Energy-efficient natural gas hydrate production using gas exchange

Breaking the bounds of classical natural gas hydrate (NGH) production processes, a newborn concept based on the gas exchange mechanism provides an opportunity to catch two birds with one stone: simultaneously achieving the sequestration of CO2 for climate change mitigation and the enhanced recovery of CH4 for energy production. As a 'new paradigm' in NGH production schemes, the non-destructive gas exchange as one of the most stable and promising NGH recovery approaches has received much attention in the fields of physics, chemistry, chemical engineering, civil engineering, petroleum engineering and geology. In this review, we assess the state-of-the-art gas exchange concept for NGH production by understanding its principles and developments, with emphasis on another technical breakthrough using the CO2 + N-2 gas mixture injection. After establishing the fundamentals of the gas exchange process, we make a general survey of the NGH field production in the North Slope of Alaska in 2012, which practically adopted the gas exchange as a key technology. Several recent international NGH field production tests that basically use depressurization are also briefly analyzed for comparison. We suggest that the gas exchange method is ready to be tested in the NGH deposits with the valuable lessons learned from past pioneering tests. (C) 2015 Elsevier Ltd. All rights reserved.