scholarly journals Averaged water potentials in soil water and groundwater, and their connection to menisci in soil pores, field-scale flow phenomena, and simple groundwater flows

2011 ◽  
Vol 15 (5) ◽  
pp. 1601-1614 ◽  
Author(s):  
G. H. de Rooij
Keyword(s):  
Potential Energy ◽  
Scale Effects ◽  
Hydrostatic Equilibrium ◽  
Subsurface Water ◽  
Depth Range ◽  
Pore Scale ◽  
Field Scale ◽  
Matric Potential ◽  
Water Potentials ◽  
Soil Pores

Abstract. The movement of subsurface water is mostly studied at the pore scale and the Darcian scale, but the field and regional scales are of much larger societal interest. Volume-averaging has provided equations at these larger scales, but the required restrictions rendered them of little practical interest. Others hypothesized a direct connection at hydrostatic equilibrium between the average matric potential of a subsurface body of water and the average pressure drop over the menisci in the soil pores. The link between the volume-averaged potential energy of subsurface water bodies and large-scale fluxes remains largely unexplored. This paper treats the effect of menisci on the potential energy of the water behind them in some detail, and discusses some field-scale effects of pore-scale processes. Then, various published expressions for volume-averaged subsurface water potentials are compared. The intrinsic phase average is deemed the best choice. The hypothesized relationship between average matric potential and average meniscus curvature is found to be valid for unit gradient flow instead of hydrostatic equilibrium. Still, this restriction makes the relationship hold only for a specific depth range in the unsaturated zone under specific conditions, and certainly not for entire fields or catchments. In the groundwater, volume-averaged potential energy is of more use: for linearized, steady flows with flow lines that are parallel, radially diverging, and radially converging, proofs are derived for proportionality between averaged hydraulic potentials and fluxes towards open water at a fixed potential. For parallel flow, a simplified but relevant transient flow case also exhibits this proportionality.

scholarly journals Big and small: menisci in soil pores affect water pressures, dynamics of groundwater levels, and catchment-scale average matric potentials

2010 ◽  
Vol 7 (5) ◽  
pp. 6491-6523
Author(s):  
G. H. de Rooij
Keyword(s):  
Soil Water ◽  
Large Scale ◽  
Soil Surface ◽  
Subsurface Water ◽  
Vertical Position ◽  
Pore Scale ◽  
Catchment Scale ◽  
Matric Potential ◽  
Groundwater Levels ◽  
Interface Curvature

Abstract. Soil water is confined behind the menisci of its water-air interface. Catchment-scale fluxes (groundwater recharge, evaporation, transpiration, precipitation, etc.) affect the matric potential, and thereby the interface curvature and the configuration of the phases. In turn, these affect the fluxes (except precipitation), creating feedbacks between pore-scale and catchment-scale processes. Tracking pore-scale processes beyond the Darcy scale is not feasible. Instead, for a simplified system based on the classical Darcy's Law and Laplace-Young Law we i) clarify how menisci transfer pressure from the atmosphere to the soil water, ii) examine large-scale phenomena arising from pore-scale processes, and iii) analyze the relationship between average meniscus curvature and average matric potential. In stagnant water, changing the gravitational potential or the curvature of the air-water interface changes the pressure throughout the water. Adding small amounts of water can thus profoundly affect water pressures in a much larger volume. The pressure-regulating effect of the interface curvature showcases the meniscus as a pressure port that transfers the atmospheric pressure to the water with an offset directly proportional to its curvature. This property causes an extremely rapid rise of phreatic levels in soils once the capillary fringe extends to the soil surface and the menisci flatten. For large bodies of subsurface water, the curvature and vertical position of any meniscus quantify the uniform hydraulic potential under hydrostatic equilibrium. During unit-gradient flow, the matric potential corresponding to the mean curvature of the menisci should provide a good approximation of the intrinsic phase average of the matric potential.

scholarly journals Seismic stimulation for enhanced oil recovery

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. O23-O35 ◽  
Author(s):  
Steven R. Pride ◽  
Eirik G. Flekkøy ◽  
Olav Aursjø
Keyword(s):  
Pressure Gradient ◽  
Numerical Simulations ◽  
Oil Recovery ◽  
Scale Effects ◽  
Fluid Pressure ◽  
Oil Production ◽  
Two Dimensions ◽  
Lattice Boltzmann Model ◽  
Pore Scale ◽  
Capillary Barriers

The pore-scale effects of seismic stimulation on two-phase flow are modeled numerically in random 2D grain-pack geometries. Seismic stimulation aims to enhance oil production by sending seismic waves across a reservoir to liberate immobile patches of oil. For seismic amplitudes above a well-defined (analytically expressed) dimensionless criterion, the force perturbation associated with the waves indeed can liberate oil trapped on capillary barriers and get it flowing again under the background pressure gradient. Subsequent coalescence of the freed oil droplets acts to enhance oil movement further because longer bubbles overcome capillary barriers more efficiently than shorter bubbles do. Poroelasticity theory defines the effective force that a seismic wave adds to the background fluid-pressure gradient. The lattice-Boltzmann model in two dimensions is used to perform pore-scale numerical simulations. Dimensionless numbers (groups of material and force parameters) involved in seismic stimulation were defined carefully so that numerical simulations could be applied to field-scale conditions. Using defined analytical criteria, there is a significant range of reservoir conditions over which seismic stimulation can be expected to enhance oil production.

scholarly journals Effect of Osmotic and Matric Potentials on the Availability of Water for Seed Germination

1971 ◽  
Vol 24 (3) ◽  
pp. 423 ◽  
Author(s):  
JR Mcwilliam ◽  
PJ Phlllips
Keyword(s):  
Soil Moisture ◽  
Seed Germination ◽  
Osmotic Stress ◽  
Soil Water ◽  
Seed Coat ◽  
Moisture Diffusivity ◽  
Matric Potential ◽  
Water Potentials ◽  
Germination Behaviour ◽  
Dry Soil

Under special conditions where soil-moisture diffusivity and seed-soil contact are non-limiting, the osmotic and matric potentials of the substrate were found to be equivalent in their effect on the germination of seeds of ryegrass and dehulled phalaris over a range of water potentials from 0 to -15 bars. However, with intact phalaris seeds it appears that the seed coat constitutes a large resistance to the absorption of soil water, and under these conditions the equivalence between osmotic and matric potential no longer holds, and results of germination under osmotic stress must be used with caution in predicting the germination behaviour of seeds in dry soil.

scholarly journals Upscaling Strategies of Porosity-Permeability Correlations in Reacting Environments from Pore-Scale Simulations

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Nikolaos I. Prasianakis ◽  
Michael Gatschet ◽  
Aida Abbasi ◽  
Sergey V. Churakov
Keyword(s):  
Temporal Evolution ◽  
A Priori ◽  
Mineral Dissolution ◽  
Pore Scale ◽  
Field Scale ◽  
Chemical Gradients ◽  
The Media ◽  
Dissolution And Precipitation ◽  
Structural Heterogeneities ◽  
Mineral Dissolution And Precipitation

In geochemically reacting environments, the mineral dissolution and precipitation alters the structural and transport properties of the media of interest. The chemical and structural heterogeneities of the porous media affect the temporal evolution of the permeability with respect to porosity. Such correlations follow a nonlinear trend, which is difficult to estimate a priori and without knowledge of the microstructure itself, especially under the presence of strong chemical gradients. Macroscopic field-scale codes require such an input, and in the absence of exact descriptions, simplified correlations are used. After highlighting the diversity of microstructural evolution paths, due to dissolution, we discuss possible upscaling strategies.

Water Table Depth and Soil Salinization: From Pore‐Scale Processes to Field‐Scale Responses

2020 ◽  
Vol 56 (2) ◽  
Author(s):  
Salomé M. S. Shokri‐Kuehni ◽  
Bernadette Raaijmakers ◽  
Theresa Kurz ◽  
Dani Or ◽  
Rainer Helmig ◽  
...  
Keyword(s):  
Water Table ◽  
Soil Salinization ◽  
Water Table Depth ◽  
Pore Scale ◽  
Field Scale

Corrigenda - Measurement of the total water potential of aqueous solutions of polyethylene glycol - A comparison between osmometer, thermocouple psychrometer and equilibrated soil cores

Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 1
Author(s):  
IM Wood ◽  
IK Dart ◽  
HB So
Keyword(s):  
Polyethylene Glycol ◽  
Water Potential ◽  
Close Correlation ◽  
Ease Of Use ◽  
Effect Of Temperature ◽  
Soil Cores ◽  
Total Water ◽  
Matric Potential ◽  
Thermocouple Psychrometer ◽  
Water Potentials

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.

Oil Configuration Under High-Salinity and Low-Salinity Conditions at Pore Scale: A Parametric Investigation by Use of a Single-Channel Micromodel

SPE Journal ◽  
2017 ◽  
Vol 22 (05) ◽  
pp. 1362-1373 ◽  
Author(s):  
W.-B.. -B. Bartels ◽  
H.. Mahani ◽  
S.. Berg ◽  
R.. Menezes ◽  
J. A. van der Hoeven ◽  
...  
Keyword(s):  
Contact Angle ◽  
Crude Oil ◽  
Single Channel ◽  
Scale Effects ◽  
Model System ◽  
Pore Scale ◽  
Clay Particles ◽  
Low Salinity ◽  
Natural Rock ◽  
Brine Salinity

Summary Low-salinity waterflooding (LSF) is receiving increased interest as a promising method to improve oil-recovery efficiency. Most of the literature agrees that, on the Darcy scale, LSF can be regarded as a wettability-modification process, leading to a more-water-wet state, although no consensus on the microscopic mechanisms has been reached. To establish a link between the pore-scale and the Darcy-scale description, the flow dynamic at an intermediate scale—i.e., networks of multiple pores—should be investigated. One of the main challenges in addressing phenomena on this scale is to design a model system representative of natural rock. The model system should allow for a systematic investigation of influencing parameters with pore-scale resolution while simultaneously being large enough to capture larger-length-scale effects such as saturation changes and the mobilization and connection of oil ganglia. In this paper, we use micromodels functionalized with active clay minerals as a model system to study the low-salinity effect (LSE) on the pore scale. A new method was devised to deposit clays in the micromodel. Clay suspensions were made by mixing natural clays (montmorillonite) with isopropyl alcohol (IPA) and were injected into optically transparent 2D glass micromodels. After drying the models, the clay particles were deposited and stick naturally to the glass surfaces. The micromodel was then used to investigate the dependence of the LSE on the type of oil (crude oil vs. n-decane), the presence of clay particles, and aging. Our results show that the system is responsive to low-salinity brine as the effective contact angle of crude oil shifts toward a more-water-wetting state when brine salinity is reduced. When using n-decane as a reference case of inert oil, no change in contact angle occurred after a reduction in brine salinity. This responsiveness in terms of contact angle does not necessarily mean that more oil is recovered. Only in the cases where the contact-angle change (because of low-salinity exposure) led to release of oil and reconnection with oil of adjacent pore bodies did the oil become mobile and the oil saturation effectively reduce. This makes contact-angle changes a necessary but not sufficient requirement for incremental recovery by LSF. Interestingly, the wettability modification was observed in the absence of clay. Osmosis and interfacial tension (IFT) change were found not to be the primary driving mechanisms of the low-salinity response.

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