原油在储层介质中的加水裂解生气模拟实验

Carbon Isotopic Composition and Yield of Gaseous Hydrocarbon by Oil Hydrous Pyrolysis in Rock Medium

采用高温高压热模拟实验方法 ,开展了原油在砂岩和火成岩储层介质中的加水裂解生气模拟实验研究。结果表明 ,原油开始大量裂解的温度是 40 0℃ ,随模拟温度增加 ,甲烷相对含量增大 ,乙烷以上重烃气尤其是丙烷相对含量减小。其中砂岩的油水混合物裂解生气主要发生在 45 0～ 5 0 0℃之间 ,生气窗范围小 ,对应的烃气产率高 ,火成岩的油水混合物裂解生气主要发生在 45 0～ 6 0 0℃之间 ,生气窗范围大 ,对应的烃气产率小。模拟烃气的组分碳同位素分馏显著 ,随模拟温度增加呈变重趋势。在裂解生气过程中 ,水解加氢和催化作用对烃气的组成。

Hydrous pyrolysis experiments of generating gas from the mixture of oil-water and reservoir rocks have been caried out in a closed system,the samples are derived from deep layer of the Songliao basin.The results show that yield quantities of gaseous hydrcarbon is very small at temperature below 350℃,which mainly derived from oil evaporation.When simulating temperature reaches 400℃,large quantities of gas are generated from oil.With increasing of temperature the proprtion of methane in the generated gas increases,while the heavier components decrease particularly the propane.The range of temperature for gas largely generated from the mixture of oil -water sandstone is 450～500℃,while the range from the mixture of oil—water and igneous rocks is 450～600℃.The quantities of gaseous hydrocarbon generated from both settings are similar and about 17m 3/t oil at the end,but the hydrocarbon yield is different at each temperature point.The maximal yield at 500℃is respectively 78.67m 3/t oil abd 66.11m 3/t oil for the two experiments hydrolysis and catalysis may be an important influence on the composition and yield of the simulated gas.The experiment also shows that δ 13C values of the gas generated from the experiment at temperature between 400～450℃(R o approximately 1.3%～1.8%) are relatively lower than that of gas derived from kerogen,and δ 13C 1 is -50.86‰～-48.43‰.When the temperature increases to 550～600℃ (R o approximately 2.8%～3.4%),δ 13C of the gas brcomes reativly higher than that of gas derived from kerogen,and kerogen,and δ 13C 1 is -39.61‰～-24.26‰.This fact indicates that fractionation of carbon isotopon of gas from the experiment is stronger than the gas directly derived from kerogen.The regular sequence of carbon isotope has been found at temperature between 400～450℃ i.e.δ 13C 1<δ 13C 2<δ 13C 3<δ 13C 4.But partial opposites sequence of carbon isotope appeared at temperature above 500℃,the sequence is δ 13C 1<δ 13C 2<δ 13C 3<δ 13C 4. Comparing the carbon isotopic composition between the mixture of oil-water and sandstone and the mixture of oil-water and igneous rocks,the latter is lighter 1.2‰～4.2‰ than the fromer at the temperature of 400～450℃ and heavier at the temperature above 550℃,which show a different influence of catalysis in various medium.This result is useful for identifying the origin and maturation of nature gas for the deep layer of the Songliao basin.