Title: Nitrogen-Driven Chromatographic Separation During Gas Injection Into Hydrate-Bearing Sediments

Abstract

Hydrates are solid phases composed of water cages enclosing gas molecules that may host large quantities of recoverable natural gas and may serve to sequester CO₂ on geological time scales. Most hydrate studies focus on hydrates containing a single gas component, such as CH₄ or CO₂. Yet, there are several settings in which multiple components form hydrate mixtures, or mixed hydrates, including a subsurface injection technique that claims to simultaneously recover CH₄ and sequester CO₂ called “guest molecule exchange.” Here, we combine multicomponent phase behavior for hydrate-forming systems with a multiphase fluid flow simulator to understand the evolution of hydrate and nonhydrate phases during subsurface injection. We simulate various scenarios for systems composed of H₂O, CH₄, CO₂, and N₂. Our study probes the impact of injection composition, initial reservoir composition, and transport of each component through the model domain. We observe chromatographic separation from the combined effect of compositional partitioning in each phase, variable flow speed of each phase, and compositional dependence of phase stabilities. We show that N₂ drives chromatographic separation to create a CH₄-free zone and a CO₂-free zone that are connected by a continuous N₂-dominated vapor phase. While our results are theoretical and should be validated experimentally,more » they imply that guest molecule exchange acts as two sequential processes rather than as a simultaneous process. Furthermore, they show that injections into reservoirs with and without free water have vastly different behaviors, which has implications for the interpretation of the guest molecule exchange field test and various laboratory studies.« less

Authors:

Darnell, K. N.  ^[1];

• Search DOE PAGES for author "Darnell, K. N."
• Search DOE PAGES for ORCID "0000-0002-5377-7740"

Flemings, P. B.  ^[1];

• Search DOE PAGES for author "Flemings, P. B."
• Search DOE PAGES for ORCID "0000-0002-5377-3694"

DiCarlo, D.  ^[1]

• Search DOE PAGES for author "DiCarlo, D."
• Search DOE PAGES for ORCID "0000-0002-3760-8808"

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+ Show Author Affiliations

1. Univ. of Texas, Austin, TX (United States)

Publication Date:

Thu Jun 27 00:00:00 EDT 2019

Research Org.:

Univ. of Texas, Austin, TX (United States)

Sponsoring Org.:

USDOE Office of Fossil Energy (FE)

OSTI Identifier:

1614157

Alternate Identifier(s):

OSTI ID: 1550673

Grant/Contract Number:  

FE0010406

Resource Type:

Accepted Manuscript

Journal Name:

Water Resources Research

Additional Journal Information:

Journal Volume: 55; Journal Issue: 8; Journal ID: ISSN 0043-1397

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources