Numerical simulation of gravel packing in multi-branch horizontal wells in hydrate reservoirs based on CFD-DEM coupling

The current single-wellbore gravel packing completion method for hydrate production is limited by its narrow pressure reduction range, leading to reduced production capacity in later stages. To address this, the "branch horizontal well completion with full-wellbore gravel packing and sand control" method has been proposed to significantly expand the pressure reduction range and enhance natural gas production. However, there is a lack of comprehensive studies on gravel packing in branch horizontal wells, the construction design for gravel packing and sand control in branch horizontal wells lacks a solid theoretical foundation. In this study, we establish a CFD-DEM coupled model to simulate gravel packing in single and multi-branch horizontal wellbores, accurately capturing particle movement. We investigate the effects of injection rate, gravel concentration, branch wellbore length, and branch wellbore angle on gravel packing efficiency. The five distinct stages of gravel packing in branch horizontal wells are elucidated. Results indicate that increasing the fluid injection rate, reducing sand concentration, and decreasing both the length and angle of the branch wellbore can significantly improve the packing efficiency. Notably, the filling ratio in the branch wellbore at an angle of 15° was 11.42% higher than that at 30°; As the length of the branch wellbore increases from 1m to 2m, the filling ratio of the branch wellbore decreases significantly. We recommend utilizing a high injection rate (0.6 m³/min), low gravel concentration (3%) to optimize the filling ratio and compaction in both the main and branch wellbores.