西湖凹陷斜缆采集关键参数优选研究

Optimizing the key acquisition parameters of variable-depth streamer in Xihu sag

西湖凹陷是东海最大的含油气凹陷,其主要储层位于中深部,埋藏较深。增加低频信息是解决西湖凹陷主要地质问题的核心之一。斜缆地震采集技术可以有效地压制鬼波,拓宽频带,尤其是低频成分,并且具有野外操作简单、成本低等优势,对解决西湖凹陷的地质问题有利。基于斜缆平均鬼波滤波特性,对斜缆缆型、沉放深度范围等关键采集参数进行了理论分析;通过二维野外试验,对不同斜缆采集模式的单炮记录、偏移剖面开展了进一步的对比研究。结论认为:对于西湖凹陷深部储层,相较于常规水平缆资料,斜缆资料的构造刻画更清楚,频带得到了一定的拓宽。常用的两种斜缆缆型中,直线型斜缆的陷波补偿效应更好,抛物线型斜缆的低频能量更强。在斜缆最浅沉放深度固定时,加大斜缆沉放深度差,有利于获取更多的低频信息。

The Xihu sag is the largest oil-bearing sag in the East China Sea.The main reservoir of the Xihu sag is located in the middle and deep strata.Adding low frequency information is one of the core issues for solving the main geological problems in the Xihu sag.The variable-depth streamer acquisition technology can effectively suppress ghost waves,broaden the frequency band,especially the low frequency,and has the advantages of simple field operation and low cost,which is beneficial to solving the geological problems of the Xihu sag.Based on the average ghost filter of variable-depth streamer,the key acquisition parameters are theoretically analyzed,such as streamer mode and the streamer depth range.Through 2 D field test,a further comparative study was carried out on the raw shot and PSTM record.It is concluded that,for the deep reservoirs of the Xihu sag,the variable-depth streamer is more clearly structured than the conventional horizontal streamer data,and the frequency band has been broadened. Among the two commonly used streamer modes,the linear streamer has better notch compensation effect,and the parabolic streamer has higher low frequency energy.When the shallowest depth of the variable-depth streamer is fixed,increasing the depth range is beneficial to obtaining more low frequency information.