Aquifer Influx Calculator
Compute cumulative water influx using the Fetkovich pseudo-steady-state aquifer model. Estimate aquifer support from reservoir pressure history.
Aquifer Parameters
Wei = aquifer pore volume × ct × Pi (maximum encroachable water)
Fetkovich: ΔWe = Wei × (P̄aq - P̄res) / Pi × [1 - exp(-J×Pi×Δt / Wei)]
Reservoir Pressure History
Enter time (days) and average reservoir pressure (psi) at each survey point.
| # | Time (days) | Pres (psi) |
|---|
Total Influx, We
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Max Encroachable
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Aquifer Depletion
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Current Influx Rate
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Step-by-Step Influx Calculation
| Step | Time (days) | Δt (days) | Pres (psi) | P̄aq (psi) | ΔWe (bbl) | We cumul. (bbl) | Rate (bbl/d) |
|---|
Cumulative Influx vs Time
Influx Rate vs Time
How this was calculated
Fetkovich Method: A pseudo-steady-state aquifer model that treats the aquifer as a tank with a productivity index J. At each time step, the influx is computed based on the pressure difference between the average aquifer pressure and the reservoir pressure.
Key Equation: ΔWe = (Wei/Pi) × (Paq_avg - Pres_avg) × [1 - exp(-J×Pi×Δt/Wei)]
Aquifer pressure update: After each step, Paq = Pi × (1 - We_cumul / Wei)
Assumptions: Radial or linear aquifer. Pseudo-steady-state flow. Constant aquifer compressibility. Single-phase water.
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Book a free strategy call →Understanding Aquifer Influx Modeling
Aquifer influx is the natural water encroachment from an aquifer into a hydrocarbon reservoir as reservoir pressure declines during production. Accurate modeling of water influx is critical for material balance calculations, production forecasting, and waterflood design. The Fetkovich (1971) method provides a practical pseudo-steady-state approach that requires only the aquifer productivity index (J) and the maximum encroachable water volume (Wei).
Unlike the Van Everdingen-Hurst unsteady-state method, which requires superposition of dimensionless solutions, the Fetkovich method is computationally simpler and often sufficient for engineering estimates. It is widely implemented in commercial tools like Petroleum Experts MBAL and Schlumberger Eclipse.
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