松辽盆地中央凹陷青山口组一段页岩生烃潜力及沉积环境研究

Study on hydrocarbon generation potential and sedimentary environment of shale in the first member of Qingshankou Formation in central depression of Songliao Basin

松辽盆地青山口组一段发育厚层富有机质页岩,是松辽盆地页岩油勘探开发的重要目标层段。综合岩心与薄片观察、岩石学矿物学以及有机地球化学等手段,系统地研究了目标区页岩岩相特征及其生烃潜力与沉积环境的差异。结果表明,研究区共发育4种主要岩相类型,分别为粉砂质泥岩岩相、纹层状泥岩岩相、块状泥岩岩相和黑色页岩岩相。粉砂质泥岩岩相主要形成于浅湖-滨浅湖等浅水区,水体较浅,水动力强,不利于有机质的保存,因而有机质丰度较低;纹层状泥岩岩相主要形成于滨浅湖-半深湖过渡区间,纹层状构造发育,含较多碎屑矿物,有机质来源以水生浮游生物和陆源高等植物混合为特征,有机质类型以Ⅰ型和Ⅱ_(1)型为主,生烃潜力较强;块状泥岩岩相主要形成于水体进一步加深的深湖-半深湖环境中,整体呈现厚层块状构造,岩石颗粒致密,有机质来源、类型及生烃潜力与纹层状泥岩相似;黑色页岩岩相主要形成于相对缺氧的深湖-半深湖环境中,黏土矿物含量高,有机质来源以湖泊低等水生生物为主,有机质丰度高(TOC为2.41%~7.34%,平均值为5.03%),有机质类型以Ⅰ型为主,生烃潜力强,具有极高的页岩油气资源潜力。

The first member of Qingshankou Formation in Songliao Basin develops thick organic rich shale, which is an important target interval for shale oil exploration and development in Songliao basin.The lithofacies characteristics, hydrocarbon generation potential and sedimentary environment of shale in the target area are systematically studied by means of core and thin section observation, petrology, mineralogy and organic geochemistry.The results show that there are four main lithofacies types in the study area, namely silt mudstome lithofacies, laminar mudstone lithofacies, massive mudstone lithofacies and black shale lithofacies.Silty mudstone litho facies is mainly formed in shallow lake shore shallow lake and other shallow water areas.The water body is shallow and the hydrodynamic force is strong, which is not conducive to the preservation of organic matter, so the abundance of organic matter is low;The laminar mudstone litho facies is mainly formed in the transition zone between shore shallow lake and semi deep lake.The laminar structure is developed and contains more clastic minerals.The source of organic matter is characterized by the mixing of aquatic plankton and terrestrial higher plants.The types of organic matter are mainly type I and type II_(1),with strong hydrocarbon generation potential;The massive mudstone lithofacies are mainly formed in the deep lake semi deep lake environment where the water body is further deepened.As a whole, it presents thick massive structure, dense rock particles, and the source, type and hydrocarbon generation potential of organic matter are similar to those of laminated mudstone;The black shale lithofacies is mainly formed in the relatively anoxic deep lake semi deep lake environment, with high clay mineral content.The organic matter is mainly derived from low aquatic organisms in the lake, with high organic matter abundance(TOC is 2.41%~7.34%,average is 5.03%),mainly type I organic matter, strong hydrocarbon generation potential and other characteristics, with high shale oil and gas resource potential.