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This paper attempts to disclose the law of critical gas velocity in the swirling flow field induced by the vortex tools. For this purpose, a critical gas velocity calculation model for vortex drainage gas wells was established based on the axial force balance between the liquid film and the gas core in swirling flow, and modified with the experimental data in previous studies. Then, the effects of helix angle and hub diameter of vortex tool on the reduction amplitude of critical gas velocity were analyzed by comparing the modified model with Turner model. Through experimental verification, it is learned that our new model can predict the critical gas velocity under different production conditions with different vortex tools. The reduction amplitude of critical gas velocity increased with the helix angle and decreased with the growth in hub diameter. The reduction amplitude ranged from 55.03% to 59.35% as the helix angle varied from 15 ° to 75 ° and the hub diameter varied from 34mm to 50 mm. The helix angle has a greater impact than the hub diameter on the reduction amplitude. The research findings shed new light on the design and application of the vortex tools. [ABSTRACT FROM AUTHOR]

The Mukherjee-Brill prediction model of pressure gradient is the common calculation model in oil-gas field development. The laboratory experimental results of multiphase flow show that the average prediction relative error is 35% and the maximum relative error reaches 72%. By comparing the prediction residual of the Mukherjee-Brill model with the test condition parameters, this paper suggests that the predicted residual of Mukherjee-Brill model has a close relationship with the gas-liquid ratio and has no clear correlation with the water content of fluid when the volume flow rate of liquid is constant. This paper first builds a cubic regression model of the prediction residual of the Mukherjee-Brill model regarding the gas-liquid ratio, and subsequently, combining the cubic regression model with the Mukherjee-Brill model, builds a new prediction model of pressure gradient, the MBM model. The results for 90 test groups show that the average prediction relative error of the MBM model is reduced to 7.66%. The MBM model improves the prediction accuracy of the pressure gradient for multiphase flow, and assists in advancing the reliability of the design and analysis of oil and gas wells. [ABSTRACT FROM AUTHOR]