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

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ELAPSED TIME, hours
Figure 5-52. H-17lCulebra Slug-Test Plot
(Figure 3-10). The interval tested extended from
685.0 to 714.1 ft deep. Thus, the lower 3.6 ft of the
Tamarisk and the upper 1.3 ft of the unnamed lower
member were included in the test interval. Inasmuch
as these overlying and underlying intervals are
composed of anhydrite/gypsum and clay,
respectively, they were not considered to have
contributed significantly to the transmissivity
measured during the Culebra testing.
The Culebra testing was performed on October 31,
1987, the day after the Culebra was cored. The
testing consisted of two DST flow periods, two
buildup periods, and a rising-head slug test
(Figure 5-53). The FFL lasted about 11 minutes, and
was followed by a 64-minute FBU. The SFL lasted
about 18 minutes, and was followed by an 89-minute
SBU. To obtain constant flow rates for buildup
analyses, the FFL was divided into two flow periods
having rates of 1.372 and 1.083 gpm, and the SFL
was divided into two flow periods having rates of
1.200 and 0.772 gpm (Table 5-1). The slug test
lasted about 90 minutes, allowing 92% of the
induced pressure differential to dissipate. The data
from these tests are presented in Stensrud et al.
(1 988).
Figure 5-54 is a log-log plot of the FBU data, along
with a simulation generated by INTERPRET. The
simulation is representative of a single-porosity
medium with a transmissivity of 2.2 ftzfday
(Table 5-3). Assuming a Culebra porosity of 20%, a
total-system compressibility of 1.0 x 10-5 psi-', and a
fluid viscosity of 1.0 cp, the skin factor for this
simulation is -0.2, indicating a minimally stimulated
well. The decline in the pressure derivative at late
time indicates the presence of an overpressure skin
created during coring and reaming of the Culebra.
This overpressure skin was strong enough to cause
the pressure to peak at 157.3 psia after 42 minutes of
the FBU (Figure 5-53). The dimensionless Horner
plot of the FBU data (Figure 5-55) shows that the
overpressure skin was driving the recovery toward a
static formation pressure of 158.6 psia until late time,
when the data began trending toward a lower
pressure (upward on the plot) as the skin dissipated.
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