Enhanced Oil Recovery – EOR
Gas Revaporization
A known volume of reservoir fluid is charged to a high-pressure PVT cell and heated to the reservoir temperature. A partial constant composition expansion (CCE) is performed on the sample down to an operating pressure selected by the client. A known volume of the gas phase is then pumped from the cell, to return the sample to a constant volume equal to the measured volume at dew point pressure. The composition of the displaced gas phase is measured.
A known volume of injection gas is then added to the cell and mixed, by inverting the cell, to create a new fluid equilibrium at test conditions. The sample is continually agitated and stabilised at operating pressure until no pressure change is observed. Once this has been achieved the total sample volume as well as the change in relative liquid and gas phase volume is determined. The excess gas phase is then removed from the cell and analysed.
The test can be repeated at several gas increments to determine change in fluid properties, composition and liquid volume as a function of the gas revaporization process. The client normally supplies the injection volumes but a typical series of tests would be 0.2, 0.5, 1.0, 3.0 and 5.0 moles of injection gas, per molar volume of original sample volume at test conditions. Following the series of injections a constant volume depletion may also be performed.
