Title: The water retention curve and relative permeability for gas production from hydrate-bearing sediments: pore-network model simulation

Abstract

Here, the water retention curve and relative permeability are critical to predict gas and water production from hydrate–bearing sediments. However, values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges. This study utilizes the combined techniques of micro–focus X–ray computed tomography (CT) and pore–network model simulation to identify proper values for those key parameters, such as gas entry pressure, residual water saturation, and curve fitting values. Hydrates with various saturation and morphology are realized in the pore–network that was extracted from micron–resolution CT images of sediments recovered from the hydrate deposit at the Mallik site, and then the processes of gas invasion, hydrate dissociation, gas expansion, and gas and water permeability are simulated. Results show that greater hydrate saturation in sediments lead to higher gas entry pressure, higher residual water saturation, and steeper water retention curve. An increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate. Hydrate morphology has more significant impacts than hydrate saturation on relative permeability. Sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability. Inmore » this sense, the Brooks–Corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate–bearing sediments.« less

Authors:

Mahabadi, Nariman ^[1]; Dai, Sheng ^[2]; Seol, Yongkoo ^[3]; Sup Yun, Tae ^[4]; Jang, Jaewon ^[1]

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+ Show Author Affiliations

1. Arizona State Univ., Tempe, AZ (United States)
2. Georgia Inst. of Technology, Atlanta, GA (United States)
3. National Energy Technology Lab. (NETL), Morgantown, WV (United States)
4. Yonsei Univ., Seoul (Korea)

Publication Date:

Thu Jul 14 00:00:00 EDT 2016

Research Org.:

National Energy Technology Lab. (NETL), Morgantown, WV (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1481163

Grant/Contract Number:  

FE0009927

Resource Type:

Accepted Manuscript

Journal Name:

Geochemistry, Geophysics, Geosystems

Additional Journal Information:

Journal Volume: 17; Journal Issue: 8; Journal ID: ISSN 1525-2027

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; hydrate‐bearing sediments; water retention curve; relative permeability; pore‐network model; van Genuchten model; Brooks-Corey model