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Smectite to illite conversion by hydrous pyrolysis

Published online by Cambridge University Press:  09 July 2018

E. Roaldset
Affiliation:
Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology (NTNU), N-7034 Trondheim, Norway
He Wei
Affiliation:
Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology (NTNU), N-7034 Trondheim, Norway
S. Grimstad
Affiliation:
Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology (NTNU), N-7034 Trondheim, Norway

Abstract

Experimental illitization of smectite has been simulated by means of hydrous pyrolysis, using a smectite-rich starting material from a Lower Tertiary claystone from the Oseberg field, North Sea. The <2 µm fraction was subjected to hydrous pyrolysis using KCL solutions at concentrations of 1.0 and 0.01 N, temperatures from 180-350°C and reaction times from 24-72 h. The conversion of smectite into illite has been identified by XRD analysis of the pyrolysed products. It was clearly demonslrated that the K+ concentration ([K+]) and temperature are the major factors controlling the rate and extent of illitization. The distributions of activation energies around 33 kcal/mol and frequency factors in the range of 10+8 to 10+9 S-1 have been calculated by applying a parallel reaction model. However, geological modelling and comparison with buried smectite clays indicates that both 1.0 n and 0.01 N KCL are too high in K+ content compared to the pore-water. The results suggest that dilute KCL solution close to pore-water should be used in hydrous pyrolysis to obtain proper kinetic models.

Information

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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