Abstract
It is generally accepted that most petroleum hydrocarbons are generated from kerogen by cracking of alkyl chains. Infrared spectroscopy can analyze the hydrocarbon generation by decreasing absorbance bands of alkyl CH2 stretching vibration (2930cm-1) during heating experiments of kerogen samples. The objective of this paper is to study hydrocarbon generation characteristics of each maceral of immature kerogen using micro-FTIR equipped with a heating unit, and to describe kinetics of kerogen decomposition.
As a result of heating from 30 to 550℃ at several different heating rates, the temperature of the maximum point in decreasing rate of the alkyl CH2 absorbance is defined as "IR2930Tmax". IR2930Tmax values appear about 300℃ (10℃/min). This evidence means that maximum hydrocarbon generation occurs around 300℃ by decomposition of alkyl chains.
Activation energy distribution at the cracking of alkyl CH2 chains falls between 35 and 60kcal/mol (maximum values between 45 and 50kcal/mol) at the frequency factor A=1016(1/s). This activation energy value seems to be too low for the direct cracking of alkyl chains, and is possible related with free radical reaction mechanism.
