From an analysis of the constant volume depletion experiments performed on 80 gas-condensates, it is concluded that serious problems exist in the detection of the actual volume of retrograde liquid in the PVT cell. The measured liquid volume is usually only a fraction of that required to give realistic liquid densities. The frequently observed concave shape of the retrograde liquid saturation curve close to the dew point is not real and is the result of experimental error. It is recommended that the data quality be improved by directly measuring the retrograde liquid density because it provides an excellent control over the liquid saturation, especially when this saturation is low.

The properties of the fluid initially in the PVT cell are normally determined mathematically. However, this often only approximates the true properties and deviations can have consequenses for the derived liquid properties. The direct measurement of the composition and properties can easily solve this problem and is therefore strongly recommended.

The analysis of the experiments leads to the following statements for constant volume depletion experiments

  • liquid densities are monotonically decreasing with pressure

  • Bom and Rsm are both monotonically increasing with pressure.

Here Bom is defined as the inverted partial density of the C5+ component fraction in the liquid, while Rsm is the mass ratio of the effraction over the C5+ mass fraction.

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