  In this study, a radial 2D analytical approach has been developed to couple
the wellbore heating process and the associated methane hydrate dissociation in
the reservoir. A coaxial wellbore is assumed as the heat source where both
conduction and convection heat transfers are considered. It consists of an
inner tube and an outer structure of casing, gravel, and cement layers. In the
reservoir, a similarity solution employing a moving boundary separating the
dissociated and undissociated zones is employed to build the analytical
solution. Two different operating schemes for water supply into wellbore heat
source have been studied: i) from the inner tube; and ii) from the annulus
section of the wellbore. Temperature distribution along the wellbore,
temperature and pressure distributions in the reservoir, hydrate dissociation
rate, and energy efficiency considering various initial and boundary conditions
and reservoir properties are evaluated. The two different operating schemes
have almost the same results with slightly higher gas production in the case of
hot water entry into annulus, which is in direct contact with the reservoir.
Increasing the inlet water temperature or decreasing the wellbore pressure
increases gas production. Applying them simultaneously results in a greater gas
production and energy efficiency. Some of the reservoir's properties, such as
porosity, thermal diffusivity, thermal conductivity, and reservoir thickness,
have direct relation with the dissociation rate, but the reservoir's
permeability and gas viscosity have almost no impact on the process. The
wellbore parameters, such as flow rate of hot water, inlet temperature, and
wellbore radius except the inner tube radius, have direct impact on the
wellbore mean temperature and the associated results in the dissociation
process.
