Pore Space Geometry (PSG) - Aims & Experimental Concept
- To study the changes of rock structural properties during sampling by comparing porosities in samples whose pore space was preserved by in-situ resin impregnation experiment results with those which were drilled and taken to the laboratory before resin impregnation.
- To study rock porosity and morphology of pore space in intact rock matrix (i.e. tortuosity and constrictivity, the connected porosity and accessible pore space).
- To use spatial porosity distribution provided by the 14C-PMMA method for the new development of modelling tools of the heterogeneous matrix diffusion.
The experiment is based on the previously developed 14C-PMMA method which consists the following steps during impregnation in the laboratory:
- Drying of centimetre scale rock samples under vacuum
- Impregnation with 14C-PMMA under vacuum
- Radiation induced polymerisation using a 60Co source
- Detection of 14C-PMMA in the rocks with autoradiography
- Digital image analysis of beta autoradiographs (*) to provide spatial porosity distribution of the rocks
The following steps were performed during the in-situ experiment at the GTS:
- Drying of the intact rock by air ventilation
- Injection of 14C-PMMA into the rock matrix
- Polymerisation of 14C-PMMA by heating
- Overcoring of the resin impregnated matrix
- Detection of the 14C-PMMA in the granite matrix using beta autoradiography techniques (*)
(*) The location of the 14C-PMMA on the rock samples can be determined by placing a thin, plastic film over the rock sample. The beta particles from the 14C-PMMA in the rock matrix interact with the film and leave a unique signal. The films are analysed in an instrument that converts the area where beta particles interacted with the film into an optical density in a technique called beta autoradiography. The images produced are called beta autoradiographs.
Pore Space Geometry (PSG) Experiment