Once the core reaches the lab, it is then removed from the barrels and layed out on a viewing table for sample selection and to view the core under UV light.
The core needs to be marked to ensure correct depths are recorded on the barrels. Usually the core is marked with red and black orientation lines with the red line indicating the right side of the core and the black indicating the left side of the core.
The core then undergoes sampling as well as slabbing.
Core Sample Plugging and Trimming
Plugs are taken as horizontal, vertical or oriented. Full diameter samples can be overcored if surface is irregular.
Samples are taken and frequency and size of the samples are determined by the geologist.
Generally horizontal plugs are taken parallel to the bedding planes and vertical plugs are taken perpendicular.
Unconsolidated cores require freezing of the core and taking plugs in frozen condition by sampling using liquid nitrogen as the bit coolant.
Samples require mounting in sleeves (usually lead) or in Nickel foil prior to cleaning and measurements.
The samples are trimmed to give cylindrical shape and the end faces grinded.
Importance of Proper Trimming
The core is then cut to expose the geological features of the rock and for Imaging of the core under white and ultra violet light
One side of the cut surface is then polished with a fine polishing machine to ensure that the surface features are clearly seen. This can be used for core description.
1/3rd section of the core is used for geological description.
2/3rd section is used for core photography.
1 inch thin slice of the core is used for preserving the core in resin.