Measuring hydraulic conductivity using streaming potentials (original) (raw)
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Geophysical Journal International, 2009
We consider the transient streaming potential response due to pumping from a confined aquifer through a fully penetrating line sink. Confined aquifer flow is assumed to occur without fluid leakage from the confining units. However, since confining units are typically clayey, and hence more electrically conductive than the aquifer, they are treated as non-insulating in our three-layer conceptual model. We develop a semi-analytical solution for the transient streaming potentials response of the aquifer and the confining units to pumping of the aquifer. The solution is fitted to field measurements of streaming potentials associated with an aquifer test performed at a site located near Montalto Uffugo, in the region of Calabria in Southern Italy. This yields an average hydraulic conductivity that compares well to the estimate obtained using only hydraulic head data. Specific storage is estimated with greater estimation uncertainty than hydraulic conductivity and is significantly smaller than that estimated from hydraulic head data. This indicates that specific storage may be a more difficult parameter to estimate from streaming potential data. The mismatch may also be due to the fact that only recovery streaming potential data were used here whereas head data for both production and recovery were used. The estimate from head data may also constitute an upper bound since head data were not corrected for pumping and observation wellbore storage. Estimated values of the electrical conductivities of the confining units compare well to those estimated using electrical resistivity tomography. Our work indicates that, where observation wells are unavailable to provide more direct estimates, streaming potential data collected at land surface may, in principle, be used to provide preliminary estimates of aquifer hydraulic conductivity and specific storage, where the latter is estimated with greater uncertainty than the former.
Hydraulic Conductivity Characterization Methods for Environmental Site Investigations
Hydraulic conductivity (K), a parameter that describes the ease with which water flows in the subsurface, is widely regarded as one of the most important hydrogeologic parameters for environmental site investigations. Mathematically, it is defined as the flow rate per unit area divided by the hydraulic gradient in the direction of flow. Many approaches have been developed to characterize K. These approaches can be grouped into two general categories based on how the K estimates are obtained: hydraulic methods that involve water or other fluid injection or extraction and the measurement of the induced pressure response, and indirect methods that rely on empirical correlations, often site-specific in nature, between K and other more readily evaluated formation properties (e.g., resistance to electric current). Because hydraulic methods can be directly related to the mathematical definition of K through Darcy's Law, K estimates obtained with those methods are generally considered to be more reliable than those obtained with indirect methods. As fluids of different composition pass through saturated porous medium, the properties of the composition of the fluid will influence hydraulic conductivity characterization. Traditional methods for in situ measurement of K include pumping tests and slug tests.
Journal of Geophysical Research: Solid Earth, 1999
Streaming potential and resistivity measurements have been performed on Fontainebleau sandstone and Villejust quartzite samples in a triaxial device during compaction, uniaxial compression, and rupture. Measurements on individual samples do not show any clear intrinsic dependence of the streaming potential coefficient with permeability. An apparent dependence of the streaming potential coefficient with permeability is, however, observed during deformation. The effect of surface conductivity is taken into account and is small compared with the observed changes in the streaming potential coefficient. The observed dependence is therefore interpreted in terms of a difference in the evolution of the electrical and hydraulic connectivity patterns during deformation. This effect causes the streaming potential coefficient, and consequently the inferred potential, to be reduced by a geometrical factor R G representing the electrical efficiency of the hydraulic network. Estimates of the R G factor varying between 0.2 and 0.8 for electrolyte resistivity larger than 100 ⍀m are obtained by comparing the values of the potential inferred from intact rock samples with the values obtained from crushed rock samples, where the geometrical effects are assumed to be negligible. The reduction of the streaming potential coefficient observed during compaction or uniaxial compression suggests that the tortuosity of the hydraulic network increases faster than the tortuosity of the electrical network. Before rupture, an increase in the streaming potential coefficient associated with the onset of dilatancy was observed for three samples of Fontainebleau sandstone and one sample of Villejust quartzite. The changes in streaming potential coefficient prior to failure range from 30% to 50%. During one experiment, an increase in the concentration of sulfate ions was also observed before failure. These experiments suggest that observable streaming potential and geochemical variations could occur before earthquakes.
Field Measurement of Hydraulic Conductivity of Rocks
Hydraulic Conductivity - Issues, Determination and Applications, 2011
Hydraulic Conductivity-Issues, Determination and Applications 286 installation. Reynolds et al. (2002) conducted infiltrometer tests under different conditions, Ledds-Harrison & Youngs (1994) used very small diameter rings (from 1.45 mm to 2.5 mm) for field measurements on individual soil aggregates, Youngs et al. (1996) used a 20 m diameter infiltrometer cylinder to measure highly structured and variable materials that could not be sampled adequately by a smaller cylinder. Castiglione et al. (2005) developed in the laboratory a tension infiltrometer ring, 4 cm in height and 27.5 cm in diameter, suitable for accurate measurements of infiltration into a big sample of fractured volcanic tuff, at very low flow rates over long equilibration times. Most field studies employ cylinder infiltrometers with diameters ranging commonly from 1 to 50 cm, which are poorly representative of the heterogeneous media, such as fractured rocks, in which hydraulically important fractures may, typically, be spaced further apart than the cylinder's diameter. Indeed, up to now infiltrometer tests have rarely been performed directly on-site on rock outcrops. This chapter describes a methodology to obtain the field-saturated hydraulic conductivity, Kfs, by using a ring infiltrometer, with a large (~2 m) adjustable diameter, developed for measuring quasi-steady infiltration rates on outcropped rock. Kfs is the hydraulic conductivity of the medium (soil or rock) when it has been brought to a nearsaturated state by water applied abundantly at the land surface, typically by processes such as ponded infiltration, copious rainfall or irrigation. The proposed device is inexpensive and simple to implement, as well as very versatile, owing to its large adjustable diameter that can be fixed on-site. Moreover, certain practical problems, related to the installation of the cylindrical ring on the rock surface, were solved in order to achieve a continuous and impermeable joint surface between the rock and the ring wall. An issue of major concern is linked to the edge effects, related to the radial spreading of the infiltrating water; obviously smaller rings are more influenced by these effects. Swartzendruber & Olson (1961) and Lai & Ren (2007) found that the ring infiltrometer needs a diameter greater than 1.2 m and 0.8 m, respectively, to avoid the edge effects. For this reason, the proposed large ring infiltrometer is made of a strip of flexible material with which build the cylinder on-site, with a suitable diameter in relation to the lithological and topographical features of the field. The flexible material, such as plastic or glass resin, allows the minimization of the size of the ring and, therefore, its movement easily, in order to acquire a large number of independent K fs measurements over a given area. In fact, because of the extreme spatial variability of K fs , its value finds statistical consistency in multiple tests. Geophysical techniques were coupled with the infiltrometer tests in order to monitor, qualitatively, the water infiltration depth, to allow a rapid visualization of the change in water content in subsurface and to ensure that the decrease in the water level in the ring was caused mainly by vertical water infiltration, and not by the lateral diversion of water flow. Since the late 1980s, many geophysical applications have been aimed at hydrogeological studies. White (1988) conducted electrical prospecting to determine the direction and the flow rate of saline aquifers using a tracer. Daily et al. (1992) used borehole electrical resistivity surveys to obtain the distribution of electrical resistivity in the subsurface, and compare the results with infiltrometer tests. Recently, electrical resistivity techniques have been used to monitor hydrogeological processes. Cassiani et al. (2006) conducted a monitoring test of a salt tracer by means of the application of electrical resistivity tomography using a time-lapse technique. The movement of the tracer was monitored with geophysical images. The methodology described in this chapter was carried out on different lithotypes in order to verify the applicability of the experimental apparatus in very different geological conditions. In particular two cases are described: the Altamura test site that represents a case of hard sedimentary rock consisting
Developments in Hydrogeophysical Research
crcleme.org.au
Measurement of groundwater physical properties of porosity and hydraulic conductivity in porous or fractured rock environments, and assessing water quality generally requires drilling a borehole. Boreholes provide accurate information at a point source, and a combination of boreholes can be used to infer regionalscale (i.e. 2 to1500 km) characteristics. However, is there a better way to fill in the gaps?
Effect of Heterogeneity of Hydraulic Conductivity on Streaming Potential
The 14th International Symposium on Recent Advances in Exploration Geophysics (RAEG 2010), 2010
Self-potential(SP) is electrical potential mainly generated by thermoelectric, chemical and streaming potentials in the subsurface. The flow of groundwater is often recognized as a bigger source of SP. Using this feature, there are many attempts to localize and quantify flows of liquid in the soil, including groundwater. In case that underground structure is homogeneous, electrical current density according to ground-water flow becomes uniform. Therefore SP on the surface increases monotonically from upstream to downstream of groundwater flow. As a basic interpretation of SP, the direction of increase in SP corresponds with the direction of groundwater flow. However, the anomalous fluctuations of SP start to appear for subsurface inhomogeneous groundwater flow due to the non-uniform conveyance of changes. Extra charge occurs on the boundary of these parameters. As a result, local minimum or maximum in the profile of SP generate just above the boundaries. Our simulation shows that the anomalies of permeability and coupling-coefficient in the subsurface are predominant parameters to effectively estimate the distribution of surface SP in the existence of inhomogeneous underground flow. The effect of coupling coefficient on the SP is often simulated on the underground flow scale. Some anomalies of SP are explained by the inhomogeneous of coupling coefficient. Simple model simulation, for example the well-pump model shows the effect of hydraulic conductivity on the SP. However, SP anomalies that are generated by inhomogeneity of hydraulic conductivity are not simulated on the underground flow scale. We compare the difference of these anomalies and study the different feature of SP anomaly that is generated by hydraulic conductivity from it by coupling coefficient.
Arabian Journal of Geosciences, 2018
The groundwater exploitation requires the evaluation of groundwater potentiality of the aquifer, particularly from the various studies such as the study of its physical characteristics. A complete hydrodynamic study requires knowledge of the properties of the aquifer system: its characterizing configuration and structure, functions of the reservoir, and its behavior. The aquifer is a complex interaction of two main functions: the storativity function and the conductivity function. This research is an integral part of a long-term research development and of a short-term operation, typically for medium-and long-term exploration of groundwater resources. In order to achieve this target, a substantial number of well-developed methods of evaluating the hydric potential and statistic calculations are currently being established. It is generally accepted that the method of estimating hydraulic parameters such as hydraulic conductivity of the aquifer is a very effective way, in case it is correlated to the results of the physical properties characterizing this aquifer. The laboratory study has been realized on an adequate sample of the soil from the aquifer by using appropriate techniques, to define its properties such as particle size, porosity, and measurements. For this case study, the physical properties of the aquifer materials are based on analysis of the test results obtained from 18 samples of the soil aquifer material, weighing from 2500 to 3000 g each, with the total mass of about 50 kg. Resulting values of the hydraulic conductivity are quite similar; all of them meet the range of the hydraulic conductivity from medium to coarse sand (8.8 E-05 to 3.27 E-03 m/s), an average value of (1.5 E-3 m/s). Nevertheless, it is possible to show the linear relationship between hydraulic conductivity and other physical properties such as void ratio (e) and the effective diameter (d 10) of the aquifer material which its mean values are respectively 52% and 0.52 mm. The hydraulic conductivity of soil depends on a variety of physical factors, including porosity, particle size and distribution, shape of particles, and arrangement of particles. Thus, it is complicated to identify a method to estimate values of hydraulic conductivity yielding a priori reliable ranges of results, when they are compared with results obtained by other methods of in situ measurement and laboratory. However, this method of empirical expression based on the particle size we have used provides satisfactory results.
Journal of Geoscience and Environment Protection, 2022
Development of groundwater needs the capabilities to distinguish the different aquifer layers found in a region, and thereafter the parameters which can be used expressly to define the aquifer type. The past studies in the Olbanita sub-basin has accorded the area as having one aquifer, which has resulted into generalization of the aquifer parameters. The objective in this study is to map the main aquifer layer and determine its parameters. The use of modeled geoelectric layers from Vertical Electrical Sounding (VES) data has been used in the study area to distinguish the major aquifer from the minor ones. There is noted an excellent correlation between the geoelectric layers and the lithologies as outlined by the driller’s log clearly delineating four aquifer stratums. The main aquifer is identified to be geoelectric layer 11 and 12, defined by a thickness of 30.18 m mainly of tuffs, and 17.39 m mainly of weathered phonolites. Hydraulic conductivity of the main aquifer averages value of 17.16389314 m/day, in consideration of the ranges 0.248690465 m/day to 74.62681942 m/day for the 31 VES points. For the aquifer breadth of 30.18 m, the Transmissivity values varied from a minimum of 57.32119 Ωm2 to 53365.49 Ωm2 and for 47.57 m breadth, the range is between 11.83021 Ωm2 and 1390.921 Ωm2. The variance of longitudinal unit conductance shows that 63.15 percent of the aquifer represented by one lithology is having lowest values of S (<1.0Ω^(-1)), an indication that the resistivity values of these points are relatively high when compared to their corresponding breadths. Notably, where the geoelectric layer is represented by more than one lithologic layer, the longitudinal unit conductance have high values of S (~1.1- 5.3 Ω^(-1)) at about 83.33 percent of the aquifer, thus giving a manifestation that a change in lithology has an implication in the aquifer characteristics. The transverse resistance values have a direct proportionality to both the aquifer layer thickness and the geoelectric layer resistivities. Evidently, using the close range of resistivities record indicates that indeed transverse resistance increases with increase in aquifer thickness. For example, for resistivities 52.677 Ω, 54.78 Ω, 54.297 Ω, 57.819 Ω, and 51.85 Ω, for 30.18 m, 47.57 m, 136.35 m, 190.84 m, 277.93 m thicknesses respectively, have their correlated transverse resistances values notably rising incrementally, from 1589.7919 Ωm^2, 2605.8846 Ωm^2, 7403.396 Ωm^2, and 11034.178 Ωm^2 correspondingly. There is confirmation that the modeled VES data can help map aquifers despite the limited resources of borehole logs that can used as control points.
Analysis of hydraulic test data from Karoo aquifers
2000
This paper discusses some of the difficulties experienced when analysing the results of hydraulic tests, in the Karoo aquifers of South Africa, with conventional methods. One particular difficulty experienced, was the rather unphysical dependence of the storativity values, S, on the distance between the observation and production boreholes. Detailed field investigations, and a three-dimensional model for these aquifers, have shown
Final Bacherlor Thesis, 2018
This study investigates the determination of aquifer parameters using step discharge tests to evaluate well performance for effective aquifer management. Single-well tests provide estimates of transmissivity in cases where cost and access preclude multi-well pumping tests. The study focused on two wells around the KNUST campus, determining aquifer loss, well loss, well efficiency, specific capacity, yield, and transmissivity. Results show transmissivity values of 3.21 m²/day and 5.82 m²/day, well efficiencies of 88.61% and 98.45%, and specific capacities of 2.89 m²/day and 3.03 m²/day for the two wells respectively.