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AGA7
AGA 7 takes a flowing volume, rate or flowing conditions and calculates base volume, base volume flow rate or volume correction factor. It requires flowing and base pressure, temperature and compressibility. Compressibility is calculated by your favourite equation of state, such as AGA 8.
The algorithm for the calculation is extremely straightforward. It is really just the application of the real gas law to the measured volume.
P
f
* V
f
= Z
f
* n
* R * T
f
so
V
f
= Z
f
* n
* R * T
f
/
P
f
P
b
* V
b
= Z
b
* n
* R * T
b
so
V
b
= Z
b
* n
* R * T
b
/
P
b
Dividing the equations, we get
V
b
/
V
f
=
(Z
b
* n
* R * T
b
/
P
b
)/(
Z
f
* n
* R * T
f
/
P
f
)
so
V
b
=
V
f
*
(Z
b
* n
* R * T
b
*
P
f
) /
(
Z
f
* n
* R * T
f
*
P
b
)
Changing the pressure and temperature doesn't change the number of moles, and R is a constant, so:
V
b
=
V
f
*
(Z
b
* T
b
*
P
f
) /
(
Z
f
* T
f
*
P
b
)
S is defined as
Z
b
/
Z
f
F
pm
is defined as P
f
/ 101.56 kPa, or P
f
/ 14.73 PSI
F
pb
is defined as
101.56 kPa /
P
b
, or
14.73 PSI /
P
b
F
tm
is defined as
288.7056 Deg Kelvin /
T
f
, or
519.67 Deg. Rankin / T
f
F
tb
is defined as
T
b
/ 288.7056 Deg Kelvin, or T
b
/ 519.67 Deg. Rankin
So
F
pm
*
F
pb
=
P
f
/
P
b
and
F
tm
*
F
tb
=
T
b
/
T
f
So V
b
=
V
f
*
F
pm
*
F
pb
*
F
tm
*
F
tb
* S
Calculate F
pm
= P
f
/ 101.56 kPa (US base conditions, defined by AGA 7 spec)
Calculate F
pb
= 101.56/P
b
Calculate F
tm
= (15.55556 + 273.15)/T
f
Deg. K (US base conditions, defined by AGA 7 spec)
Calculate F
tb
= T
b
/ (15.55556 + 273.15) Deg. K (US base conditions, defined by AGA 7 spec)
Calculate S = Z
b
/ Z
f
= F
pv
2
Calculate BMV (base multiplier value) = F
pm
* F
pb
* F
tm
* F
tb
* S
Apply meter factor to BMV (Note: this is often done to the actual volume prior to using AGA 7.)
Calculate base volume V
b
= V
f
* BMV / 1000 (Converts M
3
to E3M3, or Ft
3
to MSCF)
AGA7: Enter a flowing temperature, pressure and compressibility, a base temperature, pressure and compressibility, a flowing volume and a meter factor, then press Calculate.
Flowing Temp (Deg C) =
Flowing Pressure (kPaA) =
Flowing Compressibility =
Flowing volume (M3) =
Meter Factor =
Base Temp (Deg C) =
Base Pressure (kPaA) =
Base Compressibility =
Results Table