Experiment study on terpane under high pressure and temperature

Pyrolysis of lignite was conducted at high temperatures from 400 °C to 700 °C 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 10 (H)-des-A-lupane, 10 (H)-des-A-oleanane, C24-17, 21-secohopane and 10 (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.