# Improve Reserve Estimates Essay

1636 WordsSep 26, 20147 Pages
COMBINED METHODS IMPROVE RESERVE ESTIMATES 05/01/1995 Rene Santos, Erwin Ehrl Mobil Erdgas-Erdol GmbH Celle, Germany A comparison of deterministic and probabilistic methods can provide quality assurance for estimating hydrocarbon reserves. Proved reserves would then be calculated both deterministically and probabilistically and the two values compared. Probabilistic methods use stochastic parameters such as a Monte Carlo simulation. On the other hand, deterministic calculations are made with discrete values. If the deterministic value and the probabilistic value agree, then confidence in the reserve calculation is increased. If the two values are very different, the assumptions need to be reexamined. PROVED RESERVES Probabilistic methods for calculating proved reserves have several inherent problems. These methods are affected by all the input parameters, including the most likely and maximum values for the parameters. Proved reserves derived from probabilistic methods are intangible and impossible to "point to on a map." They also may be difficult to reconcile with legal definitions of a proved area. In a probabilistic calculation one cannot back calculate the input parameters associated with the proved reserves. One knows only the end result but not the exact value of any input parameter. On the other hand, deterministic methods derive proved reserves that are more tangible and explainable. In a deterministic calculation one knows exactly the parameters used in the calculation. However, deterministic methods may sometimes ignore the variability and uncertainty in the input data. Probabilistic methods allow the incorporation of more variance in the data. Deterministic methods use single-point parameters to obtain reserves.1 2 The result is a single value such as 10 billion cu m. Some parts of the deterministic calculation of proved reserves are