Page 261 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

430 Reservoir Engineering

place equals the sum of the volume remaining and the volume produced [19].
Material balance equations [ 191 will be given for different reservoir situations.
Nomenclature used in these equations is listed below [ 19,197,2471.

Bo = oil formation volume factor = volume at reservoir conditions per
volume at stock-tank conditions, dimensionless (reservoir barrel per
stock-tank barrel, RB/STB)
Bg = gas formation volume factor = volume at reservoir conditions per
volume at standard conditions, RB/scf (Note: if the gas formation
volume factor is expressed in cu ft/scf, divide by 5.615 or multiply by
0.1781 to get RB/scf)
Bw = water formation volume factor = volume at reservoir conditions per
volume at standard conditions, dimensionless (RB/STB)
Bt = Bo + (R* - RJ Bg = composite oil or total oil formation volume factor
= volume at reservoir conditions per volume at standard conditions
cf = formation (rock) compressibility = pore volume per pore volume per
psi
cw = water compressibility = pore-volume per pore-volume per psi
G = total initial gas in place in reservoir, scf
Gc = cumulative gas influx (encroachment), scf
AGe = gas influx (encroachment) during an interval, scf
Gi = cumulative gas injected, scf
GP = cumulative gas produced, scf
k, = relative permeability to gas, dimensionless
km = relative permeability to oil, dimensionless
m = GBgi/NBoi = ratio of initial gas-cap/gas-reservoir volume to initial
reservoir oil volume
N = initial oil in place, STB
NP = cumulative oil produced, STB
ANp = oil produced during an interval, STB
p = reservoir pressure, psia
pi = initial reservoir pressure, psia
p, = reduced pressure, dimensionless
R, = solution-gas-oil ratio (gas solubility in oil), scf/STB
Rsi = initial solution-gas-oil ratio, scf/STB
R, = gas solubility in water, scf/bbl at standard conditions
Rp = cumulative gas-oil ratio, scf/STB
So = oil saturation, fraction of pore space
Sg = gas saturation, fraction of pore space
S, = irreducible or connate water saturation, fraction of pore space
Sw = water saturation, fraction of pore space
S, = initial water saturation, fraction of pore space
W = initial water in place, reservoir bbl
We cumulative water influx, bbl at standard conditions
=
W = cumulative water produced, bbl at standard conditions
If = cumulative water injected, bbl at standard conditions
pg = gas viscosity, cp
po = oil viscosity, cp
z = gas deviation factor (compressibility factor), z = pV/nRT, dimensionless
i = subscript, initial or original conditions
1 = subscript for conditions at p,
2 = subscript for conditions at pn