What Is the Reservoir Material Balance Calculator (Havlena-Odeh Linear)?
The reservoir material balance equation (MBE) is a volumetric conservation-of-mass balance accounting for all fluids produced and remaining in an underground petroleum reservoir.
Havlena and Odeh (1963) rearranged the MBE into linear form (Y = mX), where the slope represents Original Oil In Place (N) and linearity verifies drive mechanism hypotheses.
How Does the Reservoir Material Balance Calculator (Havlena-Odeh Linear) Work?
Underground withdrawal F accounts for oil, free gas, and water removed from the reservoir at downhole conditions.
Eo represents the unit expansion of oil and dissolved solution gas as pressure drops.
Aquifer influx We supplements reservoir pressure, supporting production.
Reservoir Material Balance Calculator (Havlena-Odeh Linear) Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Equates underground withdrawal F with expansion of oil/dissolved gas Eo plus natural aquifer water influx We.
How to Use the Reservoir Material Balance Calculator (Havlena-Odeh Linear)
- Enter cumulative production volumes (Np, Gp, Wp).
- Input PVT properties (Bo, Boi, Bg, Rs, Rsi) from laboratory studies.
- Enter estimated aquifer water influx We (from Van Everdingen-Hurst or Fetkovich models).
Step-by-Step Example Calculation
Volumetric Reservoir with Modest Water Drive
Input Values:
Understanding Your Result
N is Original Oil In Place (OOIP) in million STB.
Depletion Drive Index (DDI) and Water Drive Index (WDI) quantify energy shares (summing to ~100%).
Current recovery factor shows percentage of reserves extracted to date.
Factors That Affect the Result
- PVT data accuracy: Small errors in Boi or Bo strongly distort expansion parameter Eo.
- Aquifer encroachment: Underestimating We leads to severely inflated estimates of OOIP.
When Should You Use This Calculator?
- History matching production data after 5% to 10% of reserves have been produced.
- Determining whether a reservoir has an active edge/bottom aquifer drive.
Assumptions & Limitations
- Treats reservoir as a single continuous tank with uniform average pressure.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard reservoir engineering methodology.