Calculation Algorithm for Oil PVT-Properties

Abstract

This paper describes a new algorithm for calculating oil PVT-properties and associated petroleum gas. The technique was created to increase the accuracy of the standard "Black Oil" model. The method proposed is based on new correlation dependencies, material balance and correlation dependencies published by other authors in the past. To obtain new correlations, new compositional simulator (written in Visual Basic) and synthetic-oils were used. Bank of synthetic-oils covers a range of the PVT properties of real-oils (mainly Russian oil fields). Synthetic-oils are assumed to include only hydrocarbon components. Oil and gas PVT-properties at different temperature and pressure conditions were obtained by calculation using Peng-Robinson equation of state with shift parameter. Then correlations for properties at pressure below bubble-point pressure conditions have been created. New correlations were tested on real oils from Data Bank (certain from Russian fields). For this comparative calculations have been carried out. Calculations based on the new correlations were compared with calculations based on compositional models. Resulting correlations were found applicable. Resulting correlations may be used for calculations with the proposed method as well as independently as an alternative to other existing calculate correlations. In general, for the calculations using the method concerned, parameters the only required are the same as for the model Black Oil: the density of oil and gas in standard conditions, the initial gas-oil ratio, temperature and pressure. Since the calculations with the approach developed are based on simple mathematical equations with use of minimum of input parameters and they don't require special software, the technique involved can be easily applied in making engineering decisions.