Effect of Porous Medium on Phase Behavior

Effect of porous medium on phase behavior. Several authors have studied the effect of the porous medium on the phase behavior of reservoir fluid systems. Russian authors Trebin and Zadora (1968) report a strong influence of the porous medium on the dewpoint pressure and vapor-liquid equilibrium (VLE) of gas condensate systems. The porous medium used by these authors was a silica sand mixture (0.300 to 0.215 mm diameter) ground by a special cutter-pulverizer. Three different packings with permeabilities of 5.6, 0.612, and 0.111 darcies and 

Tindy and Raynal (1966) measured the bubblepoint pressure of two reservoir crude oils in both an open space (PVT cell) and a porous medium with grain sizes in the range of 160 to 200 microns. The bubble-point pressures of those two crude oils were higher in the porous medium than in a PVT cell by 7 and 4 kg/cm, respectively. Specifically, the bubblepoint pressure of one of the two crude oils measured at 80 C in a PVT cell was 121 kg/cm and the bubblepoint pressure at the same temperature in a porous medium of 160 to 20 microns was 128 kg/cm. On the other hand, when these authors used a mixture of methane and n-heptane, they observed no differences in the saturation pressure. Sigmund et aL (1973) have also investigated the effect of the porous medium on phase behavior of model fluids. Their measurements on dewpoint and bubblepoint pressures showed no effect of the porous medium. The fluid systems used by these authors were Cj/nC. and Ci/nCs. The smallest bead size used was 30 to 40 U.S. mesh. In Example 2.3 presented at the end of this chapter, the effect of interface curvature on dewpoint pressure and equilibrium phase composition will be examined. 

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