This paper presents evaluation of compressibility factor correlations for the Niger Delta gas reservoirs. The correlations were evaluated using three principal methods. First, the use of statistical analysis - mean relative error, mean absolute error, standard deviation of the mean relative error and absolute error as well as the coefficient of correlation were computed. Secondly, these statistical parameters were combined into a single parameter called rank using the Multiple Statistical Optimization Model (MULSOM). Finally, performance plots of the experimental and estimated values of the compressibility factors were made to serve as a confirmation of the results of the statistical and ranking methods. The database consists of 513 data points obtained from Niger Delta gas reservoirs. The Z-factors evaluated are in the ranges of reduced temperature and pressure of 0.5796≤Tr≤1.758 and 0.410≤Pr≤8.985 respectively. The Carr-Kobayashi-Burrows correction for the presence of CO2 and N2 was used. The best correlation for the Niger Delta natural gas is Brill and Beggs. It has a rank of 2.82, a percentage absolute error (Ea) of 3.234 and the best performance plot. Brill and Beggs is recommended to be used in situations where laboratory PVT data of natural gas compressibility factor is not available for the Niger Delta gas reservoirs as well as other regions of the world where the gas composition is similar to that of the Niger Delta .
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