Depositional Environments And Controlling Factors Of Coal Measures Source Rocks Of Yacheng Formation Of Oligocene In Yanan Depression In Qiongdongnan Basin

Thesis focuses on the stratum bearing coal of Yacheng Formation in the Yanan Depression of Qiongdongnan Basin.Based on the drilling datas and 56 sample tests,The study focuses on the depositional environment and the geo-chemisry characteristic and the controlling foctors of the coal measures.Based on the drilling datas and the logging datas,combining the signs of sedimentary facies,there are fan delta and braided river delta and lagoon-tidal flat in the Yacheng Formation.The Coal measures of Yacheng Formation in Yanan Depression include dark mudstone and coal and carbonaceous mudstone,rich in flavor.And the hydrocarbon potential is high.Based on the organic petrology and the geo-chemistry study,the organic matter of Yacheng Formation is ?2~?.The dark mudstone and coal and carbonaceous mudstone are good source rocks.The coals and coal measures formed in the swamp in the fan delta and the lagoon-tidal flat,affected by the pale-geography and pale-climate and sea level and depositional environment.The pale-geography is the main foctor.The ancient late Eocene temperatures drop,making the ancient climate of hot,dry conditions of the Eocene-Oligocene transition is more suitable for plant prosperous warm climatic conditions.Dating back a significant decline 29 Ma temperatures,making climate Lingshui deposition period becomes cold,a coal plant prosperous condition deteriorated.Sedimentary facies controlled the coal source rocks spatial distribution,leading to a strong role in the latter part of the plot into the river previously deposited fine-grained sedimentary unit strongly erosion,making some wood measure source rocks can be saved.It is time to the coal when the sea level goes up.There are 36 figures,14 tables and 100 references in this paper.