羌塘盆地上侏罗统索瓦组烃源岩分布特征及远景分析

羌塘盆地迄今为止共发现200多处油气显示点,其中5处液态油苗,多处油页岩,表明盆地具备生烃的物质基础。上侏罗统索瓦组烃源岩以碳酸盐岩为主,厚度从几十米到几百米不等,有机碳平均含量为0.1%~1.90%,以中等至好烃源岩为主;其次为泥质岩,仅在北羌塘坳陷中、西部有所分布,有机碳含量介于3.71%~28.14%之间,为好烃源岩。根据干酪根显微组分的分析结果认为索瓦组烃源岩有机质类型主要为Ⅱ₁型,镜质体反射率介于0.94%~2.7%之间,烃源岩处于成熟—过成熟阶段。构造运动造成索瓦组烃源岩抬升剥蚀,综合分析认为该烃源岩总体上对整个盆地的油气远景贡献较差,但在北羌塘坳陷西部和东北部仍可作为重要的烃源岩。 

CHARACTERISTICS OF UPPER JURASSIC SUOWA FORMATION SOURCE ROCK IN THE QIANGTANG BASIN OF NORTHERN TIBET

Over 200 oil and gas shows were discovered so far in the Qiangtang Basin,of which including 5 oil shows and much oil shale shows.It indicates that the source rocks have favorable conditions to form gas and oil in the Qiangtang Basin.The mainly source rock of Upper Jurassic Suowa Formation is carbonate rocks in the Qiangtang Basin.It's thickness is from tens meters to hundred meters.The mean content of organic caborn is 0.1% to 1.90%.It is mainly middle to good source rock.The following source rock of Upper Jurassic Suowa Formation is mudstone.It's mean content of organic caborn is 3.71% to 27.14%. It is mainly good source rock,only distributes in the middle and west of the North Qiangtang Depression.The organic matter type is Ⅱ₁ through kerogen analysis.The vitrinite reflectance is 0.94% to 2.7%.The source rock is at stage of mature to post maturity.The source rock of Suowa Formation was uplifted and denuded because of the effect of tectonic movement.The research results show that Suowa Formation source rock has bad contribution to hydrocarbon accumulation in the whole Qiangtan Basin.But it is still important hydrocarbon source rock in the west and northeast of the North Qiangtang Depression.