岩石圈深部温压条件下萜烷演化的实验研究

EXPERIMENT STUDY ON TERPANE UNDER HIGH PRESSURE AND TEMPERATURE

在密闭体系中700℃、压力高达3GPa条件下进行褐煤加水的模拟实验,分析实验产物中的萜烷的变化规律,进而对高压高温下有机质演化进行研究。实验结果表明,相同压力条件下,温度升高有利于有机质的成熟演化;压力增加会抑制或延迟油气的生成和有机质成熟;五环三萜烷ββ生物构型转化为αβ地质构型所需能量比烯烃双键加氢饱和更高。高温超高压条件下,研究样品中C24四环萜烷存在4种同分异构体,含量由高到低依次包括10β(H)-降A-羽扇烷、10β(H)-降A-奥利烷、C24-17,21-断藿烷和10β(H)-降A-乌散烷。高碳数烷烃在地幔高压力条件下仍可以存在,这为认识超压盆地的油气资源与深层油气成藏及保存提供了新的思路。

Pyrolysis of lignite was conducted at high temperatures from 400 ℃ to 700 ℃ and high pressures from 1 GPa to 3 GPa in a closed system in order to investigate pressure and temperature effects on organic matter maturation. It was indicated that terpane showed more mature characteristics with increasing temperature at a given pressure. Conversely, high pressure significantly hindered the thermal evolution of geological organic matter. During diagenesis, compared with the addition reaction of double bonds of alkene, biological ββ configuration of hopanoid in organisms was readily converted to αβ hopane with more energy needed. The isomers of tetracyclic terpane includes 10β （ H）-des-A-lupane, 10β （ H）-des-A-oleanane, C24-17, 21-secohopane and 10β （H）-des-A-ursane according to relative abundance. The experimental results also demonstrated that the relative abundance of high molecular weight hydrocarbons may exist under the conditions of the lower lithosphere,which offered new information on the formation and conservation of the oil-gas resources in overpressure basin and enhanced the possibility to find the oil in the high temperature and pressure areas.