基于地震谱反演的地层速度估算方法及应用

本文提出将谱反演技术和波阻抗递推反演技术相结合的地层速度估计方法。该方法先通过谱反演获得地震剖面对应的反射系数剖面，再利用波阻抗递推反演方法，把反射系数剖面转换成速度剖面。既发挥了谱反演准确求取反射系数的优势，又能进一步获得与岩性密切相关的速度参数。利用Marmousi模型理论数据的测试，说明了该方法的可行性和有效性。针对南海北部陆坡神狐海域含水合物沉积层的速度和密度变化特征，采用基于Gardner指数函数的分段拟合方式，建立了由地层速度换算密度参数的分段关系式。然后，用提出的方法得到了沿该测线的地层速度剖面，较好地反映了天然气水合物的空间展布，并与速度测井曲线及钻探结果吻合较好，为天然气水合物预测提供了一种有效方法。

Seismic velocity estimation method based on spectral inversion

A method for estimating stratum velocity is proposed by combining spectral inversion and wave impedance recursive inversion. The method consists of two steps:first, a reflection coefficient section is obtained with the spectral inversion of seismic section; then, this reflection coefficient section is transformed to velocity section by wave impedance recursive inversion. The method can not only accurately calculate the reflection coefficient, but also further obtain seismic velocity which closely relates to stratigraphic lithology. Experiments on Marmousi model show that the proposed method is valid. For applications to real data, the piecewise Gardner's equations of density-velocity relations are established based on acoustic and density logging data of Well SH2 in the Shenhu area in the northern continental slope of the South China Sea, and then the proposed method is applied to estimate strata velocity sections from a seismic line passing Well SH2. Based on the estimated velocity section, gas-hydrate reservoirs are predicted. The estimated stratum velocity and predicted gas-hydrate distribution are consistent with drilling and logging data at Well SH2.