频谱分解技术在深层致密砾岩气藏检测中的应用

徐家围子营四段气藏是陆相断陷湖盆形成的深层致密砾岩气藏,具有低孔渗、厚度变化大、强非均质性等特点。该区共有96口井钻通营四段,有21口井在营四段试气,发现含气层段频谱中频率均有降低现象。据此,本文采用频谱分解技术对营四段砾岩进行了含气性检测;进而对频谱道集衰减特征进行分类,拟合出的衰减角度与产气量之间呈正相关关系。利用该方法对徐家围子营四段无井区进行了含气性检测,预测的有利储层分布范围符合断陷盆地断裂控制气藏分布规律,且与溶蚀孔隙发育带分布范围相吻合。

Application of spectral decomposition in deep tight conglomerate reservoir prediction

Gas reservoirs from the Member 4 of Yingcheng Formation in Xujiaweizi Depression were developed in early Cretaceous lacustrine rift basin and they are characterized by low porosity and low permeability,high thickness variation and high heterogeneity.Therefore they post a challenge on exploration and exploitation.In the study area,the Member 4 of Yingcheng Formation was penetrated by 96 boreholes,and DST was conducted in 21 wells.Analysis of seismic data shows the attenuation of frequency spectrum for the gas bearing conglomerate reservoir in the Member 4 of Yingcheng Formation.With spectral decomposition,gas saturation in the tight conglomerate reservoir in the Member 4 of Yingcheng Formation has been tested.Furthermore a classification is made based on different characteristics in spectral attenuation,and a positive correlation is found between spectral attenuation angle and gas production.This method has been applied to the Member 4 of Yingcheng Formation in the places where no well data is available,and the predicted distribution of favorable reservoir zone coincides with other geological evidences observed,e.g.high gas production rate agrees with high secondary dissolution high-porosity zones.