Chapter 3- More Insight

Question 1

What is bubble point pressure ?

Answer 1

This is the pressure at which the first sign of gas formation is detected.

Question 2

What is dew point pressure ?

Answer 2

This is the pressure in which the first drop of liquid condenses out of gas .

Question 3

Classification of a petroleum reservoir is based on ?

Answer 3

Reservoir and reservoir fluid

Question 4

Classify a petroleum reservoir based on reservoir?

Answer 4

1) initial pressure Pi

2) temperature

Question 5

Classify a petroleum reservoir based on reservoir fluid ?

Answer 5

1) critical pressure and temperature. Pc and Tc

2) composition x

Question 6

Reservoirs can be classified into two types namely ?

Answer 6

Oil reservoir

Gas reservoir

Question 7

How do we identify an oil reservoir?

Answer 7

If the reservoir temperature Tres is less than the critical temperature Tc of the reservoir fluid , the reservoir is classified as an oil reservoir

Question 8

How do we identify a gas reservoir?

Answer 8

If the reservoir temperature is greater than the critical temperature of the reservoir fluid , the reservoir is considered a gas reservoir.

Question 9

What are the 3 major state variables ?

Answer 9

Pressure

Volume

Temperature

Question 10

Depending on the initial pressure of the reservoir, oil reservoirs can be sub-classified into the following categories.

Answer 10

Under saturated oil reservoir

Saturated oil reservoir

Gas cap reservoir

Question 11

When do we have an under saturated oil reservoir ?

Answer 11

If the initial reservoir pressure is greater than bubble point pressure of the reservoir fluid .

Pi,res>Pb

Question 12

When do we have a saturated oil reservoir?

Answer 12

If the initial reservoir pressure is equal to the bubble point pressure

Pi, res= Pb

Question 13

When do we have a gas cap reservoir?

Answer 13

If the initial reservoir pressure is below the bubble point pressure of the reservoir fluid .

Pi,res

Question 14

What is another term for gas cap reservoir

Answer 14

Two phase reservoir because it’s in the two phase region

Question 15

Based on physical properties composition gas oil ratio, appearance and P-T phase diagram of reservoir fluid , crude oils are commonly classified into ?

Answer 15

Black oil BO
Low shrinkage LS
High shrinkage HS
Near critical NC

Question 16

When produced , black oils usually yield gas-oil ratios between ?

Answer 16

200-700 scf/STB

Question 17

What is the oil gravities of black oils?

Answer 17

15-40 degree API

Question 18

What is the color of the stock tank oil ?

Answer 18

Brown to dark green in color
According to Ahmed tarek ( reservoir engineering handbook second edition )
According to Oscar , it’s color is black

Question 19

How are the quality lines for black oils ?

Answer 19

They are approximately equally spaced

Question 20

How is the liquid shrinkage curve prepared?

Answer 20

It is prepared by plotting the liquid volume percent as a function of pressure.

Question 21

How is the liquid shrinkage curve for black oils ?

Answer 21

It is approximately a straight line except at very low pressures .

Question 22

How are the quality lines for low shrinkage oil ?

Answer 22

They are closely spaced near the dew point curve

Question 23

What is the function of liquid shrinkage curve ?

Answer 23

They show the shrinkage characteristics of the various categories of crude oils

Question 24

What are the other associated properties of low shrinkage oil ?

Answer 24

Oil formation volume factor less than 1.2 bbl/STB

Gas-Oil ratio less than 200scf/STB

Oil gravity less than 35 degree API

Black or deeply colored

Question 25

What is another name for high shrinkage Oil?

Answer 25

Volatile oil

Question 26

How are the quality lines for high shrinkage

Answer 26

They are close together near the bubble point and are more widely spaced at lower pressures.

Question 27

What is the major characteristic of high shrinkage ?

Answer 27

It is commonly characterized by a high liquid shrinkage immediately below bubble point

Question 28

What are the other characteristic properties of high shrinkage oil ?

Answer 28

Oil FVF less than 2 bbl/STB GOR between 2000-3000 scf/STB Oil gravities between 45-55 degree API Greenish to orange in color Lower liquid recovery of separator conditions

Question 29

What happens to the API gravity of the stock tank liquid in the later life of the high shrinkage oil reservoir?

Answer 29

The API gravity of the Stock Tank liquid will increase in the later life of the reservoir.

Question 30

When do we have a near critical reservoir?

Answer 30

This is when the reservoir temperature is near the critical temperature Tc of the hydrocarbon system

Question 31

How else can we identify a near critical oil without comparing the temperature of the reservoir to the critical temperature ?

Answer 31

We can do this by looking at the quality lines , because all the quality lines converge at the critical point .

Question 32

What are the other characteristic properties of the high shrinkage oil ?

Answer 32

High GOR of 3000 scf/STB Oil FVF 2.0 bbl/STB or higher