基于延迟波场特征法的海底反射系数估算方法

Estimating ocean bottom reflection coefficient using delayed wavefield characteristic method

估算海底反射系数是海底电缆(OBC)水陆检数据合并处理的一个关键步骤。针对常规扫描确定海底反射系数较为费时的问题,提出了基于延迟波场特征法直接计算海底反射系数的方法。该方法首先计算水陆检数据上行波场、一阶延迟上行波场和二阶延迟上行波场的自相关函数和它们之间的互相关函数,然后构建和求解海底反射系数特征方程,最后确定最佳海底反射系数并应用于水检数据和陆检数据的合并处理。合并数据不但消除了海水鸣震多次波干扰,而且吸收了陆检数据的低频成分和水检数据的高频成分。从而拓宽了海底电缆数据的有效频率带宽,提高了地震数据的信噪比和分辨率。数据试算结果证明了本方法的有效性和实用性。

Estimation of the ocean-bottom reflection coefficient is a key step in the merging process of the ocean-bottom cable （OBC） dualsensor seismic data. Conventional methods are very time consuming, with low accuracy. A delayed wavefield characteristic method is proposed to estimate directly the ocean-bottom reflection coefficient. Firstly, the up-going wavefield, first-order and second-order delayed up-going wavefields,as well as their autocorrelation and cross-relation functions are calculated. Secondly, when the characteristic equation is constructed and solved, three reflection coefficient values can be obtained. Then, the energy values corresponding to the three reflection coefficient values are computed, with the one corresponding to the minimum energy being the established ocean-bottom reflection coefficient, which is to be used further for merging processing of the OBC dualsensor data. The merged daa could eliminate the sea-water column reverberations and could also absorb the high-frequency components from hydrophone data and the low-frequency components from geophone data. Furthermore, the effective bandwidth of the OBC data was broadened effectively, thereby improving the SNR and resolution. Tests on field data illustrated the effectiveness of this method.