Large scale reactor details and results for the formation and decomposition of methane hydrates via thermal stimulation dissociation

An in-situ heating method to efficiently produce methane gas from hydrates was recently developed. It is a modification of the thermal stimulation method using a down-hole combustion technique, to more efficiently bring necessary heat to the desired location within the reservoir. To test the concept of methane production via in-situ heating and characterize other alternative production methods, a 701 reactor vessel has been designed, manufactured and assembled to simulate relevant field environments. Tests show that the reactor satisfies the conditions for both methane and carbon dioxide hydrate formation. During the tests hydrate was formed at 2.2 degrees C and 4.2 MPa using 99.97% pure methane gas and deionized water in unconsolidated porous quartz sand pack. Heating tests at 100 W resulted in a peak production rate of 1.5 standard liters per minute (slpm) of methane gas, resulting in the dissociation of 35% of total hydrate in the system. A thermal energy efficiency of 72% was calculated based on net thermal heat input and the total heating value of the methane produced during a 10 h test period. Based on mass balance and calculations using the Peng-Robinson EOS it was calculated that hydrate saturations of 4.5, 10.2, 21 and 33% were produced prior to heating tests. Phase equilibrium data is presented for mixed gas hydrates formed from a 50:50 mol fraction mixture of CO2:CH4. Measurements and simulations suggest that hydrate began forming at the top section of the reactor initially, and continued to form downwards within the sediment in a non-homogeneous manner. (C) 2012 Elsevier B.V. All rights reserved.