Flashcards in Chapter 8: Properties of Black Oils - Definitions Deck (20):

0

## What type of chemical species are present in black oils?

###
Heavy - 27.9 mol % C7+

Non-volatile molecules

1

## What is the conversion factor used to convert cc to bbl?

### 6.2898 x 10 ^-6 bbl/cc

2

##
What is the definition of liquid specific gravity in:

a) words

b) equation w/ units

###
a) the ratio of the density of the liquid to the density of water (at same T & P)

b) density oil / 62.37 (unit less)

3

## What are the 3 changes that cause the ST volume to be less than res volume?

###
1) evolution of dissolved gas as pressure is decreased from reservoir to surface

2) oil expansion because of reduction in pressure

3) oil contraction because of temperature reduction

4

##
What is the definition of the formation volume factor of oil in:

a) words

b) equation, with units

###
a) the vol of reservoir oil required to produce one bbl of oil in the ST

b)

Bo = vol of oil + dissolved gas leaving res @ res condition

________________________________________________

vol of oil entering ST @ STP

5

##
As the reservoir pressure increases, what happens to the oil formation factor (Bo) at the bubble point (Pb)?

Why?

###
Bo increases to a max value

Because of the expansion of the liquid in the reservoir

6

## What is the shrinkage factor?

###
The reciprocal of the vol formation factor

bo = 1

____

Bo

7

## What does the solution gas-oil ratio (Rs) represent and what equation do you use to find it?

###
It represents the solubility of gas in oil

Rs = vol of gas produced at std. conditions

____________________________________

vol of oil in ST at std conditions

8

##
What happens to the solution gas-oil ratio (Rs) above the bubble point (Pb)?

What happens to it at the bubble point (Pb)?

###
Above the Pb, Rs remains constant and at max value as pressure is decreased

At the Pb, Rs begins to decrease as pressure is decreased

9

##
When is black oil considered:

a) saturated

b) under saturated

###
a) at the Pb, where release of some gas is allowed (2 phases, liquid & gas)

b) above Pb, the oil could dissolve more gas (light molecules) if the gas were present

10

##
What is the total volume factor, Bt in:

a) words

b) an equation, with units

###
a) the total vol that would be occupied by oil & gas if all of the free gas remained in the reservoir

b) Bt = Bo + Bg (Rsb - Rs) res bbl/STB

* where Rsb is the solution gas-oil ratio at bubble point)

11

## What is the total formation volume factor (Bt) above the bubble point?

###
Bt = Bo

because above the bubble point, the Rsb & Rs are the same, therefore =0

12

##
What is the coefficient of isothermal compressibility of oil (Co) in:

a) words

b) an equation, with units

When is this applicable?

###
a) the fractional change of vol as pressure is changed at constant temperature

b) Co = - 1/v (partial V / partial P), psi-1

* only applicable at pressure above the bubble point pressure

13

## What is the equation for the coefficient of isothermal compressibility of oil (Co), if Co is assumed to be constant with pressure change?

###
Co (P2 - P1) = - ln (V2 / V1)

V2 = V1 EXT [Co (P1 - P2)]

14

##
What is Co in terms of density?

If Co is assumed constant with pressure change AND pressure is above Pb, what is the equation?

###
Co = (1/ density oil) (partial density oil / partial pressure)

Co is constant when pressure changes above the bubble point

density oil = density oil at bubble point * EXT [ Co (P - Pb)]

15

##
What happens to the vol of reservoir liquid as pressure is reduced below Pb?

What happens to the reservoir vol occupied by the mass that was originally liquid? Why?

###
The vol of reservoir liquid decreases as pressure is reduced below Pb

The reservoir volume increases, due to the evolution of gas

16

##
What is the coefficient do isobaric thermal expansion in:

a) words

b) an equation

###
a) the fractional change in vol of a liquid as temperature changes under constant pressure

b) oil vol @ high temp

___________________

oil vol @ low temp

17

##
What happens to the viscosity of oil, when:

a) temperature goes up

b) the amount of dissolved gas goes down

c) the size of HC molecules increases

###
a) temp goes up => oil viscosity goes down

b) amount of dissolved gas goes down => oil viscosity goes up

c) oil viscosity increases with the increase in size of HC molecules

18

## What are the 5 physical properties required for the reservoir engineering material balance calculations?

###
1) formation vol factor of oil (Bo)

2) solution gas-oil ratio (Rs)

3) total formation vol factor (Bt)

4) coefficient of isothermal compressibility (Co)

5) coefficient of viscosity of oil

19