Estimation of Production Forecast Uncertainty for a Mature Production License

Abstract

Abstract A comprehensive effort to estimate the range of uncertainty in the long term forecast for the mature Ekofisk and surrounding fields (Eldfisk, Embla and Tor) located in the Norwegian sector of the North Sea is presented. Even for this mature production license (PL018) which has been on production for more than 25 years we experience significant discrepancies between actual and forecasted production. This prompts the need for estimating the range of uncertainty in the reservoir production prognosis. Decision tree analysis formed the basis for our methodology in which each branch on the decision tree is coupled with a full field 3D numerical reservoir model. A large number of full field, numerical simulations were run to forecast the different realizations. Reservoir, operational and facility uncertainties were considered. These results were coupled with straightforward statistical techniques to allow estimation of probabilistic forecasts. Individual fields production forecasts were aggregated into a single license production forecast using Monte Carlo simulation. P. 331