Chapter 5- Pvt Properties Of Crude Oil Flashcards

1
Q

What is petroleum ?

A

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

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2
Q

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

A

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

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3
Q

What influences the behavior of the mixtures ?

A

The constituents

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4
Q

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

A

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

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5
Q

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

A

Yes they are

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6
Q

What is the formula for crude oil density?

A

Crude oil density = mass of oil / volume of oil

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7
Q

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

A

15.566 degree c or 60degree F

Pressure is 14.7 psia or 0psig

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8
Q

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

A

FPS

Force , pound , second

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9
Q

Full meaning of psi

A

Pound per square inch

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10
Q

What is the density of water

A

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

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11
Q

What is the formula for specific gravity of oil ?

A

Specific gravity of oil = density of oil / 62.4

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12
Q

Specific gravity of gas formula

A

Density of gas/ density of air

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13
Q

Unit for specific gravity of oil

A

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

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14
Q

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

A

The sp gr and density are low

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15
Q

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

A

The sp gr and density are high

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16
Q

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

A

Inverse relationship

17
Q

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

A

Specific gravity of oil = 141.5/131.5+API

18
Q

How many cm makes 1 inch ?

A

2.54cm

19
Q

How many pounds make 1kg?

A

2.2046 Lbm

20
Q

What is meant by dead oil

A

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

21
Q

What is meant by live oil

A

Oil which has dissolved gas

22
Q

What is solution gas ?

A

It is the amount of dissolved gas in oil

23
Q

How do we quantify solution gas?

A

Using solution gas oil ratio

24
Q

What is the formula for solution gas oil ratio

A

Volume of dissolved gas / unit volume of oil

25
Q

What is the unit of solution gas oil ratio

A

Scf/STB

26
Q

What is the difference between STB and RB

A

STB is the volume of oil in the stock tank

RB is the volume of oil in the reservoir or in the subsurface

27
Q

What is the unit for formation volume factor

A

RB/STB

28
Q

What is the formation volume factor for water

A

Bw = 1 RB/STB

29
Q

What is formation volume factor for water

A

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

30
Q

What is the relationship between Bo and Rs

A

If Rs is high , Bo is high as well

31
Q

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

A

This is because Bo and Rs change when producing the reservoir

32
Q

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

A

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

33
Q

Relationship between Rs and P for an undersaturated oil reservoir

A

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 )

34
Q

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

A

When we’re working with an undersaturated reservoir

35
Q

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

A

Rsi.

Rsi = Rsb

36
Q

For gas cap reservoir, what is the maximum Rs?

A

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