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From Microscale (400 μl) to Macroscale (425 L): Experimental Investigations of the CO 2 /N 2 ‐CH 4 Exchange in Gas Hydrates Simulating the Iġnik Sikumi Field Trial
Author(s) -
Schicks J. M.,
Strauch B.,
Heeschen K. U.,
Spangenberg E.,
LuziHelbing M.
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2017jb015315
Subject(s) - hydrate , clathrate hydrate , microscale chemistry , chemistry , dissociation (chemistry) , phase (matter) , mineralogy , thermodynamics , organic chemistry , physics , mathematics education , mathematics
Abstract In 2012 the production of CH 4 from hydrate‐bearing sediments via CO 2 injection was conducted in the framework of the Iġnik Sikumi Field Trial in Alaska, USA. In order to preserve the injectivity by avoiding a formation of CO 2 hydrate in the near‐well region, a mixture containing 77 mol% N 2 and 23 mol% CO 2 was chosen. The interpretation of the complex test results was difficult, and the nature of the interaction between the N 2 ‐CO 2 mixture and the initial CH 4 hydrate could not be clarified. In this study we present the results of our experimental investigations simulating the Iġnik Sikumi Field Trial at different scales. We conducted (1) in situ Raman spectroscopic investigations to study the exchange process of the guest molecules in the hydrate phase on a molecular level in a flow‐through pressure cell with a volume of 0.393 ml, (2) batch experiments with pure hydrates and hydrate‐bearing sediments in pressure cells with volumes of 420 ml, and (3) the injection of a CO 2 ‐N 2 mixture into a hydrate‐bearing sediment in a large‐scale reservoir simulator with a total volume of 425 L. The results indicate a dissociation of the initial CH 4 hydrate rather than an exchange reaction. The formation of a secondary mixed hydrate phase may occur, but this process strongly depends on the local composition of the gas phase and the pressure at given temperature.