Dimensionality Reduced Virtual Event Method to Suppress Internal Multiples for Land Seismic Data

XIE Fei1, AN Shengpei1, ZHU Chenghong1, LIU Jiahui2, HU Tianyue2,† 1. Petroleum Exploration and Production Research Institute, Sinopec, Beijing 100083; 2. School of Earth and Space Sciences, Peking University, Beijing 100871; † Corresponding author, E-mail: tianyue@pku.edu.cn

Abstract As the land internal multiples could not been obviously attenuated, the authors develop the dimensionality reduced virtual event method to suppress the internal multiples in pre-stack land seismic data. Compared with the traditional virtual event method, the authors apply the virtual event method trace by trace on the pre-stack gathers after accurate dynamic correction to predict internal multiples. It achieves dimensionality reduction, greatly reduces the amount of calculation, and no longer requires a regular and dense enough distribution. Meanwhile, this method introduces a weighted reference trace with high signal-to-noise ratio to participate in the cross-correlation and convolution operations of the pre-stack gathers, which improves the prediction accuracy of the virtual event method. This method is applied to actual land seismic data in western China and achieved obvious effect when suppressing internal multiples. Key words internal multiples; virtual event; reduced dimensionality; correlation; adaptive subtraction

多次波是地震勘探中常见的相干噪声, 在海洋勘探和深层陆地勘探的地震资料中均会出现。常用的地震成像技术基于一次反射波信号的假设, 但多次波不满足该假设, 因此常被视为相干噪音, 会影响目的层信号的振幅、相位和频率, 并可能产生构造假象, 降低成像结果的可靠性和信噪比[1]。多次波分为表面多次波和层间多次波。表面多次波是由地表反射产生的, 广泛存在于海洋勘探数

据中, 压制表面多次波的方法较为成熟, 已经商业化, 在主流地震数据处理软件(如Geovision, Omega和Geoeast等)中均有相应的模块。层间多次波是由地层间多次反射产生的, 常见于深部陆地和部分海洋勘探数据中。层间多次波至少在地层间反射3次, 振幅衰减较大, 只有在两个强反射界面间产生的层间多次波容易被观测到[2]。与表面多次波相比,预测和压制层间多次波的难度更大。