Enhanced depressurisation for methane recovery from gas hydrate reservoirs by injection of compressed air and nitrogen

Anthony Chizoba Okwananke, Jinhai Yang, Bahman Tohidi Kalorazi, Evgeny Chuvilin, Vladimir Istomin, Boris Bukhanov, Alexey Cheremisin

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Abstract

Enhanced depressurisation for methane recovery from gas hydrate-bearing sediments was experimentally studied by injection of compressed air and nitrogen. Experiments were conducted in simulated sediments (silica sand) from 273.4 K to 283.0 K and initial system pressures ranging from 3.8 MPa to 7.2 MPa before air or nitrogen injection. The results show that injection of air and nitrogen made it possible to implement conventional depressurisation
in multiple stages. In each pressure stage, methane hydrate was quickly dissociated by the injected air or nitrogen due to direct shift of the methane hydrate equilibrium phase boundary. Methane hydrate dissociation at high pressures enables methane recovery inside the methane hydrate stability zone. Depressurisation well above the methane hydrate dissociation pressure
generated a methane-rich gas phase of up to 90 mol% methane depending on the injected gas. Injection of compressed air or nitrogen provides a potential approach to improve the technical feasibility and economic viability of conventional depressurisation method for methane recovery from most gas hydrate reservoirs with severe conditions such as low permeability or dispersed hydrates.
Original languageEnglish
Pages (from-to)138-146
Number of pages9
JournalJournal of Chemical Thermodynamics
Volume117
Early online date1 Oct 2017
DOIs
Publication statusPublished - Feb 2018

Keywords

  • Gas hydrate
  • Methane recovery
  • Compressed air
  • Nitrogen
  • Kinetics
  • Depressurisation

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