Investigations on a controlled microwave heating technique for efficient depressurization in methane hydrate reservoirs

Abstract

Numerical investigations on a novel technique of controlled microwave heating with depressurization, applied to gas recovery from methane hydrate reservoirs are performed. An in house, multi-phase, multi-component fluid flow solver with microwave radiation is developed and validated with benchmark results in literature. The microwave heating in the reservoir is operated and controlled based on the rise and fall of temperature in the well-bore proximity. Results show that the proposed microwave control technique significantly improves the gas recovery and energy output of combined depressurization and microwave heating. The performance parameters such as total gas recovery and energy efficiency ratio of the controlled microwave heating technique are compared with pure depressurization, depressurization with continuous heating, and pure heating techniques. The proposed control method provides high overall energy efficiency than all other production techniques. Based on the pareto optimization strategy using fuzzy membership function, an optimum well-bore temperature bound for control of microwave operation is determined. The sensitivity study of the process inputs reveals that at the optimum temperature bound, the energy efficiency ratio of the controlled microwave heating becomes independent of the microwave power. The depressurization pressure differential has a linear impact on the energy efficiency ratio of the controlled microwave heating, while a microwave with 915 MHz frequency is seen to provide the maximum energy efficiency ratio.

Keywords

• Microwave heating
• Energy efficiency
• Control methods
• Numerical modelling
• Optimization
• Gas hydrate