Analysis of partially penetrating slug tests in a stratified formation by alternating piezometer and tube methods

JOURNAL OF HYDROLOGY

卷:528

Article

Sakata, Yoshitaka¹  Imai, Toshikazu²  Ikeda, Ryuji³  Nishigaki, Makoto⁴ 

[1] Hokkaido Univ, Fac Engn, Div Human Environm Syst, Environm Syst Res Lab,Kita Ku, Sapporo, Hokkaido 0608628, Japan

[2] GM Labo Inc, Kita Ku, Osaka, Osaka Fu 5300047, Japan

[3] Hokkaido Univ, Fac Sci, Div Earth & Planetary Dynam, Kita Ku, Sapporo, Hokkaido 0600810, Japan

[4] Okayama Univ, Fac Environm Sci & Technol, Dept Environm & Civil Design, Okayama, Japan

关键词: Slug tests;    Partially penetrating well;    Hydraulic conductivity;    Sensitivity analysis;    Numerical simulation;    Heterogeneity;   

DOI  :  10.1016/j.jhydrol.2015.06.019

来源: Elsevier

【 摘 要 】

In partially penetrating slug tests, hydraulic conductivity (K) estimates might not necessarily be valid because of vertical flows in heterogeneous formations. We assess the error in hypothetical stratified formations by numerical sensitivity analysis, and propose an effective method for compensation by incorporating two types of casing configuration (piezometer and tube). The hypothetical stratified formation consists of completely horizontal layers, each I m thick; the permeability is different between, but not within, layers. In this study, conductivity estimates in the piezometer and tube methods are calculated by assigning various patterns of conductivity to the test, upper, and lower layers: K-T, K-U and K-L. The effect of vertical flow becomes significant when K-T is small relative to K-U or K-L, and K-L is more important than K-U because the base of the borehole is open to the lower formation. The conductivity ratios (estimate over actual value) are treated as approximately linearly dependent on logarithms of K-T/K-U and K-T/K-L, so that conductivity estimates can be straightforwardly derived from one piezometer measurement and two tube measurements at the top and bottom of the screen. The linear relations are evaluated and constant parameters are determined under specific conditions. This study also recommends alternating piezometer and tube methods in the drilling procedure because the actual variation of K with depth is larger than that found using isolated measurements, as shown in a field study of alluvial fan gravel deposits in Sapporo, Japan. (C) 2015 Elsevier B.V. All rights reserved.

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