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

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225
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PRESSURE ABOVE TEST INTERVAL
I L
a
"i sa
........ -
#'..' \
FFL
?--
. . . . .
c_c
!\
. SBU
SFL
\
. . . . . . . . . . . . . . ;.
0 .5 I 1.5 2 2.5 3 3.5 4 4.5 5
Start Date: 1W21/1986
Start Time: 13:25:88
Elapsed Time in Hours
Linear-Linear Sequence Plot
H-I4/UPPER CULEBRA DST'S
Figure 5-26. H-l4/Upper Culebra Drillstem Test Linear-Linear Sequence Plot
FFL was divided into three flow periods with rates
ranging from 0.186 to 0.116 gpm, and the SFL was
divided into two flow periods with rates of 0.138 and
0.097 gpm (Table 5-1).
Figure 5-27 shows a log-log plot of the FBU data,
along with an INTERPRET-generated simulation.
The simulation is representative of a single-porosity
medium with a transmissivity of 0.096 ftZ/day
(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 about -0.8, indicating a slightly
stimulated well.
The sharp decline in the pressure derivative at late
time in Figure 5-27 is an indication that the
overpressure skin induced by the weight of the
drilling fluid during coring of the upper Culebra was
dissipating during the DST's. The effect of the
overpressure skin is also seen in the dimensionless
Horner plot for the FBU (Figure 5-28). The best
simulation obtained shows that the pressure was
initially recovering towards 95.5 psia (the static
pressure specified for that simulation), but then
deviated towards a lower pressure at late time. This
is also shown in Figure 5-26 by the pressure peak at
99.04 psia during the pre-test equilibration period,
the subsequent peak during the FBU at 91.36 psia,
and the near stabilization of the pressure at
88.94 psia at the end of the SBU.
Figure 5-29 shows a log-log plot of the SBU data,
along with an INTERPRET-generated simulation.
The simulation is representative of a single-porosity
medium with a transmissivity of 0.10 ftz/day
(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 about -1.3. These values are in
excellent agreement with the FBU results, and
indicate possible slight well development during the
DST's. The decline in the pressure derivative in
Figure 5-29 at late time shows the continuing
influence of the overpressure skin on the data.
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