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

Abstract

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.

Modeling Gas Hydrate Dynamics: Experimental Validation and Evolutionary Algorithm-Based Optimization

“…The experiments are carried out in 645.16 g of silica sand where the particle diameter varies from 100 to 500 Figure 9a is produced for decomposition dynamics in pure water at 287.15 K and 2.2 MPa, and Figure 9b is produced for dynamics in 3 wt % of saline seawater at 279.7 K and 2.2 MPa. It is quite obvious from Figure 9a that the predictions of the carbon dioxide gas recovery made by the proposed formulation with a decomposition reaction of 14.4093 order (3.9511% AARD) are exceedingly better than those made by the model of Palodkar and Jana 28 (5.4762% AARD) with the decomposition reaction of first order. Moreover, the noteworthiness of NSGA-II gets proved in models of gas hydrate decomposition as well, since AARD of the model of Palodkar and Jana 28 significantly reduces from a literature-reported value of 9.42% to the value of 5.4762% (Table 3).…”

“…The optimal parameters estimated using the population-based strategy of NSGA-II are given in Table S5 of the Supporting Information. 28 is first done to examine the decomposition of pure CO 2 hydrates in pure water and seawater (3 wt % salinity) for CO 2 gas recovery, where hydrate decomposition is achieved through depressurization followed by thermal stimulation. The experiments are carried out in 645.16 g of silica sand where the particle diameter varies from 100 to 500 Figure 9a is produced for decomposition dynamics in pure water at 287.15 K and 2.2 MPa, and Figure 9b is produced for dynamics in 3 wt % of saline seawater at 279.7 K and 2.2 MPa.…”

“…This experiment is conducted at 284.15 K and 7.5 MPa in pure water and in the porous environment of 645.16 g of silica sand having particle diameters in the range of 150−630 μm. Figure 9c compares the performance of the proposed nth order model and the model of Palodkar and Jana 28 with respect to the experimental gas recovery. 56 The proposed model performs comparatively better than the model of Palodkar and Jana 28 with an AARD of 2.4705%, where the order of the decomposition reaction is 0.8417.…”

“…24,25 To account for the effects of temperature, pressure, and composition, Palodkar et al 26 established an intrinsic kinetic model defining the difference in the chemical potential of water between the filled hydrate and liquid phase as the driving force for determining the formation dynamics of carbon dioxide hydrates in porous media and pure water. Palodkar and Jana 27,28 subsequently modified this model of Palodkar et al 26 to analyze the formation and dissociation kinetics of methane, carbon dioxide, and mixtures of carbon dioxide hydrates in porous media and saline environment, incorporating a couple of practical aspects involved during the formation and dissociation process of gas hydrates in offshore sediments.…”

Review of Gas Hydrate Research in India: Status and Future Directions

“…Palodkar and Jana presented a theoretical formulation combining kinetic and thermodynamic aspects of gas hydrates during their formation, growth, and dissociation in a marine sediment environment. Through this formulation, they tried to address the collective influence of water, salt ion, and porous medium, irregularity of pores in the heterogeneous porous material, surface renewal at the interface between guest and aqueous phase, surface tension, hydrate growth, and dissociation in confined nanopores.…”