Kerogen pyrolysis in the presence and absence of water and minerals: Steranes and triterpenoids

Abstract

This paper documents the distribution and maturation behavior of hopanoids and steranes released from kerogen (Estonian Kukersite) during pyrolysis experiments, performed in confined system (gold capsule) in presence and absence of water and various minerals, kaolinite, montmorillonite, calcite and dolomite respectively, at a fixed pressure of 50 MPa and temperature ranging from 240-320 °C. The abundances of hopenes and 17β(H)21β(H)-hopanes relative to stable 17α(H)21β(H)-hopanes, as well as calculated maturity parameters obtained from steranes and homohopanes are significantly different for the studied kerogen mixed with different minerals, and the presence or absence of water. The results of our experiments show that the maturation rates of hopanoids and steranes increase with mineral acidity but decrease with the addition of water. Furthermore, the stabilities of hopenes relative to 17β(H)21β(H)-hopanes also vary significantly at a same temperature among the six runs. Hopenes are more sensitive to the addition of excessive amount of water and pH value of minerals than are 17β(H)21β(H)-hopanes. © 2009 Elsevier Ltd. All rights reserved.