西藏中仓盆地古近系丁青湖组生烃潜力与沉积有机相分析

Analysis of hydrocarbon generating potential and characteristics of organic facies of Paleogene Dingqinghu formation in Zhongcang basin,Tibet

以中仓盆地古近系丁青湖组为研究对象,根据烃源岩地球化学数据分析,探讨研究区丁青湖组生烃潜力及沉积有机相。结果表明:中仓盆地中丁青湖组灰岩、泥灰岩和泥岩为主要烃源岩。其中,灰岩、泥灰岩有机碳平均质量分数为0.33%,泥岩有机碳平均质量分数为0.32%,属于较差烃源岩;有机质类型为以Ⅱ1型为主的混合Ⅱ型,烃源岩热解峰温为422~446℃,镜质体反射率为0.48%~0.59%,属于低成熟阶段。根据显微组分将沉积有机相划分为湿地草本混生(沼泽)相。综合数据分析表明中仓盆地不具有较好的生烃潜力。这对认识中仓盆地油气勘探价值,以及在伦坡拉盆地群中寻找油气具有指导意义。

Taking Dingqinghu formation of Paleogene in Zhongcang basin as research object,statistical analysis in the organic geochemical data of hydrocarbon source rocks was made.The hydrocarbon generation potential and sedimentary organic facies of Dingqinghu formation in the study area are discussed in order to provide a new theoretical support for the oil and gas data of the Tibitan plateau.After analyzing the stratigraphy,sedimentary facies and comprehensive evaluation of source rocks,the limestone,marl and shale are the main source rocks of Dingqinghu formation in Zhongcang basin.Among them,Limestone and marl organic carbon concentration is 0.33%on average,are poor source rocks.Shale organic carbon concentration is 0.32%on average,it is poor source rock.Type of organic is mixedⅡ.Thermal evolution of source rocks is a low maturity(pyrolysis peak temperature is 422~446℃,vitrinite reflectance is 0.48%~0.59%).Based on the maceral,the sedimentary organic facies are divided into the swamp-marsh forest(bog)organic facies.Comprehensive analysis shows that Zhongcang basin doesn't have a good hydrocarbon generation potential.The above conclusions are useful for understanding the value of oil and gas exploration in the Zhongcang basin.And it is instructive in finding oil and gas in the Lunpola basin.