Page 418 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

384 Production

Equllibrlum Cell Determlnations. Following the compositional analyses, portions
of the primary separator liquid and gas were physically recombined in their
produced ratio in a variable volume, glass-windowed equilibrium cell. Deter-
minations on this mixture were divided into the following two main categories.
1. Dew point pressure determination and pressure-volume relations on a
constant weight of reservoir fluid at the reservoir temperature: the pro-
cedure consisted of establishing equilibrium between gas and liquid phases
at a low pressure and measuring volumes of liquid and gas in equilibrium
at that pressure. The pressure was raised by the injection of mercury into
the cell and phase equilibrium established again at the higher pressure.
This procedure was repeated until all of the liquid phase had vaporized,
at which point the saturation pressure was observed. The cell pressure was
then raised above the dew point pressure in order to determine the
supercompressibility characteristics of the single-phase vapor. As a check
on all readings and, particularly, to verify the dew point, the cell pressure
was incrementally reduced, equilibrium established and volumetric readings
made. Reported in Table 65 are the relative volume relations (Figure 6-11)
and specific volumes of the reservoir fluid over a wide range of pressures
as well as compressibility factors (Figure 6-12), the single-phase vapor above
the dew point. Reported in Table 6-6 are the dew point pressures (Figure
6-13) resulting from recombinations at gas/liquid ratios above and below
the ratio measured at the time of sampling.
2. Compositions of the produced wellstream and the amount of retrograde
condensation resulting from a stepwise differential depletion: This pro-
cedure consisted of a series of constant composition expansions and
constant pressure displacements with each displacement being terminated

Table 6-5
Pressure-Volume Relation of Reservoir Fluld at 285OF [ll]

Relative Specific Calculated
Pressure Volume Volume Retrograde Liquid Devlation Vlscosity
(PSIA) (VNsat) (Cu.RJUI.) BPMMCF* Vol. %* Factor (2) (Centipoise)
*"12920 Res. 0.6713 0.03635 1.8485 0.0793
lo000 0.7201 0;03898 1.5346 0.0674
8000 0.7741 0.04191 1.31 97 0.0579
6000 0.8639 0.04677 1.1047 0.0471
5000 0.9373 0.05075 0.9988 0.041 2
4420 D.P. 1.0000 0.05414 0.00 0.00 0.9420 0.0374
(Two Phase)
4000 1.0677 0.05781 10.58 1.30 0.9102
3500 1.1764 0.06369 69.83 8.55 0.8775
3000 1.3412 0.07261 94.17 11.53 0.8575
2500 1.5879 0.08597 107.92 13.21 0.8460
2000 1.9831 0.10737 114.27 19.99 0.8453
1500 2.6605 0.14404 114.27 13.99 0.8505
1000 4.0454 0.21902 107.92 13.21 0.8621
'BBLS. per MMSCF of Dew Point Fluid.
"'Percent of Hydrocarbon Pore Space at Dew Point.
***Extrapolated.