Journal
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
Volume 123, Issue 7, Pages 5495-5514Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018JB015872
Keywords
fine-grained sediment fabric; electrical sensitivity; pore-fluid chemistry; sedimentation; compressibility; methane hydrate
Categories
Funding
- U.S. Geological Survey [DE-FE0026166]
- Department of Energy [DE-FE0026166]
- Department of Energy grant award [DE-FE00-28966]
- United States Government
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Fines, defined here as grains or particles, less than 75m in diameter, exist nearly ubiquitously in natural sediment, even those classified as coarse. Macroscopic sediment properties, such as compressibility, which relates applied effective stress to the resulting sediment deformation, depend on the fabric of fines. Unlike coarse grains, fines have sizes and masses small enough to be more strongly influenced by electrical interparticle forces than by gravity. These electrical forces acting through pore fluids are influenced by pore fluid chemistry changes. Macroscopic property dependence on pore fluid chemistry must be accounted for in sediment studies involving subsurface flow and sediment stability analyses, as well as in engineered flow situations such as groundwater pollutant remediation, hydrocarbon migration, or other energy resource extraction applications. This study demonstrates how the liquid limit-based electrical sensitivity index can be used to predict sediment compressibility changes due to pore fluid chemistry changes. Laboratory tests of electrical sensitivity, sedimentation, and compressibility illustrate mechanisms linking microscale and macroscale processes for selected pure, end-member fines. A specific application considered here is methane extraction via depressurization of gas hydrate-bearing sediment, which causes a dramatic pore water salinity drop concurrent with sediment being compressed by the imposed effective stress increase.
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