Throughout the life of a oil and gas field development, significant number of important decisions, such as recovery mechanism, and surface facilities, are made relying on incomplete and uncertain data.
Uncertainty assessment is necessary to evaluate risks and make consistent decisions. An integrated method of uncertainty assessment enables the management to capture the static and dynamic uncertainties.
In evaluation of uncertainty around the absolute values of reservoir properties (porosity, rock type, saturation and permeability) an attempt has to be given to account entire space of uncertainty associated with sampling bias or systematic error in collecting or calculating data (e.g. there may be a lack of data on the high side due to existence of missing sections on highly porous/permeable rock or the measurements are biased to the high or low side due to measurement errors/limitations).
Stochastically generated multiple realizations of property models are sometimes expected to account for geological uncertainties. However, the range of property variation that is controlled by the well data and the output from these realizations indicates that the stochastic realizations alone are insufficient to capture the entire space of uncertainties. A larger uncertainty band in these parameters should be considered given the limitations in data sampling, calibration, reconciliation, corrections and errors/limitations in measurements.