基于层位约束的不规则网格层析速度建模方法

网格层析成像采用离散网格点代替空间连续介质模型,通过更新网格点速度值对模型进行迭代优化,从而达到速度误差收敛的目的.常规网格层析是基于规则矩形网格进行网格剖分,横向及纵向网格采用等间距步长,该方法在网格剖分过程中没有考虑地层构造特点.本文提出一种基于层位约束的不规则网格层析成像方法.该方法通过截取时窗的策略对特殊构造部分采取加密网格的策略,从而实现根据地质构造指导网格剖分.对于简单的地质构造,本文提出方法与常规方法效果相当.对于复杂构造地层,尤其对于小尺度特殊地质构造体,本文提出方法更具针对性,对于特殊构造体速度建模精度更高.由实际数据应用证明,对于复杂地质构造,本文方法能够大幅提高速度场建模精度,为叠前深度偏移能够准确成像保驾护航.

One method of irregular grid tomography velocity modeling based on horizon constraint

Grid tomography uses discrete grid points instead of spatial continuous medium model, and optimizes the model by updating the grid point velocity value, so as to achieve the purpose of convergence of velocity error. Conventional grid tomography is based on regular rectangular grid for grid splitting. The transverse and longitudinal grids are of equal spacing step size. In this paper, an irregular grid tomography method based on layer constraint is proposed. In this method, the grid segmentation constraint is carried out by using the horizon, and the strategy of encrypting the grid for the special structure is adopted by the strategy of opening the transverse and longitudinal time windows, so as to realize the grid segmentation guided by geological structure. For the simple geological structure, the proposed method has the same effect as the conventional method. For complex structural strata, especially for small-scale special geological structures, the proposed method is more targeted, and the velocity modeling accuracy for special structures is higher. It is proved by practical data that for complex geological structures, this method can greatly improve the accuracy of velocity field modeling and ensure accurate imaging of pre-stack depth migration.