Naturally Occurring Hydrate Formation and Dissociation in Marine Sediment: Experimental Validation

Fundamental understanding of gas hydrate as a natural storehouse of carbon and a potential energy resource found in permafrost layers and marine sediments is crucial in extracting hydrocarbon fuel from hydrate reservoirs. With this, a theoretical framework is grounded involving the complicated physics of naturally occurring hydrate formation and dissociation with pure and mixed guest gases in the unconsolidated silica sand and seawater. The proposed formulation addresses various practical concerns, including the collective influence of pure water, salt ion, and porous medium; surface renewal at the interface between bulk guest and aqueous phase; pore irregularity in heterogeneous porous materials; hydrate growth and decay in those nanometer-sized pores along with interstitial spaces; and influence of surface tension, among others. To show its versatility, the dynamic model framework is tested under various experimental conditions that mimic the actual field conditions in terms of the type of guest gases (i.e., methane, and pure and mixed carbon dioxide); the concentration of salt ions in the liquid phase; the size, shape, and amount of porous silica sand; and the operating temperature and pressure. Under every aforementioned condition, the proposed model outperforms the existing models, which is quantified in terms of the percentage of average absolute relative deviation (AARD). For gas hydrate formation cases, the proposed model keeps AARD in the range of 1.23-9.57%, which is 5.46-19.58% for the existing models. On the other hand, for gas hydrate decomposition, the AARD of the proposed formulation varies from 2.73 to 9.78%, which is reasonably high (11.89-22.26%) for the existing model.

Automated summary

The theoretical framework for gas hydrate research plays a crucial role in extracting hydrocarbon fuel, involving complex physics of hydrate formation and dissociation. The proposed model outperforms existing models under various experimental conditions, with lower average absolute relative deviation percentages.