Reservoir EngineeringReserves and Recovery
Arps Exponential Decline Cumulative Production Formula
Arps Exponential Decline Cumulative Production calculates cumulative production for reserves and recovery workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (q_i, D_i, t) are known and the assumptions behind the cited reserves and recovery 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, N_p equals 305,803.349122 STB.
q_iSTB/day
1000
D_i1/day
0.001
tday
365
Inputs
q_i
STB/dayInitial Production Rate
D_i
1/dayNominal Decline Rate
t
dayElapsed Production Time
Outputs
N_p
STB
Cumulative Production
q_i
STB/day
Initial Production Rate
Source and review
reviewedArps, J.J. 1945. Analysis of Decline Curves, Trans. AIME. Exponential cumulative production model.
Source