利用上/下缆合并算子确定海上上/下缆采集的最优沉放深度组合

海上常规拖缆采集的地震数据存在受海水面虚反射(鬼波)引起的陷波特性，而近年发展的上/下缆采集技术可以压制鬼波，但仍然存在等效陷波。为此，提出了基于f-k域上/下缆合并算子确定上/下缆沉放深度的方法，进而分析了历年来国内外油公司采用的上/下缆沉放深度的合理性。针对目前国内拖缆沉放深度的最大范围，通过对不同上/下缆沉放深度下上/下缆合并算子的等效陷波特征分析，确定出等效陷波出现的频带范围在目的层有效频带范围以外的上/下缆最优沉放深度组合，系统优选出了12组上/下双缆以及3组上/中/下三缆陷波作用相对较小些的上/下缆沉放深度最优组合，为实际上/下缆采集时缆深选择提供了理论依据。

There are notch frequencies caused by receiver ghost from the sea surface in the seismic data of a conventional towed-streamer offshore seismic acquisition.The over/under towed streamers technology developed in recent years can suppress the ghost-free data,but still appeared equivalent notches in combined data.A method is proposed to determine the sinking depths of over/under towed streamers based on the merge operator in domain.Moreover,the rationality of the sinking depths of over/under towed streamers used in the oil companies at home and abroad over the years is analyzed.For the maximum depth range of towed streamer in domestic,the characteristics of equivalent notches of over/under streamers merge operator of different depths are analyzed and the optimal depths of over/under towed streamers are determined,whose range of frequency band of equivalent notches in combined data is out of the range of frequency band of effective reflections on target layers.Twelve groups of optimal sinking depth combination of over/under streamers and three groups of optimal sinking depth combination of over/middle/under streamers with relatively small effect of equivalent notch on combined data are selected,which provides a theoretical basis for the choose of sinking depths of over/under streamers in offshore surveys.