Drilling for Mining Drilling for Mining

OperationsOperations

Importance of Drilling and Importance of Drilling and

Sampling:Sampling:

•• Important mineral exploration procedureImportant mineral exploration procedure

•• Delineate subsurface conditionsDelineate subsurface conditions

•• ExpensiveExpensive

•• Number of techniquesNumber of techniques

•• Tests ideas and theories developed during Tests ideas and theories developed during

prospect and target generationprospect and target generation

•• LOCATES AND DEFINES ECONOMIC LOCATES AND DEFINES ECONOMIC

MINERALISATIONMINERALISATION

Drilling TechniquesDrilling Techniques

•• 3 main techniques used in Goldfields3 main techniques used in Goldfields

–– RAB (Rotary Air Blast)RAB (Rotary Air Blast)

–– RC (Reverse Circulation) RC (Reverse Circulation)

–– Diamond drillingDiamond drilling

Types of drilling equipment commonly

used in mineral

exploration (Marjoribanks,

1997)

Rotary Air Blast (RAB)Rotary Air Blast (RAB)

Rotary Air Blast (RAB)Rotary Air Blast (RAB)

•• CheapestCheapest

•• Least penetrative (~100m)Least penetrative (~100m)

•• Geochemical sampling to base of regolith (Geochemical sampling to base of regolith (ieieonly penetrates weathered cover over fresh only penetrates weathered cover over fresh rocks)rocks)

•• Uses compressed air to break groundUses compressed air to break ground

•• Air pumped down through drill rodAir pumped down through drill rod

•• Cuttings blown up hole between rod and hole Cuttings blown up hole between rod and hole wallwall

•• Single barrel techniqueSingle barrel technique

Advantages of RAB drilling:Advantages of RAB drilling:

•• CheapCheap

•• FastFast

•• Large sample volumeLarge sample volume

Disadvantages of RAB drilling:Disadvantages of RAB drilling:

•• No fresh rock samplesNo fresh rock samples

•• Limited depthLimited depth

•• No structural dataNo structural data

•• ContaminationContamination

RRC drilling and C drilling and

samplingsampling

Reverse Circulation (RC)Reverse Circulation (RC)

•• Moderately pricedModerately priced

•• Good penetration (to ~350m)Good penetration (to ~350m)

•• Samples fresh rockSamples fresh rock

•• Dual barrel techniqueDual barrel technique

•• High pressure fluid forced down outer pipe High pressure fluid forced down outer pipe

and returns chips to surface up inner pipeand returns chips to surface up inner pipe

Schematic presentation of RC drill rig

Advantages of RC drilling:Advantages of RC drilling:

•• Relatively cheapRelatively cheap

•• QuickQuick

•• Large sampleLarge sample

•• UncontaminatedUncontaminated

Disadvantages of RC drilling:Disadvantages of RC drilling:

•• Limited accessLimited access

•• No structural dataNo structural data

•• Sample contamination below water tableSample contamination below water table

Diamond DrillingDiamond Drilling

•• ExpensiveExpensive

•• Greatest penetrationGreatest penetration

•• Whole rock samplesWhole rock samples

Advantages of diamond drilling:Advantages of diamond drilling:

•• Maximum geological informationMaximum geological information

•• UncontaminatedUncontaminated

•• High quality samplingHigh quality sampling

Disadvantages of diamond drilling:Disadvantages of diamond drilling:

•• ExpensiveExpensive

•• SlowSlow

•• Small sample sizeSmall sample size

•• Extensive site preparation and water Extensive site preparation and water

supply requiredsupply required

Core sample (from diamond drilling)Core sample (from diamond drilling)

Core boxes at core house, Core boxes at core house, BulgahBulgah gold gold

mine, KSA (photo taken in 6 Dec. 2006)mine, KSA (photo taken in 6 Dec. 2006)

Appropriate Drilling MethodsAppropriate Drilling Methods

•• RABRAB–– Early explorationEarly exploration

–– First pass and infill drillingFirst pass and infill drilling

•• RCRC–– Intermediate explorationIntermediate exploration

–– Delineate ore bodyDelineate ore body

–– Grade controlGrade control

•• DiamondDiamond–– Late stageLate stage

–– Structural controlsStructural controls

DrillingDrilling

Site preparation and water Site preparation and water

supply required. Small supply required. Small

sample size. Slow. sample size. Slow.

ExpensiveExpensive

Maximum geological Maximum geological

information. information.

Uncontaminated high Uncontaminated high

quality sample. Accurate quality sample. Accurate

hole positioninghole positioning

High quality sampling to High quality sampling to

greater than 1000km. greater than 1000km.

Geological understandingGeological understanding

DiamondDiamond

Large heavy rig. No Large heavy rig. No

structural data. Possible structural data. Possible

sample contamination sample contamination

below water tablebelow water table

Large sample. Large sample.

Uncontaminated. Rock chip Uncontaminated. Rock chip

returns. Relatively quick returns. Relatively quick

and cheapand cheap

Geochemical sampling in Geochemical sampling in

hard and soft rocks at hard and soft rocks at

greater than 200m depthgreater than 200m depth

Reverse CirculationReverse Circulation

Small sample sizeSmall sample sizeMinimal contamination. Minimal contamination.

Quick and cheap. Some Quick and cheap. Some

core recoverycore recovery

Geochemical sampling into Geochemical sampling into

bedrockbedrockAir CoreAir Core

WonWon’’t penetrate hard rock. t penetrate hard rock.

Sample contamination. Sample contamination.

Limited depth. No structural Limited depth. No structural

datadata

Large sample volume. Large sample volume.

Quick and cheap. Rock Quick and cheap. Rock

chipschips

Geochemical sampling to Geochemical sampling to

base of regolithbase of regolithRotary Air Blast (RAB)Rotary Air Blast (RAB)

Poor penetrationPoor penetrationPortable, usually Portable, usually

LandcruiserLandcruiser mounted, mounted,

uncontaminated sample,uncontaminated sample,

Quick, cheapQuick, cheap

Geochemical sampling, top Geochemical sampling, top

few few metresmetres of of

unconsolidated materialunconsolidated material

AugerAuger

DisadvantagesDisadvantagesAdvantagesAdvantagesDataDataDrill TypeDrill Type

Marjoribanks, 1997