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Blank Liner Mechanics

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Installation of FLUTe Blank Liner

There are many other advantages of the liner's sealing of the borehole:
1. The flow in the formation is not perturbed by flow in the open hole. Therefore measurements of various kinds, such as temperature distributions due to flow in the formation, are more realistic of the natural hydrologic state.

2. The borehole is not likely to collapse on geophysical sondes which can “see” through the thin liner such as sonic tele-viewer, radiation logs, induction coupled electric logs, radar, etc… can traverse the borehole without concern about collapse of the borehole on the instrument.

3. Salt water intrusion in the formation can be sensed with a deionized water fill of the liner, as was done in Majorca, Spain, without the open hole perturbing the salt water front.

4. Removal of the blank liner can enhance the borehole development as described in the paper Open Hole Well Development Problems.

5. The liner installation is used to obtain a high resolution transmissivity profile of the borehole in a few hours as compared to days for straddle packer testing with lower spatial resolution. And a head distribution can be obtained during the stepwise removal of the liner after a continuous transmissivity profile has been measured.

6. The liner conforms to the borehole wall better than packers because it is thin and flexible. And, the liner is not abraded by the borehole wall as it is everted into, or inverted out of, the borehole.

7. The liner seals the entire hole where it can be sealed as compared to multiple packers in boreholes. This is especially useful in karst formations. A packer must be placed in an aquitard to be fully effective.

8. Liners are shipped on a small reel with no need of heavy equipment for the liner installation such as a drill rig or crane truck. The blank liner is easily installed by simply adding water to the interior of the liner.
9. The FLUTe liners are made of fabrics with tensile strengths ranging from 100-400 lb/inch and therefore have low risk of puncture by sharp rock.

10. FLUTe liners have never yet been trapped by slough of the borehole because of the gentle nature of the liner propagation and associated support of the borehole. Hence there is little risk of entrapment as compared to packer systems.

11. One can deduce the highest head in the formation by slowly pumping down the water level in the liner until it no longer drops, because the liner is being collapsed by the highest head in the formation.

12. The blank liner is used as a carrier for installation of many kinds of coverings for a variety of measurements (NAPL FLUTe, FACT, vadose absorbers). The blank liner presses the cover against the borehole wall and isolates the cover against flow along the borehole.

13. Liners are used to tow instruments through the protected interior of the liner as the liner is being emplaced. See geophysical applications and landfill monitoring.

14. Blank liners can be equipped with many special features for custom applications such as cure-in-place liners, transparent liners, heaters on the tether, fiber optic sensors, insulation of various kinds as well as special fill materials like weighted mud, DI water, sand, freezing fluids to stabilize the hole, etc….

15. Liners can prevent the loss of annular sealing grouts outside a casing emplaced in karst formations. –a common problem with oil and gas borehole casings.

16. Liners can seal shallow portions of municipal wells preventing contaminants entering the well. An interior casing in place of the tether allows the pump emplacement to greater depths. A grout fill of the liner makes it a permanent seal.
However, urethane liners are susceptible to mistreatment such as lowering heavy tools inside of pressurized liners or dragging the liner on a paved surface which abrades the liner coating. A blank liner installation and removal instruction video, available from FLUTe, teaches the methods and precautions for the use of blank liners.

The basic mechanism for installation and removal of the blank flexible liner is described in liner mechanics.

The most common application of blank liners is to seal boreholes immediately after they are drilled.

The liner seals the borehole against contaminant migration through the open hole and stabilizes the borehole against collapse.
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