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For a medley of innovative designs
TRANSMISSIVITY PROFILING

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MEASURING THE FLOW PATHS FROM BOREHOLES
Profiler Drawing

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, ...). 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.
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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 transmissivity profile for the hole like that shown in Fig. 3 (calculated from the history of Fig. 2). In most transmissivity measurements, a transducer if first lowered to the bottom of the hole to directly measure the borehole driving head at the time each flow path is sealed. This direct measurement allows an even more precise calculation of the transmissivity profile.

The measurements performed are of more than just the velocity and excess head. FLUTe Transmissivity Profiler™ 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 borehole.

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In most cases, the FLUTe Transmissivity Profiler™ 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 FLUTe 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 liner is usually left in the borehole to seal the hole.

Flute has performed over 300 of these profiles in boreholes to depths of 1400 ft. These boreholes were from 3 to 12 inches in diameter. Publications and professional papers comparing the results to straddle packers are can be downloaded on our
publications page.

Given the continuous transmissivity profile, the head profile can be determined by removing the liner in a step wise fashion using a technique described at
head profile.