Application of numerical, experimental and life cycle assessment methods to the investigation of natural gas production from methane hydrate deposits using carbon dioxide clathrate sequestration.

摘要

Natural gas hydrates, commonly called methane (CH4 ) hydrates, are ice-like materials belonging to the family of clathrates that form at low temperature and high pressure. They can be found in permafrost and oceanic environments. The amount of natural gas trapped into worldwide hydrate deposits has been estimated at 18000 trillion m3 of methane [1] and it surpasses the world natural gas proven reserves (180 trillion m3 [2]) by two orders of magnitude. Fossil fuel based energy is still a major source of carbon dioxide (CO2) emissions. Hence, it contributes greatly to the issues of global warming and climate change. Geological sequestration of carbon dioxide appears as the safest and most stable way to reduce such emissions for it involves CO2 entrapment into hydrocarbon reservoirs and aquifers. Indeed, CO2 can also be sequestered as hydrates while assisting in the dissociation of in-situ methane hydrates. This approach could help mitigate the emissions of CO 2 in the atmosphere and improve the economics of carbon dioxide sequestration and natural gas production from hydrate deposits. The proposed research focused on investigating the feasibility of the CO2-CH4 exchange in hydrates as a gas hydrate mining method through experimental studies and numerical modeling of the exchange, as well as the application of a life-cycle assessment (LCA) approach to the evaluation of CO2 emissions resulting from the use of the replacement technique. Under the limitations of our numerical model and experiments, we were able to establish the influence of initial reservoir temperature and pressure on the performance of the exchange. We also noticed the influence of the presence of excess water during the exchange. These observations have been confirmed in the relevant literature. The application of the life cycle assessment method to the process of gas production from a hypothetical hydrate reservoir allowed us to highlight conditions where the use of the exchange technique could lead to emission-neutral gas extraction from methane hydrate deposits.