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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.