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