(3.1-3.2) Flashcards
What are the functions of physical properties of petroleum fluids?
Pressure, Temperature, and Composition
Gibb’s rule
F = C - P + 2
What does F, C, and P in Gibb’s rule indicate?
F is the number of degree of freedom
C is the number of components
and P is the number of phases
The thermodynamic fluid properties will be studied in 3 steps:
- Pure substances
- Binary mixtures
- Multi-component systems
Reservoir hydrocarbons exist as:
vapor, liquid or solid phases
A phase is defined as a part of a system which is ___
physically distinct from other parts by definite boundaries
A reservoir oil (liquid phase) may change form into gas (vapor phase) during ___
depletion
The subject of phase behavior focuses only on the ___
state of equilibrium, where no changes will occur with time
The state of a phase is fully defined when it’s __ are specified
chemistry, composition, temperature and pressure
It is a key aspect in understanding nature and behavior of fluids both in the reservoir and also during the production and transport process
Phase behavior
It divides the regions where the substance is a liquid from regions where it is a gas
Vapor pressure line
It separates the pressure and temperature at which solids exists from the area where the liquid exists
Melting point line
It represents the pressure and temperature at which solid, liquid and vapor coexist under equilibrium conditions
Triple point
What is the triple point of pure water?
0.01°C (273.16 K, 32.01°F) and
4.58 mmHg (611.2 Pa)
A point on a phase diagram at which both the liquid and gas phases of a substance have the same density, and are therefore indistinguishable
Critical point
Tc, Pc
Critical temperature and critical pressure
•Such a system is called “A Binary System”
•One component is more volatile than the other
•Components are miscible
Two Component Systems
It is the point at which all properties of the liquid and the gas become identical
Critical point
The maximum pressure defined by the envelope
cricondenbar
The maximum temperature defined by the envelope
cricondentherm
What happens to the pressure if the process passes from the bubble point to the dew point
decreases
What causes the decrease in pressure
the changes in the compositions of the liquid and gas as the process passes through the two-phase
What mixture is plot above the envelope
completely liquid
What mixture is plot below the envelope
Gas
What mixture is plot within the envelope
gas and liquid
It is the locus of composition of the liquid when two phases are present
bubble-point line
It is the locus of composition of the gas and liquid are in the equilibrium
dew-point line
The line which ties the composition of the liquid with the composition of gas in equilibrium
equilibrium tie-line
What do you call the compositional phase diagram for three-component mixtures
Ternary diagrams
For a single diagram, both pressure and temperature are constant; only ___ change
composition
Why the petroleum engineer should identify the type of reservoir fluids?
•To design proper surface facilities
•To estimate oil and gas in place
•To predict oil and gas reserves
•To select a proper EOR method
•Contracting
•Marketing
The petroleum reservoir are broadly classified as ___
oil or gas reservoirs
___ are classified on the basis of the location of the points representing the initial reservoir pressure and temperature with respect to the P-T diagram for the reservoir fluid
Reservoirs
Tres < Tc
Oil reservoirs
Tres > Tc
Gas reservoirs
3 categories of oil reservoirs
•undersaturated oil reservoir
•saturated reservoir
•gas-cap reservoir
Pi > Pb
Undersaturated oil reservoir
Pi = Pb
Saturated oil reservoir
Pi < Pb
Gas-cap reservoir
5 fluid types in petroleum fluids classification
•black oil
•volatile oil
•retrograde oil (gas condensate)
•wet gas
•dry gas
how to identify types of fluids?
•Gas-oil ratio (GOR)
•Oil Gravity
•Color of the stock tank liquid
reservoir pressure > BP pressure
undersaturated fluid and only one-phase is exists
reservoir pressure < BP pressure
saturated fluid and two phase are exist
GOR < 2000
Oil gravity < 40
dark black in color
Black oil
GOR: 2000 - 3300
Oil gravity: 40 - 50
Brown to orange in color
Volatile oil
GOR: 3300 - 150,000
Oil gravity: 50 - 70
Water-white or slightly colored
Retrograde gas (Gas condensate)
GOR: > 50, 000 (stable)
Oil gravity: 60 - 70
Wet gas
GOR: > 100,000
•it lies below the reservoir temperature
Dry gas
