Sedimentary Characteristics Of Carboniferous In Margin Of The Qaidam Basin And Its Effect On Source Rocks

Based on the field of geological survey and laboratory tests of samples and fully absorb the results of previous studies, the author have studied in detail the sedimentary characteristics of the 18 sections. in margin of the Qaidam Basin, identified the main types of sedimentary facies, summarize the evolution model of carboniferous deposition in the study area. The author studied the source rocks in the geochemical data carefully, and identified the type of source rocks, the quality characteristics. The Carboniferous source rocks are analyzed, and selected a more favorable area for oil and gas potential.The author investigated one by one for each section and took sample at first, draw a histogram profiles and lithology absorbed the report of regional geological investigation about the Qaidam Basin and the other results of previous studies. After that, some conclusions are drawn.(1) The sedimentary environment of Carboniferous is the shore - shallow carbonate platform facies.There are ten types of sedimentary facies, and it detailed analysis of coastal environment and its evolution model. Coastal environment of study area, are mainly two models that tidal flat - lagoon - limited platform model and Delta - restricted platform model. When the coastal areas rich in terrigenous material, the tidal flat, lagoon, sand bar relatively developed vasospasm. When the coastal zone terrigenous material in short supply, in addition to tidal flat, lagoon outside, vasospasm dam was replaced by carbonate deposition.(2)On each section through the detailed stratigraphic division and contrast, The authors concluded the deposition of the Carboniferous evolution. C1a is mainly terrestrial alluvial deposits, and unconformity on the Devonian or older strata. With the continuous expansion of the scope of transgression, sedimentary environment gradually turned into shore - shallow marine carbonate platform. During the deposition to the C2k, tidal flat - lagoon - Sand Barriers (carbonate platform) deposition system is more development, large sediment thickness, lateral distribution and stability.Evaluation of Carboniferous source rocks in this area is based on data of organic geochemistry analysis and research The main features of source rocks is that:(1)A possible source rocks of Carboniferous type is dark mudstone. Sedimentary environment controls the abundance of organic matter. Lagoon is the main environment of the hydrocarbon source rock development. (2) The type of organic matter is mainly typeâ…¡2, and visible typeâ… ,â…¡1. (3) C2k is the best formation for the hydrocarbon source rock. Rise and fall of the exchange period of the Sedimentary base level of C2k may be a period of hydrocarbon source rocks. (4) Maturity of organic matter is the medium that has entered the mature stage. Maturity is the lowest in the eastern Qaidam Basin. A small amount of hydrocarbon source rocks show characteristics of low mature or immature. From east to west, from north to south, the maturity of organic matter changes in the high. After the comprehensive analysis of the distribution of source rocks, Qaidam Basin, Carboniferous oil and gas potential of the more favorable areas are the west of Mountain Xitie, the east of Shihuigou, the west of Zabushagaxiu.