Modeling cross-hole slug tests in an unconfined aquifer

Abstract

A modified version of a published slug test model for unconfined aquifers is applied to cross-hole slug test data collected in field tests conducted at the Widen site in Switzerland. The model accounts for water-table effects using the linearised kinematic condition. The model also accounts for inertial effects in source and observation wells. The primary objective of this work is to demonstrate applicability of this semi-analytical model to multi-well and multi-level pneumatic slug tests. The pneumatic perturbation was applied at discrete intervals in a source well and monitored at discrete vertical intervals in observation wells. The source and observation well pairs were separated by distances of up to 4 m. The analysis yielded vertical profiles of hydraulic conductivity, specific storage, and specific yield at observation well locations. The hydraulic parameter estimates are compared to results from prior pumping and single-well slug tests conducted at the site, as well as to estimates from particle size analyses of sediment collected from boreholes during well installation. The results are in general agreement with results from prior tests and are indicative of a sand and gravel aquifer. Sensitivity analysis show that model identification of specific yield is strongest at late-time. However, the usefulness of late-time data is limited due to the low signal-to-noise ratios.Comment: 6 figures, 2 table

Bayesian Monitoring Design for Streambed Heat Tracing: Numerical Simulation and Sandbox Experiments

“…According to some previous laboratory heat tracing studies (Rau et al 2012;Mamer and Lowry 2013;Malama et al 2016), a numerical case was first set up to demonstrate the implementation details of the Bayesian experimental design. The 2D model domain is shown in Figure 2.…”

A Semi‐Analytical Solution for Slug Test by Considering Near‐Well Formation Damage and Nonlinear Flow

“…Many studies (e.g., Bouwer & Rice, 1976; Bredehoeft & Papadopulos, 1980; Butler & Zhan, 2004; Cooper et al., 1967; Malama et al., 2016; Morozov, 2020; Zurbuchen et al., 2002) developed analytical models for slug tests for the water level displacement in the test well. The mathematical model for the slug test typically constitutes two parts.…”

“…The nonlinear flow significantly affects this response and may be expressed in terms of a squared velocity term. A substantial number of studies (e.g., Dausse et al., 2021; Hommersen et al., 2021; Kabala et al., 1985; Liu et al., 2020; Malama et al., 2011; Malama et al., 2016; McElwee, 2001; McElwee & Zenner, 1998; McGuire & Zlotnik, 1995; Stone & Clarke, 1993) reported such a nonlinear phenomenon for slug test in a high‐conductivity formation. Those studies however mainly focused on investigating the critically damped or underdamped water level response in the wellbore (Wang et al., 2015).…”

A Numerical Study of Slug Tests in a Three‐Dimensional Heterogeneous Porous Aquifer Considering Well Inertial Effects

“…Some researches point out that the magnitude of the oscillation will increase as the hydraulic conductivity of the aquifer and the water column height increase (Bredehoeft et al, 1966;Butler & Zhan, 2004). Since Bredehoeft et al (1966) discussed the role of water-column inertia in hydraulic tests, many researchers also considered inertial effects in their analytical slug test models to interpret the oscillatory head (Butler & Zhan, 2004;Kabala et al, 1985;Kipp, 1985;Malama et al, 2011Malama et al, , 2016McElwee & Zenner, 1998;Springer & Gelhar, 1991;Zurbuchen et al, 2002). Butler and Zhan (2004) presented a homogeneous slug test model for confined aquifers which considers inertial mechanisms both in the observation and test wells.…”

“…Butler and Zhan (2004) presented a homogeneous slug test model for confined aquifers which considers inertial mechanisms both in the observation and test wells. Malama et al (2016) further developed the model for unconfined aquifers. Considering the inertial effects in both wells makes their model more adequate for interpreting cross-well slug tests.…”