Calculate original oil in place (OOIP) using simplified Havlena-Odeh material balance method
Total cumulative oil production from the reservoir at the time of evaluation, measured in stock tank barrels.
STB
Oil formation volume factor at initial reservoir pressure. From PVT report or correlations. Typical 1.1 to 1.8 rb/STB.
rb/STB
Oil formation volume factor at current average reservoir pressure. Bo increases as pressure drops below bubble point due to gas liberation.
rb/STB
Cumulative gas-oil ratio = total gas produced / total oil produced. Average GOR over the production life.
scf/STB
Solution gas-oil ratio at initial reservoir pressure from PVT data. Equal to bubble point Rs if reservoir was initially at or above Pb.
scf/STB
Solution gas-oil ratio at current average reservoir pressure. Decreases as pressure drops below bubble point.
scf/STB
Gas formation volume factor at current reservoir pressure. Bg = 0.0283(zT/P). Typical range 0.0005-0.02 rb/scf.
rb/scf
Results
Original Oil In Place (N)-MMSTB
Underground Withdrawal (F)-MMrb
Oil Expansion Term (Eo)-rb/STB
Recovery Factor-%
Remaining Oil In Place-MMSTB
References & Formulas:
Havlena-Odeh (no water influx, no gas cap): F = N × Eo
F = Np[Bo + (Rp − Rs)Bg] — underground withdrawal
Eo = (Bo − Boi) + (Rsi − Rs)Bg — oil + dissolved gas expansion
N = F / Eo — original oil in place
Havlena & Odeh (1963), JPT. Dake: Fundamentals of Reservoir Engineering.