Drillcore sampling for porewater analyses

A cardinal prerequisite of any porewater investigation is a sample, such as a piece of drillcore, that represents the in‑situ conditions as closely as possible. This requires approaches in the field that exclude or at least reduce sampling induced artefacts such as evaporative loss of porewater or degassing of dissolved gases by minimizing the exposure time of the drillcore to air.

After a drillcore has been recovered, washed and surveyed, sampling is done in specific ways, depending on the intended use of the sample:

• Vacuum-sealing into aluminium lined plastic bags (for chemical porewater analysis)
• Sealing into an evacuated steel container for outgassing of dissolved gases (for noble and reactive gas analysis)
• Embedding into Epoxy-resin (for geomechanical investigations)

As any sample taken from a drillcore results in a gap in the material available for detailed stratigraphic investigations, a thin slab is cut off along the rim, parallel to the core axis whenever the sample purpose allows it. These “stratigraphy-slabs” thus allow to retain a near-continuous stratigraphic record, even in case of extensive sampling.

During the entire core processing and sampling procedure, a stringent log is kept, documenting all important metadata such as timestamps and durations of the various processing steps for QA purposes and to help identify potential causes for anomalous analytical results later on.