煤层气AVO分析预处理关键技术

利用地震勘探AVO技术预测煤层气(CBM)的风险主要来自地震预处理对反射振幅的改造,这种改造对高信噪比、高分辨率和高保真处理虽然是必要的,但是对煤层气AVO分析却存在一定影响。类似砂岩含气储层的AVO预处理,相对振幅保持是煤层气AVO分析预处理秉持的基本原则,煤层气储层第IV类AVO异常使得其预处理又区别于一般砂岩含气储层。径向道滤波线性噪音衰减技术、高低频分离地表一致性振幅补偿技术、保幅Kirchhoff叠前时间偏移技术是解决煤层气AVO分析预处理中线性干扰、近地表异常、空间成像引起的振幅变化问题的关键技术。野外数据试验表明:3项关键技术可以满足相对振幅保持处理要求,最大程度保留煤层气AVO第IV类振幅异常,有利于实现煤层气AVO分析和提高煤层气预测精度。

Key preprocessing technology for CBM AVO analysis

The hazard of amplitude versus offset (AVO) analysis for coalbed methane (CBM) mainly comes from amplitude modifications during seismic preprocessing that is nevertheless necessary for high signal-to-noise of ratio (SNR),high resolution,and high fidelity,and yet exhibits a favorable or unfavorable possibility to implement CBM AVO analysis.Similar to sandstone gas reservoir,AVO preprocessing for CBM reservoir should abide by a relative amplitude preserved (RAP) principle and additionally emphasize differences on the class IV AVO anomaly.As for dealing with linear noise attenuation,near surface variety compensation and spatial imaging,the key technologies adapted to CBM AVO preprocessing include radial trace (RT) filter,high-low frequency surface-consistent amplitude compensation (SCAC),and RAP Kirchhoff pre-stack time migration (PSTM).A real 3D data demonstrates that the key technologies compliant to RAP principle in CBM AVO preprocessing can preserve the class IV AVO anomaly and benefit CBM AVO analysis and improve CBM estimation.