Differential Liberation Expansion
The differential liberation experiment (DLE or DL) is one of the standard depletion experiments. The main output of the DLE experiment is the oil expansion, GOR and oil viscosity. The DLE was origionally made to emulate the depletion production of oil reservoirs.
The procedure for DLE experiment is shown as an animation and as a schematic below. A PVT-cell is fill with a fluid sample and pressurized to the saturation pressure. The PVT-cell volume is then expanded at a constant temperature, reducig the pressure. Once the pressure is below the saturation pressure, the incipient phase is either condensed or vaporized out of solution. When the PVT-cell volume has reasched a certain value, all the gas is removed (keeping the pressure contstant). The DLE experiment is basically the same experiment as the multistage separator test but at a constant temperature.
Animation 1: Animation of a DLE procedure for a saturated reservoir oil.
Figure 1: Schematic of a DLE experiment for a saturated reservoir oil.
The main results of the DLE experiment is the relative volume at different pressure and a range of properties for the removed gas at each stage: gas Z-factor and specific gravity. The density of the oil can also be measured for the undersaturated region. The DLE GOR can also be reported (either directly or indirectly).