A simple and practical method for estimating undiscovered hydrocarbons for a specified timeframe

Abstract

A simple approach has been developed to predict yet-to-find (YTF) hydrocarbons to be discovered in a basin within a specified timeframe. The methodology uses basic exploration and resource data to address the requirement of oil companies, governments, utilities and financial institutions so that these understand the resources available for future markets within a defined timeframe (e.g, in the next 15 years). In contrast, conventional approaches to estimate the YTF in a moderately mature basin tend to predict the ultimate resource of a basin, unqualified by time. Such techniques reply on data-intensive geological assessments or use the parabolic form of a log-log plot of cumulative hydrocarbon resource against field rank, coupled with an extrapolation of a cumulative resource against field rank (the creaming curve) to an asymptote. The approach uses annual exploration data, dry hole and discoveries, and the discovery size. Three parameters are defined for the forecast period: the average number of wells per year, the average chance of a discovery, and its average size. Low, mid and high case values of each parameter are estimated, and these are combined probabilistically to produce P90, P50, P10 YTF volumes. These become end points for the forecast period, that are used to extrapolate the creaming curve. Iterating with the input parameters optimises forecasts with respect to the historical dataset. The approach can be extended to predict future field size distributions. Forecasts are made for the Bonaparte, Browse, Carnarvon and Perth Basins. The total P50 undiscovered gas resource for these basins for the next 15 years is estimated at 25.1 Tcf.