Sampling:

The sampling is realized using a Diamant Boart plugging machine. In order to cool the drill bit, and avoid any jamming in the sample, water is sent through the inside of the drill bit. The sample is strongly fixed between the jaws of a vise, and the drill bit is brought down until it reaches the sample’s surface. After verifying the correct trajectory of the drill bit, and assuming there is enough length, the plug is drilled in order to obtain a maximum length sample. Exceeding lengths will be cut off and used for thin section preparations.

Sample Trimming:

Once a plug is obtained, the purpose is to obtain two flat and parallel end faces. Therefore, a Vinci Technologies trimming machine is used. It is a double blade diamond saw, on which the spacing between both blades can be adjusted. For this purpose, and in order to obtain the maximum length, blades are situated at 5 cm of each other. The bigger the plug sample, the more precise analysis results are obtained. The remains on both sides of the plug are stored for thin section preparation. As these have a circular shape, and were in direct contact with the plug sample, petrological analyses will be reliable withpetrophysics.

Sample Cleaning:

In order to determine the porosity and permeability of the samples, their pores have to be cleaned of any organic matter. Therefore, a Soxhlet extraction method is used. Toluene, an organic solvent, is heated until it evaporates. The Toluene vapour rises above the samples, and is sent through a refrigerating column. Once refrigerated, the liquid Toluene drips on the samples which are placed in a cellulose holder, and when the Toluene reaches the top of the samples it is flushed back to its original heating bowl. This way, organic matter is collected in the bottom of the system, while evaporation guarantees that the Toluene which is in contact with the samples is always exempt of any organic matter. The system goes in a closed circuit until all the samples are cleaned.

Sample Drying and Desiccating:

Once the samples are cleaned, they rest for 24 hours under the extractor fan, and are then placed in a dry off oven for another minimum of 24 hours. This dry off oven is programmed at temperatures below 60°C in order to prevent any damage to clay minerals. Afterwards, the samples are placed and stored in desiccators in order to remove any residual water from the pores. Therefore, silica gel combined with a colour indicator of moisture issued. The remains of the plug trimming process are kept in order to prepare thin sections. First of all, the samples are indured with a blue coloured resin that has the same refractive index as quartz. The samples, while the resin is still liquid, are put under vacuum conditions in order to replace air bubbles in the pores with the resin. This step is repeated three times. Afterwards, the samples are put in the dry off oven to allow the resin toharden. The hardened samples are then lapped to remove the first layer of resin, until the rock is reached, and then polished for gluing on a glass plate. The glass plates are de-polished so that the bonding resin sticks correctly. The bonding resin has the same characteristics as the impregnation resin and quartz, so that no changes can be observed through optical microscopy. The samples are then put into a press, and in the dry off oven to allow them toharden. Once hardened, a 1mm thick slice is cut parallel to the glass plate. This slice is then gridded until a thickness of 0,100 mm is obtained, before being lapped and polished at its final thickness, 30µm.