中文摘要：

海底地层速度结构是识别海洋天然气水合物储层的直接依据,本文应用地震反射走时层析成像建立了海底地层速度模型.采用不规则网格对模型进行离散化,使速度单元与反射界面单元完全耦合;利用基于不规则单元波前扩展和走时插值的射线追踪方法,精确确定反射射线路径和反射波走时;在反演中同时使用先验约束、平滑约束、归一化和正则化技术,提高了层析反演的稳定性和结果的可靠性.对南海北部神狐海域SH2井附近的二维地震测线资料,利用多域人机交互法拾取了反射走时,用反射走时层析成像方法获得了SH2井附近含水合物目标区的速度结构.该反演结果与测井声波速度和钻探结果一致,其中的高速带对应水合物储层,表明反射走时层析成像能够有效地得到海洋天然气水合物储层的速度结构,为海洋天然气水合物储层识别提供依据.

英文摘要：

A velocity structure of submarine strata is a direct evidence for gas hydrate reservoir identification,in this paper we build the velocity model of submarine strata using seismic reflection traveltime tomography. The tomography is based on an irregularly discretized model so that the interface can couple well with the cell boundary. The ray tracing method is based on a bilinear traveltime interpolation and wavefront group marching method and it can calculate the ray path and traveltime accurately. Priori constraint,smoothing,normalization as well as regularization were introduced in the tomographic inversion for stabilization of the inversion process and reliability of the inversion results. We applied the tomography method to the 2-D seismic data near well SH2 in Shenhu area of the South China Sea. For the seismic data,we picked the reflection traveltimes using a human-computer interaction technique in different seismic gathers. Finally the velocity structure of submarine strata along the seismic profile was built. The tomography result is consistent with the drilling and logging data and the high velocity zone in the velocity profile is corresponds to the gas hydrate reservoir. Accordingly,we conclude that the reflection traveltime tomography is an effective technique to obtain the velocity structure of the marine gas hydrate reservoir and can provide direct evidence for its reservoir identification.