Deterministic and Stochastic Methods of Oilfield Reserves Estimation: A Case Study from Ka. Oilfield

Abstract

Reserves Estimation is a process that continues during almost all the life of the Oilfield. And it is always affected by uncertainty and errors. The first level of uncertainty is associated with first data taken from geophysical profiles, wells, cores, water etc. These data provide reservoir properties such as areas, depth, porosity, saturation, temperature, etc. The second level of uncertainty is produced when reservoir properties are used in formulas and correlated with the help of geology, seismic and production tests. Reserves-estimation methods are broadly classified as analogy, volumetric and production types. The choice of methodology depends on timing of development and production, amount of data, reservoir characteristics. Analogy Method is the simplest is based on geologic analogy with a nearby producing area. The method is reliable to the extent that the analogy is valid, which can be estimated by statistical test. The two volumetric methods for Reserves estimation are deterministic and stochastic, (Derminem F., 2007). In case of deterministic method, mathematical formulas are used to estimate volumes or reserves. The stochastic method considers the fact that each parameter is not presented with a single value, but is included in an interval of values and fit a probability distribution which is to be found out, estimated and used properly, (Prifti I, Kosova R., 2014). The results from stochastic calculations are concluded generally by a reverse cumulative probability function, the expectation curve, (Wadsley A. W., 2011). We will use both, deterministic and stochastic methods, in estimating reserves in the case study of KA. Oilfield.