基于杨氏模量、泊松比和各向异性梯度的裂缝介质AVAZ反演方法

为了全面地描述裂缝介质的储层特征、流体性质和各向异性特征，提出了由宽方位叠前道集数据直接获取裂缝介质弹性参数和各向异性梯度参数的振幅随方位角变化(Amplitude Versus Azimuth,AVAZ)反演方法。首先推导了基于杨氏模量、泊松比和各向异性梯度的各向异性AVO方程,通过与Ruger近似进行对比,分析了该方程的近似精度。然后利用实际测井资料和二维逆掩断层模型建立了不同方位角的合成叠前角度道集,对未加噪声和信噪比为3的宽方位叠前角度道集进行了AVAZ反演方法测试,结果表明,未加噪声和信噪比为3的合成宽方位叠前道集均能反演得到符合地震反演精度的杨氏模量(E),泊松比(σ)和各向异性梯度(Γ),噪声对杨氏模量的反演影响较小,不含噪声时泊松比和各向异性梯度的反演精度更高,与真实值吻合程度较高。

 In order to fully describe the reserroir characteristics,fluid properties and anisotropy in fractured media,we proposed an algorithm of Amplitude Versus Azimuth (AVAZ) inversion to obtain elastic parameters and anisotropy parameters of fractured media by using wide azimuthally pre-stack seismic data.Firstly,a new P-wave azimuth AVO approximate equation based on Young’s modulus,Poisson’s ratio and anisotropy gradient is deduced.The precision of this new equation was analyzed and compared with Ruger’s equation.Then,we utilized actual log data and 2D overthrust model to generate synthetic pre-stack angle gathers of wide-azimuth data.The algorithm is tested through the wide-azimuth synthetic angle gathers without noise and with random noise (SNR=3) respectively.The result shows that the inverted Young’s modulus,Poisson’s ratio and anisotropy gradient without noise is estimated exactly and agreed with the original data.Meanwhile,the inversion result of the data with random noise (SNR=3) is stable and can meet the demand of seismic inversion.Noise causes less influence on the inversion of Young’s modulus,the invesion accuracy of Poisson’s ratio and anisotropy gradient is higher without noise which is well coinciding with the actual data.

国家科技重大专项(2011ZX05019-008-005)资助。