New insights into the dissociation of mixed CH4/CO2 hydrates for CH4 production and CO2 storage

Jyoti Shanker Pandey*, Qian Ouyang, Nicolas von Solms*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Recent but limited studies have shown that multistep slow depressurization based on mixed CH4/CO2 hydrate dissociation can enhance CH4 recovery and increases CO2 storage after CO2 injection into CHhydrate [1], [2]. For the first time, the resistivity variation and gas recovery and storage variation was investigated to study the change in hydrate saturation and production/storage yield. Lab-scale CH4 and CO2 rich mixed hydrates were synthesized to mimic the production and injection well scenario. The mixed hydrates were synthesized in sandstone with moderate to high water saturation using two different CH4/COgas mixtures. Furthermore, mixed CH4/CO2 hydrates were dissociated three to six steps based on cyclic depressurization. Pressure, resistivity and gas chromatography data were collected. The presence of two thermodynamic stability zones provided an opportunity for additional CH4 recovery and CO2 storage during mixed hydrate dissociation. Gas and water migration between the injection and production well caused COhydrate reformation, improvement in CO2 sweep area and movement of the CO2 hydrate front toward the production well. Multiple peaks in CH4 recovery and CO2 storage suggest major dissociation and reformation. Peak values were independent of mixed hydrate type. Peaks values of CH4 rich hydrates occurred at high pressure than peak values of COrich hydrates. The slight change in resistance during depressurization below pure CH4 hydrate stability pressure confirms the loss of CH4 hydrate mass recovered by the formation of CO2 hydrate mass. This study discusses the correlation between the change in resistivity and type of guest molecule and its concentration and initial water saturation. The results of this study will be useful to explore the application of slow depressurization for the dissociation of CH4/CO2 mixed hydrates to improve CHrecovery and COstorage.
Original languageEnglish
Article number131915
JournalChemical Engineering Journal
Volume427
Number of pages16
ISSN1385-8947
DOIs
Publication statusPublished - 2021

Keywords

  • Resistance measurement
  • Enhanced CH Recovery
  • Production and storage optimization

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