Micromechanical tangential force measurements between tetrahydrofuran hydrate particles.

• Tangential force between hydrate particles under different normal force, contact time and temperature are tested for the first time. • The results of tangential forces at macro and micro scales are compared. • Cohesion and friction Angle between hydrate particles are obtained. • The microscopic process of tangential failure between particles is observed and the failure mechanism is proposed. To reveal the mechanism of shear failure between gas hydrate particles can provide an important theoretical basis for controlling hydrate aggregation in oil and gas pipelines and for controlling sand production during gas production from natural gas hydrate reservoirs. Here we used a self-built micromechanical force test device to investigate the effects of normal forces, contact time, and temperature on tangential forces exerted between hydrate particles. The main controlling factors were analyzed according to the Mohr-Coulomb strength criterion. The test results show that the tangential force is proportional to the normal force and contact time, and that the temperature has a significant impact on the friction angle. Also, at a given temperature and for a short contact time (<30 s), the friction angle at the particle scale is very close to the friction angle measured by geotechnical tests at the macroscopic scale. Due to hydrate dissociation, the friction angle and cohesive force display the greatest variations around the phase-equilibrium temperature. In addition, possible tangential failure modes under various conditions are proposed to deeply reveal the mechanism of micro force between hydrate particles. [ABSTRACT FROM AUTHOR]