Analysis of Slug Tests in Formations of High Hydraulic Conductivity

Abstract

A new procedure is presented for the analysis of slug tests performed in partially penetrating wells in formations of high hydraulic conductivity. This approach is a simple, spreadsheet-based implementation of existing models that can be used for analysis of tests from confined or unconfined aquifers. Field examples of tests exhibiting oscillatory and nonoscillatory behavior are used to illustrate the procedure and to compare results with estimates obtained using alternative approaches. The procedure is considerably simpler than recently proposed methods for this hydrogeologic setting. Although the simplifications required by the approach can introduce error into hydraulic-conductivity estimates, this additional error becomes negligible when appropriate measures are taken in the field. These measures are summarized in a set of practical field guidelines for slug tests in highly permeable aquifers.

Results of Detailed Hydrologic Characterization Tests?Fiscal and Calendar Year 2005

“…It should be noted that the High-K analysis method requires that the pressure sensor used during testing be located in close proximity to the water-table surface, as discussed in Zurbuchen et al (2002), Butler et al (2003), and Chen and Wu (2006). This is due to the effects of water-column acceleration within the well.…”

“…For standard Hanford Site RCRA wells exhibiting under-damped test conditions, the maximum stress level used for such test sites should not generally exceed ~ 1 / 10 of the saturated well-screen length. Methods for analyzing unconfined aquifer tests exhibiting high-permeability under-, over-, or criticallydamped characteristics include techniques described in Springer and Gelhar (1991), Butler (1998), McElwee and Zenner (1998), Butler and Garnett (2000), Zurbuchen et al (2002), and Butler et al (2003). Because of the ease provided by a spreadsheet-based approach, the analysis method presented in Butler and Garnett (2000) has been used in previous characterization reports by the authors (e.g., to analyze all tests exhibiting under-damped response behavior (i.e., high permeability/oscillatory pattern).…”

“…Due to the larger test responses produced, better analytical results were obtained for the high-stress tests. As discussed in Butler et al (2003), for tests conducted in high-permeability formations, the pressure sensor should be situated in close proximity to the top of the well water-column to avoid well acceleration effects. For the slug-test characterization conducted at well 299-E33-49, the pressure sensor was situated within 0.5 meters of the top of the well water-column for only two of the high-stress slug tests.…”

“…All slug tests exhibited critically-damped (transitional response) behavior, which is indicative of moderate to high-permeability aquifer conditions. Because of the exhibited critically-damped response behavior, the High-K analysis method presented in Butler and Garnett (2000) and Butler et al (2003) (see Section 3.1.4) was used to analyze the slug tests at well 299-E33-49.…”

Analysis of slug-tests with high-frequency oscillations

“…The slug tests were initiated by a sudden release of water in the inner casing (falling-head initiation), with the help of a 3 m 3 capacity tank equipped with a rapid flow valve. Experiments were conducted following the recommendations by (McElwee, 2002) and (Butler et al, 2003): (1) in each well, multiple slug tests involving various initial head displacements (injection of various volumes of water) were performed to test for repeatability and nonlinear effects, and (2) for each slug test, the water-level recovery was monitored over time with a pressure transducer placed within 0.5 m below the static level, which minimised the errors in measured heads caused by the acceleration of the water column.…”