Separator volume factor: calculation

Finally, a separator volume factor is calculated. It is the volume of separator liquid measured at separator conditions divided by the volume of stock-tank oil at standard conditions, SP bbl/STB. 

EXAMPLE 8-2 A sample of reservoir liquid with volume of 400 cc under reservoir conditions was passed through a separator and into a stock tank at atmospheric pressure and 6CTF. The liquid volume in the stock tank was 274 cc. A total of 1.21 scf of gas was released. Calculate the oil formation volume factor. 

A liquid sample from a black oil reservoir had a volume of 227.0 cc in a laboratory cell at reservoir temperature and bubble-point pressure. The liquid was expelled through laboratory equipment which is the equivalent of the field separator-stock tank system. The oil volume collected in the stock tank was 167.4 cc. The separator produced 0.537 scf of gas, and the stock tank produced 0.059 scf of gas. Calculate the formation volume factor of the oil and the solution gas-oil ratio. 

The first step in calculating fluid properties is selection of separator conditions. There may be circumstances for a particular field which dictate a specific separator pressure. If not, the separator pressure which produces the maximum amount of stock-tank liquid is selected. This pressure is known as optimum separator pressure. It is identified from the separator tests as the separator pressure which results in a minimum of total gas-oil ratio, a minimum in formation volume factor of oil (at bubble point), and a maximum in stock-tank oil gravity ( API). Most black oils have optimum separator pressures of 100 to 120 psig at normal temperatures. 

The value of fonnatipn volume factor of oil at the selected separator pressure is BoSb in the following calculations. The corresponding value of total gas-oil ratio is Rssb- Bosb will be used as the formation volume factor of oil at the bubble point, Bot,. 11 will be used as the solution gas-oil ratio at the bubble point, Rsb. 

At pressures above bubble-point pressure, oil formation volume factors are calculated from a combination of flash vaporization data and separator test data. 

EXAMPLE 10—5 Calculate formation volume factors of oil for Good Oil Co. No. 4. Use optimum separator conditions. 

Separator calculations are performed to determine the optimum operating pressure for processing a particular hydrocarbon mixture. Normally for a black oil, the composition of the produced gases, the gravity of the stock-tank oil, the producing gas-oil ratio, and the formation volume factor of the oil are calculated. Other physical properties can be calculated from the compositions of the gases or liquids. 

EXAMPLE 13-1 Calculate the producing gas-oil ratio, stock-tank oil gravity, and oil formation volume factor which will result from a two-stage separation of the hydrocarbon mixture below. Use separator conditions of75°F and 100 psig and a stock-tank temperature qf75°F. The mixture is a liquid at its bubble point at reservoir conditions of 2620 psig and 220°F. Use K-factors from Appendix A. Use decane K-factors for heptanes plus. 

The calculations of Example 13-1 could be repeated for different separator pressures to determine the separator pressure which produces the largest amount of stock-tank liquid. Results of a laboratory separation of the hydrocarbon mixture of Example 13-1 are given in Figure 10-5. Optimum separator pressure is about 100 psig. This corresponds to minima in gas-to-oil ratio and formation volume factor and maxima in quantity of stock-tank oil and stock-tank oil gravity. 

Then the inventory loops are revisited. The liquid holdups in surge volumes are calculated so that the time constants of the liquid level loops (using proportional-only controllers) are a factor of 10 larger than the product-quality time constants. This separation in time constants permits independent tuning of the material-balance loops and the prod-... 

The columns must be designed or chosen such that the critical pair are separated and, as a second priority, the last peak must be eluted in a reasonable time. The first peak in the chromatogram is not considered part of the reduced chromatogram and is included as the dead volume marker from which the capacity factors of each solute can be calculated, together with the separation ratio of the critical pair. 

Influence on Electrolyte Conductivity In porous separators the ionic current passes through the liquid electrolyte present in the separator pores. Therefore, the electrolyte s resistance in the pores has to be calculated for known values of porosity of the separator and of conductivity, o, of the free liquid electrolyte. Such a calculation is highly complex in the general case. Consider the very simple model where a separator of thickness d has cylindrical pores of radius r which are parallel and completely electrolyte-filled (Fig. 18.2). Let / be the pore length and N the number of pores (all calculations refer to the unit surface area of the separator). The ratio p = Ud (where P = cos a > 1) characterizes the tilt of the pores and is called the tortuosity factor of the pores. The total pore volume is given by NnrH, the porosity by... 

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