Euler characteristic of the gas clusters – which is a measure for connectivity – vs. gas saturation for the pressure depletion experiments (left) and gas injection experiments (right). Euler characteristic χ > 0 indicates disconnected gas clusters while χ < 0 indicates connectivity. χ = 0 coincides approximately with the percolation threshold, and hence serves as an indication for the critical gas saturation S_gc. For the pressure depletion experiments (A) the critical gas saturation S_gc = 0.2 for pressure depletion and S_gc = 0.25 for re-pressurization, which is overall in the range of percolation thresholds for porous objects in 3D. For the gas-injection experiments we observe an overall not-connected (χ > 0) situation for the low injection case (B) and an overall connected situation (χ < 0) for the high injection case (C).