Figure 1
From: Origins of pressure dependent permeability in unconventional hydrocarbon reservoirs
Areal electron probe microanalysis (EPMA) scans of various North American tight rocks with the Dean sandstone sample (A) shown for comparison. The tight samples were characterized for pressure dependent porosity and permeability. The samples are arranged in order of increasing clay content from left to right (also see Table 1). The legend shows colors corresponding to the predominant elements (and the associated mineral proxy in parentheses) which are used in a weighted sum dictated by the elemental mass fraction to determine the pixel color. Both Wolfcamp samples (E,F) have bedding parallel delamination cracks, but the cracks in the cemented Wolfcamp sample are barely perceptible. For this sample one crack emanates a few pixels below the top left corner of the elemental map, and the other is located about 0.4Â cm from the bottom of the map.
