Study On Pyrolysis Of Tarim Basin Crude Oil At High Temperature And High Pressure

The thermal simulation of Tarim Basin crude oil and its fractions were carried out in closed and confined system in the temperatures range 350℃to 480℃and pressure range 10MPa to 50MPa, with and without water and carbonate mineral. The generated gas components were analyzed by gas chromatograph (GC). The differences or similarities of gas generation mechanism and pyrolysis behavior of crude oil were discussed on the basis of total gas yield and gas components yield.Pressure effected oil cracking in certain temperature range. High temperature made pressure's effect more obvious. The increase in total gas yield was observed under 22MPa, and decrease was observed above 22MPa. The more asphaltene content in crude oil, the less relative content of hydrocarbons heavier than propane and more methane and ethane in total gas generation.Gas generation yield was small under 390℃. The temperature of obvious gas generation was 390℃for light oil-Y2, and 420℃for heavy oil-Y2 and Y3. Gas generation yield increased with temperature increasing, the maximum gas generation yield appeared at 450℃for the three oil samples, and then gas generation yield steady decreased with temperature increasing. However, oil to gas conversion rate at this temperature was less than 60%. The temperature at which generates maximum gas yield of asphaltene obtained was higher than that of crude oil. Thus, conclusion was made: crude oil which is rich in asphaltene was kept at higher temperature in geological condition. Total gas generation sequence of Y3's four components was: saturate>resin>asphaltene>aromatics. Saturate was the first contributor to total gas generation, and then comes resin. Methane yield sequence generated from Y3's four components was: asphaltene>saturate> resin >aromatics.Water had no obvious effect on heavy oil cracking; however, it propelled light oil cracking. Carbonate mineral promoted light crude oil cracking, while inhibit heavy oil cracking.Kinetic parameters were calculated by using first order parallel reaction: activation energy of Y2 and Y3 oil to gas activated energy was about 57Kcal?mol-1-63Kcal?mol-1, and 49Kcal?mol-1-55Kcal?mol-1 for light oil sample Y2.The conclusion from DSC experiments at normal pressure were obtained: dramatic endothermic temperature at normal pressure was lower than that of crude oil pyrolysis at high pressure. Moreover, the heavier the oil, the easier its pyrolysis at normal pressure. Thus, the maximum endothermal and exothermic temperatures were also high.