Kinetic studies of the secondary hydrate formation in porous media based on experiments in a cubic hydrate simulator and a new kinetic model

The challenge of secondary hydrate formation (SHF) is frequently encountered in hydrate formation and dissociation experiments. However, there is currently a lack of modeling theory of SHF kinetics in the field and laboratory tests. In this work, the hydrate formation experiments concerning the SHF are carried out in a cubic hydrate simulator (CHS), where the pressure profiles and temperature spatial distributions are measured. A new kinetic model of hydrate formation integrating hydrate pore-scale morphology and SHF characteristics is developed. The newly developed model with unified kinetic parameters is employed in the Tough + hydrate (T + H) simulator to duplicate the experiment processes numerically, which achieves excellent agreement with the experimental data. The results show that the evolutions of the spatial distributions of the temperature and hydrate saturation behave in heterogeneous manners in the hydrate formation processes. This also reveals that the SHF can significantly exacerbate the hydrate heterogeneity in the CHS. Two additional experiments and comparisons with currently available models have validated the feasibility and accuracy of the new model. This work provides a reliable and adaptable model for describing the entire lifecycle of the hydrate formation kinetics in the porous media.