On the development of a hydrate formation by thermal impact

This paper proposes a technological scheme and the corresponding theoretical model of the process of natural gas extraction from a formation completely saturated with hydrate under the thermal action. According to the accepted scheme, the producing wellbore is a system of coaxial cylindrical pipes. In the interpipe channel, the liquid heat-transfer agent, for instance, water, flows. The internal pipe channel is in flow communication with the formation which receives the gas generated by the decomposition of the hydrate. In the composition of the theoretical model, it is accepted that the decomposition of the hydrate occurs at the frontal boundary and the water generated at the hydrate decomposition is motionless. In addition to that, the hydraulic resistance of the hydrate skeleton–water system is ignored; i.e., the pressure between the wellbore's boundary and the decomposition front of the hydrate is uniform. This paper considers the mode of wellbore functioning when the pressure $P_{(\mathrm{w})}$, equal to the equilibrium value for the phase processes of the hydrate at the initial value of the temperature $T_0(P_{(\mathrm{w})} = P_{\mathrm{s}}(T_0))$ is maintained in the internal channel. The impact of the temperature of the heat-transfer agent and of the hydrate's saturation of the formation on the evolution of temperature fields, as well as on the propagation law of the frontal boundary of the thermal decomposition of the hydrate, is studied. The energy efficiency of the proposed method for extracting gas from a hydrate formation is analyzed.