TITLE:
Thermal Effect on the Distribution of Regular Sterane and Geological Significance
AUTHORS:
Yunfei Yang, Min Zhang, Julin Chen, Xiaohui Chen
KEYWORDS:
Sterane, Maturity, Pyrolysis Experiment, Geochemistry Characteristic, Oil-Rock Correlation
JOURNAL NAME:
Open Journal of Yangtze Oil and Gas,
Vol.2 No.4,
October
30,
2017
ABSTRACT: In order
to study thermal effect on distribution characteristics of regular sterane in humic coals, a suit of 25
coals derived from Kuqa Depression in Tarim Basin and Ordos Basin are studied
to investigate the distribution of regular sterane in different maturity, which
mainly discusses the thermal effect. The results show that the C27ααα/C29ααα regular sterane ratio has a linear
relationship with Ro (tmax) and aromatic hydrocarbon maturity parameters in the coals from mature
to high-mature stage. It
suggests that the distribution of the C27, C29regular steranes will fail to
reflect original source input in high evolutionary stage. On the basis of thermal
simulation experiment results, it further proves that the distribution patterns
result from the demethylation effect of C29 sterane
in the mature to high mature evolution stage and the C27ααα/C29ααα regular sterane increases with
increasing maturity. The breakage of C-C key in branched chain from C27, C29 regular steranes to make C27ααα/C29ααα regular sterane ratio invariance
at high and over mature stage. Therefore, the ratio can be used to distinguish
the maturity in high and over mature stage.