Numerical analysis of microwave stimulation for enhancing energy recovery from depressurized methane hydrate sediments

• Main Authors: Wang, Bin, Dong, Hongsheng, Fan, Zhen, Liu, Shuyang, Lv, Xin, Li, Qingping, Zhao, Jiafei
• Format: Article in Journal/Newspaper
• Language: unknown
• Subjects: Methane hydrate
• Online Access: http://www.sciencedirect.com/science/article/pii/S0306261920300714

In addressing the global demand for clean and renewable energy, natural gas hydrate stands out as one of the most suitable alternative energy resources with great potential and has aroused intense research interest. In this study, a two-dimensional axisymmetric model was developed and validated to investigate the effect of microwave stimulation on energy recovery from depressurized methane hydrate sediments. Simulation results indicate that the microwave stimulation can provide timely and sufficient energy to promote the rapid and continuous hydrate dissociation. Discrepant energy absorption and conversion leads to a rapid hydrate dissociation rate in the upper region of the sediments. The increasing microwave radiation density accelerates the average gas production rate but weakens the energy efficiency ratio. For evaluating the effects of selected factors including initial conditions and sediment's physical properties on hydrate dissociation, an optimal value of microwave radiation density was determined by using the Pareto optimality criterion. Compared results of the energy efficiency reveal that the effect of microwave heating on the hydrate dissociation is advantageous in the sediments with the condition of high initial water and hydrate saturation, low specific heat capacity, high thermal conductivity, and low absolute permeability. Moreover, the intensity of thermal stimulation and the range of depressurization should be adjusted to be suitable for the reservoir conditions through considering the balance between the gas generation rate and the gas production rate. Although there are still many uncertainties in the hydrate dissociation behaviors, the findings of this study can provide some insights for evaluating and optimizing the methodology for gas recovery from gas hydrate reservoirs. Methane hydrate; Energy recovery; Pareto optimality; Microwave stimulation; Depressurization; Energy efficiency;