Study On The Properties And Kinetics Of Crude Oil Pyrolysis At High Pressure

The cracking gas of reservoir oil is an important source of natural gas. Crude oil to gas is related to the natural gas production and oil consumption, thus the objective evaluation is of great importance to hydrocarbon exploration. A set of simulation pyrolysis device with nitrogen to achieve high pressure has been established and oil to gas process is characterized with the generated gas components analyzed by gas chromatograph (GC). The synergic and collaborative effects of comprehensive factors such as the temperature, pressure, water and minerals to the pyrolysis generating gas process of crude oil and asphaltene were discussed. The first order parallel reaction kinetic model is established for the pyrolysis generating gas process and the kinetic parameters of three kinds of oil from tarim basin and their asphaltenes are obtained. The remaining oil is calculated for the three kinds of Tarim Basin crude oil in 8000m reservoir.The result shows that under 480℃the influence of pressure on oil pyrolysis is staggered and1#,2# and 3# oil's maximum gas yield appears at about 20MPa. Pressure promotes the process of oil to gas below 20MPa and inhibite the process above 20MPa.But under 390℃, pressure has different influence on three kinds of oil. For 1# oil, pressure always inhibite the process of oil to gas. For 2# oil, it's maximum gas yield is at 40MPa, and Pressure promotes the process of oil to gas below 40MPa and inhibite the process above 40MPa.For 3# oil, there is a minimum gas yield at about 30MPa, and Pressure inhibite the process of oil to gas below 30MPa and the promotes process above 30MPa. For the existence of crude oil's cracking reaction and polycondensation reaction, the maximum gas yield appears at about 450℃. when temperature is elevated in the range of 450℃～480℃, oil to gas production rate decreases. According to pure oil's pyrolysis kinetic parameters, 1# oil to gas window appears late, 2# and 3# oil to gas windows appears earlier, thus the rate of pyrolysis of 2# and 3# oil is rapid. it shows that components of crude oil have significant influence on kinetics of oil pyrolysis. The simulation experiments of real environmental strata show that at the existence of water and carbonate mineral, the rates of pyrolysis of 1#,3# crude oil slow down and remaining oil increased. But for 2# oil, water and carbonate mineral have positive catalysis for its pyrolysis rate of hydrothermal reaction is higher than that of pure pyrolysis conversion. It shows that water and mineral are unfavorable for 2# oil's retention in reservoir.According to the asphaltene activation energy distribution, asphaltene to gas window appears earlier and plenty of gas is obtained in the process of oil's pyrolysis, which has important influence on oil cracking gas yield.By the kinetics calculation of oil formation, 1#,2# and 3# crude oil residual are76%, 35% and 49% respectively. It is proved that there exists uncracked crude oil in these three kinds of crude oil reservoirs under the condition of 8000m. By the results of simulation experiment of crude oil's pyrolysis, the deep reservoir preservation floor and the mechanism are determined, which provides theoretical support for the exploration and development of the deep reservoir .