鄂尔多斯盆地北部杭锦旗地区上古生界气源岩分析

鄂尔多斯盆地北部杭锦旗地区上古生界天然气来源问题一直存在争议。在烃源岩沉积环境、分布特征分析的基础上，讨论了烃源岩的评价方法和标准，利用有机质类型、丰度、成熟度及生烃强度，开展烃源岩评价，确定了主力气源岩层位及分布特征。结果表明：研究区气源岩主要为上古生界太原组及山西组煤系烃源岩，岩性为煤层、炭质泥岩、暗色泥岩，其中煤层为主要的烃源岩;沉积相控制源岩展布，地质历史时期泥炭坪、扇三角洲平原、冲积扇扇缘沼泽等环境煤层发育好，泥岩厚度大；煤层有机质丰度高，炭质泥岩次之，暗色泥岩最差，参照煤系源岩评价标准，区内烃源岩为较好—非常好的烃源岩；研究区镜质体反射率值分布于0.6%~1.8%之间，呈由北向南增大趋势，全区进入生气阶段，泊尔江海子断裂附近及以南进入大量生气阶段；研究区内生气强度主要介于(10~40)×10⁸ m³/km²之间，具备形成大气田的气源条件。因此，研究区天然气来源具有原地性的特征，泊尔江海子断裂南部烃源岩优于北部烃源岩。

Research on the Upper Paleozoic Gas Source of the Hangjinqi Block in the Northern Ordos Basin

Based on the analysis of depositional environment and distribution characteristics of source rocks,by means of organic type,organic abundance,thermal evolution and the gas-generating intensity,evaluation of source rocks was carried out.The source rocks in Hangjinqi area are coal beds,carbonaceous mudstones and dark mudstones,which are located in the Upper Paleozoic Taiyuan and Shanxi Formations,and the coal bed is the major source rocks.Coal beds and thick mudstones were well-developed in sedimentary environment such as peat flat,fan delta plain,and the swamp at the edge of alluvia fan.Coalbed is the best in organic abundance,followed by carbonaceous mudstones and dark mudstones.By the standards of evaluation of the coal source rocks,the source rocks in Hangjinqi area are better-best.The source rocks in Hangjinqi area reaches the stage of gas-generating with a vitrinite reflectance from 0.8% to 1.3%.Particularly,the source rocks near the Boerjianghaizi fault and south of this fracture are in the stage of gas-generating climax.The gas-generating intensity of source rocks in Hangjinqi block is (10-40)×10⁸m³/km²,having the conditions of gas source for developing large gas field.In conclusion,the gas accumulation in study area is characteristic of generating in situ,and the quality of gas source rocks in the south of Boerjianghaizi fault is better than rocks in the north.