Beauheim 1987 - Waste Isolation Pilot Plant - U.S. Department of ...

A.2 SLUG-TEST AND DST FLOW-PERIOD DATA ANALYSIS
Slug-test and DST flow-period data were analyzed using a method first presented by Cooper et al. (1967) for
slug tests, and adapted to DST's by Ramey et al. (1975). The method is used for calculating the transmissivity of
a homogeneous, isotropic, confined porous medium of uniform thickness which is fully penetrated by a well.
To initiate a slug test. a pressure differential is established between the wellbore and the surrounding formation
by shutting in the test interval, swabbing the fluid from the tubing (in the case of a rising-head or slugwithdrawal
test) or adding fluid to the tubing (in the case of a falling-head or slug-injection test), and then
opening the test interval to the tubing. The problem is described mathematically in radial geometry by the
diffusivity equation:
a2h 1 ah Sah
-++=ar*
rar Tat
(A-30)
where in consistent units:
h = hydraulic head differential (at radius r and time t). L
r = radius from well center. L
t = elapsed time, T
S = formation storativity
T = formation transmissivity, L2/T.
This equation describes nonsteady, radial flow of groundwater.
The solution to this equation utilized for analysis of slug-test (or DST flow-period) data is presented in the form
of curves of [H/H,] (Figure A-5) and [(H,-H)/H,] (Figure A-6) versus the dimensionless time parameterp for
each of several values of a, where in consistent units:
p = Tt/r,*
(A-31)
a = r,2S/rc2
(A-32)
and
H, = initial (maximum) head differential, L
H = head differential at timet, L
t = time elapsed since test began. T
rs = radius of borehole. L
r~ = inside radius of tubing string, L.
Plots of the quantities [H/H,] and [
the same scale as the type curves.
H,-H)/H,] versus t are made on semilog and log-log paper, respectively, of
Semilog plotting and type curves are best used when a minimum of about
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