How a staged flash test works in the laboratory: primary separation, low-pressure flash of the retained liquid, gasometry, condensate recovery and a closed material balance, with a worked example.
Five laboratory methods measure gas permeability across ten orders of magnitude, from steady-state Darcy flow to pulse decay on nanodarcy shale. None covers the whole range, and the physics that limits each is worth knowing before you choose an instrument.
Gas recombination is not a "measurement" in the same sense as a CCE or CVD experiment: it is the sample-preparation and quality-control step that creates the live reservoir fluid on which every subsequent gas-condensate or wet-gas PVT study depends.
The Gas Flash test takes a sample of reservoir gas at reservoir pressure and temperature and subjects it to a single, abrupt pressure reduction to a defined flash pressure (separator or atmospheric).
The Gas Depletion test reproduces, at the cell scale, the non-equilibrium material-balance history that a dry or wet gas reservoir undergoes as it is produced down its decline curve.
The retrograde condensation (liquid dropout) test maps how much liquid phase forms inside a gas condensate as reservoir pressure declines below the dew point.
