宽线技术在下扬子地区页岩气勘探中的应用

Wideline acquisition for shale gas exploration in Lower Yangtze area

下扬子地区广泛分布的泥页岩有机碳含量高,是页岩气勘探的有利区域。但该区构造复杂,地层褶皱发育,地震资料信噪比低,成像质量差,造成页岩气勘探、开发难度大。基于对工区现有资料的分析,通过正演模拟对采集参数进行精细论证,设计出宽线(3线2炮,60m炮距)大组合(Crossline方向)地震数据采集方法,所采集资料信噪比大幅提高,有效反射的波组特征明显,构造清晰,剖面品质提高。模型正演和实际应用都证明该方法是下扬子构造变形区提高地震资料信噪比、改善成像效果的适用技术。

Lower Yangtze area is favorable for shale gas exploration due to widely spread shale with high TOC.However,structures in this area are rather complicated with complex folds.So signal to noise ratio of seismic data is low and data imaging is poor,which result in huge difficulty in shale gas exploration and development.Based on analysis of existing data,we analyze acquisition parameters with forward modeling,and propose a wideline acquisition geometry:3receiver lines with large array(in crossline direction),and 2source lines with source interval of 60 m.Seismic data acquired bythis design show that signal to noise ratio is greatly enhanced and much better reflections are obtained.Both forward modeling study and field data acquisitions have proved that this approach is appropriate to improve signal to noise ratio and imaging quality in Lower Yangtze area.