Numerical Simulation of Dufour and Soret Effects on Heat and Mass Transfer in Double-diffusive Convection in Methane Hydrate Reservoirs

In this paper, the behavior of methane-containing fluids in methane hydrate reservoirs is numerically simulated by investigating the transient thermal solute convection with the Dufour and Soret effects. A three-dimensional mathematical model is constructed by coupling the diffusion terms for the effects of temperature and concentration gradients, taking into account both the extended Darcy model and the thermal non-equilibrium model. The effects of different buoyancy ratios (N), Dufour factors (Du) and Soret factors (Sr), as well as porosity gradients, on double-diffusive convection in porous media are explored. The numerical results show that as N increases, the centrosymmetric flow structure is gradually destroyed. When the Du number is larger, the Sh number is inversely proportional to the Sr number, which may be due to the fact that the Dufour effect is more significant compared with the Soret effect. The smaller the porosity gradient, the concentration gradient decreases. As the pore spacing decreases, the Nu number and Sh number decrease by 6.74% and 8.51%, respectively.