Natural Gas Compressibility Factor Correlation Evaluation for Niger Delta Gas Fields

Natural gas compressibility factor (Z) is key factor in gas industry for natural gas production and transportation.This research presents a new natural gas compressibility factor correlation for Niger Delta gas fields.First, gas properties databank was developed from twenty-two (22) laboratory Gas PVT Reports from Niger Delta gas fields.Secondly, the existing natural gas compressibility factor correlations were evaluated against the developed database (comprising 22 gas reservoirs and 223 data sets).The developed new correlation was used to compute the z-factors for the four natural gas reservoir system of dry gas, solution gas, rich CO 2 gas and rich condensate gas reservoirs, and the results were compared with some exiting correlations.The performances of the developed correction indicated better statistical ranking, good graph trends and best crossplots parity line when compared with correlations evaluated.From the results the new developed correlation has the least standard error and absolute error of (stdEr) of 1.461% and 1.669% for dry gas; 6.661% and 1.674% for solution; 7.758% and 6.660% for rich CO 2 and 7.668% and 6.661 % for rich condensate gas reservoirs.The new correlation also show high correlation coefficient of: 93.39%, for dry gas; 89.24% for solution gas; 83.56% for rich CO 2 and 83.34% for rich Condensate gas reservoirs.Also the proposed new model maintained good graphical trends for four z-factors matched it: experimental, estimated (Standing -Katz) and the best evaluated correlation when matched.Very good crossplots parity line performance when compared with the evaluated correlations.It could then be concluded that the new developed correlation and that of Papay correlation are most appropriate correlations for calculating natural compressibility for Niger Delta gas fields.Carr, Kobayashi, and Burrows (1954) and Wichert-Aziz (1972), correction factor methods; were applied to correct the presence of non-hydrocarbons.But the major setbacks on laboratory analyses for PVT behavior are sometimes expensive and time consuming.Correlations, which are used to predict gas compressibility factor, are much easier and faster than equations of state, invariably save cost.