Modeling slug tests in unconfined aquifers taking into account water table kinematics, wellbore skin and inertial effects

Malama, Bwalya; Kuhlman, Kristopher L; Barrash, Warren; Cardiff, Michael; Thoma, Michael

doi:10.1016/j.jhydrol.2011.07.028

Cited by 28 publications

(46 citation statements)

References 18 publications

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“…McElwee and Zenner (1998) derived a new solution of slug test by using the Navier-Stokes equation for flow in the wellbore and the Hvorslev model for flow in the aquifer, of which the robustness of solution was subsequently tested by field data (McElwee, 2001). Malama et al (2011) modeled slug tests in unconfined aquifers taking into account water table kinematics, wellbore skin and inertial effects. In addition to above mentioned studies, other scientists also devoted significant efforts to slug test reasearch by incorporating the effects of partial penetration, anisotropy, short well screens, aquifer compressibility and finite radius well skins (Brown et al, 1995;Hyder and Butler, 1995;Hyder et al, 1994;Mills, 2010;Singh, 2007;Widdowson et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Non-Darcian effect on slug test in a leaky confined aquifer

Wang

Zhan

Wang

2015

Journal of Hydrology

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Section: Introductionmentioning

confidence: 99%

Non-Darcian effect on slug test in a leaky confined aquifer

Wang

Zhan

Wang

2015

Journal of Hydrology

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“…Details of the slug-test procedures, data quality assessment, and analysis are given in Malama et al (2011, and Barrash and Cardiff (2013). Figure 5 shows example K profiles from a few wells within the central well field.…”

Section: Hydraulic Conductivity From Multilevel Slug Testsmentioning

confidence: 99%

The hydrogeologic information in cross-borehole complex conductivity data from an unconsolidated conglomeratic sedimentary aquifer

et al. 2016

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Accurate estimation of the hydrological properties of nearsurface aquifers is important because these properties strongly influence groundwater flow and solute transport. Laboratorybased investigations have indicated that induced polarization (IP) properties of porous media may be linked, through either semiempirical or fully mechanistic models, to hydrological properties including hydraulic conductivity. Therefore, there is a need for field assessments of the value of IP measurements in providing insights into the hydrological properties of aquifers. A cross-borehole IP survey was carried out at the Boise Hydrogeophysical Research Site (BHRS), an unconsolidated fluvial aquifer that has previously been well-studied with a variety of geophysical and hydrogeologic techniques. High-quality IP measurements were inverted, with careful consideration of the data error structure, to provide a 3D distribution of complex electrical conductivity values. The inverted distribution was further simplified using k-means cluster analysis to divide the inverted volume into discrete zones with horizontal layering. Identified layers based on complex electrical conductivity inversions are in broad agreement with stratigraphic units identified in previous studies at the site. Although mostly subtle variations in the phase angle are recovered through inversion of field data, greater contrasts in the IP data are evident at some unit boundaries. However, in coarse-grained aquifers, such as the BHRS, the discrimination of mildly contrasting lithologic units and associated changes in hydraulic conductivity of one or two orders of magnitude are unlikely to be achieved through field IP surveys. Despite the difficulty of differentiating subtle differences between all units, overall estimates of hydraulic conductivity purely from our field IP data are typically within an order of magnitude of independently measured values.

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“…The result indicated that the assumption of water table as a constant‐head boundary will overestimate transmissivity. Malama, Kuhlman, Barrash, Cardiff, and Thoma () extended the solution of Hyder et al () by replacing the constant‐head condition at the water table with a free boundary that represented the linearized kinematic water table boundary condition (Neuman, ) and by considering the inertial wellbore effects (kinematic water table condition [KWTC] model). The results of Malama et al () indicated that the model with a KWTC essentially yielded the same head distribution as the confined KGS model, except in the region close to the water table where it produced a more physically realistic result.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, the well drilling and development often generate a disturbed near‐well zone (wellbore skin) that may have higher or lower hydraulic conductivity than that of the formation. Interpretation of slug test results using a model without the wellbore skin will lead to incorrect hydraulic conductivity estimation if the wellbore skin exists (Hyder et al, ; Malama et al, ; Yang & Gates, ; Yeh & Chen, ). More specifically, in the case of a skin less permeable than the formation, one might underestimate the hydraulic conductivity over an order of magnitude; whereas in the case of a high‐conductivity case, one will overestimate the hydraulic conductivity.…”

Section: Introductionmentioning

confidence: 99%

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Underdamped slug tests with unsaturated‐saturated flows by considering effects of wellbore skins

Liang

Zhang

et al. 2018

Hydrological Processes

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An analytical solution is presented for the slug tests conducted in a partially penetrating well in an unconfined aquifer affected from above by an unsaturated zone. The solution considers the effects of wellbore skin and oscillatory responses on underdamped slug tests. The flow in the saturated zone is described by a two‐dimensional, axially symmetric governing equation, and the flow in the unsaturated zone above the water table by a linearized one‐dimensional Richards' equation. The unsaturated medium properties are represented by the exponential constitutive relationships. A Laplace domain solution is derived using the Laplace and finite Fourier transform and the solution in the real‐time domain is evaluated using the numerical inverse Laplace transform method. The solution derived in this study is more general and reduces to the most commonly used solutions for slug tests in their specified conditions. It is found that the unsaturated flow has a significant impact on the slug test conducted in an unconfined aquifer. The impact of unsaturated flow on such a slug test is enhanced with a larger anisotropy ratio, a shorter well screen length, a shorter distance between the well screen and the water table, or a larger well screen radius. The impact of unsaturated flow on slug tests decreases as the degree of penetration (the length of well screen) increases. For a fixed well screen length, the impact of unsaturated flow on slug tests decreases as the distance between the centre of screen and the water table increases. A large dimensionless well screen radius (>0.01) leads to significant effects of unsaturated flow on slug tests. The unsaturated flow reduces the oscillatory responses to underdamped slug tests. The unsaturated zone has significant impact on slug test under high‐permeability wellbore skin.

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Modeling slug tests in unconfined aquifers taking into account water table kinematics, wellbore skin and inertial effects

Cited by 28 publications

References 18 publications

Non-Darcian effect on slug test in a leaky confined aquifer

Non-Darcian effect on slug test in a leaky confined aquifer

The hydrogeologic information in cross-borehole complex conductivity data from an unconsolidated conglomeratic sedimentary aquifer

Underdamped slug tests with unsaturated‐saturated flows by considering effects of wellbore skins

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