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Drilling and testing

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Groundwater Training Course Groundwater Training Course SOPAC, April 2005 SOPAC, April 2005 Drilling & Testing Drilling & Testing Selected methods Selected methods
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Page 1: Drilling and testing

Groundwater Training CourseGroundwater Training Course

SOPAC, April 2005SOPAC, April 2005

Drilling & TestingDrilling & Testing

Selected methodsSelected methods

Page 2: Drilling and testing

Drilling and testingDrilling and testing

• Can provide detailed information about: ♦ aquifer thickness♦ geological formations♦ hydrogeological properties (porosity, permeability, major

structural features such as unconformities)♦ groundwater quality

• Boreholes enable:– Pumping (‘production boreholes’)– Monitoring systems to be installed (‘monitoring

boreholes)– Water samples to be obtained– Cores to be obtained (geological information)– Samples for dating (eg CFC)

Page 3: Drilling and testing

Drilling methodsDrilling methods

• Water drilling methods are many & varied. Common ones are:– Auger– Cable tool (percussion)– Rotary drilling (using drilling muds)– Rotary & percussion drilling using rotary rig and down-

the-hole hammer, air compressor, drilling foam

Page 4: Drilling and testing

Drilling and Drilling and testingtesting

Rotary drilling rig

Page 5: Drilling and testing

Rotary drill rigRotary drill rigCocos (Keeling) Islands, AustraliaCocos (Keeling) Islands, Australia

‘Mud’ tank

Page 6: Drilling and testing

Rotary drilling rigRotary drilling rig

Application:• Small coral island (Lifuka, Tonga)• Depth to water table = 3 – 5 m• Reason: investigate groundwater resources and install multi-level monitoring systems (nylon tubes and PVC pipes

Page 7: Drilling and testing

Rotary drilling rig with ‘mud pit’Rotary drilling rig with ‘mud pit’

Rock roller drill bitRock roller drill bit

Mud pit

Application:• Small coral island (Penrhyn, Cook Islands)• Depth to water table = 2 m• Reason: investigate groundwater resources, install multi-level monitoring systems (nylon tubes)

Page 8: Drilling and testing

Down the hole hammer drilling using foamDown the hole hammer drilling using foam

Page 9: Drilling and testing

Down the hole hammer drilling using foamDown the hole hammer drilling using foam

Application:• Raised limestone island (Christmas Island, Australia)• Depth to water table = 30 – 160 m• Reason: investigate groundwater resources and install multi-level monitoring systems (25mm PVC pipes)

Page 10: Drilling and testing

Christmas Island (Australia) deep monitoring boreholesChristmas Island (Australia) deep monitoring boreholes

• 5 monitoring boreholes in ‘Smithson Bight’ area• Closer look at 3 of these (BH1, BH2 and BH3)

Page 11: Drilling and testing

Christmas Island (Australia) deep monitoring boreholesChristmas Island (Australia) deep monitoring boreholes

Depth to base of lowest monitoring tube = 190m

Page 12: Drilling and testing

Christmas Island (Australia) deep monitoring boreholesChristmas Island (Australia) deep monitoring boreholes

Volcanic rock basement (intersected in BH1 at 22m below sea level)

Page 13: Drilling and testing

Monitoring data, boreholes BH1 & BH3Monitoring data, boreholes BH1 & BH3

Borehole BH1• 1,200m from coast• Freshwater to > 30m

Borehole BH3• 400m from coast• No Freshwater

Page 14: Drilling and testing

Simple Simple monitoring monitoring boreholeborehole

(open borehole)(open borehole)

Useful for measuring:– water level– water quality near

groundwater surface

Where the aquifer material is not granular (sand/gravel), a gravel pack is placed around the pipe slots (or well screen)

Page 15: Drilling and testing

MultiMulti--level monitoring boreholelevel monitoring borehole

Multi-level system

• useful for monitoring water quality (e.g. salinity) at different depths

Note: open boreholes, tend to allow mixing of water from different depths (e.g. can underestimate true freshwater thickness on small island due to mixing within the borehole)

Page 16: Drilling and testing

Measuring level and obtaining water sample in deep Measuring level and obtaining water sample in deep monitoring boreholesmonitoring boreholes

Page 17: Drilling and testing

Salinity monitoring at Salinity monitoring at boreholesboreholes

usingusing•• monitoring pump monitoring pump andand•• salinity metersalinity meter

Procedure at each borehole•• for each tube, pump sample to for each tube, pump sample to

bucket & testbucket & test•• repeat 2 to 3 times to ensure repeat 2 to 3 times to ensure

stable readingstable reading•• plot salinity v depth for all tubesplot salinity v depth for all tubes

Page 18: Drilling and testing

Salinity monitoring borehole dataSalinity monitoring borehole data

LIF1 salinity profiles

-15.0

-10.0

-5.0

0.00

2,50

05,

000

7,50

010

,000

12,5

0015

,000

17,5

0020

,000

22,5

0025

,000

27,5

0030

,000

32,5

0035

,000

37,5

0040

,000

42,5

0045

,000

47,5

0050

,000

52,5

0055

,000

Electrical Conductivity (uS/cm)

Dep

th b

elow

wat

er

tabl

e (m

)

Aug 98 Sept 98 Oct 98 Nov 98 Dec 98Jan 99 Apr 99 Jul 99 Oct 99

Page 19: Drilling and testing

Permeability testsPermeability tests

Falling head Falling head testtest

(during drilling (during drilling process)process)

Refer to paper on Tarawa and Christmas Island for equation and example of use

Page 20: Drilling and testing

Permeability testsPermeability tests

Constant head Constant head testtest

(during drilling (during drilling process)process)

Refer to paper on Tarawa and Christmas Island for equation and example of use

Page 21: Drilling and testing

Groundwater mappingGroundwater mapping

TabiteueaTabiteueaisland, island, Tarawa Tarawa atoll, atoll, KiribatiKiribati

These freshwater contours were mapped using both borehole salinity measurements and geophysics data

Page 22: Drilling and testing

Dating of water

Page 23: Drilling and testing

Concepts

• Atmosphere Groundwater interaction– At time of recharge, groundwater concentrations

reflect atmospheric conditions• Types of tracer

– Natural isotopes• Carbon 14• Tritium

– Contaminants• CFC’s• Tritium (atmospheric weapons testing)

Page 24: Drilling and testing

Time• >20,000 BP• recent

Page 25: Drilling and testing

Tritium

Page 26: Drilling and testing

CFC-12

Page 27: Drilling and testing

Outlook

• Sampling & analysis techniques– Have been complex and costly– Some improvements have been achieved

• Environmental changes– Contamination controls lead to a reduction

in sensitivity of dating– New compounds and improved

measurement techniques likely to continue to provide opportunities


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