一种基于粗网格的多算子模拟成像方法

A multi-operator combination simulated imaging method based on coarse grid

对于已知速度模型,传统的叠前深度偏移成像方法都是以快速获得高精度偏移剖面为目的。基于成像算子的模拟叠前深度偏移成像方法无需进行波场正演和偏移处理便可快速得到偏移结果,但成像算子却是根据单一散射点散射向量构建的,只能对散射点附近的局部区域进行精准模拟成像。为了提高直接模拟成像结果的可靠性和兼顾直接模拟成像计算效率高的优势,先在粗网格离散原速度模型的前提下建立粗点扩散算子,在波数域对粗点扩散算子进行不同插值方法测试,测试不同尺寸粗网格以及不同插值方法对模拟成像结果的影响。在此基础上,又提出一种多算子协同模拟成像,设置多个局部偏移成像窗,每个窗内布置散射点并求取射线路径,分区构建较为精准的控制局部成像的成像算子,使模拟成像结果能更好地体现观测系统对不同区域的理论成像结果的影响。该方法不仅保留了快速成像的高计算效率,同时得到控制局部成像的成像算子,可以模拟不同区域在同一观测系统的理论模拟成像结果,并检测观测系统对全局成像的影响,可以直接展示观测系统对不同区域理论成像的控制。

For models with known velocities,traditional pre-stack depth migration imaging methods aim to quickly obtain high-precision profiles.The pre-stack depth migration imaging method based on the imaging operator can quickly obtain the migration results without the forward modeling and migration processing of the wave field,but the imaging operator is constructed according to the scattering vector of a single scattering point,and can only accurately simulate the local area near the scattering point.In order to improve the authenticity of the direct simulated imaging results and take into account the advantages of high computational efficiency of direct simulated imaging,the coarse point diffusion operator is established under the premise of the coarse mesh discrete original velocity model,and different interpolation methods are tested on the coarse point diffusion operator in the wavenumber domain to test the influence of different scales of coarse mesh and different interpolation methods on the simulated imaging results.On this basis,a multi-operator cooperative simulated imaging is proposed,in which multiple local migration imaging windows are set up,scattering points are arranged in each window and the ray path is calculated,and the imaging operator for controlling the local imaging is constructed in the partition,so that the simulated imaging results can better reflect the influence of the acquisition geometry on the theoretical imaging results of different regions.This method not only retains the high com putational efficiency of fast imaging,but also obtains the imaging operator that controls local imaging,which can simulate the theoretical simulated imaging results of different regions under the same acquisition geometry and detect the influence of the acquisition geometry on global imaging,which can directly demonstrate the control of the acquisition geometry on theoretical imaging in different regions.