松辽盆地北部上二叠统林西组烃源岩特征及地质意义

Source rock characteristics and geological significance of Upper Permian Linxi Formation in Northern Songliao Basin

松辽盆地北部石炭系—二叠系钻遇大套上二叠统林西组厚层暗色泥板岩。采用烃源岩地球化学及饱和烃气相色谱—质谱等方法,分析研究区烃源岩特征,研究有机质地球化学特征、母质类型和沉积环境的地质意义。结果表明:研究区烃源岩有机质丰度较高,多为中等—好烃源岩,有机质类型主要为Ⅱ型,R_o平均为2.58%,大部分小于3.00%,成熟度处于高—过成熟的演化阶段。烃源岩Pr/Ph主要介于0.16~1.81,平均为0.49,植烷优势较明显,指示强还原到还原的沉积环境,有利于有机质保存。Pr/nC_(17)、Ph/nC_(18)及C_(27)-C_(28)-C_(29)规则甾烷反映沉积有机质为高等植物与藻类等低等水生生物混合来源,以浮游植物贡献为主。松辽盆地北部上二叠统林西组烃源岩进入生气阶段,具有较好的页岩气勘探前景。该结果为松辽盆地深部油气勘探提供参考。

In order to explore the oil and gas resource prospects of the Carboniferous-Permian in Northern Songliao Basin,and the thick dark mudstone and slate of the Upper Permian Linxi Formation were encountered.Based on the analysis of source rock geochemistry and saturated hydrocarbon and gas chromatography-mass spectrometry of Linxi Formation samples,the geochemical characteristics of organic matter,parent material type and sedimentary environment were analyzed.The study shows that the organic matter abundance of the Upper Permian Linxi Formation source rock in the North Songliao Basin is relatively high,and it is a medium to good source rock.The organic matter belongs to typeⅡ.The average value of R o is 2.58%,and most values are less than 3.00%,and it is in the evolution stage of high maturity and over maturity.The Pr/Ph ratios of the source rocks range from 0.16 to 1.81,with an average of 0.49.The phytane predominance is obvious,indicating that the sedimentary environment is a strong reduction to reduction environment,which is conducive to the preservation of organic matter.Pr/nC 17,Ph/nC 18 and C 27-C 28-C 29 regular steranes indicate that the organic matter is derived from a mixture of higher plants and lower aquatic organisms such as algae,and is mainly contributed by phytoplankton.Through comprehensive analysis,it is considered that the source rocks of the Upper Permian Linxi Formation in Northern Songliao Basin have entered the gas generation stage and have certain shale gas exploration prospects.These results provide data support and research basis for deep oil and gas exploration in Songliao Basin.