基于Gray近似的弹性波阻抗方程及反演

Gray approximation-based elastic wave impedance equation and inversion

为得到更准确的岩石物理参数数据体,减小计算误差的累积效应,人们希望通过某种方法直接提取岩石物理参数。用Connolly的弹性阻抗(EI)公式进行反演只能直接得到纵、横波速度和密度的信息,再通过计算得到相应的弹性参数,而且不同角度的弹性阻抗的量纲不统一。本文针对Connolly方法的不足,通过Gray近似把佐普里兹方程表示为反射系数是剪切模量μ、拉梅系数λ和密度ρ的函数,提出了以Gray的AVO近似方程为基础的一种新的弹性波阻抗反演公式,并对该公式进行了标准化以实现不同角度的弹性波阻抗间量纲的统一。文中用标准化后的弹性波阻抗反演公式对A地区的实际地震数据进行了反演,从反演得到的弹性阻抗数据体中可直接提取剪切模量μ、拉梅系数λ,表明用文中方法提取弹性参数更加稳定、准确。

In order to more accurate petrophysical parameters data volume and reduce the accumulation effects of computed errors, the people want to directly pick up petrophysical parameters by some approach. Using Connolly elastic impedance (EI) formula to carry out inversion only directly yields the information of P-, S-waves velocities and density, and again yields corresponding elastic parameters by computation. The dimension of elastic impedance in different angles is non-uniform. In view of the shortage of Connolly approach and representing Zoeppritz's equation as the reflectivity being the function of shear modulus μ, Lame coefficient λ and density ρ by Gray approximation, the paper presented a new elastic wave impedance inversion formula based on Gray's AVO approximate equation, standardized the formula in order to uniform the dimension among the elastic wave impedances in different angles. The inversion was carried out for practical seismic data in A area by standardized elastic wave impedance inversion formula in the paper, shear modulus μ and Lame coefficient λ can be directly picked up from inverted elastic impedance data volume, which showed using the approach presented in the paper to pick up elastic parameters is more robust and accurate.