The use of clay minerals and inorganic and organic geochemical indicators for evaluating the degree of diagenesis and oil generating potential of shales |
| |
| Authors: | AE Foscolos TG Powell |
| |
| Institution: | Institute of Sedimentary and Petroleum Geology, Geological Survey of Canada, Calgary, Alberta T2L 2A7, Canada |
| |
| Abstract: | A detailed geochemical study has been made on clay minerals and organic matter from two stratigraphic sequences (Sully-Lepine Series and Buckinghorse Formation) in Lower Cretaceous shales from northeastern British Columbia. The characteristics of the discrete illites, mineralogy and chemistry of the mixed layer clays, organic extract yields and kerogen composition indicate that little diagenesis has occurred in the Sully-Lepine Series whereas extensive diagenesis verging on the anchizone of metamorphism has occurred in the Buckinghorse Formation.On the basis of this study and the results of other workers, a preliminary classification of diagenesis is proposed. Diagenesis is divided into three stages: eodiagenesis (early), mesodiagenesis (middle) and telodiagenesis (late). The mesodiagenesis stage is divided into two sub-stages. Eodiagenesis corresponds to the zone in which pore water is lost from the shales, little hydrocarbon generation occurs and coals are of lignitous or sub-bituminous types. Mesodiagenesis corresponds to the main phase of oil genesis and coals are of the high volatile to low volatile bituminous type. The first stage of clay dehydration occurs during early mesodiagenesis and the second stage of clay dehydration occurs in late mesodiagenesis. During telodiagenesis, extensive cracking of the organic matter occurs; dry gas is the main hydrocarbon product and coals fall in the semi-anthracite range.The preliminary classification has been applied to the Lower Cretaceous shales used in this study. The Sully-Lepine Series falls in the eodiagenesis and early mesodiagenesis zones whereas in the Buckinghorse Formation the diagenetic zones range from early mesodiagenesis to telodiagenesis. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
