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In the previously published studies, the calculations of critical liquid-carrying gas velocity in a horizontal well were based on conventional calculation models of a droplet in a vertical well and do not consider the influence of the inclination angle of the well on the liquid-carrying ability of gas. Horizontal wells are currently widely used in the gas fields, while the traditional critical liquid-carrying velocity models cannot be applied to evaluate gas flow characteristics in the inclined sections of horizontal wells. In this paper, based on experimental results, we established that the critical liquid-carrying conditions in an inclined well occur when the inclination angle is 55°. Considering the flow characteristics of the liquid phase in a gas well, we obtained the flow mode of the liquid film in the pipeline. The established liquid-film model provides a calculation method of the critical liquid-carrying velocity for different inclination angles. The accuracy of the new method has been verified by the field data. [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]