优化的多震源最小二乘逆时偏移  

Optimized multi-source least-squares reverse time migration

作　　者：李庆洋 黄建平[1] 李振春[1] 李娜[2] 李闯 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国石化中原油田分公司物探研究院,河南濮阳457001

出　　处：《石油地球物理勘探》2016年第2期334-341,207-208,共8页Oil Geophysical Prospecting

基　　金：国家"973"项目(2014CB239006);国家自然科学基金项目(41104069;41274124);中央高校基本科研业务费专项资金项目(14CX06072A)联合资助

摘　　要：最小二乘逆时偏移相比于常规偏移具有较大优势,但计算量过大限制了其推广、应用;相位编码技术通过将多炮数据组合成一个超道集,可有效提高计算效率、压制串扰噪声,编码策略种类繁多,但缺少对比分析。为此,在实现多种编码策略最小二乘逆时偏移算法的基础上,通过模型试算,详细对比、分析了四种较为常用的编码策略(振幅编码、极性编码、随机时延编码、平面波编码),并将随机最优化思想推广到相位编码最小二乘逆时偏移中,提出了优化的相位编码最小二乘逆时偏移算法。该算法考虑了梯度的随机特性,即每次迭代的梯度都是之前迭代梯度的指数衰减加权平均,通过合并之前的信息,减小了梯度的随机波动。模型试算证实,优化的相位编码最小二乘逆时偏移算法比传统相位编码最小二乘逆时偏移方法收敛更快,可节省计算成本、提高计算效率。Compared with conventional migration method,least-squares migration has a greater advantage,but the large amount of calculation limits its popularization and application. Phase encoding which combines multi-shot data into a super-gather can effectively improve the computational efficiency,and suppress crosstalk noise.However there are a quite few coding strategies,and very few comparison and analysis among them are carried out.Based on least-squares reverse time migration method,we have conducted a detailed comparison of four kinds of commonly used encoding schemes(amplitude encoding,polarity encoding,random time delay encoding,and plane wave encoding)by numerical tests.Besides,we extend the stochastic optimization idea to multi-source least squares reverse-time migration and propose an optimized multi-source least-square reverse time migration.Our algorithm considers the random characteristic of the gradient,and the gradient at current iteration is the exponential decay weighted average of the previous iteration.Through the weighted average of the previous gradient,it reduces the random fluctuations of the gradient. Theoretical model processing confirms that convergence of the proposed optimized multi-source least-square reverse time migration is faster than conventional phaseencoding least-square reverse-time migration method.Therefore,it can save computational cost and improve computational efficiency.

关 键 词：最小二乘逆时偏移 相位编码 随机最优化 多震源 

分 类 号：TN957.51[电子电信—信号与信息处理]