Drilling for Mining Drilling for Mining
Operations
Operations
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 generation
prospect and target generation
•• LOCATES AND DEFINES ECONOMIC LOCATES AND DEFINES ECONOMIC MINERALISATION
MINERALISATION
Drilling Techniques Drilling 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 (ieie only 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
R R C drilling and C drilling and sampling
sampling
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 pipe and 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 Drilling Diamond 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 required
supply 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 Methods Appropriate 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
Drilling Drilling
Site preparation and water Site preparation and water supply required. Small supply required. Small sample size. Slow.
sample size. Slow.
Expensive Expensive Maximum geological
Maximum geological information.
information.
Uncontaminated high Uncontaminated high quality sample. Accurate quality sample. Accurate hole positioning
hole positioning High quality sampling to
High quality sampling to greater than 1000km.
greater than 1000km.
Geological understanding Geological understanding Diamond
Diamond
Large heavy rig. No Large heavy rig. No structural data. Possible structural data. Possible sample contamination sample contamination below water table below water table Large sample.
Large sample.
Uncontaminated. Rock chip Uncontaminated. Rock chip returns. Relatively quick returns. Relatively quick and cheap
and cheap Geochemical sampling in
Geochemical sampling in hard and soft rocks at hard and soft rocks at greater than 200m depth greater than 200m depth Reverse Circulation
Reverse Circulation
Small sample size Small sample size Minimal contamination.
Minimal contamination.
Quick and cheap. Some Quick and cheap. Some core recovery
core recovery Geochemical sampling into
Geochemical sampling into bedrock
bedrock Air Core
Air Core
Won’Won’t penetrate hard rock. t penetrate hard rock.
Sample contamination.
Sample contamination.
Limited depth. No structural Limited depth. No structural data
data Large sample volume.
Large sample volume.
Quick and cheap. Rock Quick and cheap. Rock chips
chips Geochemical sampling to
Geochemical sampling to base of regolith
base of regolith Rotary Air Blast (RAB)
Rotary Air Blast (RAB)
Poor penetration Poor penetration Portable, usually
Portable, usually Landcruiser
Landcruisermounted, mounted, uncontaminated sample, uncontaminated sample,
Quick, cheap Quick, cheap Geochemical sampling, top
Geochemical sampling, top few metresfew metresof of
unconsolidated material unconsolidated material Auger
Auger
Disadvantages Disadvantages Advantages
Advantages DataData
Drill Type Drill Type
Marjoribanks, 1997
