Lesson 1: Oil and Gas Reservoir

Question 1

Pi > Pb

Answer 1

Undersaturated oil reservoir

Question 2

Pi = Pb

Answer 2

Saturated oil reservoir

Question 3

Pi < Pb

Answer 3

Gas-cap reservoir / two-phase reservoir

Question 4

4 types of crude oils

Answer 4

•ordinary black oil
•low-shrinkage crude oil
•high-shrinkage (volatile) crude oil
•near-critical crude oil

Question 5

GOR: 200 – 700 scf/STB
Oil gravity: 15 - 40 °API
brown to dark green in color

what type of crude oil is this?

Answer 5

Ordinary black oil

Question 6

Oil formation volume factor < 1.2 bbl/STB
Gas-oil ratio < 200 scf/STB
Oil gravity < 35° API
Black or deeply colored

what type of crude oil is this?

Answer 6

Low-shrinkage oil

Question 7

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

what type of crude oil is this?

Answer 7

Volatile crude oil

Question 8

Oil formation volume factor ≥ 2 bbl/STB
GOR: ≥ 3,200 scf/STB

Answer 8

Near-critical crude oil

Question 9

4 categories of natural gas

Answer 9

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

Question 10

The reservoir temperature T lies between the critical temperature Tc and cricondentherm Tct of the reservoir fluid

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

what category is this in natural gas?

Answer 10

Retrograde gas-condensate reservoir

Question 11

The reservoir temperature is near the critical temperature

Answer 11

Near-critical gas-condensate reservoir

Question 12

The reservoir temperature is above the cricondentherm of the
hydrocarbon mixture

what type of natural gas is this?

Answer 12

Wet gas reservoir