Jessica STRYDOM

Etude de la production d’eau douce à partir de formations argileuses dans les zones de foothills

Supervisors:
Dragan Grgic and Jérôme Sterpenich
Université de Lorraine, Nancy, France

*the range of Cl isotopic fractionation was down to – 0.5‰.

Major Results

Significant Cl and Br isotope fractionation (between 0.5 ‰ and 1.5 ‰) was observed during the long term experimental compaction of two different clay rich materials.

Abstract

In sedimentary basins, fluid overpressures are caused by clay compaction. It represent a major risks during oil and gas exploration. Fresh waters are produced by this, but little tracers are available to calibrate this process. We followed the chemical and Cl and Br isotope evolutions of clay pore water expelled during three long term high pressure high temperature clay compaction experiments, on a smectite and a marl equilibrated with ocean water.

It was found that significant retention of Cl and Br in the pore water of the compacted MX-80 (less in the marl) is indicative of ultrafiltration. Higher negative surface charge of the MX-80 smectite clay more strongly fractionated Cl isotopes due to anion exclusion. Increasing the temperature increase the Cl isotope fractionation. However for the larger Br isotopes, fractionation was more strongly affected by reducing the porosity.

Cl/Br and δ37Cl evolution in seawater expelled during the compaction of MX-80 smectite.

Strydom, J., Eggenkamp, H., Sterpenich, J., Agrinier, P., Richard, A., Grgic, D., Gaire, P., Mosser-Ruck, R. & Gaucher, E. C. (2019), Cl/Br and δ37Cl evolution in seawater expelled during the compaction of MX-80 smectite. E3S Web of Conferences Volume 98.

keywords: Ultrafiltration, Br concentrations, Compacted clays, Compaction experiments, Diffuse double layers, Stable isotopes

DOI: https://doi.org/10.1051/e3sconf/20199812022