A practical pressure drop calculation method for pipe flow in gas wells with high gas-liquid ratios

The resistance coefficient method is one of the most simple and practical methods among multiple models calculating the pressure drop of two-phase flow in gas wells. However, the traditional resistance coefficient charts are mostly proposed for oil wells, only applicable to such wells with relatively low gas-liquid ratio. Besides, most coordinates in the charts are in inconvenient imperial units. In view of this, based on the data from 66 gas wells in south Sichuan and Ordos basins with the gas-liquid ratio ranging from 480 to 344, 360 m3/m3, a dimensionless resistance coefficient chart is developed as follows for such gas wells with high gas-liquid ratios. First, non-slip liquid holdup was adopted, and the resistance coefficient of each tested point was calculated according to site tested data based on the multi-phase flow pressure gradient equation. Second, a dimensionless two-phase Reynolds number was introduced and the relation schema was drawn between the resistance coefficient and two-phase Reynolds number. The two-phase Reynolds number was a function of the gas-liquid Reynolds number and the gas-liquid mass ratio. Finally, upon multiple regression trials for the two-phase Reynolds number of the above relation schema, the number to a function with three correction factors was corrected, thus a new resistance coefficient chart was obtained with favorable fitting. The evaluation was conducted on the pressure drop data of 50 gas wells from open literatures, and the results showed that the flow pressure calculated with the proposed method has an average relative error of only 2.48%, and an average absolute error of only 5.37%, fully satisfying the engineering requirements.