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

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Start Date: 08/29, i985
Start Time: 18: li:D5
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Hormr Plot: tp = 0.268 Hours
h;??-12/3ST 1120-2450/MR lE3-CCYDEFi FBU
Figure 5-8. WIPP-I2/Salado Marker Bed 103 to Cowden First Buildup Horner Plot
5.1.3.4 Well Casing to Cowden Anhydrite. The
final test of the Salado at WIPP-12 was performed on
an interval extending from the base of the well casing
to the Cowden anhydrite, 1004.5 to 2450 ft deep.
The test was performed on August 30, 1985, and
consisted of a 30-minute flow period followed by a
buildup period lasting about 139 minutes
(Figure 5-9). As was the case with the other Salado
tests, very little fluid entered the tubing during the
flow period. The pressure buildup was slow, with a
final rate of about 10 psi/hr, and showed no
indication of trending towards a positive surface
pressure.
Figure 5-10 is a Horner plot of the buildup data. The
static formation pressure (p*) estimated by
extrapolating from the last two points to infinite time
is 333 psia. This estimate must be too low because
the data curve was continuing to steepen when the
buildup was terminated. The curve would have to
steepen considerably, however, to extrapolate to the
approximately 813 psia that, with the transducer at a
depth of 990.7 ft, would correspond to the 288 psig
measured at the WIPP-12 wellhead. As was the case
with all the other Salado tests, the test of the interval
from the well casing to the Cowden anhydrite gave
no clear indication of that portion of the Salado
containing the source of the high pressures
measured at the WIPP-12 wellhead.
5.1.4 Conclusions From Castile and Saiado
Tests. The tests of the brine-reservoir plug and the
Castile Formation showed a constant-pressure
response apparently governed by the brine reservoir
in the lower part of the Anhydrite 111 unit of the
Castile. This constant pressure, however, is lower
than the pressures measured at the WIPP-12
wellhead, and therefore cannot be their source.
None of the tests of the Salado provided any
indication of the source of the high pressures. All of
the zones tested exhibited pressure buildups, but
none of the buildups clearly extrapolated to positive
surface pressures. In fact, given the 6.5+ years of
high pressures to which the entire borehole was
subject preceding these tests, we cannot say with
certainty which, if any, of the observed pressure
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