TI介质多波AVA联合反演岩性参数方法及应用

AVA岩性参数反演方法大都是基于各向同性理论的近似公式利用P-P波单分量资料来反演。对于大角度入射的地震资料，基于各向同性理论的AVA近似公式与基于各向异性理论的AVA精确公式的计算结果存在较大差异。仅利用P-P波振幅反演地层岩性参数无论在理论基础还是反演精度上都存在不足，而同时用P-P波和P-SV波振幅联合反演岩性参数，可增加约束条件，提高反演结果的可靠性。以TI介质中的振幅特征方程为理论基础，进行多波AVA联合反演纵、横波速度、地层密度和地层各向异性系数。实际资料计算结果表明，此方法不仅能够可靠的求取地层岩性参数，还能得到与地层裂缝有关的各向异性系数。联合反演结果比单分量反演的结果更稳定可靠，是一种行之有效的叠前弹性阻抗参数反演方法。用反演得到的岩性参数求取对油气反应敏感的弹性阻抗，进而可以利用不同角度弹性阻抗的梯度变化进行油气水的识别。

METHOD FOR LITHOLOGY PARAMETER INVERSION WITH JOINT MULTIWAVE AVA IN TRANSVERSELY ISOTROPIC MEDIA AND ITS APPLICATION

AVA inversion methods for lithology parameters mostly are based on the approximation formula of the isotropic theory,and only P-P wave data is used.For the seismic data with large incidence angles,there are large differences between the computation results from AVA isotropic approximation formula and that from AVA anisotropic precise formula.If only P-P wave amplitude is used for lithology parameters inversion,there are some shortages in the respect of the theory basis and the inversion precision.However,inverting the lithology parameter by jointly using P-P wave amplitude and P-SV wave amplitude can increase the additional constraint conditions,and improve the reliability of the inversion results.Taking amplitude characteristic equation of the transversely isotropic media as the theory basis,the paper inverted P wave velocity,S wave velocity,density and anisotropic coefficients with joint multiwave AVA data.The calculation results from the real data indicate that not only the lithology parameters,but also the anisotropic coefficients related to the fractures in the layer can be obtained with this method.The results from the joint inversion method are more stable and reliable than that from P wave data inversion.Therefore,the AVA joint inversion method is an effective inversion method for prestack elastic impedance parameters,the elastic impedance sensitive to the hydrocarbons can be gained with the lithology parameters from the joint inversion,then,oil-and gas-filled,and water-saturated reservoirs can be detected with the gradient changes of the elastic impedance at different incidence angles.