Proppant Flowback Behaviors in the Deep Coalbed Methane Wells Completed in the Ordos Basin

This study investigates proppant flowback using field data, numerical simulations, and machine learning for deep coalbed methane (CBM) wells in the Linxing–Shenfu Block, Ordos Basin. Field data show that most proppant production occurs during the early flowback stage, and progressive choke opening under remaining wellhead pressure creates a high-risk operating window. We conducted computational fluid dynamics–discrete element method (CFD-DEM) simulations to examine the physics of proppant transport at the particle scale for representative wells. CFD-DEM simulations show that particles first mobilize near the outlet and then form a preferential flowback channel. Higher fluid velocity and wider fractures promote proppant flowback. Larger particles, higher effective closure stress, greater fracture roughness, and deeper embedment improve pack stability. We also trained machine-learning models with field data to predict proppant flowback risk. The models achieved high predictive accuracy. Also, the models captured field-scale flowback risk and identified well type, startup pressure, formation thickness, pressure decline, and choke variation as important predictors for proppant flowback. The findings improve the understanding of proppant flowback mechanisms in deep-CBM wells and provide practical guidance for choke management, flowback optimization, and proppant flowback prevention in target fields.