Stochastic analysis of production decline data for production prediction and reserves estimation

The purpose of this study is to develop a stochastic method which analyzes production data to predict future performance and to estimate reserves probabilistically. A methodology for the stochastic analysis, using the statistical properties of production data and the rate–time equation, is presented. Data from an oil field was analyzed by the stochastic method. For comparison, both deterministic decline curve analysis and conventional probabilistic analysis are conducted. In deterministic decline curve analysis, only a single value for the reserves is estimated and a smooth curve for the production rates is predicted. The analysis does not take into consideration the uncertainty of the data. In probabilistic analysis and stochastic analysis, the ranges of reserves which include the uncertainty of the production history data are estimated. The results from conventional probabilistic analysis depend on the distribution of input parameters which are assumed or subjectively determined by an evaluator. In analysis by stochastic method, the result, however, is fully dependent on the production history data instead of subjective judgment.