Chapter 10: Reservoir Fluid Studies

Question 0

What 3 properties of evolved gas in the reservoir at P < Pb, can a field study determine?

Answer 0

1. Z-factor
2. Formation vol factor of gas (Bg)
3. Gas viscosity

Question 1

What 6 properties can be determined from the results of a black oil reservoir fluid study?

What are these properties a function of?

Answer 1

1. Bubble-point pressure
2. Formation vol factor of oil (Bo)
3. Solution GOR (Rsb)
4. Total formation vol factor (Bt)
5. Coefficient of isothermal compressibility of oil (Co)
6. Oil viscosity

Properties are a function of pressure as P decreases from initial res pressure through the Pb to very low pressure

Question 2

What 3 additional properties & quantities can be determined at various separator pressures from a field study?

Answer 2

1. Separator gas
2. ST gas
3. ST oil

Question 3

What are the 5 major procedures in the black oil reservoir fluid study?

Answer 3

1. Composition measurement
2. Flash vaporization
3. Differential vaporization
4. Separator tests
5. Oil viscosity measurements

Question 4

What does a flash vaporization procedure determine?

How do you plot the results & what can you determine from the plot?

Answer 4

Determines the bubble-point pressure (Pb)

Pressure is plotted against total volume, & the slope of the pressure is the Pb of the mixture

Question 5

What does the differential vaporization procedure determine?

Answer 5

Differential vaporization determines the

1. compressibility factor (z)
2. the formation volume factor of the gas (Bg)
3. the total volume of gas in solution @ Pb

Question 6

How do you calculate the relative total volume (BtD) at any pressure?

Answer 6

BtD = BoD + Bg (RsDb - RsD)

BoD = relative oil vol by Differential vaporization

RsDb = gas in solution at Pb by Differential vaporization

RsD = gas remaining in solution by Differential vaporization

Question 7

How do you determine Pb & V(relative) from flash vaporization data?

Answer 7

1. Plot Vt (x-axis) against P (y-axis)
2. Determine the point where the two lines cross
3. Read Pb & Vb
4. Divide all volumes in the data set by Vb
5. Add column Pb to the table

Question 8

How do you determine the z-factor used in the calculations for Bg of gas removed during differential vaporization?

Answer 8

Z = V(R) * P(R) * Tsc
_______________
Vsc * Psc * T(R)

(R) is conditions in the cell
sc is standard conditions

Question 9

How do you calculate Bg of the gas removed from the cell during the Differential vaporization procedure?

What are the units?

Answer 9

Bg = 0.0282 [(zT) / P] , ( cu ft / scf)