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Classification and Diagenetic Characteristics of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa

Classification and Diagenetic Characteristics of the Cretaceous Sandstones in the Southern... A systematic petrographic and geochemical studies of 92 representative sandstone samples from exploration wells E‐AH1, E‐AJ1, E‐BA1, E‐BB1 and E‐D3 in the southern part of the Bredasdorp Basin was undertaken to classify the sandstones as well as unravel the main diagenetic processes and their time relations. Petrographic study shows that the sandstones are largely subarkosic arenite and arkosic litharenite, which have underwent series of diagenetic processes as a result burial, rifting and subsequent uplift. The main diagenetic processes that have affected the reservoir properties of the sandstones are cementation by authigenic clay, carbonate and silica, growth of authigenic glauconite, dissolution of minerals and load compaction. The major diagenetic processes reducing the porosity are calcite cementation in the subarkosic arenite, and compaction and quartz cementation in arkosic litharenite. On the other hand, the formation of secondary porosity due to the partial to complete dissolution of early calcite cement, feldspars and minor grain fracturing has improved the reservoir property of the sandstone to some extent. The clay minerals in the sandstones commonly acts as pore choking cement, which reduces porosity. In general, there is no particular diagenetic process that exclusively controls the type or form of porosity evolution in the sandstones. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Geologica Sinica (English Edition) Wiley

Classification and Diagenetic Characteristics of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa

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References (53)

Publisher
Wiley
Copyright
© 2021 Geological Society of China
ISSN
1000-9515
eISSN
1755-6724
DOI
10.1111/1755-6724.14701
Publisher site
See Article on Publisher Site

Abstract

A systematic petrographic and geochemical studies of 92 representative sandstone samples from exploration wells E‐AH1, E‐AJ1, E‐BA1, E‐BB1 and E‐D3 in the southern part of the Bredasdorp Basin was undertaken to classify the sandstones as well as unravel the main diagenetic processes and their time relations. Petrographic study shows that the sandstones are largely subarkosic arenite and arkosic litharenite, which have underwent series of diagenetic processes as a result burial, rifting and subsequent uplift. The main diagenetic processes that have affected the reservoir properties of the sandstones are cementation by authigenic clay, carbonate and silica, growth of authigenic glauconite, dissolution of minerals and load compaction. The major diagenetic processes reducing the porosity are calcite cementation in the subarkosic arenite, and compaction and quartz cementation in arkosic litharenite. On the other hand, the formation of secondary porosity due to the partial to complete dissolution of early calcite cement, feldspars and minor grain fracturing has improved the reservoir property of the sandstone to some extent. The clay minerals in the sandstones commonly acts as pore choking cement, which reduces porosity. In general, there is no particular diagenetic process that exclusively controls the type or form of porosity evolution in the sandstones.

Journal

Acta Geologica Sinica (English Edition)Wiley

Published: Oct 1, 2021

Keywords: diagenesis; cementation; reservoir properties; sandstones; Bredasdorp Basin

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