A stable inversion of effective fluid bulk modulus
Liu Xiaojing1, Yin Xingyao2, Zong Zhaoyun2, Cui Wei3
1. Exploration Branch Co., SINOPEC, Chengdu, Sichuan 610041, China;
2. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China;
3. CNOOC Research Institute, Beijing 100028, China
Abstract：Combining the reflection coefficient approximation in terms of effective fluid bulk modulus proposed by Yin with the idea of elastic impedance equation published by Connolly,this paper derives a novel elastic impedance equation based on effective fluid bulk modulus.The novel elastic impedance is normalized,and then the elastic impedance has the same dimension as P-wave impedance.However,weighting coefficients of inversion parameters are linearly dependent,so it is difficult to stably estimate effective fluid bulk modulus.This study aims at stabilizing the inversion implementation.First the elastic impedance inversion is implemented under the Bayesian framework,and the elastic impedance inverted results are used to estimate the porosity information through Bayesian classifier methods.Then we combine the elastic impedances with inverted porosity to extract effective fluid bulk modulus.As the estimated porosity is set as a priori,the coefficients of the parameters became linearly independent,and the required number of angle-stack seismic data becomes 3 rather than 4.Therefore the effective fluid bulk modulus inversion is stable and reliable.Model tests and practical application verify the effectiveness of the proposed method.
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