Real-Time Estimation of Flow Rate in Dry Gas Wells – A New Field

Abstract

Abstract There are well-known correlations and technologies which estimate the flow rate in dry gas wells. Measuring the surface rate is challenging, especially when there is no measuring equipment. Nevertheless, the choke equation and some well-known correlations can provide an estimate of the flow rate whether the gas at the surface is single-phase or multi-phase but with a certain accuracy and basic assumptions. Another tool to estimate flow rate is the surface venturi meter, which is being used for dry gas wells. In this paper, a new method was established to calculate and verify measured gas flow rates. An empirical correlation was developed to calculate the real-time flow rate in dry gas wells at the surface utilizing the most appropriate parameters: upstream flowing wellhead pressure, downstream flowing wellhead pressure, upstream flowing wellhead temperature, and choke size. The proposed equation consists of a coefficient for each individual parameter which is fine-tuned in the equation using an advanced non-linear regression method. Moreover, a comparison between calculated rate using the new method and measured gas rate shows accurate values with an average absolute error of 11%. A comparison between the measured rate, Beggs equation, and Gilbert's correlation showed highly deviated values, with an average absolute error of 60% for Beggs's and more for Gilbert's. It is worth highlighting that there is a major difference between the new correlation and Beggs' equation or any other that the new correlation is customized for the selected field. Another difference that the new correlation uses real and field data whereas the Beggs's equation and Gilbert's correlation used experimental data which might not be applicable to the selected field. Hence, this correlation provides a matching trend to the measured flow rate from venturi readings in dry gas wells. The new correlation would enable production engineers to enhance their rate validity and furthermore it might replace the meter readings when the meter device become defective. Also, this correlation is aimed at calculating the gas flow rate in real-time measurements of wellhead parameters which enhances the monitoring of the well's performance on a real-time basis.