漠河盆地依列克得组火山活动间歇期烃源岩有机地球化学特征研究

Organic Geochemical Characteristics of Source Rocks from Yiliekede Formation in the Intermittent Stages of Volcanic Activity in Mohe Basin

漠河盆地早白垩世为一火山岩断陷盆地,广泛发育火山岩夹沉积岩的二元沉积建造。依列克得组烃源岩为一套发育在玄武岩系之间的湖沼相沉积岩系,烃源岩岩性为油页岩、页岩及煤岩。该套烃源岩与其周围玄武岩为同期不同相产物,与该套烃源岩直接接触的火成岩为火山熔岩或火山碎屑直接进入湖盆水体而形成。利用热解、GC,GC—MS等地球化学分析技术,对该套烃源岩生油潜力进行了初步评价,并探讨了该套烃源岩的沉积环境、母源特征及火山活动对该套烃源岩的影响。分析显示,该套烃源岩有机质丰度较高,有机质类型油页岩以Ⅱ型为主,页岩和煤岩主要为Ⅲ型,火山岩浆活动对烃源岩的烘烤作用不明显(Ro=0.56%～0.59%),有机质热演化处于刚进入生烃门限的低成熟阶段,综合评价具有较好的生烃潜力;该套烃源岩沉积于强还原—弱还原水体环境,在垂向上含盐度具有较快的波动,处于淡水—咸水交替变化状态;母质来源具有水生生物和陆生植物混源输入特征,煤岩陆源有机质输入更丰富。

Mohe basin is a fault basin infilled with Lower Cretaceous volcanic rock and with growth of dual structure consisting of volcanic rock and sedimentary rock.The Yiliekede group source rock in Mohe basin belongs to limnetic facies and is developed in basaltic series.The source rocks including oil shale,shale and coal.The source rocks were deposited in the same time with the basalts,and the igneous rock were formed for the volcanic lava or pyroclastic into lake water directly.Based on the analytic technique of GC and GC-MS,the depositional environment,biogenetic derivation and maturity of the source rocks were discussed.The results show that the abundance of the organic material of source rock is rather high,the kerogen of the oil shale is mainly of type Ⅱ,the coal and the shale is mainly of type Ⅲ;The source rocks were not heated by the basalt magma（Ro=0.56%0.59%）,and the thermal evolution of the samples have reached low maturation stage,and just entered the oil generation threshold.Thus the source rock is a set of excellent source rock measures with much better hydrocarbon generation potential.The source rocks are deposited in an water body of strong-weakly reduction.The salt of the water bowere changed between salt and freshwater-tiny salt quickly.The hydrocarbon came from the mixed-source of organics from the input of aquatic organisms and terrigenous plant,and the terrigenous plant is more enough in coals.