Impact of Pore Fluid Chemistry on Fine‐Grained Sediment Fabric and Compressibility. Issue 7 (17th July 2018)

• Record Type: Journal Article
• Authors: Jang, Junbong; Cao, Shuang C.; Stern, Laura A.; Jung, Jongwon; Waite, William F.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 7(2018)
• Page Start: 5495
• Page End: 5514
• Publication Date: 2018-07-17
• Subjects: fine‐grained sediment fabric -- electrical sensitivity -- pore‐fluid chemistry -- sedimentation -- compressibility -- methane hydrate; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2018JB015872
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: Fines, defined here as grains or particles, less than 75 μm 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. Key Points: The liquid limit‐based electrical sensitivity index indicates the extent to which sediment compressibility depends on pore fluid chemistry Pore fluid chemistry influences initial void ratio, as observed in sedimentation and consolidation tests, and thus affects compressibility Pore fluid chemistry changes occur when extracting methane from hydrate‐bearing sediments, potentially altering in situ compressibility