塔里木盆地海相原油及其沥青质裂解生气动力学模拟研究

应用50MPa高压封闭体系,对塔里木盆地海相原油及其沥青质进行了热裂解模拟实验,对气态烃产率及碳同位素演化、焦沥青的生成等方面进行了比较,探讨了原油裂解和沥青质裂解生气机理。研究发现,原油和沥青质裂解气各组分及焦沥青的产率变化类似。完全发生裂解时,沥青质裂解的总气体产率为原油裂解的50%,原油裂解和沥青质裂解生成总气体和焦沥青的质量比值分别为6:4和3:7。在裂解过程中,气态烃碳同位素δ¹³C值的特点是δ¹³C₁<δ¹³C₂<δ¹³C₃,且原油裂解气各组分(C₁—C₃)碳同位素δ¹³C值小于沥青质裂解气的相应组分。运用kinetics软件,计算得到原油和沥青质裂解的动力学参数(活化能和指前因子)。在此基础上,将实验结果外推至地质条件下,探讨了动力学模型的实际应用,为原油裂解气的判识、资源评价、勘探决策提供实验和理论依据。

Kinetic simulation study on generation of gaseous hydrocarbons from the pyrolysis of marine crude oil and its asphaltene in Tarim Basin

The pyrolyses simulation of marine oil and its asphaltene from Tarim Basin were carried out in an anhydrous closed system under a constant pressure of 50 MPa. The differences or similarities of gas generation mechanism between crude oil and its asphaltene were discussed on the basis of the yields and carbon isotopic composition of gaseous hydrocarbons and the yields of pyrobitumen. The yields of gaseous hydrocarbon had the analogy change trend with the yields of pyrobitumen. The yield of methane generated from asphaltene cracking was 50% of that generated from oil cracking when oil and alsphsltene were cracked completely. The quality ratio of total gas to pyrobitumen generated from oil and its alsphsltene was 6∶4 and 3∶7, respectively. In the process of pyrolysis, the relation of δ¹³C₁<δ¹³C₂ <δ¹³C₃ existed as a whole, and the δ¹³C value of methane, ethane and propane generated from oil was less than that of asphaltene correspondingly. The kinetic parameters for pyrolysis of gaseous hydrocarbons generated from crude oil and its asphaltene were obtained by kinetic calculation and extrapolated geological conditions. The application result can provide a theoretical basis for the identification and assessment of oil cracking gas and exploratory decision of marine carbonate area in China. 