Improved K-values correlation for UAE crude oil components at low pressures using PVT laboratory data

Several techniques are available in the literature to estimate the K-values , In this paper, results of PVT analysis for 22 crude oil samples from diff erent reservoirs in UAE are used. Sixty-eight single-stage flash laboratory experiments were conducted for these samples. Material balance techniques were used to extract the K-values of crude oil components. These K-values w ere then correlated and compared with values obtained from published correl ations. Comparisons show that current correlations, while they generally gi ve good results for light hydrocarbons in addition to carbon dioxide and hy drogen sulfide, give widely different results for nitrogen and the heptane- plus pseudocomponent. Average absolute deviations in excess of 1000% were o bserved for nitrogen and in excess of 500% were observed for heptane-plus w hen current methods were used. The proposed new correlation improves signif icantly the average absolute deviation for both the heptane-plus Fraction a nd for nitrogen, in addition to improving relatively the average absolute d eviation for the C-1-C-6 hydrocarbons, H2S, and CO2. The average absolute d eviation for all components was reduced to 28.6% in the new correlation com pared to 240% for the Standing correlation and 156.8% for the Wilson correl ation. As a test for reliability of the new correlation, bubble point press ures were calculated for 10 samples. The average absolute error for the pro posed correlation was 5.2% compared with 6.9% for the Standing correlation, 16.1% for the Wilson correlation, and 7.3% for the Peng-Robinson equation of state. (C) 2000 Elsevier Science Ltd. All rights reserved.