Aiming at the problems of unclear flow field distribution characteristics in the wellbore during the bubble flow stage of the coalbed methane horizontal well section and unknown influence of the liquid retention effect, COMSOL Multiphysics software was applied to simulate the flow field distribution under four kinds of trajectory patterns of the horizontal section during the bubble flow state. This study analyzed the influence of the bubbles on the liquid flow under different conditions such as trajectory pattern of the horizontal well section and inclination angle, and optimized the trajectory of borehole of the horizontal section of the coalbed methane wells. The results show that with the increase of dip angle, the stagnation effect of bubbles on liquid is the largest in bow-type wells, followed by spoon-type wells and upward-dipping wells, and the influence of downward-dipping wells is the smallest. When the upward inclination angle of the coal seam is 8°-25°, the upward inclination type wellbore trajectory of 3°-7° is preferred; when the upward inclination angle of the coal seam is 0°-8°, the upward inclination type wellbore trajectory of 1°-4° is preferred; when the downward inclination angle of the coal seam is 0°-8°, the downward inclination type wellbore trajectory of 1°-4° is preferred. The research conclusions provide theoretical guidance for the optimal design of horizontal well section trajectories for coalbed methane.
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