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松辽盆地北部徐家围子断陷主要发育泥岩、火山岩和泥质砾岩3种类型的岩性盖层,其分布已趋于明朗,但针对断裂对盖层的破坏程度及断裂与天然气藏分布之间关系的研究则相对比较薄弱。综合利用地质及地球物理资料,分析断裂发育分布特征及其对盖层的破坏程度,发现徐家围子断陷发育有不同方向的断层,由下至上断裂密度逐渐增大。以下白垩统登娄库组二段为界,上部主要发育T32～T2、T31～T2、T3～T2断裂,下部主要发育T5～T32、T41～T32、T42～T32断裂,下白垩统营城组一段顶部局部盖层被断裂完全破坏,登娄库组二段及其以上区域性盖层被断裂破坏程度小。总之,区域性盖层被断裂破坏程度小,有利于天然气在其下大规模聚集成藏;局部盖层被断裂破坏程度大,造成天然气聚集分散。
There are three types of lithologic caprock of mudstone, volcanic rock and argillaceous conglomerate in the Xujiaweizi fault depression in the north of Songliao Basin. The distribution of lithologic caprock has tended to be clear. However, according to the damage of the fault to the cap rock and the distribution of faults and natural gas reservoirs The relationship between the research is relatively weak. According to the geologic and geophysical data, the distribution of faults and their damage to the overburden are analyzed. It is found that faults of different orientations develop in the depression of Xujiaweizi, and the density of the fractures gradually increases from bottom to top. Following the second member of Dengloukou Formation in the Cretaceous, the upper part mainly develops T32 ~ T2, T31 ~ T2 and T3 ~ T2 faults, while the lower part mainly develops T5 ~ T32, T41 ~ T32 and T42 ~ T32 faults, and the Lower Cretaceous Yingcheng Formation Part of the top of the local cap layer was completely ruptured by faults, and the second half of Denglouku Formation and its regional caprocks were less damaged by faults. In short, the regional cap rock is less damaged by faults, which is favorable for large-scale natural gas accumulation and accumulation beneath it. The local cap rock is severely damaged by fractures, resulting in the accumulation and dispersion of natural gas.