Characteristics Of Sedimentary And Evaluation Of Source Rock Of Palaeogene Niupu Formation In Lunpola Basin,Tibet

The oil sands and asphalt were found out from the layers of Palaeogene Niupu Formation in Lunpola basin,the south side of the Tanggula mountain of the northern Tibetan Plateau,based on the 1:1000000 of petroleum geological surveys and the1:200000 of general surveys and special subject studies for the Lunpola basin,and geological fine tests in the area.Eight fault noses in the central depression were recongnited from the 31 ground structure with the 1:50000 of the airborne gravity,magnetic and the 1:100000 of seismic survey.The characteristics of sedimentary system of Niupu Formation in the basin was studied based on the existing geological data in this paper.Based on 3 measured stratigraphic sections and combined with more than 30drilling data,statistics and comparison to Niupu Formation of the lithology combination,the thickness of the strata and the sedimentary characteristics,it is considered that the content of feldspar and impurity is higher in sandstone,low structure maturity,near source sediments is the main.Combined with regional data,the sedimentary framework and variation law of different periods were analyzed,it provides the basis for the analysis of lithofacies and ancient geography and basin.The recognition of sedimentary facies can be divided:river course,diara and embankment so on in sedimentary sub facies and micro phase;delta and delta-fan facies;shore lacustrine,shallow lake facies,semi-deep and deep lacustrine ect.The main development flood alluvial system,fluvial system,delta system and lake system in Paleogene.Based on the above information and analysis,lithofacies palaeogeography maps of 6 sedimentary periods were compiled,with E_1-2n¹,E_1-2n^2-1,E_1-2n^2-2,E_1-2n^3-1,E_1-2n^3-2,E_1-2n^3-3,system analysis:Lunpola Basin is the Paleogene continental rift basin on the Bangonghu-Nujiang suture,after three stages of evolution,faulted period,depression period,compression period.Integrated predecessors'research achievements and organic geochemical analysis,The characteristics of hydrocarbon source rocks and the oil and gas system in Niupu Formation were evaluated.