Tight Gas Pore Volume from Squared-Pressure Decline Formula
Tight Gas Pore Volume from Squared-Pressure Decline calculates pore volume for unconventional reservoirs workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (T, mu_g_avg, z_avg, q_i, mu_gi, c_ti, P_i, P_wf, D_i) are known and the assumptions behind the cited unconventional reservoirs relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, PV equals 29,212,333.333333 reservoir volume units.
620
0.02
0.9
500
0.018
0.00001
4000
1000
0.002
Inputs
T
degRReservoir Temperature
mu_g_avg
cPAverage Gas Viscosity
z_avg
dimensionlessAverage Gas Compressibility Factor
q_i
MSCF/dayInitial Gas Rate
mu_gi
cPInitial Gas Viscosity
c_ti
1/psiInitial Total Compressibility
P_i
psiInitial Reservoir Pressure
P_wf
psiBottom-Hole Flowing Pressure
D_i
1/dayInitial Decline Rate
Outputs
PV
Pore Volume
q_i
Initial Gas Rate
D_i
Initial Decline Rate
Source and review
reviewedAdvanced Reservoir Engineering, Ahmed, T., McKinney, P. D. (2005)
Ahmed, T. and McKinney, P. D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 252.
Source