The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform
Per Moldrup - One of the best experts on this subject based on the ideXlab platform.
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transport properties and pore network structure in variably saturated sphagnum peat soil
European Journal of Soil Science, 2016Co-Authors: Shoichiro Hamamoto, Shiromi Himalika Dissanayaka, O Nagata, T Komtatsu, Ken Kawamoto, Per MoldrupAbstract:Summary Gas and water transport in peat soil are of increasing interest because of their potentially large environmental and climatic effects under different types of land use. In this research, the water retention curve (WRC), gas diffusion coefficient (Dg) and air and water permeabilities (ka and kw) of layers in peat soil from two profiles were measured under different moisture conditions. A two-region Archie's Law (2RAL)-type model was applied successfully to the four properties; the reference point was taken at −9.8 kPa of soil-water matric potential where volume shrinkage typically started to occur. For WRC in the very decomposed peat soil, the 2RAL Saturation Exponents (n) obtained for both the wetter (nw) and drier regions (nd) were smaller than those for the less decomposed peat. For Dg, the Saturation Exponent in the wetter region was larger than that in the drier one for all layers, which indicated enhanced blocking effects of water on gas diffusion in the wetter region. For the peat layers within each soil, there was a linear relation between Saturation Exponents in the drier region for ka and Dg. The larger Saturation Exponent of the wetter region for kw in peat than in sand suggests a need for specific hydraulic functions for peat soil. The 2RAL model for Dg agreed well with measured data, and performed better than existing unimodal models. To facilitate use of the 2RAL for Dg, we developed a simple predictive expression for Dg at the reference point. The pore-network tortuosity factor and equivalent pore diameter for gas transport confirmed very different pore structure and mass transport behaviour for peat soil and uniform sand.
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two region extended archie s law model for soil air permeability and gas diffusivity
Soil Science Society of America Journal, 2011Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Lis Wollesen De Jonge, Per Schjonning, Toshiko KomatsuAbstract:The air permeability (k a ) and soil gas diffusion coefficients (D p ) are controlling factors for gas transport and fate in variably saturated soils. We developed a unified model for k a and D based on the classical Archie's law, extended by: (i) allowing for two-region gas transport behavior for structured soils, with the natural field moisture condition (set at -100 cm H 2 O matric potential [pF 2]) as the reference (spliced) point between the large-pore (drained pore diameter ≥30 μm at pF ≤ 2) and the small-pore (subsequently drained pores 2) regions, and (ii) including a percolation threshold, set as 10% of the total porosity for structureless porous media or 10% of the porosity in the large-pore region for structured soils. The resulting extended Archie's law with reference point (EXAR) models for k a and D were fitted to the measured data. For both structureless and structured porous media, Archie's Saturation Exponent (n) was higher for D p than for k a , indicating higher water blockage effects on gas diffusion. For structured soils, the Saturation Exponent for the large-pore region (n 1 ) was lower than for the small-pore region (n 2 ). Generally, n 1 values of ∼1 for k a and 2 for D p and n 2 values of 4/3 for k a and 7/3 for D described the data well. Two reference-point expressions for k a at pF 2 were also developed and tested together with existing models for D at pF 2 against independent data across soil types. The best-performing reference-point models were a k a model based on the classical Kozeny equation and the Moldrup D p model.
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excluded volume expansion of archie s law for gas and solute diffusivities and electrical and thermal conductivities in variably saturated porous media
Water Resources Research, 2010Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Toshiko KomatsuAbstract:[1] Describing and predicting gas and solute diffusivities and electrical and thermal conductivities under variably saturated fluid conditions are necessary for simulating gas, solute, and heat transport in soils. On the basis of comprehensive data for gas (Dp) and solute (Ds) diffusivities and electrical (EC) and thermal (TC) conductivities for differently textured and variably saturated soils, we investigated analogies and differences between the four parameters. At fluid (water or air) Saturation, relative parameter values for Dp, Ds, and EC were all well described by an excluded-volume expansion of Archie's first law. The cementation Exponent in Archie's first law was close to 1.5 for all parameters. At fluid-unsaturated conditions, relative values of Dp, Ds, and EC (normalized at fluid Saturation) were well described by an excluded-volume expansion of Archie's second law. In the case of relative TC, the Saturation Exponent in Archie's second law was substituted by the inverse of it for the three other parameters since water bridge effects dramatically enhance the TC with increasing moisture contents in relatively dry porous media. If appropriate but different expressions for a percolation threshold in Archie's second law were applied for the four parameters, a Saturation Exponent value of around 2.0 generally gave accurate predictions of all four parameters for differently textured soils. Finally, the excluded-volume expansion of Archie's second law was modified to also represent porous media with bimodal pore size distribution and well-described data for Dp and Ds in aggregated soil.
Ken Kawamoto - One of the best experts on this subject based on the ideXlab platform.
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transport properties and pore network structure in variably saturated sphagnum peat soil
European Journal of Soil Science, 2016Co-Authors: Shoichiro Hamamoto, Shiromi Himalika Dissanayaka, O Nagata, T Komtatsu, Ken Kawamoto, Per MoldrupAbstract:Summary Gas and water transport in peat soil are of increasing interest because of their potentially large environmental and climatic effects under different types of land use. In this research, the water retention curve (WRC), gas diffusion coefficient (Dg) and air and water permeabilities (ka and kw) of layers in peat soil from two profiles were measured under different moisture conditions. A two-region Archie's Law (2RAL)-type model was applied successfully to the four properties; the reference point was taken at −9.8 kPa of soil-water matric potential where volume shrinkage typically started to occur. For WRC in the very decomposed peat soil, the 2RAL Saturation Exponents (n) obtained for both the wetter (nw) and drier regions (nd) were smaller than those for the less decomposed peat. For Dg, the Saturation Exponent in the wetter region was larger than that in the drier one for all layers, which indicated enhanced blocking effects of water on gas diffusion in the wetter region. For the peat layers within each soil, there was a linear relation between Saturation Exponents in the drier region for ka and Dg. The larger Saturation Exponent of the wetter region for kw in peat than in sand suggests a need for specific hydraulic functions for peat soil. The 2RAL model for Dg agreed well with measured data, and performed better than existing unimodal models. To facilitate use of the 2RAL for Dg, we developed a simple predictive expression for Dg at the reference point. The pore-network tortuosity factor and equivalent pore diameter for gas transport confirmed very different pore structure and mass transport behaviour for peat soil and uniform sand.
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two region extended archie s law model for soil air permeability and gas diffusivity
Soil Science Society of America Journal, 2011Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Lis Wollesen De Jonge, Per Schjonning, Toshiko KomatsuAbstract:The air permeability (k a ) and soil gas diffusion coefficients (D p ) are controlling factors for gas transport and fate in variably saturated soils. We developed a unified model for k a and D based on the classical Archie's law, extended by: (i) allowing for two-region gas transport behavior for structured soils, with the natural field moisture condition (set at -100 cm H 2 O matric potential [pF 2]) as the reference (spliced) point between the large-pore (drained pore diameter ≥30 μm at pF ≤ 2) and the small-pore (subsequently drained pores 2) regions, and (ii) including a percolation threshold, set as 10% of the total porosity for structureless porous media or 10% of the porosity in the large-pore region for structured soils. The resulting extended Archie's law with reference point (EXAR) models for k a and D were fitted to the measured data. For both structureless and structured porous media, Archie's Saturation Exponent (n) was higher for D p than for k a , indicating higher water blockage effects on gas diffusion. For structured soils, the Saturation Exponent for the large-pore region (n 1 ) was lower than for the small-pore region (n 2 ). Generally, n 1 values of ∼1 for k a and 2 for D p and n 2 values of 4/3 for k a and 7/3 for D described the data well. Two reference-point expressions for k a at pF 2 were also developed and tested together with existing models for D at pF 2 against independent data across soil types. The best-performing reference-point models were a k a model based on the classical Kozeny equation and the Moldrup D p model.
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excluded volume expansion of archie s law for gas and solute diffusivities and electrical and thermal conductivities in variably saturated porous media
Water Resources Research, 2010Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Toshiko KomatsuAbstract:[1] Describing and predicting gas and solute diffusivities and electrical and thermal conductivities under variably saturated fluid conditions are necessary for simulating gas, solute, and heat transport in soils. On the basis of comprehensive data for gas (Dp) and solute (Ds) diffusivities and electrical (EC) and thermal (TC) conductivities for differently textured and variably saturated soils, we investigated analogies and differences between the four parameters. At fluid (water or air) Saturation, relative parameter values for Dp, Ds, and EC were all well described by an excluded-volume expansion of Archie's first law. The cementation Exponent in Archie's first law was close to 1.5 for all parameters. At fluid-unsaturated conditions, relative values of Dp, Ds, and EC (normalized at fluid Saturation) were well described by an excluded-volume expansion of Archie's second law. In the case of relative TC, the Saturation Exponent in Archie's second law was substituted by the inverse of it for the three other parameters since water bridge effects dramatically enhance the TC with increasing moisture contents in relatively dry porous media. If appropriate but different expressions for a percolation threshold in Archie's second law were applied for the four parameters, a Saturation Exponent value of around 2.0 generally gave accurate predictions of all four parameters for differently textured soils. Finally, the excluded-volume expansion of Archie's second law was modified to also represent porous media with bimodal pore size distribution and well-described data for Dp and Ds in aggregated soil.
Shoichiro Hamamoto - One of the best experts on this subject based on the ideXlab platform.
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transport properties and pore network structure in variably saturated sphagnum peat soil
European Journal of Soil Science, 2016Co-Authors: Shoichiro Hamamoto, Shiromi Himalika Dissanayaka, O Nagata, T Komtatsu, Ken Kawamoto, Per MoldrupAbstract:Summary Gas and water transport in peat soil are of increasing interest because of their potentially large environmental and climatic effects under different types of land use. In this research, the water retention curve (WRC), gas diffusion coefficient (Dg) and air and water permeabilities (ka and kw) of layers in peat soil from two profiles were measured under different moisture conditions. A two-region Archie's Law (2RAL)-type model was applied successfully to the four properties; the reference point was taken at −9.8 kPa of soil-water matric potential where volume shrinkage typically started to occur. For WRC in the very decomposed peat soil, the 2RAL Saturation Exponents (n) obtained for both the wetter (nw) and drier regions (nd) were smaller than those for the less decomposed peat. For Dg, the Saturation Exponent in the wetter region was larger than that in the drier one for all layers, which indicated enhanced blocking effects of water on gas diffusion in the wetter region. For the peat layers within each soil, there was a linear relation between Saturation Exponents in the drier region for ka and Dg. The larger Saturation Exponent of the wetter region for kw in peat than in sand suggests a need for specific hydraulic functions for peat soil. The 2RAL model for Dg agreed well with measured data, and performed better than existing unimodal models. To facilitate use of the 2RAL for Dg, we developed a simple predictive expression for Dg at the reference point. The pore-network tortuosity factor and equivalent pore diameter for gas transport confirmed very different pore structure and mass transport behaviour for peat soil and uniform sand.
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two region extended archie s law model for soil air permeability and gas diffusivity
Soil Science Society of America Journal, 2011Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Lis Wollesen De Jonge, Per Schjonning, Toshiko KomatsuAbstract:The air permeability (k a ) and soil gas diffusion coefficients (D p ) are controlling factors for gas transport and fate in variably saturated soils. We developed a unified model for k a and D based on the classical Archie's law, extended by: (i) allowing for two-region gas transport behavior for structured soils, with the natural field moisture condition (set at -100 cm H 2 O matric potential [pF 2]) as the reference (spliced) point between the large-pore (drained pore diameter ≥30 μm at pF ≤ 2) and the small-pore (subsequently drained pores 2) regions, and (ii) including a percolation threshold, set as 10% of the total porosity for structureless porous media or 10% of the porosity in the large-pore region for structured soils. The resulting extended Archie's law with reference point (EXAR) models for k a and D were fitted to the measured data. For both structureless and structured porous media, Archie's Saturation Exponent (n) was higher for D p than for k a , indicating higher water blockage effects on gas diffusion. For structured soils, the Saturation Exponent for the large-pore region (n 1 ) was lower than for the small-pore region (n 2 ). Generally, n 1 values of ∼1 for k a and 2 for D p and n 2 values of 4/3 for k a and 7/3 for D described the data well. Two reference-point expressions for k a at pF 2 were also developed and tested together with existing models for D at pF 2 against independent data across soil types. The best-performing reference-point models were a k a model based on the classical Kozeny equation and the Moldrup D p model.
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excluded volume expansion of archie s law for gas and solute diffusivities and electrical and thermal conductivities in variably saturated porous media
Water Resources Research, 2010Co-Authors: Shoichiro Hamamoto, Per Moldrup, Ken Kawamoto, Toshiko KomatsuAbstract:[1] Describing and predicting gas and solute diffusivities and electrical and thermal conductivities under variably saturated fluid conditions are necessary for simulating gas, solute, and heat transport in soils. On the basis of comprehensive data for gas (Dp) and solute (Ds) diffusivities and electrical (EC) and thermal (TC) conductivities for differently textured and variably saturated soils, we investigated analogies and differences between the four parameters. At fluid (water or air) Saturation, relative parameter values for Dp, Ds, and EC were all well described by an excluded-volume expansion of Archie's first law. The cementation Exponent in Archie's first law was close to 1.5 for all parameters. At fluid-unsaturated conditions, relative values of Dp, Ds, and EC (normalized at fluid Saturation) were well described by an excluded-volume expansion of Archie's second law. In the case of relative TC, the Saturation Exponent in Archie's second law was substituted by the inverse of it for the three other parameters since water bridge effects dramatically enhance the TC with increasing moisture contents in relatively dry porous media. If appropriate but different expressions for a percolation threshold in Archie's second law were applied for the four parameters, a Saturation Exponent value of around 2.0 generally gave accurate predictions of all four parameters for differently textured soils. Finally, the excluded-volume expansion of Archie's second law was modified to also represent porous media with bimodal pore size distribution and well-described data for Dp and Ds in aggregated soil.
Yan Jin - One of the best experts on this subject based on the ideXlab platform.
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estimation of water Saturation from nuclear magnetic resonance nmr and conventional logs in low permeability sandstone reservoirs
Journal of Petroleum Science and Engineering, 2013Co-Authors: Liang Xiao, Changchun Zou, Zhiqiang Mao, Yujiang Shi, Xiaopeng Liu, Yan Jin, Haopeng GuoAbstract:Abstract It is difficult to obtain rock resistivity parameters by using the cross plots of porosity vs. formation factor and water Saturation vs. resistivity index to calculate reservoir water Saturation in low permeability sandstones. The cementation and Saturation Exponents ( m and n separately) are divergent, and no fixed values can be obtained due to the complicated pore structure. This leads to a problem in water Saturation calculation. To investigate the main factors that heavily affect the cementation and Saturation Exponents, 36 core samples, which were drilled from low permeability sands of Xujiahe Formation, Sichuan basin, southwest China, are chosen for laboratory resistivity and nuclear magnetic resonance (NMR) measurements, 20 of them for mercury injection capillary pressure (MICP) measurements and 10 of them for casting thin-section analysis. The results show that these two parameters are associated with rock pore structure. For rocks with good pore structure, the proportion of macropore components is dominant, high cementation Exponents and low Saturation Exponents can be obtained, and on the contrary, rocks with poor pore structure will be dominated by the proportion of small pore components, and they will contain low cementation Exponents and high Saturation Exponents. To quantitatively acquire reliable cementation and Saturation Exponents for water Saturation estimation, a logarithmic function is established to calculate cementation Exponent from porosity. Irreducible water Saturation ( S wi ), which is estimated from NMR logs by using the optimal T 2cutoff , is presented to characterize the proportion of small pore components. A technique of calculating Saturation Exponent by combining with S wi , (1− S wi ) and the logarithmic mean of NMR T 2 spectrum ( T 2 lm ) is proposed, and the corresponding model is established. The credibility of these techniques is confirmed by comparing the predicted cementation and Saturation Exponents with the core analyzed results. The absolute errors between the predicted cementation Exponents and the experimental results are lower than 0.08, and the absolute errors between the predicted Saturation Exponents and the experimental results are lower than 0.2. These techniques proposed in this study are extended to several low permeability sands for field applications; the field examples illustrate that cementation and Saturation Exponents can be accurately estimated in the intervals with which NMR logs were acquired. By using the variable rock resistivity parameters, precisely water Saturation can be calculated for low permeability sandstones evaluation.
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estimation of Saturation Exponent from nuclear magnetic resonance nmr logs in low permeability reservoirs
Applied Magnetic Resonance, 2013Co-Authors: Liang Xiao, Zhiqiang Mao, Yan JinAbstract:The resistivity experimental measurements of 36 core samples, which were drilled from low permeability reservoirs of southwest China, illustrate that the Saturation Exponents are not agminate, but vary from 1.627 to 3.48; this leads to a challenge for water Saturation estimation in low permeability formations. Based on the analysis of resistivity experiments, laboratory nuclear magnetic resonance (NMR) measurements for all 36 core samples, and mercury injection measurements for 20 of them, it was observed that the Saturation Exponent is proportional to the proportion of small pore components and inversely proportional to the logarithmic mean of NMR T2 spectrum (T2lm). For rocks with high proportion of small pore components and low T2lm, there will be high Saturation Exponents, and vice versa. The proportion of small pore components is characterized by three different kinds of irreducible water Saturations, which are estimated by defining 30, 40 and 50 ms as T2 cutoffs separately. By integrating these three different kinds of irreducible water Saturations and using T2lm, a technique of calculating the Saturation Exponent from NMR logs is proposed and the corresponding model is established. The credibility of this technique is confirmed by comparing the predicted Saturation Exponents with the results from the core analysis. For more than 85 % of core samples, the absolute errors between the predicted Saturation Exponents from NMR logs and the experimental results are lower than 0.25. Once this technique is extended to field application, the accuracy of water Saturation estimation in low permeability reservoirs will be improved significantly.
A Revil - One of the best experts on this subject based on the ideXlab platform.
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Saturation dependence of the quadrature conductivity of oil bearing sands
Geophysical Research Letters, 2012Co-Authors: Myriam Schmutz, A Blondel, A RevilAbstract:[1] We have investigated the complex conductivity of oil-bearing sands with six distinct oil types including sunflower oil, silicone oil, gum rosin, paraffin, engine oil, and an industrial oil of complex composition. In all these experiments, the oil was the non-wetting phase. The in-phase (real) conductivity follows a power law relationship with the Saturation (also known as the second Archie's law) but with a Saturation Exponentn raging from 1.1 to 3.1. In most experiments, the quadrature conductivity follows also a power law relationship with the water Saturation but with a power law Exponent p can be either positive or negative. For some samples, the quadrature conductivity first increases with Saturation and then decreases indicating that two processes compete in controlling the quadrature conductivity. One is related to the insulating nature of the oil phase and a second could be associated with the surface area of the oil / water interface. The quadrature conductivity seems to be influenced not only by the value of the Saturation Exponent n (according to the Vinegar and Waxman model, p = n− 1), but also by the surface area between the oil phase and the water phase especially for very water-repellent oil having a fractal oil–water interface.
