Flexible Liner Special Utility inFlexible Liner Special Utility in Karst Formations

by

Carl KellerCarl Keller

Midwest Ground Water ConferenceOctober 1‐3, 2012; Minneapolis, Minnesota

TopicsTopics

•Common problems in karst formationsCommon problems in karst formations

•How liners normally work

li f b h l i k•Sealing of boreholes in karst•Transmissivity measurement adaptations to karst

•Multi level sampling systems in karst

•Mapping of NAPLsMapping of NAPLs

The karst situationCrossconnectingflow

Solution channels

Highflow ratesin largechannels

More or lesscompetentmatrixmatrix

The grout problem in karst

S d G iScreenedcasing

Grout pipe

(Karst)Solution channels

Flow outof theborehole

(Grout)

Grout infracture

Sand packedscreen interval

Potential packer problem in karstPotential packer problem in karst

The packer sealis bypassed in

Solution channel

is bypassed inthe formation

Other common karst problemsOther common karst problems

•Large vertical flow rates in the open hole, and cross connection obscures contaminant distribution.

•High flow rates in the fractures and other transmissive features exceed the limits oftransmissive features exceed the limits of many measurement devices.

•Tracer tests are frustrated by both of the•Tracer tests are frustrated by both of the above, and by the open hole storage volumevolume.

The blank liner quickly seals the hole1a. Linerattachmentto casing

1b. Wateraddition

1c. Linerdescentbeneathwater table

Tether

water table

Air vent tube

Clamp

ΔH

Air vent tube Air vent tube

HlBlended Headin borehole

Eversion Point “EP”

HHh

The flexible liner everts through large openings in the boreholeopenings in the borehole

No grouts or bentoniteare required to seal theare required to seal theborehole.

Solutio

The liner can not bebypassed in the formation

ution channel

The liner melds with the borehole structure

An occasional difficulty in karst is the propagation of the liner through a very large cavern into the hole beyondg y g y

One solution is to drop the driving pressure in the liner to allow it to h l ti lhang more nearly vertical.

In some cases, “eversion aids” have been used to aid the liner propagation through voids. 

Rarely has the presence of a large void prevented the linerRarely has the presence of a large void prevented the liner installation.

B the a no liner has e er been trapped b slo gh of the hole allBy the way, no liner has ever been trapped by slough of the hole wall.

Eversion through a cavern may need an eversion aidneed an eversion aid

Liner may be divertedfrom top to bottomMechanical from top to bottomof cavern

Mechanicaleversion aid

Or, Weighted fluideversion aid

Many logging tools can be run inside y gg gthe sealing liner

1. High resolution temperature logs

2. Sonic logs (sonic vel. or ATV)

3. Radiation logs of several kindsg

4. Radar

5 Induction coupled electric logs5. Induction coupled electric logs

However, the sondes must be padded and "f i d” t id d t th li"faired” to avoid damage to the liner

Hitting tool onthis edge on retrieval can also c t liner

Hitting toolagainst this

also cut liner

against this edge cancut liner

Pad the top and bottom of tools to reduce pimpact on ledges and damage to liner

Measurement of the blank liner installation velocity i i i i fil i 1 2 h i llgives a transmissivity profile in 1‐2 hrs typically

Water Addition Liner on reelVelocity TensionAddition hose

Liner on reel(inside out)

yMeter

Pressuremeasurement

Tensioncontrol

Surface casing

h FracturesWater table

Liner velocity

11

2

34 in

hol

e

1

2

4

Dep

th 3

4

Each time a fracture is sealed, the l l dliner velocity drops

Liner Velocity

dV

Z1

z2dZ

Dep

th in

hol

eZ2

Flow rate into the fracture, dQ = A(V -V ) , where >1 2 V V1 2

DT = dQ ln(r/r ) dH02

A velocity history in NJ -0 1 0 4 0 9 1 4 1 9 2 4 2 9

flow rate/driving pressure (ft in2/s/psi) or Trans. (cm2/s)

history in NJ produced this 

50

70

-0.1 0.4 0.9 1.4 1.9 2.4 2.9

transmissivity profile 90

.Flow rates of 50‐

110

Dep

th (f

t BG

S)

100 gal/min are common in karst 

130

150Flow/dH

boreholes170

Flow/dH

Monotonic fit of Flow/dH

Transmissivity

190

A pressure transducer was added toA pressure transducer was added to improve the data.

Liner on reel(i id t)

VelocityMeter Tension

(inside out)Meter

Pressuremeasurement

control

HLInitial HBH

Second pressuretransducer at bottomtransducer at bottom of hole on very slender cable

Once the sampling intervals are defined, the blank liner is replaced with a multi level sampling systemliner is replaced with a multi level sampling system

•The “Water FLUTe” MLS liner seals the entire hole

•All of the water in the borehole is inside the liner

Th l d di tl f th f ti•The samples are drawn directly from the formation

•Up to 15 ports are installed in a 6 inch diameter hole

•All ports can be purged and sampled simultaneously

•It is fully removable•It is fully removable

Here is how it is done:Here is how it is done:

(Single port system shown for clarity)Pump quick connectMulti level sampling 

Formationhead in pump

Tether support oftubing bundle

system called a Water FLUTe liner

No grout or sand is 

Sealing liner

Spacerdefiningmonitoring

head in pump

requiredinterval

Port behindspacer thruliner

The liner seal t b

“Sample tube”

“Pump tube”

Second

can not be bypassed to an open hole

check valve

First h k l

“Bottom of the U”

an open hole check valve

Port to pumptube

The unique Water FLUTe characteristics are:

• Seals the entire hole against vertical flow

• Easy to install ( typically 1 4 hr )• Easy to install ( typically, 1-4 hr.)

• Draws each sample directly from the formation. There is no need for “low flow sampling”.

• Is easily removed.y

• Produces a large sample volume per pump strokestroke.

• Pressure tested fully assembled in the factory to 300 i300 psi.

Other attractive Water FLUTe characteristics:

• Allows many ports in one hole (1 - 30+)

• Allows a head measurement for each port

• Easy to purge and sample (e.g., 1 hr./5 ports or 10 ports)

• Recording pressure transducers can be added at each port with no conflict with sampling or manual head measurementshead measurements.

Liner systems have been used at many k t itkarst sites

•Knoxville, TN•Huntsville, AL•Pittsburg, PA•Fort Erie, Ontario, Canada•Kokomo, IN

•Rome, GA

•San Antonio, TX•and Denmark

•Plus many other sites with karst like yconditions.

Some multi‐level systems have

CasingLiner insidecasingsystems have 

been installed through driventhrough driven 

casing in unstableunstable formations

Liner against

(Karst)

hole wall

SlenderSlender trimmiepipe supportingliner in casing

A color reactive cover on a blank liner dcan map NAPL pure product

In summary:In summary:

•The liner systems require no annular sealing y q gmaterial to be added to the borehole, and therefore none is lost to the formation.•A liner can propagate through voids, providing a continuous seal of the hole.S h i l l b i id th•Some geophysical logs can be run inside the sealing liner.•The transmissivity profiling method works in•The transmissivity profiling method works in karst formations.

Summary (cont)

• All the water in the borehole is inside the linerAll the water in the borehole is inside the liner and the sampling system can be short stroked to monitor for tracersto monitor for tracers.

• The systems are fully removable and not t d b h l l hentrapped by hole slough.

• Use of these several liner systems minimizes the total time the hole is open to cross connection.

Thanks for your attentionThanks for your attention

More details are available on our website www.flut.com

Note, the liner methods described are protected by several patents.