Reducing Uncertainties in Hydrocarbon Volumetric Estimation: A Case Study of Fuba Field, Onshore Niger Delta


  •   Franklin Fubara

  •   Nnamdi J. Ajah

  •   Jude U. Igweajah

  •   Olayinka Yinka

  •   Abdulmaliq Abdulsalam

  •   Paul Mogaba


Reducing uncertainties to the barest minimum before reserve estimation aids in making a better decision regarding field development. This study analyses uncertainty in hydrocarbon reserve estimation in Fuba Field using both scenario-based deterministic and stochastic methods. Two hydrocarbon reservoirs (A and I) were selected and mapped. Depth structure maps revealed fault supported collapsed crestal closures for both reservoirs. Uncertainty analysis was conducted using low case (P90), base case (P50), and the high case (P50) reservoir properties. On average, porosity, NTG and Sw are 31%, 89%, 10%, and 24%, 84%, 23% for A and I reservoirs. Hydrocarbon volumes recorded for the high case, base case, and low case using a deterministic versus stochastic approach are 30.52 MMSTB, 12.46 MMSTB, 4.57 MMSTB, and 18.52 MMSTB, 13.59 MMSTB, and 9.40 MMSTB for reservoir A, 58.87 MMSTB, 10.94 MMSTB, 1.51 MMSTB, and 25.56 MMSTB, 14.59 MMSTB and 7.63 MMSTB for reservoir I. While the base case was similar for both methods (stochastic and deterministic), there is a huge difference in the low and high-case hydrocarbon volumes recorded in both methods. This change could be attributed to the reservoir bulk volume with (>85%) with little contribution from oil saturation and porosity. Cross plot analysis confirms that bulk volume is the main control of the estimated stock tank original oil in place (STOIIP). Hence, a slight alteration in bulk volume will significantly affect the estimated STOIIP. It is recommended that bulk volume be given most attention when conducting reservoir simulation as this will increase simulation time, reduce simulation cost, and provide more accurate simulation results.

Keywords: Bulk Volume, Deterministic, Stochastic, Uncertainty


Caldwell, R. H., and Heather, D. I. Characterizing Uncertainty in Oil and Gas Evaluations. Society of Petroleum Engineers. doi:10.2118/68592-MS, 2001.

Rahimov, F. V., and Huseynov, R. M. Risk and Uncertainty Assessment While Estimating Reserves, Bull. Society of Petroleum Engineer; DOI: 10.2118/189019-MS, 2017.

Samimi, A.K., and Karimi, G. Sensitivity and uncertainty analysis of original oil-in-place in carbonate reservoir modelling, A case study. Petroleum and Coal 56(3) 332-338, 2014.

Hamada, G., Almajed, A., Okasha, A., Taha, A., and Algathe, A. Uncertainty analysis of Archie's parameters determination techniques in carbonate reservoirs. Journal of Petroleum Exploration and Production Technology. 2012.

Doust, H. and Omatsola, E. Niger Delta: Edwards, J.D. and Santogrossi, P.A. (eds.), Divergent/passive Margin Basins, AAPG Memoir 48, 239-248.,1990.

Short, K.C., Stauble, A.J. Outline of Geology of Niger Delta. Am. Assoc. Petr. Geol. Bull., 51(5): 761–779, 1967.

Ekweozor, C. M., and Daukoru, E. M. Petroleum Source Bed Evaluation of Tertiary Niger Delta. American Association of Petroleum Geologists Bulletin, Vol. 70, 48-55, 1984.

Weber, K.J., and Daukoru, E.M. Petroleum geology of the Niger Delta. Ninth World Petroleum Congress. Tokyo. 2: 202 – 221, 1975.

Adegoke, O.S., Oyebamiji, A.S., Edet, J.J., Osterloff, P.L., Ulu, O.K. Cenozoic foraminifera and calcareous nannofossil biostratigraphy of the Niger Delta. Cathleen Sether, United States, 570, 2017.

Clavier, C., Hoyle, W. R., and Meunier, D. Quantitative Interpretation of TDT Logs. Parts I and II: Journal of Petroleum Technology, Vol 23, 743–763, 1971.

Gluyas, J., and Swarbrick, R. Petroleum Geosciences. Publication. Blackwell. Publishing, 32, 2004.

Archie, G.E. The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics. Trans, 54-62, 1942.

Woodhouse, R., and Warner, H.R. Sw and Hydrocarbon Pore Volume Estimates in Shaly Sands - Routine Oil-Based-Mud Core Measurements Compared with Several Log Analysis Models. Society of Petroleum Engineers Annual Technical Conference and Exhibition, Dallas, Texas, 2005.

Rider M. "The Geological Interpretation of Well Logs", Blackie, Glasgow, 151-165. 1986.


Download data is not yet available.


How to Cite
Fubara, F., Ajah, N.J., Igweajah, J.U., Yinka, O., Abdulsalam, A. and Mogaba, P. 2021. Reducing Uncertainties in Hydrocarbon Volumetric Estimation: A Case Study of Fuba Field, Onshore Niger Delta. European Journal of Engineering and Technology Research. 6, 2 (Feb. 2021), 118-127. DOI: