A correlation of dew-point pressure with reservoir fluid composition and temperature

For prediction of future performance of condensate reservoirs, it is essential to know the dew-point pressures. At the present time the only reliable method of obtaining a dew-point pressure is laboratory measurement which is time consuming and expensive. This investigation was performed to develop a relationship between the dew-point pressure of a hydrocarbon reservoir fluid and its composition, temperature and the characteristics of the heptanes-plus fraction. This is part of an overall program to develop correlations for the essential properties of reservoir fluids with their composition, temperature and pressure. 579 dew-point pressures determined experimentally on 480 different condensate systems along with their compositions and formation temperatures were obtained from the literature and from previously unpublished sources. The compositions were expressed in terms of mol fractions of methane through heptanes-plus, nitrogen, carbon dioxide and hydrogen sulfide and the molecular weight and specific gravity of the heptanes-plus fraction. The distribution of the samples assured a good representation of most of the major oil producing areas in the world. A multiple regression analysis program written for the IBM 7094 Digital Computer was used to calculate the coefficients for the specific equations. The final equation containing eleven coefficients resulted in an average absolute deviation of for all the samples. Segregation of data on the basis of one or more variables did not materially improve the results. The correlation developed, is useful in predicting the dew-point pressure of condensate reservoirs from variables normally measured in a laboratory examination of fluid samples