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

4.0
MATCH PARAMETERS
.A. L.
21%
3.0
.
Y
n
: 2.0
n
AP
= 1.0 psi
t
= 1.0 hr
PO = 0.064
tdC, =14
P*
1 .o
+ DATA
- SIMULATION
I
I
0.0 --- 0.0 1 .o 2.0 3.0
DIMENSIONLESS SUPERPOSITION FUNCTION: FLOW PERIOD 3
Figure 5-1 04. H-1 G/Forty-Niner Clay First Buildup Dimensionless Horner Plot with INTERPRET Simulation
The log-log plot of the SBU data (Figure 5-105) is
very similar to that of the FBU data (Figure 5-103).
The INTERPRET simulation is also similar, using a
transmissivity of 5.6 x 10-3 ftz/day and a skin factor of
0.6 (Table 5-2). Again, overpressure-skin effects are
evident in the late-time behavior of the pressure
derivative.
Figure 5-1 06 is an early-time log-log plot of the Fortyniner
slug-test data. Because of the low degree of
pressure recovery during the slug test, the data are
inadequate to provide definitive results on their own,
but they do serve to confirm the DST results. The
type-curve match shown provides a transmissivity
estimate of 5.0 x 10-3 ft*/day (Table 5-2), and uses a
static formation pressure estimate of 116.1 psia. Both
of these values are in reasonable agreement with the
DST interpretations.
In contrast, the transmissivity value provided by the
pulse-test interpretation is over an order of
magnitude lower than the transmissivity values
estimated from the DST and slug-test analyses. This
low apparent value of transmissivity may hwe been
caused by two, perhaps interrelated, factors. First,
pulse tests inherently test very small volumes of rock
around a borehole, much smaller than do DST's and
slug tests. The average transmissivity of the rock
tested could easily change between the two scales
of tests. Second, the pulse test was the first test
performed and was an injection test, whereas the
DST's and slug test were withdrawal tests. Any skin
that may have been present on the borehole wall
after drilling, such as a mud cake, could be loosened
by a withdrawal test, but would be intensified by an
injection test. Consequently, the pulse-injection test
may have measured an average transmissivity of
both the nearby rock and the wellbore skin. The
subsequent DST's and slug test, which caused water
to flow into the well, should have served to decrease
any skin present, and this may be evidenced by the
slight drop in skin values between the FBU and the
SBU (Table 5-2). For these reasons, and because of
the consistency of the DST and slug-test results, the
most reliable value for the transmissivity of the Fortyniner
clay at H-16 is probably about 5.3 x 10-3 ftz/day.
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