浅海地震采集缆—源空间组合对激发子波特性的影响分析

Analysis of influence of cable-source spatial combination on excitation wavelet behavior in seismic acquisition of shallow sea

地震资料分辨率低是当前渤海油田深层地震勘探面临的突出问题,而改善该问题首先须在地震采集尤其是震源设计方面寻求突破,但鲜有针对渤海浅水条件下的拖缆与震源空间组合研究的报道。为此,首先分析了渤海浅水条件下气枪脉冲的传播特征,确定了影响气枪脉冲传播的主要因素;再基于非理想气体条件气枪子波模型对浅水条件下单枪子波进行模拟,研究了考虑缆鬼波时子波及其频谱特征,提出采用考虑缆鬼波的子波对震源性能进行评价的方法;然后以渤海油田渤中地区实际地理和地质条件为基础,设计了不同缆—源沉放深度组合、震源平面展布的模拟试验,系统分析了渤海浅水条件下拖缆、震源空间组合对子波及其频谱的影响规律;最后将文中总结的规律认识和震源设计技术应用于渤中二次数据采集,并对比该区新、老三维拖缆单炮数据,验证了所提方法的正确性,对渤海浅水区气枪震源的优化设计及评价具有指导意义。

The low resolution of seismic data is a prominent problem in the current deep seismic exploration in Bohai Sea.In order to solve this problem,it is necessary to find breakthroughs in seismic acquisition,especially in the source design.However,there are few reports on the research of spatial combination of the streamer and source in shal-low water conditions of Bohai Sea.This paper firstly analyzes the characteristics of air gun pulse propagation in shal-low water conditions of Bohai Sea and determines the main factors affecting the air gun pulse propagation.Then,the paper simulates the single gun wavelet in shallow water based on the non-ideal gas condition air gun wavelet model,studied the spectral characteristics of the wavelet by considering the streamer ghost,and proposes the method of evaluating the source performance with the wavelet including streamer ghost.Secondly,based on the actual geo-graphical and geological conditions in Bozhong area of Bohai Sea,the paper designs the simulation tests of different cable-source sinking depth combinations and source plane distribution and analyzes systematically the influence law of spatial combination of the streamer and source on wavelet and its frequency spectrum under the condition of shal-low water in Bohai Sea.Finally,the paper applies the summarized law understanding and source design technology to the secondary data acquisition of Bozhong and compares the new and old three-dimensional towing cable single shot in Bozhong area,which verifies the correctness of the proposed method.The research results have a certain guiding significance for the optimal design and evaluation of air gun sources in the shallow water area of Bohai Sea.