可变网格高阶有限差分法逆时偏移研究

在高阶有限差分法逆时偏移成像过程中,成像精度和计算效率是一对矛盾体,特别是对于小尺度细微地质构造的刻画。为了能在精细刻画局部地质体结构的同时,保证逆时偏移的计算效率,采用多尺度可变网格有限差分算法求解一阶应力-速度声波方程,将可变网格有限差分算法引入到逆时偏移中,对传统常规逆时偏移算法进行了改进,并将可变网格步长倍数的变化范围推广至任意奇数倍,分析了可变网格对有限差分算法数值频散的影响。不同模型偏移成像试验结果表明,可变网格逆时偏移算法能在保证地下地质体成像精度的同时提高偏移效率,有利于局部构造特征的精细刻画。

During reverse time migration imaging (RTM) using the high-order finite-difference method,imaging accuracy and computational efficiency is a pair of contradiction,especially for the fine migration of small-scale geological structure.In order to fine characterize the structure of local geological structure while ensuring the RTM computational efficiency,a multi-scale variable grid finite-difference method is used to solve the first-order stress-velocity acoustic wave equation.The variable grid finite-difference algorithm is introduced to RTM to improve the traditional RTM algorithm.The variation range of the variable grid step is extended to any odd times.Furthermore,the numerical dispersion is analyzed in the process of variable grid finite-difference algorithm.The variable grid RTM test results for different models show that the variable grid RTM algorithm can improve the imaging accuracy of subsurface geological structure and improve the migration efficiency,which is beneficial for the fine description of the local structural features.

中海石油(中国)有限公司湛江分公司综合科研项目“东方气田群高温高压天然气藏开发关键技术研究”(YXKY-2016-ZHJ-02)资助。