Title: Archie's Saturation Exponent for Natural Gas Hydrate in Coarse-Grained Reservoirs

Abstract

Accurately quantifying the amount of naturally occurring gas hydrate in marine and permafrost environments is important for assessing its resource potential and understanding the role of gas hydrate in the global carbon cycle. Electrical resistivity well logs are often used to calculate gas hydrate saturations, S_h, using Archie's equation. Archie's equation, in turn, relies on an empirical saturation parameter, n. Though n = 1.9 has been measured for ice–bearing sands and is widely used within the hydrate community, it is highly questionable if this n value is appropriate for hydrate–bearing sands. In this work, we calibrate n for hydrate–bearing sands from the Canadian permafrost gas hydrate research well, Mallik 5L–38, by establishing an independent downhole S_h profile based on compressional–wave velocity log data. Using the independently determined S_h profile and colocated electrical resistivity and bulk density logs, Archie's saturation equation is solved for n, and uncertainty is tracked throughout the iterative process. In addition to the Mallik 5L–38 well, we also apply this method to two marine, coarse–grained reservoirs from the northern Gulf of Mexico Gas Hydrate Joint Industry Project: Walker Ridge 313–H and Green Canyon 955–H. All locations yield similar results, each suggesting n ≈ 2.5 ± 0.5. Furthermore,more » for the coarse–grained hydrate bearing ( S_h > 0.4) of greatest interest as potential energy resources, we suggest that n = 2.5 ± 0.5 should be applied in Archie's equation for either marine or permafrost gas hydrate settings if independent estimates of n are not available.« less

Authors:

Cook, Ann E.  ^[1];

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Waite, William F.  ^[2]

• Search DOE PAGES for author "Waite, William F."
• Search DOE PAGES for ORCID "0000-0002-9436-4109"
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+ Show Author Affiliations

1. The Ohio State Univ., Columbus, OH (United States)
2. U.S. Geological Survey, Woods Hole, MA (United States)

Publication Date:

2018-02-17

Research Org.:

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

Sponsoring Org.:

USDOE Office of Fossil Energy (FE)

OSTI Identifier:

1537315

Alternate Identifier(s):

OSTI ID: 1425505

Grant/Contract Number:  

FE0023919

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Solid Earth

Additional Journal Information:

Journal Volume: 123; Journal Issue: 3; Journal ID: ISSN 2169-9313

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; Geochemistry & Geophysics; gas hydrate; resistivity; velocity; hydrate saturation; Mallik; Gulf of Mexico