Rapid decomposition of methane hydrates induced by terahertz bidirectional pulse electric fields

Abstract

Electric field improving hydrates decomposition has broad applications in methane extraction and transportation, which benefits from polarization of water molecular and subsequent low energy cost. However, it is still challenging whether there are approaches to further accelerate decomposition of methane hydrates. Herein, molecular dynamics simulations are performed to investigate the effects of five electric fields on methane hydrates, including terahertz bidirectional pulsed electric field (BPEF), terahertz unidirectional pulsed electric field (PEF0.5), terahertz sinusoidal electric field (SEF), terahertz sinusoidal electric field with duty cycle of 50 % (SEF0.5) and static electric field (DC). We propose that BPEF, at amplitude of 0.06 V/Å and frequency of 18.5 THz, achieve highest efficiency in hydrate decomposition. The underlying mechanism is revealed to involve BPEF-induced structural phase transition of hydrate from crystalline to liquid due to resonance of electric field with vibration modes of water. Furthermore, Amplitudes of BPEF show positive correlation in promoting methane hydrate decomposition, while frequencies close to 1.8, 7.0 and 18.5 THz exhibit superior decomposition efficiency. Increasing amplitude from 0.12 to 0.16 at 1.8 THz accelerates the hydrate decomposition by 29-fold. These findings are expected to improve hydrate extraction and transportation and promote the application of terahertz electric field to hydrate domains.