Figure 1

Experimental protocol followed with each sample. The sample was exposed to a series of effective pressure cycles (A), first with Nitrogen (N₂), then with Xenon (Xe). After the effective pressure stabilized a tomography measurement was performed (B). The computed tomography images collected with N₂ (not shown) were analyzed to check for structural changes caused by varying the effective stress. As indicated in panel (A), a small leak in the upstream pore fluid pump resulted in a relatively small effective pressure increase between steps 8 and 9. The reconstructed core volumes shown in panel (B) consist of the difference between the x-ray CT measurements with N₂ (step 5) and Xe for the various effective stress conditions imposed through steps 6–12. The difference images, where white (black) indicates maximum increase (decrease) in x-ray absorption, map out the spatial distribution of Xe as a function of effective pressure. The time indicated in each panel is the cumulative experimental time at which the CT scan was finished for each step.