Lesson 1 Oil and Gas Reservoir

Question 1

3 types of oil reservoirs

Answer 1

1. Undersaturated Oil Reservoirs
2. Saturated Oil Reservoirs
3. Gas Cap/ Two phase

Question 1

the initial pressure it greater than the bubble point

Answer 1

Undersaturated Oil Reservoirs

Question 2

Th initial pressure is less than the bubble point

Answer 2

Two phase

Question 2

The initial pressure is equal to the bubble point

Answer 2

Saturated oil reservoir

Question 3

Crude oils are classified into the following
types

Answer 3

1. Ordinary Black Oil
2. Low shrinkage Crude Oil
3. High shrinkage Crude Oil / Volatile
4. Near Critical Crude Oil

Question 4

GOR: 200 – 700 scf/STB

Oil gravity : 15 – 40 API

Brown to Dark green in color

Answer 4

ORDINARY
BLACK OIL

Question 5

Oil formation volume factor < 1.2 bbl/STB

Gas-oil ratio < 200 scf/STB

Oil gravity < 35° API

Black or deeply colored

Answer 5

Low shrinkage Crude Oil

Question 6

Oil formation volume factor < 2 bbl/STB
GOR: 2,000-3,200 scf/STB
Oil gravities: 45-55° API
Lower liquid recovery of separator conditions as indicated
by point G
Greenish to orange in color

Answer 6

High Shrinkage Crude Oil or Volatile Crude Oil

Question 7

Oil Formation Volume Factor: Greater than 2 bbl/STB
GOR: Greater than 3,200 scf/STB

Answer 7

Near Critical Crude Oil

Question 8

Natural gases can be classified
into four categories based on their
phase diagram and reservoir
conditions:

Answer 8

Retrograde gas-condensate
Near-critical gas-condensate
Wet gas
Dry gas

Question 9

GOR: 8,000 – 70, 000 scf/STB
Condensate gravity above 50° API
Stock-tank liquid is usually water-white or slightly
colored.

Answer 9

Retrograde Gas-Condensate
Reservoir

Question 10

the reservoir temperature is near the critical temperature volumetric behavior is described through the isothermal
pressure declines as shown by the vertical lines 1-3

Answer 10

Near-critical gas-Condensate Reservoir

Question 11

the reservoir temperature is above the cricondentherm of the
hydrocarbon mixture
Because the reservoir temperature exceeds the cricondentherm
of the hydrocarbon system, the reservoir fluid will always remain in the vapor phase region as the reservoir is depleted
isothermally

Answer 11

Wet-gas
Reservoir

Question 12

GOR: 60,000 to 100,000 scf/STB
Stock-tank oil gravity above 60° API
Liquid is water-white in color
Separator conditions, i.e., separator pressure and temperature,
lie within the two-phase region

Answer 12

Wet-gas
Reservoir

Question 13

the hydrocarbon mixture exists as a gas both in the reservoir
and in the surface facilities
only liquid associated with the gas from a dry-gas reservoir is
water.
GOR: greater than 100,000 scf/STB

Answer 13

Dry-gas
Reservoir