Study on the application and mechanism of enhanced methane recovery from hydrate

• Main Author: Shi, Meng
• Format: Book
• Language: English
• Published: Technical University of Denmark 2021
• Subjects: Methane hydrate
• Online Access: https://orbit.dtu.dk/en/publications/908fd970-76f8-4ca9-aec7-ef4a683f43f6; https://backend.orbit.dtu.dk/ws/files/262904175/thesis_Meng_Shi_updated_august21.pdf; https://backend.orbit.dtu.dk/ws/files/262904177/Errata_Meng_Shi.pdf

Energy is a key element for human survival and development. The current dominant primary energy sources worldwide are natural gas, oil, and coal, the supply of which is dwindling and causing environmental problems. Highly efficient and clean energy sources are of great importance for sustainable development. Natural gas hydrates, the main component of which is methane, have received growing attention in the global energy system due to their abundance in nature and CO 2 neutrality, if properly extracted with CO 2 injection, compared to conventional fossil fuels. Although discovered in 1883, extensive research was only initiated during the last 50 years by scientists from the micro to macro scales. Major gas hydrates exploitation methods include chemical injection, thermal stimulation, pressure reduction, and CO 2 replacement. Each method has advantages and disadvantages, but the depressurization and CO 2 replacement methods show relative superiority compared to the others. The combination of depressurization and CO 2 replacement shows a higher recovery rate and efficiency. At the present research stage, the replacement gas employed in the laboratory studies varies from pure CO2 (either in liquid or gaseous form) to simulated flue gas (a CO 2 and N 2 gas mixture). Limited studies on hydrate production with the injection of air, which is cheap and abundant, have been conducted. Many factors of the swapping recovery process have been considered, but the hydrate decomposition mechanism behind these factors is complex and challenging to elucidate. To investigate the effects of certain factors on the depressurization production process, three groups of spherical methane hydrate samples with variant diameters of 11mm, 17mm, and 22mm were prepared to simulate hydrate particles macroscopically. Each sample group has approximately the same overall volume of 8980 mm3. Hydrate decomposition starts with an initial pressure of 6.1 to 6.4 MPa and ends at a final constant pressure between 1.6 MPa and 2.4 MPa. The results show ...