As the everting blank liner is installed, the water in the
borehole is forced from the hole
into the formation by whatever flow paths are available
(e.g., fractures, permeable beds, solution channels, ä.).
The liner descent rate is controlled by the rate at which water can
flow from the hole via those paths. The everting liner is somewhat like
the perfectly fitting piston sliding down the hole, except the liner doesn't
slide in the hole, it grows in length at the bottom end of the dilated liner
at the "eversion point" as we call it. As the liner everts, it covers the
flow paths sequentially. Each time that the liner covers a flow path,
the transmissivity of the hole beneath the liner is decreased and the total
flow rate out of the hole is reduced. This reduction in flow rate causes a
reduction in the descent rate of the liner. Figure 1 is a drawing of the
simple everting liner with two additional features. The roller at the wellhead
measures the liner velocity and the pressure gauge measures the excess head in
the liner which is driving the liner down the hole.
When the liner begins its descent in the hole, all of the flow paths are open and
the descent rate is highest.
As the liner sequentially covers those flow paths, the liner descent rate
decreases to produce a monotonically decreasing velocity with depth in the hole.
The velocity profile looks like that of Fig. 2. At each step change in velocity,
one can determine the location of the flow path in the hole, and the magnitude
of the velocity change is the measure of the flow that was occurring in that
flow path before it was covered by the everting liner. From the velocity profile,
one can calculate a conductivity profile for the hole like that shown in Fig. 3
(calculated from the history of Fig. 2).
The actual machine used for the measurement is shown in
Fig. 4. The measurements performed are of more than just the velocity
and excess head.
The FLUTe Hydraulic Conductivity ProfilerTM measures all of the significant parameters which can influence the velocity of the liner descent.
Those are incorporated into a software package that calculates the
conductivity profile of Fig. 3. In this manner, all significant
flow paths can be mapped in the borehole in the time it takes to install
the flexible liner. That time varies from half an hour to three to four
hours depending upon the transmissivity distribution in the hole.
In most cases, the FLUTe Hydraulic Conductivity ProfilerTM can map all of
the significant flow paths in the hole in less than 10 percent of the
time required to do the same mapping
with a straddle packer. Furthermore, the detail in the FHC Profiler
measurement is not even possible with straddle packers.
The direct measurement of the flow paths with the Profiler may also reduce
the need for those geophysical measurements which are used to deduce possible
flow path locations in a borehole. Another advantage is that the blank liner
is often installed to seal the hole against vertical contaminant migration.
The conductivity profile is obtained by carefully measuring the normal blank
liner installation.
Flute has performed over 150 of these profiles in boreholes to depths of 900 ft. These
boreholes were from 4 to 10 inches in diameter. Publications and papers comparing the results
to straddle packers are can be downloaded on our publications page.
Contact us at
for more information and prices for this service
* patent numbers 6,910,374 B2 and 7,281,422
