松辽盆地深层断陷沙河子组烃源岩分布预测与生气潜力

摘要

Shahezi Formation of Lower Cretaceous is the main source rock in the deep fault-depression of Songliao Basin .The present drilling data reveal that it is large in thickness ( >700 m ) and deep in burial (>3 500 m).However, most wells are located in the margin of the deep fault depression , which brought about relatively rare information on the source rocks in the internal fault basin .On the basis of the structural style and seismic reflection feature of the fault depression , two development models of source rocks in Shahezi Formation are summarized , including the dustpan shape unilateral fault depression and graben bilateral fault depression .Mean-while , there exist five types of deep source rocks .The source rocks in the central fault depression which have paral-lel structural , stratified and continuous seismic reflections are most reliable .These source rocks are characterized by deep and semi-deep lacustrine facies with large thickness and big ratio of dark mudstone and stratum (45%~70%) .The quantity of gas generating in the studied area is 148.38 ×10 12 m3 , which indicates a huge po-tential of gas .%松辽盆地下白垩统沙河子组是深层断陷的主要烃源岩发育层系，目前钻井揭示其厚度大（＞700 m），埋藏深（＞3500 m），但钻井大都分布于深层断陷的边部，断陷内部烃源岩层揭示少。根据断陷结构样式及地震反射特征，总结出单断箕状断陷和双断地堑式断陷两种沙河子组烃源岩发育模式，并确定深层烃源岩主要有五种存在形式。断陷中部席状平行结构、成层性、连续性好的地震反射特征的烃源岩最为落实，主要为深湖-半深湖相，暗色泥岩厚度大，暗地比高（45％～70％）。深层沙河子组烃源岩总生气量约148.38×1012 m3，天然气资源潜力巨大。