Microscale friction and interparticle bonding between hydrate and gravel-pack particles

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.