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

seventy percent recovery has occurred. For lesser degrees of recovery, log-log plotting techniques provide a
more definitive type-curve match (Ramey et al., 1975). The type curves are placed over the test-data plots and
translated horizontally with the horizontal axes coincident until the best possible match between the data and
one of the type curves is achieved. In this position an arbitrary match point is chosen, and the corresponding
values of a and p are read from the type curve, and t is read from the data plot. The transmissivity (T) is then
calculated from the following rearrangement of Eq (A-31), using the coordinates of the match point:
(A-33)
The vertically averaged hydraulic conductivity. K, can be calculated from:
K = T/b
(A-34)
where: b = thickness of tested interval, L.
When static formation pressures are unknown, they may be approximated from flow-period or slug tests in the
following manner. A log-log plot of (H,-H)/H, versus elapsed time is prepared, using a "best-guess" value of
the static formation pressure to calculate H, and H. At late time, the data should become asymptotic to the
(H,-H)/H, value of 1.0. If the data become asymptotic to a lower value, the "best-guess'' static formation
pressureestimate was too high and should be revised downward. If thedataexceed the (H,-H)/H,value of 1 .O,
the estimate was too low and should be revised upward. In general, Horner extrapolations of buildup data,
when possible, provide greater resolution in estimating static formation pressures than do slug-test
interpretations.
A.3 PRESSURE-PULSE TEST ANALYSIS
Pressure-pulse tests were first described by Bredehoeft and Papadopulos (1980). The solution technique is
very similar to that developed by Cooper et al. (1967) for slug tests. The only difference between the two
methods is that in a slug test the water level changes in a tubing string of radius rc, while in a pressure-pulse test
water is only compressed in an isolated interval of the borehole. Analytically, the solution technique for
pressure-pulse tests is the same as that derived for slug tests with the rc2 terms in Eqs (A-31). (A-32), and (A-33)
replaced by V,C,pwg/n, where in consistent units:
V, = volume of water within the pressurized section of the system, L3
C, = compressibility of water, LT*/M
p, = density of water, M/L3
g = gravitational acceleration, L/T?
With this substitution, and subject to the constraint that a 5 0.1 [see Eq (A-32)], the analysis proceeds as
described above under Section A.2, Slug-Test Analysis.
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