黏弹性介质叠前地震反演方法

前人只是从理论上分析了黏弹性介质中各种波的传播特征和衰减特征,并未对黏弹性介质精确的Zoeppritz方程进行近似,无法用于实际反演;沈章洪等以完全弹性介质为背景,推导了黏弹性介质反射系数近似方程,由于该近似方程的实部为完全弹性项,虚部为黏弹性项,因此也无法用于实际资料。为此,本文以黏弹性介质为背景,推导了黏弹性介质反射系数近似公式,以此为基础,基于贝叶斯理论的叠前地震反演,将纵横波速度、密度的反演推广到纵横波速度、密度和地层品质因子(Q值)的联合反演,建立了黏弹性介质近似方程,再根据贝叶斯理论建立反演方程,最终利用共轭梯度法对方程进行求解,得到纵横波速度、密度和地层Q值。模型试算与实例分析结果表明,根据联合反演所得的纵横波速度、密度和Q值进行储层描述,可提高储层预测精度。

Prestack seismic inversion of viscoelastic medium

Various wave propagation and attenuation characteristics in viscoelastic medium were analyzed without approximating the exact Zoeppritz equation, which cannot be used for inversion. Shen Zhanghong deduced the reflection coefficient approximate equation of viscoelastic medium in the background of fully elastic medium. The real part of the equation is fully elastic, and the imaginary part is viscoelastic. So it cannot be used in real data. We deduce in this paper reflection coefficient approximate equation of viscoelastic medium in the background of viscoelastic medium. Based on this and Bayesian prestack seismic inversion, the inversion of P-wave velocity, S-wave velocity and density is extended to the joint inversion of P-wave velocity, S-wave velocity, density, and Q value. We put forward the approximate equation of viscoelastic medium, and then the inversion equation according to the Bayesian theory. Finally, the conjugate gradient method is used to solve the inversion equation, and then the P-wave velocity, S-wave velocity, density, and Q value are obtained. Model and real data tests show that reservoirs are better predicted with P-wave velocity, S-wave velocity, density, and Q value obtained by the proposed joint inversion.