In order to address the challenges of proppant transport and placement difficulties due to strong heterogeneity, complex stress-rock structure coupling, and tortuous fracture morphologies from circumventing/penetrating gravels in tight conglomerate reservoirs, as well as the inability of traditional smooth-plate models to reflect real fracture characteristics, an integrated approach combining digital fracture reconstruction via large-scale true triaxial tests, quantitative surface characterization, and a DEM-CFD fluid-solid coupling model was used to investigate the influence of gravel content, proppant combination schemes, and injection velocity on proppant migration and settling. The results show that gravel-induced fracture deflection/penetration significantly intensifies surface roughness, with the mean value increasing from 11.6 mm to 17.6 mm; although proppant coverage increases by 8.99% and sandbank height rises by 15.61 mm, it hinders distal migration and accelerates sedimentation. When injecting mixed particle sizes, smaller particles filling gaps between larger ones readily cause “bridging”, whereas a “smaller-first then larger” injection sequence optimizes filling and reduces sand-plugging risks. As injection velocity increases from 0.1 m/s to 0.4 m/s, the final proppant coverage decreases by up to 80.5% and sandbank height is reduced by 19.06 mm, while higher velocity extends particle travel distance, it deteriorates near-wellbore filling effectiveness. It is concluded that the established three-dimensional rough fracture reconstruction method and multi-factor coupled analysis model provide a theoretical foundation for optimizing fracturing parameters in conglomerate reservoirs, offering crucial guidance for enhancing short-term conductivity and practical engineering applications.