煤系地层地震强反射剥离方法研究及低频伴影分析

煤系地层具有低速、低密度的特点,导致地震剖面上出现强反射同相轴,淹没煤层上、下含油气目的层反射信息,低频伴影现象也被掩盖,无法利用此现象直接进行油气检测。文中提出层位及子波约束匹配追踪的煤层强反射剥离方法,可以高效地剥离三维数据体中的煤层强反射,并利用广义S变换时窗可变的特性,在两个调整参数控制下根据频率分布特点灵活调整窗函数,对地震道进行时频分析,比较煤层强反射剥离前、后的时频特性。模型测试和实际资料处理表明,用文中方法剥离强反射后,在储层下方发现明显的伴影异常,应用效果良好。

A method for stripping coal seam strong reflection and low-frequency shadow analysis

Coal seams are characterized by low velocity and low density, which result in strong reflection on seismic sections. Hydrocarbon reflection information may be hidden in strong events, and low-frequency shadow will be covered up. This phenomenon makes hydrocarbon direct detection fail. In this paper, we propose a method for stripping coal seam strong reflection by wavelet-constrained matching pursuit. This method can efficiently strip strong reflection in 3D seismic data. We use generalized S transform(GST) to do time-frequency analysis and compare time-frequency characteristics before and after stripping coal seam strong reflection. Two parameters adjust window functions according to the feature of frequency distribution. Model and real data tests show that the proposed method achieves good results and abnormal shadow appears under a reservoir after stripping strong reflection of coal seams.