Ceochemical Study of Thermal Simulation of Carboniferous Source Rock in the Tarim Basin-I. Yield of gaseous and liquid products and the evolution characteristics

Key words: 
• Tarim Basin /
• Carboniferous System /
• mudstone and limestone /
• thermal simulating experiment

Abstract: In this paper,low mature mudstone and limestone from Carboniferous System in Tarim Basin have been studied by the thermal simulating experiment. The results show that amount of gaseous hydrocarbon become more and more with increasing simulation temperature and begin increasing rapidly at 400℃. The yield of gaseous hydrocarbon at 450℃ is 834.94m³/tC_otg for mudstone and 483.23m³/tC_otgfor limestone,indicating that mudstone has higher yield of gaseous hydrocarbon than limestone under the relative high values simulating temperature. The yields of methane, ethane and hydrogen reach the largest at 400℃.The carbon isotopic values of methan.es are from-36.5‰ to-31.7‰ for mudstone and from-37.5‰ to-34.0‰ for limestone. These values show that urethanes formed by source rocks from Carboniferous System in Tarim Basin has a heavy carbon isotopic composition. The largest yield of liquid hydrocarbon is 27.12kg/tC_otg for mudstone and 18.69kg/tC_otg for limestone. Their corresponding simulating temperature is 300℃ and 350℃, respective1y. This shows that oil-forming high peak value of limestone is higher than that of mudstone. These data reflect that Carboniferous mudstone and limestone have different process of hydrocarbon Qeneration and evolution. Therefore,in the region of distribution of low generation,and natural gases from Carboniferous mature source rock mudstone is source rock should have a heavy important to hydrocarbon carbon isotopic composition.