Difference between revisions of "Gas Flowing Material Balance"

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==Workflow==
 
==Workflow==
 
# Calculate the red P/z line:
 
# Calculate the red P/z line:
−
**Calculate the P/z, <math> \frac{P}{z}=\frac{P_i}{z_i} \left (1- \frac{G_p}{GIIP}\right )</math>
+
##Calculate the P/z, <math> \frac{P}{z}=\frac{P_i}{z_i} \left (1- \frac{G_p}{GIIP}\right )</math>
 
# Calculate the orange <math> \frac{\bar{P}}{z}</math> curve  
 
# Calculate the orange <math> \frac{\bar{P}}{z}</math> curve  
−
** Calculate initial pseudopressure, <math>P_{Pi}</math>
+
## Calculate initial pseudopressure, <math>P_{Pi}</math>
−
** Calculate flowing bottomhole pressures, given flowing wellhead pressures, <math>P_{wf}</math>
+
## Calculate flowing bottomhole pressures, given flowing wellhead pressures, <math>P_{wf}</math>
−
** Calculate the flowing pseudopressures, <math>P_{P_{wf}}</math>
+
## Calculate the flowing pseudopressures, <math>P_{P_{wf}}</math>
  
  

Revision as of 07:50, 11 December 2017

Brief

Gas Flowing Material Balance is the advanced engineering technique to determine the Reservoirs GIIP and recovery as well as Well's EUR and JD.

Gas Flowing Material Balance is applied on the Well level given readily available well flowing data: production rate and tubing head pressure.

The interpretation technique is fitting the data points with the straight line to estimate GIIP and JD.

Math & Physics

Combining the gas pseudo state flow equation and the Gas Material Balance equation to get Gas Flowing Material Balance equation:

P_{\bar{P}}= P_{P_{wf}} + q_g b_{pss} [1]

where

b_{pss} = \frac{1422 \times 10^3\ T_R}{kh\ J_D}

Material balance pseudo-time:

t_{ca} = \frac{\mu_{gi} c_{gi}}{q_g}\int\limits_{0}^{t}\frac{q_g}{\bar{\mu_g} \bar{c_g}}dt

Discussion

Workflow

  1. Calculate the red P/z line:
    1. Calculate the P/z, \frac{P}{z}=\frac{P_i}{z_i} \left (1- \frac{G_p}{GIIP}\right )
  2. Calculate the orange \frac{\bar{P}}{z} curve
    1. Calculate initial pseudopressure, P_{Pi}
    2. Calculate flowing bottomhole pressures, given flowing wellhead pressures, P_{wf}
    3. Calculate the flowing pseudopressures, P_{P_{wf}}


  1. Calculate material balance pseudo-time, t_{ca}
  2. Plot \frac{P_{P_i}-P_{P_{wf}}}{q} versus t_{ca}. The intercept gives b_{pss} and J_D.
  3. Calculate the average reservoir pseudopressure from Gas Flowing Material Balance equation, P_{\bar{P}}

Data required

Nomenclature

A_p = flow area, ft2
B = correlation group, dimensionless
B = formation factor, bbl/stb
C = coefficient for liquid viscosity number, dimensionless
D = pipe diameter, ft
h = depth, ft
H = correlation group, dimensionless
H_L = liquid holdup factor, dimensionless
f = friction factor, dimensionless
GLR = gas-liquid ratio, scf/bbl
M = total mass of oil, water and gas associated with 1 bbl of liquid flowing into and out of the flow string, lbm/bbl
N_D = pipe diameter number, dimensionless
N_GV = gas velocity number, dimensionless
N_L = liquid viscosity number, dimensionless
N_LV = liquid velocity number, dimensionless
p = pressure, psia
q_c = conversion constant equal to 32.174049, lbmft / lbfsec2
q = total liquid production rate, bbl/d
Re = Reynolds number, dimensionless
R_s = solution gas-oil ratio, scf/stb
SG = specific gravity, dimensionless
T = temperature, °R or °K, follow the subscript
v = velocity, ft/sec
WOR = water-oil ratio, bbl/bbl
z = gas compressibility factor, dimensionless

Greek symbols

\varepsilon = absolute roughness, ft
\mu = viscosity, cp
\rho = density, lbm/ft3
\bar \rho = integrated average density at flowing conditions, lbm/ft3
\sigma = surface tension of liquid-air interface, dynes/cm (ref. values: 72 - water, 35 - oil)
\psi = secondary correlation factor, dimensionless

Subscripts

g = gas
K = °K
L = liquid
m = gas/liquid mixture
o = oil
R = °R
SL = superficial liquid
SG = superficial gas
w = water

References

  1. ↑ Mattar, L.; Anderson, D (2005). "Dynamic Material Balance (Oil or Gas-In-Place Without Shut-Ins)" (PDF). CIPC. 
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