The measurement of flowing bottom-hole pressures in gas wells is a frequently incurred and costly operation in natural gas production. The calculation of this pressure from surface data is complex involving a trial and error solution of Bernoulli's differential equation. A number of methods have been used previously for this solution - usually requiring computer methods. A new procedure for calculating flowing bottom-hole pressures using only simple algebraic equations has been developed.

The new procedure uses factorial design analysis from statistical experimental theory to determine the parameters in an algebraic equation which best fit the "experimental" data for the bottom-hole pressures for a given field. However, instead of actual field data, bottom hole pressures are calculated with a computer using any of several methods (Aziz, Cullender-Smith, Gray, etc.). These calculated "experimental" values are used to determine an algebraic equation which best fits the data. The day-to-day use of the resulting algebraic equation is very simple and can be performed by field personnel using a hand-held calculator for any wellhead pressure for the particular field.

Actual flowing bottom-hole pressure measurements for three gas fields containing 55 wells were used to test the accuracy of the procedure developed. Corrections for condensate flow and sour gas components were required in the calculations. The calculated bottom-hole pressures agreed with measured ones with an average absolute accuracy of 1.9%.

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