12:166, Zhang

Spring, 2002

Slug/Bail Test and Analysis

· Hvorslev Method (1951)

· Assumption

1. Non-leaky confined aquifer of “apparently” infinite extent;

2. Homogeneous, isotropic aquifer of uniform thickness;

3. Water table is horizontal prior to the test;

4. Instantaneous injection/withdrawal of a volume of water results in an instantaneous change in water level;

5. Inertia of water column and non-linear well losses are negligible;

6. Full or partially penetrating well;

7. The well is considered to be of an infinitesimal width;

8. Flow is horizontal toward or away from the well.

· Formula

where r is the well casing radius;

L_e is the screen length;

R is the radius of the well including the gravel pack;

T₀ is the time lag when H/H₀ =0.37.

· Bouwer-Rice Method (1976)

· Assumption

1. Unconfined aquifer of “apparently” infinite extent;

2. Homogeneous, isotropic aquifer of uniform thickness;

3. Water table is horizontal prior to the test;

4. Instantaneous change in water level;

5. Inertia of water column and non-linear well losses are negligible;

6. Full or partially penetrating well;

7. The well storage is not negligible, thus it is considered;

8. Flow to well is in steady-state.

· Formula

where r is the well casing radius;

L_e is the screen length;

R is the radius of the well including the gravel pack;

R_cont is the contributing radial distance over which the difference in head,

H₀, is dissipated in the aquifer;

i is the slope of the line of ln(H/H₀) vs. time, i.e., i = ln(H/H₀) /t

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