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

TL;DR

This paper develops an analytical radial model to study methane hydrate dissociation during thermal stimulation, analyzing temperature, pressure, and gas production considering wellbore structure and heat source types.

Contribution

It introduces a novel analytical model incorporating wellbore effects and compares different heat source configurations for methane hydrate dissociation.

Findings

Higher dissociation rates with line heat source compared to wellbore heating.

Increasing heat source temperature or decreasing pressure boosts gas production.

Dissociation rate correlates with porosity and thermal properties, but not permeability.

Abstract

In this study, a radial analytical model for methane hydrate dissociation upon thermal stimulation in porous media considering the effect of wellbore structure has been developed. The analytical approach is based on a similarity solution employing a moving boundary separating the dissociated and undissociated zones. Two different heat sources are considered: i) line heat source; and ii) wellbore heat source with specific thickness consisting of casing, gravel, and cement. The temperature and pressure distributions, dissociation rate, and energy efficiency considering various initial and boundary conditions, and reservoir properties are investigated. Direct heat transfer from the heat source to the reservoir without considering the heat conduction in the wellbore thickness causes higher the dissociation rate and gas production in the line heat source model compared to the wellbore heating model. Increasing the heat source temperature or decreasing its pressure increases gas production. However, employing them simultaneously results in greater gas production but reduces energy efficiency. The dissociation rate has direct relation with porosity, thermal diffusivities, and thermal conductivities of the reservoir, but is not dependent on the reservoirs permeability.