Reactivity of glauconitic clasts during burial diagenesis

Weibel, Rikke; Keulen, Nynke; Hillier, Stephen; Friis, Henrik; Petersen, Henrik Ingermann; Olivarius, Mette; Malkki, Sebastian Naesby; Stokkendal, Jesper; Schovsbo, Niels Hemmingsen

doi:10.1016/j.sedgeo.2023.106519

Abstract

Palaeogene glauconitic reservoir sandstones in the produced Nini West oilfield in the Siri Canyon, Danish North Sea, are chosen as the first pilot CO2 storage site in Denmark. Since glauconitic clasts comprise up to 35 vol% of the sandstones, their stability is crucial for the reservoir permanence. The likely reactivity of glauconitic clasts during CO2 injection is evaluated from their changes during burial diagenesis (long-term reactions) as a contribution to experimental testing (short-term reactions) of sandstone resilience towards CO2. Cored wells penetrate the Palaeogene gravity-flow sandstone units in depth intervals of 1700 m ( 2200 m. Chloritisation of glauconitic clasts is intensive in the central parts of the gravity-flow sandstone units in the deepest (2800-3000 m) and most distal settings. Consequently, authigenic chlorite precipitation in pores occurs at shallower burial depth than chloritisation of glauconitic clasts. The microporous structure of the glauconitic clasts controls the slow gradual illitisation during increased burial. Abrupt lowering of pore-water salinity is considered the main reason for expansion of smectite components in the mixed-layer glauconitic mica/Fe-smectite, opening of the micropores and thereby intense chloritisation of glauconitic clasts in the deep and distal gravity-flow units. Hence, glauconitic clasts are potentially highly reactive, although slow to react due to their microporous structure unless the water composition is distinctly changed.(c) 2023 Elsevier B.V. All rights reserved.

Keywords

Glauconitic clasts; Formation water composition; Illitisation; Chloritisation; Microporosity; Burial depth

Published in

Sedimentary Geology
2023, volume: 458, article number: 106519
Publisher: ELSEVIER

SLU Authors

Hillier, Stephen
- Department of Soil and Environment, Swedish University of Agricultural Sciences
- Geological Survey of Denmark and Greenland (GEUS)

UKÄ Subject classification

Geosciences, Multidisciplinary

Publication identifier

DOI: https://doi.org/10.1016/j.sedgeo.2023.106519

Permanent link to this page (URI)

https://res.slu.se/id/publ/127578