Chapter 6: Properties Of Dry Gas Flashcards
What order (i.e. 10^[]) should compressibility be reported?
What are the units?
10^[-6] sips
Or
1 microsip
What is the equation for formation vol factor of a gas?
Define each term
Bg = VR = z T Psc
___ = ________
Vsc zsc Tsc P
VR = vol at res conditions Vsc = vol at standard conditions
What are the 5 steps to calculate the coefficient of isothermal compressibility of the dry gas at T & P?
- Determine the pseudo critical properties (T/Tc and P/Pc)
- Calculate the pseudo reduced properties (T/Tpr and P/Ppr)
- Determine z and (partial z/partial Ppr) at constant Tpr
(slope of tangent line) - Calculate Cpr = (1/Ppr) - (1/z) (slope of tangent)
- Calculate Cg = (Cpr/Ppc)
What equation would you use to calculate the vol occupied by 1 lb-mol of natural gas at std conditions?
(Specify the values for standard conditions)
Assuming ideal behavior
Vm = RTsc
___
Psc
Vm = molar vol Tsc = 60 F Psc = 14.65 psia
For a DRY gas, relate the composition & specific gravity in the reservoir to that on the surface.
Composition of the gas in the reservoir is EQUAL to the composition of the gas at the surface
Specific gravity of the reservoir gas is EQUAL to the specific gravity at the surface
How is the gas formation vol factor (Bg) defined?
What are the typical units?
The vol of gas at reservoir conditions required to produce 1 standard cubic foot of gas at the surface
Typical units are reservoir barrels of gas per standard cubic foot
(res bbl/scf)
When is the Joule-Thomson effect valid?
What values do you need to solve the equation?
What sign (+/-) are the values?
Its valid when the change in pressure is adiabatic & small
Vm, T, z, Cp
They are always positive
The temperature change in the Joule-Thomson effect is directly related to what?
The attraction of the molecules for each other
What is the Joule-Thomson effect?
The temperature change as pressure is reduced when a flowing stream of gas passes through a throttle*
- throttle = a valve, choke, or perforation in casing
How do you convert gross heating value (dry) into gross heating value (wet)?
Gross: Lc(wet) = (1-0.0175) * Lc(dry) + 0.9
0.9 accounts for the heat released (BTU/scf) during condensation of the water vapor which was in the gas prior to combustion
How do you convert net heating value (dry) into net heating value (wet)?
Net: Lc(wet) = (1- 0.0175) * Lc(dry)
= (1 - 0.0175) * sum (y * Lc)
Where 0.0175 is the mole fraction of water vapor in the gas when saturated at standard conditions
How do you calculate the heating value of an IDEAL gas? [dry basis]
What type of heating value(s) does this calculate?
Lc(ideal,dry) = sum(y * Lc)
Calculates gross & net heating values
How do you convert the gross or net heating values from IDEAL gas to REAL gas?
Lc = Lc(ideal) = Sum(y * Lc)
________ ___________
Z Z
What is the difference between net and gross heating values?
The heat of vaporization of the water of combustion;
- The water of combustion remains vapor @ standard conditions
What does the net heating value mean?
The heat produced in:
- complete combustion
- under constant pressure
- with the combustion products cooled to standard conditions
- the water in the combustion products remains in the vapor state
