocity, S-wave velocity and density are more accurate and stable.

【Keywords】 elastic impedance; parameter resolution matrix; shear wave velocity; k value iteration; joint inversion;

【DOI】

【Funds】 National Natural Science Fund Project (41174100, 41074087); National Science and Technology Major Project of China (2011ZX05019-008-08, 2011ZX05014-004-003HZ); China National Petroleum Corporation Project (2014A-3609);

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This Article

ISSN:1000-7210

CN: 13-1095/TE

Vol 51, No. 01, Pages 97-105+20

February 2016

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Article Outline

Abstract

  • 1 Introduction
  • 2 Linearization of EI and parameter resolution matrix analysis
  • 3 The k value iteration method for the extraction of P-wave velocity, S-wave velocity and density based on EI
  • 4 EI and SEI joint k value iteration parameter extraction
  • 5 Conclusions
  • References