Formation Volume Factors

Question 1

Ideal Gas Law

Answer 1

PV=nRT

Question 2

Gas Z-Factor

Answer 2

AKA Gas Deviation Factor, Gas Compressibility Factor

*determined by experiment, but can be estimated from critical T and P of the gas (if known
Standing-Katz Charts)

Question 3

Formation Volume Factors tell us how the __ of the reservoir fluids change when they come to surface

Answer 3

volume

Question 4

What are the Standard Conditions?

Answer 4

P = 1 atm. = 101.325 kPa and T = 15.5°C = 288.65 K

Question 5

Gas Expansion Factor - E

Answer 5

helps us define how the volume of gas changes from when it is in the reservoir to that of the surface (standard conditions)

E = Vsc / Vres

Question 6

Gas Formation Volume Factor - Bg

Answer 6

The RECIPROCAL of E.
Bg = (Vfg)res / (Vf) sc
or
Bg = Vres / Vsc

Question 7

Oil Formation Volume Factor - Bo

Answer 7

helps us define how the volume of oil changes from when it is in the reservoir to that of the surface (standard conditions)

Bo = (Vo)res / (Vo)st
*Where st is Stocktank Conditions

Question 8

Solution Gas Oil Ratio - Rs

Answer 8

describes the release of solution gas from oil as the P and T change from the reservoir to the surface

Rs = (Vsg) / (Vo)/st

Question 9

st

Answer 9

stocktank

Question 10

fg

Answer 10

freegas

Question 11

Unsaturated Reservoirs

Answer 11

• above BPL
• res. is filled with liquid oil and when brought to surface, solution gas is released from oil
• Rs is constant, Bo increases up to BP

Question 12

Saturated Reservoirs

Answer 12

• located below BPL
• res. is filled with free gas together with liquid oil;
• Bo and Rs decrease with decreasing pressure