Topic
Pore water pressure
About: Pore water pressure is a research topic. Over the lifetime, 11455 publications have been published within this topic receiving 247670 citations. The topic is also known as: pwp.
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TL;DR: In this article, halogen concentrations (Cl, Br and I) in pore waters and sediments from three deep cores in gas hydrate fields of the Nankai Trough area were analyzed.
101 citations
TL;DR: In this article, the authors measured deformation properties of three North Sea Malm shales in the laboratory under pressures to 800 bars and temperatures to 100 degrees C. The deformation in the shales is dominated by inelastic processes which cause time-dependent changes in velocity, resistivity, and pore pressure.
Abstract: Deformational properties, P‐wave and S‐wave velocities, and electrical resistivity were measured for three North Sea Malm shales in the laboratory under pressures to 800 bars and temperatures to 100 °C. These data were used to evaluate how factors such as mineralogy, microstructure, compaction, and pore‐fluid conductivity affect a shale’s seismic and electrical responses. Deformation in the shales is dominated by inelastic processes which cause time‐dependent changes in velocity, resistivity, and pore pressure. Overall, shales are less sensitive to pressure changes as compared to sandstones of similar porosity. However, changes in temperature result in large changes in physical properties as compared to sandstones or shaly sands. P‐wave and S‐wave velocities may decrease by as much as 10 percent over the temperature range studied, and calculated activation energies for surface conduction are nearly twice those observed in shaly sands. These comparisons emphasize fundamental differences in fabric among the...
101 citations
TL;DR: It is concluded that proper knowledge of the pore size distribution is crucial to an understanding of the retention of bacteria in aquifers and that straining in Dead End Pores was an important process that dominated bacteria breakthrough in fine-grained sediment.
101 citations
TL;DR: Tritium profiles from boreholes at Yucca Mountain indicate tritium-concentration inversions (larger tritium concentrations are located below the smaller titium concentration in a vertical profile) occur in many places as discussed by the authors.
Abstract: Analyses of pore water from boreholes at Yucca Mountain indicate that unsaturated-zone pore water has significantly larger concentrations of chloride and dissolved solids than the saturated-zone water or perched-water bodies. Chemical compositions are of the calcium sulfate or calcium chloride types in the Paintbrush Group (Tiva Canyon, Yucca Mountain, Pah Canyon, and bedded tuffs), and sodium carbonate or bicarbonate type water in the Calico Hills Formation. Tritium profiles from boreholes at Yucca Mountain indicate tritium-concentration inversions (larger tritium concentrations are located below the smaller tritium concentration in a vertical profile) occur in many places. These inversions indicate preferential flow through fractures. Rock-gas compositions are similar to that of atmospheric air except that carbon dioxide concentrations are generally larger than those in the air. The delta carbon-13 values of gas are fairly constant from surface to 365.8 meters, indicating little interaction between the gas CO{sub 2} and caliche in the soil. Model calculations indicate that the gas transport in the unsaturated zone at Yucca Mountain agrees well with the gas-diffusion process. Tritium-modeling results indicate that the high tritium value of about 100 tritium units in the Calico Hills Formation of UZ-16 is within limits of a piston-flow model with a water residence time of 32 to 35 years. The large variations in tritium concentrations with narrow peaks imply piston flow or preferential fracture flow rather than matrix flow. In reality, the aqueous-phase flow in the unsaturated zone is between piston and well-mixed flows but is closer to a piston flow.
100 citations
TL;DR: In this article, the principles behind using measured pore water chloride concentrations to estimate gas hydrate amounts are reviewed, along with data from selected sites around the world, and the potential causes for these low chloride anomalies below the base of gas hydrates stability are discussed.
Abstract: In marine sediments gas hydrate growth removes water and gas molecules from the pore water while dissolved ions are excluded from the clathrate cage. As a consequence, the surrounding pore waters become more saline. Conversely, when gas hydrates decompose, water is released, causing pore water to become fresher. Ion exclusion produces distinctive geochemical signatures that are used to identify the presence of gas hydrate and to calculate the amount of gas hydrate in marine sediment samples. These calculations, however, require knowledge of the dissolved ion concentration of the in situ pore water prior to gas hydrate decomposition. Because arguably no useable pore water samples have been collected in situ from gas-hydrate-bearing sediments, the calculated amounts of gas hydrate are very dependent on the assumed in situ dissolved ion concentrations. In this paper, the principles behind using measured pore water chloride concentrations to estimate gas hydrate amounts are reviewed, along with data from selected sites around the world. These data clearly define local pore water anomalies in the sediment zones that are believed to currently contain gas hydrate, but also document the occurrence of thick zones of low chloride concentrations immediately below the base of gas hydrate stability. The potential causes for these low chloride anomalies below the base of gas hydrate stability are discussed.
100 citations