Remaining Gas in Place in Coalbed Methane Reservoirs Formula
Remaining Gas in Place in Coalbed Methane Reservoirs calculates remaining gas at reservoir pressure for unconventional reservoirs workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (A, h, phi, B_w, W_p, S_wi, P_i, P, c_f, c_w, E_g) 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, G_R equals 535,708,633.503759 SCF.
640
20
0.04
1.02
100000
0.35
1200
700
0.000005
0.000003
200
Inputs
A
acresDrainage Area
h
ftCoal Seam Thickness
phi
fractionPorosity
B_w
bbl/STBWater Formation Volume Factor
W_p
bblCumulative Water Produced
S_wi
fractionInitial Water Saturation
P_i
psiInitial Reservoir Pressure
P
psiCurrent Reservoir Pressure
c_f
1/psiFormation Compressibility
c_w
1/psiWater Compressibility
E_g
SCF/bblGas Expansion Factor
Outputs
G_R
Remaining Gas at Reservoir Pressure
Source and review
reviewedAhmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 227.
Source