Gravel packing is an effective completion technique to meet sand-control and productivity-enhancement needs of natural gas hydrate reservoirs. Friction at gravel-gravel interfaces and their bonding with hydrates directly affect the packing process and the mechanical properties of the gravel-pack structure. However, particle-scale studies that systematically clarify the mechanisms of friction and bonding between hydrates and packing gravel are still lacking, and quantitative characterization of inter-particle micro-forces under the coupled effects of “wetting-temperature-contact type” remains insufficient. In this study, a customized high-precision micro-force testing apparatus, combined with in-situ high-resolution microscopic observation, was employed to investigate inter-particle interactions at the single-particle contact scale. Three wetting states-dry, partially wetted, and fully wetted-and multiple contact configurations, including bare contact, ice-coated contact, and hydrate-coated contact, were clearly distinguished. The friction coefficients and bond strengths among tetrahydrofuran (THF) hydrate, ice, and gravel particles were systematically measured. The results show that: (1) THF-hydrate particles exhibit overall higher friction coefficients than ice, primarily due to their roher surfaces and the higher propensity for brittle micro-fracture during sliding; (2) interfacial friction varies nonlinearly with water content: compared to dry particle contacts, a modest amount of liquid water reduces the friction coefficient due to thin-film lubrication, whereas excess water increases the friction coefficient again through viscosity and capillary-bridge effects; when gravel is coated by ice or hydrate, the friction coefficient decreases markedly; (3) at low temperatures, pronounced bonding occurs at both hydrate-gravel and ice-gravel interfaces, with failure dominated by interfacial brittle fracture, indicating that rupture preferentially occurs at the particle-hydrate interface rather than within the hydrate itself. These particle-scale findings elucidate how wetting, temperature, and contact configuration govern friction coefficient and bond strength among hydrates, ice, and gravel, and they provide a basis for parameterized modeling of gravel-packing operations and for reliability assessment in sand control and productivity enhancement.

Cross-scale studies in geomechanical and hydrological systems employ a variety of approaches, either experimental, simulation or theoretical, each characterized by corresponding scale-specific methodologies. This perspective identifies and discusses challenges encountered at various scales, ranging from molecular to field scale, and examines issues related to integrating these scales. It highlights discrepancies in resolution and data compatibility, emphasizing the necessity for improved scale transition techniques. Insights and recommendations are proposed for future research to enhance multiscale modeling frameworks. These suggestions are crucial for bridging knowledge gaps on geological systems and improving the analyses accuracy for better engineering applications or earth system modelling.