Chapter 5- Pvt Properties Of Crude Oil Flashcards
What is petroleum ?
It is a complex mixture consisting predominantly of hydrocarbons , containing nitrogen, sulphur , oxygen and helium as minor constituents .
What does the physical and chemical properties of crude oil depend on ?
They depend on the concentration of the various types of hydrocarbon and minor constituents present .
What influences the behavior of the mixtures ?
The constituents
List the physical properties that are of primary interest in petroleum engineering studies
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
Are all correlation for solution gas oil ratio the same for bubble point pressure?
Yes they are
What is the formula for crude oil density?
Crude oil density = mass of oil / volume of oil
What is the standard temp and pressure of the surface in petroleum engineering
15.566 degree c or 60degree F
Pressure is 14.7 psia or 0psig
Which kind of imperial system do we use for petroleum engineering?
FPS
Force , pound , second
Full meaning of psi
Pound per square inch
What is the density of water
1g/cm^3 or 1000kg/m^3 or 62.4 lbm/ft^3
What is the formula for specific gravity of oil ?
Specific gravity of oil = density of oil / 62.4
Specific gravity of gas formula
Density of gas/ density of air
Unit for specific gravity of oil
60/60 since density of oil and density of water are both measured at 60degree F
What happens to the specific gravity and the density when the API gravity is high?
The sp gr and density are low
What happens to the specific gravity and the density when the API gravity is low ?
The sp gr and density are high
What kind of relationship is the between sp gr and API gr ?
Inverse relationship
What is the mathematical relationship between API and specific gravity Of oil ?
Specific gravity of oil = 141.5/131.5+API
How many cm makes 1 inch ?
2.54cm
How many pounds make 1kg?
2.2046 Lbm
What is meant by dead oil
It is oil which has no dissolved gas , essentially methane and ethane
What is meant by live oil
Oil which has dissolved gas
What is solution gas ?
It is the amount of dissolved gas in oil
How do we quantify solution gas?
Using solution gas oil ratio
What is the formula for solution gas oil ratio
Volume of dissolved gas / unit volume of oil
What is the unit of solution gas oil ratio
Scf/STB
What is the difference between STB and RB
STB is the volume of oil in the stock tank
RB is the volume of oil in the reservoir or in the subsurface
What is the unit for formation volume factor
RB/STB
What is the formation volume factor for water
Bw = 1 RB/STB
What is formation volume factor for water
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
What is the relationship between Bo and Rs
If Rs is high , Bo is high as well
What is the reason for having initial values for Bo and Rs
This is because Bo and Rs change when producing the reservoir
What is the relationship between Bo and P for an undersaturated oil reservoir
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
Relationship between Rs and P for an undersaturated oil reservoir
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 )
What is the only time Rsi is the maximum Rs and corresponds to the Rsb ?
When we’re working with an undersaturated reservoir
For undersaturated and saturated oil reservoirs, what is the maximum Rs?
Rsi.
Rsi = Rsb
For gas cap reservoir, what is the maximum Rs?
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
