One Dimensional Advancing Solidification Front in the Hydrate System

We use a simplified one dimensional model to study the advancing solidification front of a methane hydrate system fed by gas from below for a laboratory scale problem. We assume the system is initially fully saturated with water, no long range transport of salt by diffusion or advection, and equal density of hydrate and liquid. We express the velocity of the solidification front as a function of the gas supply rate when hydrate formation is not limited by formation kinetics. When the hydrate formation is only limited by formation kinetics, we express the velocity of the solidification front as a function of the methane consumption rate, which is described by an Arrhenius-type equation. By comparing these two types of advancing solidification fronts, we find that the advance of the solidification front will be limited by hydrate formation kinetics if the gas supply rate is greater than 0.2 kg m-2 hour-1. Our analysis is based on the porosity of 0.4, the permeability of 10-13 m2, the temperature of 5 oC, the pressure of 7 MPa and the salinity of 3.5 wt.%. For the same settings, if the gas supply rate is less than 0.2 kg m-2 hour-1, the advancing of the solidification front will be limited by methane advection. We also compare the velocity of the solidification front with the salt diffusion transport. We find that if the gas supply rate is greater than 0.002 kg m-2 hour-1, the advancing of the solidification front will not be influenced by salt diffusion.