DISTRIBUTION AND ISOMERIZATION OF TERPANES IN PYROLYZATES OF LIGNITE AT HIGH PRESSURES AND TEMPERATURES

Chuanyuan Wang^a,c, Jianguo Du^b*,  Wanchun Wang^c,

Baoxiang Wu^c and Xiaocheng Zhou^b

^a Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.

^b Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China.

^c Lanzhou Research Center of Oil & Gas Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China.

email for correspondence: jianguodu@hotmail.com

Experimental pyrolysis of Eocene lignite in the presence of water was conducted in a closed system for a heating duration of 120 min at temperatures of 400, 500, 600 and 700 ^oC and pressures of 1 to 3 GPa (equivalent to burial depths of about 30 to100 km). The distribution of terpanes in the resulting pyrolysates was analyzed in order to investigate the effects of pressure and temperature on maturation of organic matter for this heating time at mantle depths. The results indicate that terpanes show more mature characteristics with increasing temperature at a given pressure. However, high pressures significantly retarded the thermal evolution of organic matter.  Also, high pressures had a non-linear effect on maturation, resulting in anomalous variations of maturity parameters and ratios (tricyclics / hopanes, Ts/Tm, C₃₁22S / (22S+22R), and ba-moretane / ab-hopanes). In addition, the isomerization of hopanes at the C-22 position did not reach typical end-point values, even at 700^oC. These results are a preliminary step towards a better understanding of organic matter maturation and oil and gas exploration in high temperature and pressure regimes.

JPG Home (opens in this window)