拖缆与海缆联合宽频采集设计

Combined Broad-seis Survey Design of Streamer and OBC

传统的海洋地震勘探采用拖缆进行数据采集,拖缆采集数据的信噪比受外部环境影响较大,通过改变拖缆的沉放深度,可以降低环境对采集地震数据的影响。受国内海洋地震勘探装备作业能力的限制,在中国海域实现海洋宽频地震采集相对较困难。为了打破这一限制,探讨了拖缆与海缆联合宽频采集设计的方法,对联合采集的参数论证、面元合并、羽角对宽频的影响和深度优化求解等4项关键技术进行了分析。在参数论证方面,论证了如何通过最浅目的层深度设计线间距的方法;针对拖缆和海底电缆检波器间距差异设计了面元合并方案,同时考虑了面元合并对信噪比的改变;在羽角存在的情况下,讨论了横向变化率对采集数据限波点频率和能量的影响;最后论述了深度变化试验求取拖缆最优沉放深度的方法。通过对拖缆与海底电缆联合宽频采集设计4项关键技术的分析,搭建了拖缆与海缆联合宽频采集设计的基本流程。

Towed streamer seismic acquisition is used in the traditional marine seismic exploration,and the signal-to-noise ratio of the collected data are greatly influenced by external environment. The influence of environment on seismic data can be reduced by changing the depth of the streamer. It′s difficult to collect broad-seis data in China sea due to the limitations of seismic equipment. In order to break the limitation,a combined broad-seis survey of streamer and ocean bottom cable（OBC）was discussed in the article. There are four key techniques in survey design,including parameter argumentation,bin combined, feather angle and depth optimization. In parameter argumentation the method to compute line spaces through the most shallow purpose layer is discussed. For the space differences between towing and submarine cable detector,bin combined method was designed. In the situation of feather angle existence,we discussed the effect of horizontal change rate on limited wave point frequency and energy in data collection. In the end,we discussed the optimization of sinking depth of towing through depth changing test. Through analysis of these techniques,we have established the basic process of survey design of combined broad-seis acquisition of streamer and OBC.