Heat Transfer Analysis of Methane Hydrate Sediment Dissociation in a Closed Reactor by a Thermal Method

Abstract

Abstract:The heat transfer analysis of hydrate-bearing sediment involved phase changes is one of the key requirements of gas hydrate exploitation techniques. In this paper, experiments were conducted to examine the heat transfer performance during hydrate formation and dissociation by a thermal method using a 5L volume reactor. This study simulated porous media by using glass beads of uniform size. Sixteen platinum resistance thermometers were placed in different position in the reactor to monitor the temperature differences of the hydrate in porous media. The influence of production temperature on the production time was also investigated. Experimental results show that there is a delay when hydrate decomposed in the radial direction and there are three stages in the dissociation period which is influenced by the rate of hydrate dissociation and the heat flow of the reactor. A significant temperature difference along the radial direction of the reactor was obtained when the hydrate dissociates and this phenomenon could be enhanced by raising the production temperature. In addition, hydrate dissociates homogeneously and the temperature difference is much smaller than the other conditions when the production temperature is around the 10 °C. With the increase of the production temperature, the maximum of ΔT oi grows until the temperature reaches 40 °C. The period of ΔT oi have a close relation with the total time of hydrate dissociation. Especially, the period of ΔT oi with production temperature of 10 °C is twice as much as that at other temperatures. Under OPEN ACCESSEnergies 2012, 5 1293 these experimental conditions, the heat is mainly transferred by conduction from the dissociated zone to the dissociating zone and the production temperature has little effect on the convection of the water in the porous media.

Review of natural gas hydrates as an energy resource: Prospects and challenges

“…The heat transfer aspect of thermal stimulation was investigated in one study by measuring the temperature difference between two points at different radial position, DT oi [105]. Heat was supplied and controlled by water bath within a range of temperatures from 10°C to 40°C.…”

Hydrate Formation/Dissociation in (Natural Gas + Water + Diesel Oil) Emulsion Systems

“…The formation and dissociation of hydrates in pure water or porous media system are widely reported [9][10][11][12]. However, the situations in emulsion systems are somewhat different for that of pure water systems or porous media systems, where gas first needs to transfer through the oil phase and then reach the water surface to form a hydrate.…”

Numerical Simulation of the Depressurization Process of a Natural Gas Hydrate Reservoir: An Attempt at Optimization of Field Operational Factors with Multiple Wells in a Real 3D Geological Model

“…The hydration process in Equation (1) has also been thoroughly studied in the past few years as a promising method to separate methane from gaseous mixtures [8][9][10][11]. Recently, several ways of developing hydrate reservoirs ( Figure 2) have been put forward, including thermal stimulation [12][13][14], injection of hot brine, steam or hot water to heat the hydrate reservoir to exceed the dissociation temperature; depressurization [15][16][17], to lower the original pressure of hydrate reservoir under the dissociation pressure at a specific temperature; thermodynamic inhibitor injection [18,19], to change the hydrate pressure-temperature equilibrium conditions by injecting chemicals, such as alcohols and salts; and CO 2 exchange which is most promising method to reduce the emissions of greenhouse gases [20,21]. Figure 3 indicates the former three methods presented above are based on the mechanism that changes the pressure or temperature condition to destroy the stability of the original equilibrium of the hydrate deposit, resulting in its dissociation and the production of methane.…”