Chapter 5- Pvt Properties Of Crude Oil

Question 1

What is petroleum ?

Answer 1

It is a complex mixture consisting predominantly of hydrocarbons , containing nitrogen, sulphur , oxygen and helium as minor constituents .

Question 2

What does the physical and chemical properties of crude oil depend on ?

Answer 2

They depend on the concentration of the various types of hydrocarbon and minor constituents present .

Question 3

What influences the behavior of the mixtures ?

Answer 3

The constituents

Question 4

List the physical properties that are of primary interest in petroleum engineering studies

Answer 4

1) Fluid density
2) specific gravity of solution gas
3) oil density
4) gas solubility
5) bubble point pressure
6) oil formation volume factor
7) isothermal compressibility coefficient of understated crude oil
8) undersaturated oil properties
9) total formation volume factor
10) crude oil viscosity
11) surface tension

Question 5

Are all correlation for solution gas oil ratio the same for bubble point pressure?

Answer 5

Yes they are

Question 6

What is the formula for crude oil density?

Answer 6

Crude oil density = mass of oil / volume of oil

Question 7

What is the standard temp and pressure of the surface in petroleum engineering

Answer 7

15.566 degree c or 60degree F

Pressure is 14.7 psia or 0psig

Question 8

Which kind of imperial system do we use for petroleum engineering?

Answer 8

FPS

Force , pound , second

Question 9

Full meaning of psi

Answer 9

Pound per square inch

Question 10

What is the density of water

Answer 10

1g/cm^3 or 1000kg/m^3 or 62.4 lbm/ft^3

Question 11

What is the formula for specific gravity of oil ?

Answer 11

Specific gravity of oil = density of oil / 62.4

Question 12

Specific gravity of gas formula

Answer 12

Density of gas/ density of air

Question 13

Unit for specific gravity of oil

Answer 13

60/60 since density of oil and density of water are both measured at 60degree F

Question 14

What happens to the specific gravity and the density when the API gravity is high?

Answer 14

The sp gr and density are low

Question 15

What happens to the specific gravity and the density when the API gravity is low ?

Answer 15

The sp gr and density are high

Question 16

What kind of relationship is the between sp gr and API gr ?

Answer 16

Inverse relationship

Question 17

What is the mathematical relationship between API and specific gravity Of oil ?

Answer 17

Specific gravity of oil = 141.5/131.5+API

Question 18

How many cm makes 1 inch ?

Answer 18

2.54cm

Question 19

How many pounds make 1kg?

Answer 19

2.2046 Lbm

Question 20

What is meant by dead oil

Answer 20

It is oil which has no dissolved gas , essentially methane and ethane

Question 21

What is meant by live oil

Answer 21

Oil which has dissolved gas

Question 22

What is solution gas ?

Answer 22

It is the amount of dissolved gas in oil

Question 23

How do we quantify solution gas?

Answer 23

Using solution gas oil ratio

Question 24

What is the formula for solution gas oil ratio

Answer 24

Volume of dissolved gas / unit volume of oil

Question 25

What is the unit of solution gas oil ratio

Answer 25

Scf/STB

Question 26

What is the difference between STB and RB

Answer 26

STB is the volume of oil in the stock tank RB is the volume of oil in the reservoir or in the subsurface

Question 27

What is the unit for formation volume factor

Answer 27

RB/STB

Question 28

What is the formation volume factor for water

Answer 28

Bw = 1 RB/STB

Question 29

What is formation volume factor for water

Answer 29

It tends to be greater than 1 For black oil reservoir Bo is less than or equal to 1.2 For near critical , Bo is far greater than 2

Question 30

What is the relationship between Bo and Rs

Answer 30

If Rs is high , Bo is high as well

Question 31

What is the reason for having initial values for Bo and Rs

Answer 31

This is because Bo and Rs change when producing the reservoir

Question 32

What is the relationship between Bo and P for an undersaturated oil reservoir

Answer 32

Above bubble point pressure , as you produce the reservoir and pressure is reducing oil expands This expansion of oil occurs until saturation pressure is reached ( bubble point pressure ) , where gas begins coming out of solution. As a result , the oil shrinks

Question 33

Relationship between Rs and P for an undersaturated oil reservoir

Answer 33

Beyond bubble point Pressure, gas doesn’t come out of solution , although as pressure declines , the oil expands , but regardless of the expansion of oil , the volume of gas contained in the oil doesn’t change until the pressure gets to bubble point pressure . Below bubble point , gas continually comes out of solution, thereby reducing Rsi ( volume of gas initially contained in the oil )

Question 34

What is the only time Rsi is the maximum Rs and corresponds to the Rsb ?

Answer 34

When we’re working with an undersaturated reservoir

Question 35

For undersaturated and saturated oil reservoirs, what is the maximum Rs?

Answer 35

Rsi. | Rsi = Rsb

Question 36

For gas cap reservoir, what is the maximum Rs?

Answer 36

Rsb is the maximum Rs, because for gas cap, Pi,res < Pb. So gas already begins to come out of solution, thereby reducing the Rs( volume of gas dissolved in the oil) . But At Pb, gas just initially begins to come out oil, thereby making the volume of gas dissolved greater than compared to Pi,res. Hence making Rsb the maximum Rs