A known volume of reservoir fluid is charged to a high-pressure PVT cell and heated
to reservoir temperature. A partial constant composition expansion (CCE) is performed
to determine saturation pressure, relative volume, liquid density and liquid shrinkage
data. The pressure is reduced until the sample volume has been expanded to at least
two times the original volume at saturation pressure. The liquid shrinkage data
is also measured.
A predetermined volume of injection gas is added to the fluid and the sample agitated
until single-phase equilibrium is achieved. The total sample volume is measured
and the increase in sample volume is determined. The newly created sample is subjected
to a CCE experiment, as described above and the saturation pressure and liquid shrinkage
The composition of each fluid mixture is calculated from the measured reservoir
fluid and gas injection compositions, together with the mole/mole recombination
ratio. The composition of the final mixture is measured on a small volume of the
The asphaltene content of the original reservoir fluid and the final swollen fluid
can also be measured to determine if possible flocculation has occurred.
The swelling test consists of several gas injections but it is fairly typical to
perform five fluid mixtures and CCE experiments, culminating in the creation of
a gas condensate fluid after the last gas addition.
Mixtures of the reservoir fluid and injection gas are physically recombined in the
same proportions as each of the swollen oil mixtures in the solubility-swelling
study described above. The viscosities of the oil mixtures are measured using an
Electro Magnetic Viscometer (EMV) at reservoir temperature.