(187o) Modeling the Decomposition Kinetics of the Gas Hydrates in Porous Medium

The hydrates present in the onshore and offshore reservoirs are the potential source of the natural gas for the future energy demand. Destabilizing these hydrates by the thermal stimulation, depressurization and inhibitor injection lead to recovering the entrapped natural gas. To extract the natural gas at a commercial scale, one needs to model the complex decomposition kinetics of the gas hydrates. In this view, we propose a rigorous kinetic model that can predict the methane gas recovery during the hydrate dissociation in the presence of a porous medium. This framework consists of a novel driving force (i.e., the difference in chemical potentials of water in the hydrate and liquid phase) and the reasonable reaction interface area (i.e., the effective surface area of the porous medium). In estimating the chemical potential of water in hydrate phase, we have used a rigorous approach^[1] that incorporates the effect of movement of water molecules of the hydrate lattice, the guest-water interaction beyond first shell and the guest-guest interactions. Optimal values of the process parameters are determined by applying the generalized reduced gradient nonlinear optimization technique. The predictions from the proposed simulator are compared with the experimental^[2] methane recovery in three systems that differ by the amount of silica sand and the operating temperature of the dissociation process. For the concerned situations, the proposed model has predicted the methane gas recovery with the absolute average relative deviation (AARD) in the range of 4.83-6.50%. This formulation can be significant to interpret the production potential of the natural gas hydrates present in the unconsolidated sand reservoirs.

References

[1] Ravipati S. and Punnathanam S. N. Improving the rigor and consistency of the thermodynamic theory for clathrate hydrates through incorporation of movement of water molecules of hydrate lattice. The Journal of Physical Chemistry C 119(22) (2015) 12365-12377.

[2] Linga P., Haligva C., Nam S. C., Ripmeester, J. A., Englezos P. Recovery of methane from hydrate formed in a variable volume bed of silica sand particles. Energy & Fuels 23(11) (2009) 5508-5516.