To study the phase transition processes in the intensive pressure reduction in gas-condensate systems a series of experiments on the sharp decrease and increase pressure in the PVT cell by dierent values relative to the initial pressure is carried out, corresponding to the equilibrium gas state. Basic controlled in the study parameters pressure in the recombinator
and temperature. Experiments to determine the relaxation time of phase transitions were performed by static method. In this case, the phase transition occurred in a stationary gas in a closed volume.
In the framework of mathematical formulation of the problem, one resolving equation with
respect to the phase velocities is obtained from the system of fluid motion equations. The calculation of the thermodynamic properties (TDS) of a multicomponent hydrocarbon mixture under volume change (adiabatic compression expansion) is presented and sharp pressure uctuations in the cell recombinator, as well as the relaxation time of phase transitions on the example of 4-component mixture: CH4 - C3H8 - C5H12 - C7H16. Comparison of the obtained pressure distribution by the developed mathematical model on the boundary sections of the recombination cell with the obtained from the experiment data on the measurements of pressure at the corresponding points of the recombination cell gives an
error of less than 5%, that is a satisfactory result of the mathematical model approbation.