Gas Mud Ratio from Drilled Gas Formula
Gas Mud Ratio from Drilled Gas calculates gas/mud ratio for drilling operations and economics workflows in drilling engineering.
How engineers use this formula
Use this formula when the listed inputs (d_b, R, phi, S_g, p, z, T, q_m) are known and the assumptions behind the cited drilling operations and economics 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, r_m equals 0.606939 scf/bbl.
8.5
50
0.2
0.35
3000
0.9
560
8
Inputs
d_b
inBit diameter
R
ft/hPenetration rate
phi
fractionFormation porosity
S_g
fractionGas saturation
p
psiFormation pressure
z
dimensionlessGas compressibility factor
T
degRAbsolute gas temperature
q_m
bbl/minMud circulation rate
Outputs
r_m
Gas/mud ratio
q_m
Mud circulation rate
R
Penetration rate
p
Formation pressure
Source and review
reviewedAdvanced Well Control, Watson, D., Brittenham, T., Moore, P.L. (2003)
Watson, D., Brittenham, T., and Moore, P.L. 2003. Advanced Well Control, Vol. 10, Society of Petroleum Engineers, Page 19.