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 266580, China;
2. Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China
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.
杜启振, 霍国栋, 陈刚. 基于横纵波速度比值迭代的纵横波联合反演方法[J]. 石油地球物理勘探, 2016, 51(1): 97-105.
Du Qizhen, Huo Guodong, Chen Gang. Joint inversion of PP- and PS- waves based on the iteration of ratio of S-wave velocity and P-wave velocity. OGP, 2016, 51(1): 97-105.
Connolly P.Calibration and inversion of non-zero offset seismic.SEG Technical Program Expanded Abstracts,1998,8:182-184.
[2]
Connolly P. Elastic impedance.The Leading Edge,1999,18(4):438-452.
[3]
Lu Shaoming,McMechan G A.Elastic impedance inversion of multichannel seismic data from unconsolidated sediments containing gas hydrate and free gas.Geophysics,2004,69(1): 164-179.
Li Chao, Yin Xingyao, Zhang Guangzhi et al.AVO approximation elastic impedance equation and inversion based on incidence angle. Journal of Jilin University (Edition of Earth Science),2013,43(5):1663-1671.
Chen Tiansheng,Liu Yang,Wei Xiucheng.Study on method of PP and PS waves joint AVO inversion.Journal of China University of Petroleum(Edition of Natural Science), 2006,30(1):33-37.