Chapter 16 Kruseman and Ridder 1970 Stephanie Fulton March 25 2014 Background Small volume of wateror alternatively a closed cylinderis either added to or removed from the well ID: 404960
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Slide1
Slug Tests
Chapter 16Kruseman and Ridder (1970)
Stephanie Fulton
March 25, 2014Slide2
Background
Small volume of water—or alternatively a closed cylinder—is either added to or removed from the wellMeasure the rise and subsequent fall of water level
Determine aquifer transmissivity (T or KD) or hydraulic conductivity (K)
If T is high (i.e., >250 m
2
/d), an automatic recording device is needed
No pumping, no piezometers
Cheaper and faster than conventional pump tests
But they are NO substitute for pump tests!!!
Only measures T/K in immediate vicinity of
well
Can be fairly accurateSlide3
Types of Slug Tests
Curve-Fitting methods (conventional methods)Confined, fully penetrating wells: Cooper’s Method
Unconfined, partially or fully penetrating wells:
Bouwer
and Rice
Oscillation Test (more complex method)Air compressor used to lower water level, then released and oscillating water level measured with automatic recorderAll methods assume exponential (i.e., instantaneous) return to equilibrium water level and inertia can be neglectedInertia effects come in to play for slug tests in highly permeable aquifers or in deep wells oscillation testPrior knowledge of storativity neededSlide4
Cooper’s Method (1967)
Confined aquifer, unsteady-state flowInstantaneous removal/injection of volume of water (V) into well of finite radius (r
c
) causes an instantaneous change of hydraulic head:
(16.1
)
Slide5
Cooper’s Method (cont.)
Subsequently, head gradually returns to initial headCooper et al. (1967) solution for the rise/fall in well head with time for a fully penetrating large-diameter well in a confined aquifer:Slide6
Cooper’s Method (cont.)
Annex 16.1 lists values for the function F(α,
β
) for different values of
α
and
β given by Cooper et al. (1967) and Papadopulos (1970)
These values can be presented as a family of curves (Figure 16.2)Slide7
Cooper’s Method: Assumptions
Aquifer is confined with an apparently infinite extentHomogeneous, isotropic, uniform thicknessHorizontal piezometric surface
Well head changes instantaneously at t
0
= 0
Unsteady-state flow
Rate of flow to/from well = rate at which V changes as head rises/fallsWater column inertia and non-linear well losses are negligibleFully penetrating wellWell storage cannot be neglected (finite well diameter)Slide8
Remarks
May be difficult to find a unique match of the data to one of the family of curves
If
α
< 10
-5
, an error of two orders of magnitude in α will result in <30% error in T (Papadopulos et al. 1973)
Often
r
ew
(i.e.,
r
ew
=
r
w
e
-skin
) is not known
Well radius
r
c
influences the duration of the slug test: a smaller rc shortens the testRamey et al. (1975) introduced a similar set of type curves based on a function F, which has the form of an inversion integral expressed in terms of 3 independent dimensionless parameters: KDt/rwS, rc2/2rw2S and the skin factor
Slide9
Uffink’s Method
More complex type of slug test for “oscillation tests”Well is sealed with inflatable packer and put under high pressure using an air line
Well water forced through well screen back into the aquifer thereby lowering head in the well (e.g., ~50 cm)
After a time, pressure is released and well head response to sudden change is characterized as an “exponentia
lly damped harmonic oscillation”
Response is typically measured with an automatic recorderSlide10
Uffink’s Method (cont.)
This oscillation response is given by Van der Kamp (1976) and Uffink (1984) as:Slide11
Uffink’s
Method (cont.)
Damping constant,
γ
=
ω
0B (16.7)Angular frequency of oscillation,
ω
=
ω
0
(16.8)
Where
ω
0
= “damping free” frequency of head oscillation (Time
-1
)
B = parameter defined by Eq. 16.13 (dimensionless)
Slide12
Uffink’s Method (cont.)Slide13
Uffink’s Method (cont.)
The nomogram in Figure 16.4 (below) provides the relation between B and
r
c
2
/
ω04KD for different values of α as calculated by
Uffink
:
Figure 16.4Slide14
Uffink’s
Method: Assumptions and ConditionsAssumptions are the same as with Cooper’s Method (Section 16.1), EXCEPT:Water column inertia is NOT negligible and
Head change at t > t
0
can be described as an “exponentially damped cyclic fluctuation”
Added condition:
S and skin factor are already known or can be estimated with fair accuracySlide15
Bouwer-Rice’s Method
Unconfined aquifer, steady-state flowMethods for full or partially penetrating wells
Method is based on
Thiem’s
equation for flow into a well following sudden removal of slug of water:
The well head’s
subsequent rate of rise:
Figure 16.5Slide16
Bouwer-Rice’s Method
Combining Eqs. 16.16 and 16.17, integrating, and solving for K:Slide17
Bouwer-Rice’s Method
Values of Re were experimentally determined using a resistance network analog for different values of
r
w
, d, b, and D
Derived two empirical equations relating R
e to the geometry and boundary condition of the systemPartially penetrating wells:A and B are dimensionless parameters which are functions of d/
r
w
Full
y penetrating wells:
C is a dimensionless parameter
which
is a function
of
d/
r
wSlide18
Bouwer-Rice’s MethodSlide19
Bouwer-Rice’s
Method: Assumptions and ConditionsSlide20
Bouwer
-Rice’s Method: Remarks