Analytical modeling of methane hydrate dissociation under thermal stimulation

Abstract

In this study, a one-dimensional analytical model to describe heat and mass transfer during methane hydrate dissociation under thermal stimulation in porous media has been developed. The model is based on a similarity solution that considers a moving dissociation boundary which separates the dissociated zone containing produced gas and water from the un-dissociated zone containing only methane hydrate. The results of temperature distribution, pressure distribution, energy efficiency, and parametric study considering various initial and boundary conditions as well as various reservoir properties are presented and compared with previous studies. Sensitivity analysis of gas production on reservoir properties is also presented in this paper. The dissociation boundary moves faster by increasing the heat source temperature while decreasing the heat source pressure simultaneously, but the associated energy efficiency decreases. Increasing the well thickness has a negative effect on the energy efficiency of the process. Among the proposed thermal properties of the system, only the thermal diffusivities and conductivites of the reservoir as well as the porosity of the sediment affect the dissociation. The main contribution of this work is investigating analytically the hydrate dissociation using thermal stimulation by taking into account the effect of wellbore thickness and structure.

Analytical investigation of gas production from methane hydrates and the associated heat and mass transfer upon thermal stimulation employing a coaxial wellbore

“…These results are in line with those reported by Roostaie and Leonenko [79], mainly because the temperature at the wellbore was not constant in their work due to the heat conduction through the wellbore structure. In accordance with the present results, a study by Tsimpanogiannis and Lichtner [29], who built a semi-analytical model for hydrate dissociation, demonstrated that increasing the temperature of the wellbore raised the pressure at the interface.…”

“…Selim and Sloan [62] and Roostaie and Leonenko [79] performed a similar parametric study and reported similar results for the rate of dissociation (Figure 8). Zhao et al [117] mathematically showed that increasing the thermal conductivity had a direct positive effect on a dissociation process based on thermal stimulation.…”

“…These results are consistent with those of the previous work by Selim and Sloan [62] with the same trend, but (approximately 66%). These differences may be due to the following reasons: i) Selim and Sloan [62] considered a 1D flat heat source without wellbore thickness was considered; and ii) both of the previous works [62,79] Furthermore, the locus at which the dissociation temperature is equal to 280 K (MH equilibrium temperature) is also shown on Figure 4. At the points on the left and right sides of this locus, the dissociation temperature decreases and increases, respectively.…”

“…However, no analytical study has considered the effect of wellbore geometry and associated structure-generally consisting of casing, cement, and gravel [73][74][75]-and wellbore heating (i.e., heat pump) on MH dissociation upon thermal stimulation so far [58,[76][77][78]. Recently, Roostaie and Leonenko et al [79] designed an analytical semi-infinite 1D model and addressed this gap of knowledge. Their results, which were verified against previous numerical and experimental works, showed that the wellbore structure (casing, gravel, and cement) affects the dissociation upon thermal stimulation.…”

Gas production from methane hydrates upon thermal stimulation; an analytical study employing radial coordinates

“…The analytical works conducted about the hydrate dissociation to present [47,[49][50][51] have not considered the impact of wellbore geometry and the associated structure (i.e., wellbore radius and the associated outer layers) on MH dissociation upon thermal stimulation by wellbore heating, which might induce unreliability while comparing to experiments or field works. Recently, Roostaie and Leonenko [52] mathematically overcame this gap of knowledge and showed that the wellbore structure, consisting of layers: casing, gravel, and cement, can also affect the interactions in the reservoir and the efficiency of the process upon thermal stimulation. They designed an analytical semi-infinite 1D model and verified it against previous numerical and experimental works.…”