Probabilistic Estimation of Potential Gas Reserves for the Emerging Nigerian Gas Market

Proved reserves for the Emerging Nigerian Gas Market is estimated to be around 186 trillion cubic feet (Tcf). In the short to medium term, only 54% or approximately 100 Tcf will be available for utilisation, the remaining locked up as Gas Cap Gas, only available on the long term (constrained by OPEC production quota and lack of Gas Utilisation Infrastructure). The objective of this study was to estimate the growth potential of Associated Gas (AG) reserves and more importantly determine probabilistic estimates for potential reserves additions from the extensive Non-associated Gas (NAG) accumulations in the Niger Delta.

The Niger Delta potential AG reserves growth (deterministic) was investigated using historical reserves figures and the probabilistic potential reserves additions from NAG were explored using simple triangular distributions. The Society of Petroleum Engineers (SPE) Reserves classification framework was employed to categorize the Proved reserves (1P or P1) as AG Reserves and Reserves additions from NAG as P2 for Probable reserves (2P or P1+P2) generated as a cumulative distribution till 2050.

The results obtained indicated NAG reserves addition to the proved reserves has a 90% confidence limit of reaching between 78.39 and 89.80 Tcf, and a Standard deviation of 3.42 Tcf in 2050. The 2P reserves estimate in 2050 is expected to lie between 267.06 Tcf and 278.49 Tcf within a confidence interval of 90%. Standard deviation from these values was also estimated as 3.42 Tcf. About total reserves of 275 Tcf would lie below the 75th percentile.

The distribution of reserves obtained would significantly improve future gas reserves availability estimates and plausible production profiles for prospective investors planning to participate in gas to power and other gas utilisation projects in the emerging Nigerian gas market.