A New Pyrolysis Technique Using a Diamond Anvil Cell: In Situ monitoring using luminescence and FTIR Spectroscopy

Wuu-Liang Huang, G. A. Otten, J. A. Clouse

We have monitored in situ the reaction pathways of organic maturation during transformation of a Green River kerogen in a Diamond Anvil Cell using luminescence and FTIR spectroscopy. This technique can be applied to pyrolysis in open or closed system at dry or hydrous condition. The preliminary results in an open system show that the absorbance intensity ratio of the asymmetrical deformation of aliphatic H-C-H (peak at approximately ^approx1460 cm^-1) to the aromatic ring (C=C) stretching (approximately ^approx1630 cm^-1) progressively decreases with time and temperature, implying that the concentration of the aliphatic functional group relative to aromatic groups in the sample progressively decreases with increasing maturity. The results also show a decrease in the absorbance band ratio of C=O stretching (approximately ^approx1710 cm^-1) to C=C stretching within the same temperature interval, suggesting that the decomposition of carbonyl or carboxyl groups in the kerogen occurs with maturity. The two major reaction pathways found in this study are consistent with those widely observed in natural kerogen samples with increasing burial depths. In a closed system, monitored using micro-FTIR, the decrease in aliphatic compounds relative to aromatic compounds during kerogen transformation is also shown by the decrease of the intensity ratio of aliphatic/aromatic CH stretching bands with maturity. However, the abrupt reverse of the aliphatic/aromatic trend and the dramatic increase in the CH₃/CH₂ rat o of asymmetrical aliphatic stretching at the late stage of experiments, are attributed to the cracking of the neoformed oils. The results also reveal and early CO₂ generation from the kerogen.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995