Chapter 5: The Five Reservoir Fluids

Question 0

For a volatile oil, with the following C7+ mol %, what is the phase of the reservoir fluid:

a) C7+ > 12.5 mol %
b) C7+ < 12.5 mol %

What kind of point (bubble or dew) does each have?

Answer 0

a) > 12.5 mol % is liquid & has a bubble point

b) < 12.5 mol % is gas & has a dew point

Question 1

What are the 5 types of reservoir fluids?

Answer 1

1. Black oil
2. Volatile oil
3. Retrograde gas
4. Wet gas
5. Dry gas

Question 2

What are the 3 properties used to identify fluid type without lab observation.

Answer 2

1. Initial producing gas-oil ratio (GOR)
2. Specific gravity of ST liquid
3. Color of ST liquid

Question 3

How do you calculate sp gravity from API?

Answer 3

Specific gravity = 141.5 / (API + 131.5)

Question 4

What is the vol of gas in a reservoir on a percentage basis .

Answer 4

Vg = 100% - VL %

Question 5

What is the initial oil formation factor (Boi)?

Answer 5

The quantity of reservoir liquid in bbl required to produce 1 ST bbl

Question 6

What type of molecules make up the following:

a) black oil
b) volatile oil
c) retrograde gas
d) wet gas
e) dry gas

Answer 6

a) large, heavy, & nonvolatile
52. 6% C1, 27.9% C7+

b) intermediate (C2 - C6)
66. 7% C1

c) some intermediate (C2 - C3)
72. 7% C1

d) mostly light, some C2 & C3
88. 7% C1

e) almost all light
96. 3% C1

Question 7

What are the following properties of volatile oil:

a) common names
b) initial GOR
c) STO gravity range
d) color
e) Boi
f) C7+ mol %

Answer 7

a) high-shrinkage oil & near-critical oil
b) GOR: 2000 - 3300 scf/STB
c) STO gravity: > 40 API
d) brown, orange, or green
e) Boi: > 2.0 res bbl/STB
f) C7+: 12.5 - 20 mol %

Question 8

What are the following properties of retrograde gas:

a) common names
b) initial GOR
c) STO gravity range
d) color
e) C7+ mol %

Answer 8

a) retrograde condensate gas, gas condensate
b) GOR: 3300 -150,000 scf/STB
c) STO gravity: 40 - 60 API
d) lightly colored brown, orange, greenish, or water-white
e) C7+ < 12.5 mol %

Question 9

What are the following properties of wet gas:

a) common names for liquid & gas produced
b) producing GOR range when other gases can be treated as wet
c) color
d) C7+ mol %

Answer 9

a) liquid = condensate, gas = condensate gas
b) GOR: > 50,000 scf/bbl
c) ST liquid is usually water-white
d) C7+ < 0.2 mol %

Question 10

What are the following properties of volatile oil:

a) common names
b) ability to form hydrocarbon liquid at the surface

Answer 10

a) simply, gas

b) does not contain enough heavier molecules to form hydrocarbon liquid

Question 11

What are the following properties of black oil:

a) common names
b) initial GOR
c) STO gravity range
d) color
e) Boi
f) C7+ mol %

Answer 11

a) low-shrinkage crude oil, ordinary oil
b) GOR: < 2000 scf/STB
c) STO gravity: < 45 API
d) black, sometimes with a greenish cast, or brown
e) Boi: < 2.0 res bbl/ STB
f) C7+ > 20 mol %