Safe Work Procedures for Truck and Trailer Mounted Drilling Operations

Vehicle Mounted Borehole Drilling Safe Work Method Statement

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Vehicle mounted borehole drilling uses truck or trailer mounted drilling rigs to create boreholes for geotechnical investigation, environmental sampling, groundwater monitoring, mineral exploration, and foundation installation. These mobile rigs employ rotary, percussion, or combination drilling methods capable of reaching depths from 10 to 300+ metres depending on rig capacity and geological conditions. Operations involve rotating drill strings under high torque, applying substantial feed pressure, circulating drilling fluids, and managing downhole samples. This Safe Work Method Statement addresses the specific hazards of vehicle mounted borehole drilling including drill string breakage and whip, hole collapse during drilling operations, sudden pressure releases from confined aquifers, and whole-body vibration exposure from prolonged drilling equipment operation.

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Overview

What this SWMS covers

Vehicle mounted drilling rigs represent the primary platform for borehole investigation and installation work across Australian construction, mining, and environmental sectors. These rigs range from compact trailer-mounted units suitable for restricted access sites and shallow investigations (10-30 metre depth capacity), to heavy truck-mounted rigs capable of drilling hundreds of metres through competent rock formations. The drilling methodology employed depends on ground conditions and investigation objectives: rotary drilling using tri-cone or PDC (polycrystalline diamond compact) bits for rock penetration, auger drilling for soft formations and environmental sampling, percussion drilling for rapid advance through hard formations, and specialised techniques including sonic drilling and directional boring for specific applications. The drill string comprises interconnected drill rods (typically 1.5-3.0 metres length) transmitting rotation and feed force from surface drive head to downhole cutting tools. As drilling advances, additional rods are added to the string creating columns potentially exceeding 100 metres length under substantial tensile, torsional, and bending loads. The drill string operates in hostile downhole environment subjected to abrasion from rock cuttings, corrosion from groundwater, and fatigue from rotation cycles. Drill rod connections use threaded pin and box joints requiring specific torque values for reliable operation - insufficient torque permits joint loosening during operation, while excessive torque damages threads reducing connection strength. The management of drill string integrity throughout operations is critical to preventing catastrophic failures. Drilling fluid circulation serves multiple essential functions: cooling and lubricating drill bits extending tool life, transporting cuttings to surface for geological logging and disposal, stabilising borehole walls preventing collapse, and balancing downhole pressures when penetrating confined aquifers or gas zones. Fluid types range from clean water for simple environmental investigations, to bentonite-polymer mud systems for deep drilling in unstable formations, to compressed air for percussion drilling in competent rock. The fluid circulation rate, pressure, and characteristics must be carefully controlled matching geological conditions encountered. Loss of circulation when fluid escapes into permeable formations requires immediate response preventing hole collapse and maintaining drill string cooling. Drilling operators work from control stations managing complex interrelated systems: feed pressure applying downhole force on cutting tools (typically 5-50 kilonewtons depending on rig capacity and formation), rotational speed varying from 30 RPM for large diameter core drilling to 300+ RPM for percussion drilling, and fluid circulation pressure maintaining adequate flow. Modern rigs feature automated controls monitoring multiple parameters including penetration rate, torque load, and hydraulic pressures providing early warning of developing problems. However, operator skill and experience remain essential for interpreting these parameters, recognising abnormal conditions, and taking appropriate corrective actions. Understanding these operational characteristics is fundamental to implementing effective safety controls for borehole drilling operations.

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Why this SWMS matters

Drill string failures represent the most severe mechanical hazard in borehole drilling operations. When drill rods break under load, the sudden release of stored rotational and tensile energy causes violent whipping of the broken string potentially extending several metres above ground level. The whipping drill string weighing hundreds of kilograms moves with tremendous force striking anything in its path. Workers have sustained fatal head injuries from being struck by whipping drill rods, while others suffered severe fractures and lacerations. The failure typically occurs at threaded connections that have been inadequately torqued, fatigued through repeated loading cycles, or damaged by over-torquing during makeup. Corrosion of threads in acidic groundwater substantially reduces connection strength creating unexpected failure under normal operating loads. Borehole collapse during drilling operations creates immediate entrapment hazards for drill strings and can cause catastrophic rig damage. Unstable geological formations including saturated sands, weathered clays, and fractured rock masses cave into boreholes when unsupported. If collapse occurs while drill string in hole, the string becomes gripped by collapsed material requiring extensive recovery efforts potentially including abandoning the drill string and starting new holes. Rapid collapse can generate upward forces on drill string as displaced material flows to surface potentially lifting the drilling rig. Workers standing near boreholes during collapse events have been struck by material ejected from the hole. The costs of string recovery and hole re-drilling are substantial, but the safety implications of collapsed holes creating unstable ground conditions and the potential for secondary collapses affecting surrounding areas represent the primary concerns. Pressure releases from confined aquifers or gas zones penetrated during drilling can cause violent blowouts projecting drilling fluid, formation water, and rock fragments from boreholes at high velocity. Artesian aquifers under pressure seek outlets through boreholes creating flow rates that can overwhelm circulation systems. If drilling fluids lighter than formation fluids, the density imbalance creates upward pressure forcing material from hole. Gas zones including naturally occurring methane or carbon dioxide penetrated in coal measures or decomposing organic deposits create explosive hazards when released at surface. The pressure release can occur suddenly when drill bit penetrates confining layer providing no warning to operators. Workers have been injured by projectile impacts from blowout events, while fires have occurred when gas ignited from static electricity or other ignition sources. Whole-body vibration exposure during drilling operations affects operators throughout long shifts controlling equipment from rig-mounted platforms. The vibration sources include diesel engines powering hydraulic systems, percussion hammers impacting thousands of times per minute, rotary drive heads transmitting unbalanced loads, and hydraulic pump pulsations. Operators experience multi-axis vibration simultaneously including vertical oscillation, lateral shaking, and torsional movement. Extended shifts common in drilling work (often 10-12 hours due to mobilisation costs and project deadlines) amplify vibration exposure duration. The vibration magnitude increases when drilling through hard formations, when drill string becomes unbalanced from wear, or when operating older rigs lacking vibration isolation systems. Long-term exposure to whole-body vibration is associated with chronic lower back pain, degenerative disc disease, and circulatory disorders affecting career longevity and quality of life beyond work. From a regulatory perspective, borehole drilling operations near existing infrastructure, utilities, or environmentally sensitive areas require compliance with multiple regulatory frameworks. Drilling near buried utilities requires compliance with asset protection legislation and coordination with service owners. Groundwater extraction during drilling may require water licences and compliance with sustainable water use regulations. Drill spoil and contaminated groundwater disposal must meet environmental protection requirements. Operators must hold appropriate licences for operating mobile plant, and employers must ensure competency in drilling techniques and emergency response. Following serious incidents, investigations have examined adequacy of drill string inspection and maintenance procedures, whether operators possessed necessary competencies, and compliance with manufacturer operating limits for rig equipment.

Reinforce licensing, insurance, and regulator expectations for Vehicle Mounted Borehole Drilling Safe Work Method Statement crews before they mobilise.

Hazard identification

Surface the critical risks tied to this work scope and communicate them to every worker.

Risk register

Drill String Breakage and Whip Injuries

High

Drill strings operating under high rotational torque and tensile loading can fail catastrophically when connections break, rods fracture, or coupling threads strip. The sudden failure releases stored rotational energy causing violent whipping of broken drill string potentially extending metres above ground. The whipping movement occurs at high speed in unpredictable directions striking workers, equipment, and rig structures within reach. Rod failures typically occur at threaded connections fatigued by repeated loading cycles, inadequately torqued during makeup permitting loosening during operation, corroded by acidic groundwater weakening threads, or damaged by over-torquing crushing thread forms. Drill rods rotating at 100+ RPM and weighing 20-40kg each create tremendous kinetic energy released during breakage. Workers positioned near drill head attempting to add rods, adjust drilling parameters, or observe drilling progress are in primary strike zone when failures occur.

Consequence: Fatal head and spinal injuries from being struck by whipping drill rods, severe fractures and crushing injuries, traumatic amputations if limbs contacted by rotating equipment, damage to rig structures and hydraulic systems requiring expensive repairs, loss of downhole drill string requiring costly recovery operations or hole abandonment, project delays from equipment damage and investigation of failure causes.

Borehole Collapse and Ground Instability

High

Unstable geological formations cave into unsupported boreholes during drilling creating entrapment of drill strings, ground subsidence around drill locations, and ejection of material from holes under pressure from displaced fluids. Saturated sands, soft clays, and highly fractured rock masses lack sufficient cohesion to maintain open boreholes particularly at depths where overburden pressure increases. Collapse occurs suddenly when drilling penetrates weak zones, when circulation fluid loss deprives hole walls of stabilising pressure, or when vibration from drilling equipment triggers failure in marginally stable formations. The collapsed material grips drill string requiring substantial pull force to extract potentially exceeding rig capacity. Rapid collapse generates upward flow of displaced material and fluids potentially lifting rig if drill string anchored. Ground subsidence around drill collar can undermine rig stability causing rollover or damage to nearby structures.

Consequence: Entrapment of drill strings requiring extensive recovery efforts potentially including abandonment and re-drilling, rig damage or rollover from ground subsidence affecting stability, workers struck by material ejected from collapsing holes, contamination release if drilling through contaminated zones that collapse and mix with groundwater, substantial project delays and costs from string recovery and remediation.

Pressure Release and Blowout from Confined Aquifers

High

Penetrating confined aquifers or gas-bearing formations during drilling can cause sudden pressure releases forcing fluids, cuttings, and formation gas from boreholes at high velocity. Artesian aquifers under pressure from surrounding geology seek relief through boreholes creating flow that overwhelms circulation systems. The pressure differential between formation and borehole drives rapid upward flow. If drilling mud density insufficient to balance formation pressure, material erupts from borehole. Gas zones in coal measures or organic-rich formations release methane or carbon dioxide creating explosive atmospheres at surface and displacing oxygen in excavations. The blowout can occur suddenly when drill bit breaches confining layer providing minimal warning. Projectile hazards include rock fragments, drill cuttings, and drilling fluid projected from hole at high velocity. Continuous flow from artesian zones floods work areas and releases potentially contaminated groundwater.

Consequence: Workers struck by projectile material ejected during blowouts suffering impact injuries, explosive atmosphere ignition causing fires and burns, flooding of work areas from uncontrolled artesian flow, environmental contamination from release of contaminated groundwater or formation fluids, oxygen-deficient atmospheres from gas releases causing asphyxiation, rig damage from sustained pressure on drill string and circulation systems.

Whole-Body Vibration Exposure from Drilling Equipment

Medium

Drilling operators experience sustained whole-body vibration transmitted through rig control stations from diesel engines, hydraulic systems, rotary drive heads, and percussion drilling mechanisms. The vibration intensity varies with drilling method and formation characteristics: percussion drilling in hard rock generates high-magnitude impulse vibration, rotary drilling in competent formations produces sustained moderate vibration, and drilling through variable formations creates alternating vibration patterns. Operators standing on rig platforms or sitting in operator seats absorb vibration through feet, buttocks, and spine. The vibration characteristics include vertical oscillation from percussion hammers, lateral shaking from unbalanced rotation, and torsional movement from torque reactions. Extended shift durations common in drilling work (10-12 hours) amplify total vibration exposure. Older rigs lacking vibration isolation systems expose operators to higher magnitudes.

Consequence: Chronic lower back pain and degenerative disc disease from long-term vibration exposure, reduced blood circulation affecting hands and feet (vibration white finger), digestive system disturbances, increased fatigue affecting alertness and safety, musculoskeletal disorders developing over years of exposure, reduced career longevity and quality of life beyond work, exacerbation of pre-existing back conditions.

Hydraulic Fluid Injection and Hose Burst

High

Drilling rigs employ extensive hydraulic systems operating at 3000+ psi generating force for feed cylinders, rotary drive motors, mast raising, and stabiliser deployment. High-pressure hydraulic hoses convey fluid throughout rig subjected to flexing during operation, abrasion from contact with drill rods and equipment, UV degradation from sunlight exposure, and temperature extremes. Hose failure releases hydraulic fluid under extreme pressure creating injection injury hazards if fluid contacts skin. Pinhole leaks in hoses produce invisible high-velocity jets penetrating skin when workers run hands along hoses attempting to identify leak sources. Burst hoses whip violently projecting hot hydraulic fluid over wide areas. Failed hydraulic systems can cause loss of critical rig functions including inability to lower mast, release feed pressure, or retract stabilisers creating additional emergency situations.

Consequence: Injection injuries requiring emergency surgical debridement and multiple revision surgeries, severe tissue damage and potential amputation from hydraulic fluid toxicity, burns from hot hydraulic fluid released under pressure, eye injuries and blindness from hydraulic spray contact, loss of rig control creating secondary hazards from unintended equipment movement, environmental contamination from hydraulic fluid spills, equipment damage requiring extensive repairs.

Control measures

Deploy layered controls aligned to the hierarchy of hazard management.

Implementation guide

Drill String Inspection and Torque Verification

Engineering

Systematic inspection and correct makeup procedures for drill rod connections preventing fatigue failures and ensuring reliable operation

Implementation

1. Inspect drill rod threads visually before each use checking for damage, corrosion, or unusual wear patterns 2. Use thread gauges verifying thread forms within tolerance, reject rods with damaged or elongated threads 3. Clean threads thoroughly removing drilling mud, cuttings, and debris before rod makeup 4. Apply manufacturer-approved thread compound to pin threads providing lubrication and corrosion protection 5. Make up rod connections using calibrated torque wrenches or automated torque systems achieving specified torque values 6. Document torque values for critical connections particularly when drilling deep holes requiring high pull forces 7. Inspect rod shoulders after makeup confirming proper engagement with no gaps indicating incomplete makeup 8. Mark rods approaching manufacturer service life limits (typically 2000-5000 hours) for detailed inspection or retirement 9. Use magnetic particle inspection or ultrasonic testing on high-time rods detecting internal cracks before failure 10. Maintain drill string inventory records tracking usage hours enabling proactive replacement before failures occur

Geological Review and Drilling Fluid Selection

Administrative

Pre-drilling geological assessment and appropriate drilling fluid selection preventing borehole collapse and managing downhole pressures

Implementation

1. Review available geological information including previous drilling logs, geological maps, and local knowledge identifying unstable formations 2. Contact nearby drilling contractors or geotechnical consultants seeking information on formation behaviour and recommended practices 3. Select drilling fluid type matching anticipated conditions: clean water for competent formations, bentonite mud for unstable zones, polymer additives for maximum wall stabilisation 4. Calculate fluid density required to balance anticipated formation pressures in confined aquifer zones 5. Prepare fluid mixing and circulation equipment before drilling ensuring adequate volumes available throughout operations 6. Monitor fluid returns during drilling observing for changes indicating circulation loss or formation instability 7. Respond immediately to circulation loss by increasing fluid viscosity or converting to cement-based plugging fluids 8. Install casing strings promptly in unstable formations providing mechanical support preventing collapse 9. Maintain fluid circulation whenever possible when adding or removing drill rods maintaining borehole stability 10. Document all formation changes, circulation losses, and fluid adjustments in drilling log enabling pattern recognition

Exclusion Zone Establishment During Drilling

Engineering

Physical barriers and procedural controls preventing workers entering hazardous zones around active drilling operations

Implementation

1. Establish primary exclusion zone extending 3 metres radius from drill head prohibiting all personnel during active drilling 2. Mark exclusion zone using high-visibility bunting, barriers, or painted lines on ground clearly visible to all workers 3. Position drill operator controls outside exclusion zone enabling operation from protected position 4. Prohibit workers approaching drill head while rods rotating or while under feed pressure regardless of production demands 5. Stop rotation and relieve feed pressure before allowing rod handlers to approach for rod additions or adjustments 6. Assign dedicated observer monitoring exclusion zone during drilling operations immediately alerting if violations occur 7. Install physical guards around exposed rotating components including drive head and rod connections 8. Implement interlock systems preventing rotation or feed activation if guards removed for maintenance 9. Require two-person protocol for rod handling with one person controlling drill while second manages rod addition staying clear of rotation zone 10. Review exclusion zone adequacy after any near-miss or if new hazards identified adjusting boundaries as required

Drilling Operator Competency and Licensing

Administrative

Training and competency verification ensuring operators possess skills and knowledge for safe rig operation

Implementation

1. Verify operators completed recognised drilling operator training covering rig systems, drilling techniques, and emergency procedures 2. Conduct practical competency assessment demonstrating ability to control drilling parameters, recognise abnormal conditions, and respond to emergencies 3. Provide site-specific induction covering geological conditions, confined aquifer locations, and environmental constraints 4. Ensure operators hold appropriate mobile plant operator licences if required by rig configuration and weight 5. Train operators in drill string inspection, torque procedures, and recognition of fatigue indicators in rods and connections 6. Provide specialised training for high-risk drilling including directional boring, large diameter drilling, or operations near critical infrastructure 7. Implement supervised operating period for new operators working under experienced driller guidance before independent operation 8. Conduct annual refresher training reviewing incidents from industry and reinforcing critical safety practices 9. Maintain training records documenting completion of initial training, competency assessments, and refresher training attendance 10. Review operator performance regularly providing feedback on technique, efficiency, and safety practice compliance

Vibration Exposure Management for Operators

Engineering

Controls reducing whole-body vibration exposure through equipment selection and operational practices

Implementation

1. Specify vibration-dampened operator platforms or seats when purchasing or upgrading drilling rigs 2. Maintain seat suspension systems ensuring proper function and adjust to operator weight per manufacturer guidance 3. Install vibration-isolating mounts between control stations and rig frame reducing transmission of machine vibration 4. Limit continuous drilling periods to maximum 2-hour duration followed by 30-minute break from vibration exposure 5. Rotate operators between drilling and other duties including sample logging, equipment maintenance, or site preparation 6. Monitor drilling technique avoiding excessive feed pressure or rotation speed creating unnecessary vibration 7. Maintain drill strings in balanced condition replacing worn or bent rods that create eccentric rotation and increased vibration 8. Conduct vibration monitoring using accelerometers if operators report discomfort comparing to exposure action values 9. Provide operators with back support belts and training in proper posture reducing spinal loading during vibration exposure 10. Document vibration-related discomfort or injuries investigating and implementing additional controls if patterns emerge

Blowout Prevention for Confined Aquifer Drilling

Engineering

Equipment and procedures managing formation pressures preventing uncontrolled flow from confined aquifers and gas zones

Implementation

1. Research formation pressures anticipated in drilling area using existing bore logs and geological reports 2. Increase drilling fluid density when approaching known confined aquifer depths using barite or other weighting materials 3. Install blowout preventer (BOP) equipment at surface when drilling through high-pressure formations enabling hole closure if flow begins 4. Test BOP functionality before drilling critical depth intervals ensuring rapid closure capability 5. Monitor for early warning signs of pressure zones including increased penetration rate, fluid returns containing gas bubbles, or changes in formation cuttings 6. Maintain full circulation during rod changes in pressure zones preventing pressure differential developing 7. Have cement plugging materials prepared and ready for rapid deployment if circulation lost in pressure zones 8. Establish emergency response procedures for blowout events including immediate area evacuation and emergency service notification 9. Position fire extinguishers accessible but outside immediate hazard zone in case gas ignition occurs 10. Brief all personnel on pressure zone depths and required responses before commencing drilling in high-risk areas

Hydraulic System Inspection and Maintenance

Elimination

Proactive hydraulic hose and system maintenance preventing failures and eliminating injection injury hazards

Implementation

1. Replace hydraulic hoses at maximum 4-year service life regardless of visual condition due to internal degradation 2. Inspect all visible hydraulic hoses daily checking for abrasion, bulging, leaking at fittings, or surface cracking 3. Use infrared thermography identifying hot spots in hydraulic systems indicating developing failures 4. Route hoses avoiding sharp edges, excessive flexing, and contact with rotating drill components causing wear 5. Install protective sleeving on hoses in high-wear areas subject to abrasion from drill rod movement 6. Mark installation dates on hoses enabling tracking of service life and ensuring timely replacement 7. Train operators to identify hydraulic leaks using cardboard or paper held near suspected areas never using hands 8. Install pressure gauges on hydraulic circuits monitoring for unusual pressure fluctuations indicating developing problems 9. Shut down hydraulic systems and relieve pressure completely before attempting any hose replacement or repair 10. Document all hydraulic system maintenance including hose replacements, system flushing, and filter changes in equipment log

Rig Stability Assessment and Outrigger Deployment

Engineering

Site assessment and proper rig stabilisation preventing rollover during drilling operations

Implementation

1. Assess ground bearing capacity before positioning drilling rig using plate load testing or penetrometer if soft ground suspected 2. Position rig on level ground using spirit levels verifying levelness in both directions before commencing operations 3. Deploy all outriggers or stabiliser pads to manufacturer specifications extending fully and contacting ground firmly 4. Install timber mats or steel plates beneath outrigger pads if ground soft or uneven distributing loads over larger area 5. Avoid positioning rig on slopes exceeding manufacturer limits (typically 5-degree maximum for most rigs) 6. Monitor ground conditions around outriggers during operations watching for settlement or ground deformation 7. Prohibit drilling with mast extended if weather conditions include winds exceeding manufacturer limits (typically 40-50 km/h) 8. Retract mast to transport position if high winds forecast or if leaving rig unattended for extended periods 9. Verify stability before applying maximum pull forces during string extraction particularly from deep holes 10. Re-assess stability if repositioning rig on site ensuring adequate setup before resuming drilling operations

Download complete control procedures

Personal protective equipment

Hard Hat with Chin Strap

Requirement: Type 1 hard hat with secure chin strap preventing dislodgement during emergency egress from rig platforms

When: Mandatory at all times when working on or near drilling rig during operations

Safety Footwear

Requirement: Steel toe cap work boots with penetration-resistant midsoles, slip-resistant soles for rig platform surfaces

When: Required at all times in drilling work areas, must provide ankle support for working on uneven ground

High-Visibility Clothing

Requirement: Class D day/night vest or coveralls with reflective tape, long sleeves protecting from drill cuttings and hydraulic fluid

When: Mandatory when working in areas with mobile plant, near roadways, or as specified by site requirements

Hearing Protection

Requirement: Class 4 or 5 earmuffs or fitted earplugs providing minimum 25dB attenuation for drilling equipment noise

When: Required when within 10 metres of operating drilling rig due to engine and drilling noise exceeding 85dB(A)

Safety Glasses

Requirement: Impact-resistant safety glasses with side shields providing protection from airborne drill cuttings and debris

When: Required at all times in drilling work areas, particularly during rod handling and drilling fluid circulation

Work Gloves

Requirement: Heavy-duty leather gloves providing cut and abrasion resistance for rod handling, avoid loose-fitting gloves near rotation

When: Required when handling drill rods, cleaning equipment, or conducting maintenance, removed during certain operations to prevent entanglement

Protective Clothing

Requirement: Long-sleeved cotton or flame-resistant shirt and long pants, no loose clothing or jewellery

When: Required at all times protecting from UV exposure, minor abrasions, and drilling fluid contact

Inspections & checks

Before work starts

  • ✓Complete documented pre-start inspection of drilling rig covering all safety-critical systems and components
  • ✓Verify operator holds required licences and competencies for rig type and drilling technique being employed
  • ✓Inspect drill rods and connections checking thread condition, identifying any damaged or corroded rods requiring removal
  • ✓Test hydraulic systems checking for leaks, verify pressure gauge accuracy, confirm emergency shutdown systems functional
  • ✓Verify outriggers or stabiliser pads deploy and retract correctly providing adequate rig stability for operations
  • ✓Review geological information and drilling program understanding anticipated formation conditions and required drilling fluids
  • ✓Check drilling fluid supplies adequate for planned depth, verify fluid circulation pump operational
  • ✓Confirm emergency equipment available including fire extinguisher, first aid kit, and communication devices

During work

  • ✓Monitor drilling parameters continuously watching for changes indicating formation instability or equipment problems
  • ✓Observe drill string behaviour during rotation detecting unusual vibration or wobble indicating developing failures
  • ✓Check hydraulic systems hourly for new leaks or temperature changes indicating excessive loading
  • ✓Verify exclusion zones maintained with no unauthorised personnel approaching drill head during active drilling
  • ✓Monitor fluid returns observing for circulation loss, gas bubbles, or colour changes indicating formation changes
  • ✓Watch for penetration rate changes that may indicate approaching confined aquifer zones or unstable formations
  • ✓Verify ground conditions around rig checking for settlement or movement affecting stability
  • ✓Ensure operators taking regular breaks from vibration exposure particularly during extended drilling operations

After work

  • ✓Raise drill string from hole and secure properly preventing accidental deployment or damage during transport
  • ✓Lower mast to transport position if moving rig or leaving unattended overnight
  • ✓Retract outriggers ensuring full retraction before transport, verify hydraulic systems properly secured
  • ✓Clean drill rods removing cuttings and drilling fluid, inspect for damage sustained during operations
  • ✓Flush drilling fluid circulation system with clean water preventing buildup and corrosion
  • ✓Check all hydraulic fluid levels adding as required, investigate any significant consumption indicating leaks
  • ✓Document drilling progress, geological observations, and any equipment defects or incidents in drilling log
  • ✓Secure rig and equipment preventing unauthorised access, public interaction with machinery, or weather damage

Step-by-step work procedure

Give supervisors and crews a clear, auditable sequence for the task.

Field ready
1

Site Assessment and Rig Positioning

Review job requirements including borehole locations, depths, and investigation objectives. Examine site access identifying overhead power lines, underground services, and obstacles affecting rig placement. Contact Dial Before You Dig obtaining service plans for underground utilities in drilling area. Use electromagnetic cable locators verifying service positions before positioning rig. Assess ground bearing capacity using visual inspection supplemented by penetrometer testing if ground appears soft. Select rig position providing access to all planned borehole locations while maintaining stable level platform. Consider proximity to sample storage areas, water sources for drilling fluid, and disposal areas for cuttings. Verify adequate clearance for mast raising considering overhead power lines (minimum 6 metres clearance), structures, and tree branches. Position rig using spirit level achieving level platform in both directions. Deploy all outriggers to manufacturer specifications extending fully until firm ground contact achieved. Install timber mats or steel plates beneath outrigger pads if ground soft distributing loads over larger area. Verify rig stability before raising mast or commencing drilling operations.

2

Drill String Assembly and Inspection

Select drill rods and downhole tooling appropriate for planned drilling depth and anticipated geological conditions. Inspect each drill rod before use examining threads visually for damage, corrosion, elongation, or unusual wear patterns. Use thread gauges verifying thread dimensions within tolerance, reject any rod with damaged threads. Check rod bodies for cracks, bends, or corrosion requiring retirement from service. Clean threads thoroughly using wire brush removing old thread compound, drilling mud, and debris. Apply fresh manufacturer-approved thread compound to pin threads providing lubrication and corrosion protection. Make up initial rod connection to drive head using calibrated torque wrench achieving specified torque value (typically 300-600 Nm depending on rod size). Verify proper shoulder engagement with no visible gap indicating incomplete makeup. Install bit or cutting tool appropriate for formation type: tri-cone roller bit for competent rock, drag bit for soft formations, coring bit for sample recovery. Secure bit using correct installation torque preventing loosening during operation.

3

Pre-Operational System Checks

Start drilling rig engine and allow warm-up period achieving normal operating temperature before applying loads. Check all hydraulic system gauges confirming pressures within normal operating range. Test rotary drive head rotating slowly without load verifying smooth operation without unusual noise or vibration. Verify feed system operates correctly extending and retracting without jerking or binding. Test drilling fluid circulation pump achieving adequate pressure and flow rate for planned operations. Check fluid supply level ensuring sufficient volume available for anticipated drilling depth. Activate and test emergency shutdown systems from operator position confirming all systems stop within 2 seconds. Verify two-way radio or other communication systems functional between rig operator and support personnel. Check that required PPE available for all personnel including hard hats, safety glasses, and hearing protection. Review drilling program with crew ensuring all understand depth targets, anticipated formations, and required procedures. Brief on emergency response procedures including actions for drill string failure, borehole blowout, or equipment malfunction.

4

Commence Drilling Operations

Position drill bit at planned borehole location establishing accurate start point. Apply light feed pressure initiating penetration into ground surface while starting rotation at low speed (30-50 RPM). Commence drilling fluid circulation maintaining flow rate adequate for cutting removal. Monitor penetration rate adjusting feed pressure and rotation speed for formation conditions encountered. Increase rotation speed gradually as bit establishes proper cutting action and borehole advances. Maintain drilling parameters within rig specifications avoiding excessive feed force or rotation speed. Observe cuttings in fluid returns identifying formation types and watching for changes indicating formation boundaries. Document drilling parameters and geological observations at regular intervals in drilling log. Monitor torque and pull indicators watching for unusual increases indicating developing problems. If penetration rate decreases substantially, reduce feed pressure and increase rotation speed improving cutting efficiency. Maintain steady drilling progress avoiding abrupt parameter changes that stress drill string components.

5

Add Drill Rods During Deep Hole Advancement

When drill string advanced such that next rod addition required, stop rotation and reduce feed pressure to zero. Raise drill string slightly (100-200mm) relieving bit contact with hole bottom. Maintain drilling fluid circulation throughout rod addition maintaining borehole stability. Position next drill rod in rod handler or on drill table with pin thread upward. Clean both pin and box threads thoroughly removing any cuttings or debris. Apply thread compound to pin thread ensuring complete coverage. Guide rod into alignment with drive head using rod handling tools keeping hands clear of connection area. Engage threads carefully avoiding cross-threading that damages thread forms. Rotate rod using power drive head or breakout tongs achieving specified makeup torque. Verify proper shoulder engagement with no gap visible at connection. Lower combined drill string resuming drilling at hole bottom. Resume rotation and apply feed pressure continuing advancement. Repeat rod addition process at each successive rod length throughout drilling to target depth.

6

Manage Circulation Loss and Borehole Stability

If drilling fluid returns to surface reduce or cease indicating circulation loss, immediately reduce penetration rate and monitor situation. Minor circulation loss may self-seal as clay particles in drilling fluid plug permeable zones. If loss continues, increase fluid viscosity by adding bentonite or polymer creating more effective sealing. For total circulation loss where no returns occur, consider converting to compressed air drilling if formation competent enough. If drilling through unstable formations where borehole collapse risk exists, install casing promptly providing mechanical support. Stop drilling and trip out drill string if borehole showing signs of instability including increasing torque, difficulty rotating, or audible collapse noises. Consider abandoning current hole and starting new hole nearby if instability cannot be managed with casing or fluid adjustments. Install surface casing through loose surface formations preventing ongoing collapse from shallow depths. Cement casing in place if required creating permanent seal preventing material ingress.

7

Respond to Abnormal Drilling Conditions

If abnormal conditions develop during drilling including sudden penetration rate increase suggesting cavity or void, unusual vibration indicating drill string imbalance, torque spikes suggesting stuck tooling, or fluid returns containing gas bubbles indicating gas zones, respond immediately reducing drilling intensity. For sudden penetration increase, reduce feed pressure preventing excessive drill string drop potentially damaging equipment. If gas detected in returns, stop drilling and test for combustible gas concentrations using gas detector. Evacuate area if dangerous gas levels detected and eliminate all ignition sources. For stuck tooling, stop rotation and feed, work drill string gently up and down attempting to free without excessive force. If string remains stuck, circulate drilling fluid vigorously attempting to erode blockage. Consider applying jarring impacts using hydraulic jar tools if available. For artesian flow from hole indicating confined aquifer penetration, increase drilling fluid density attempting to balance formation pressure. Install blowout preventer if flow becomes uncontrolled enabling hole closure. Document all abnormal conditions and responses in drilling log providing information for future operations.

8

Complete Drilling and Retrieve Drill String

Upon reaching target depth, stop feeding and maintain rotation while raising bit clear of hole bottom. Maintain fluid circulation during string retrieval preventing cuttings settlement around string causing sticking. Raise drill string in increments matching single rod lengths stopping at each connection. Break out top rod connection using breakout tongs applying correct torque in reverse direction. Lift rod clear and lay in rod rack inspecting threads during removal. Repeat process retrieving entire drill string one rod at a time. Observe each rod during retrieval watching for damage, unusual wear, or contamination requiring cleaning or repair. If string becomes difficult to extract indicating wall friction or minor collapse, work string gently up and down while maintaining circulation attempting to free. Apply steady upward pull avoiding sudden jerks that stress connections. If string firmly stuck despite gentle working, cease extraction efforts and consider specialized recovery techniques. Clean each rod as retrieved removing cuttings and drilling fluid extending rod service life. Inspect threads post-drilling identifying damage requiring rod retirement or repair.

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Frequently asked questions

What licences and training do I need to operate a vehicle mounted drilling rig in Australia?

Operating vehicle mounted drilling rigs requires appropriate truck driving licences depending on rig configuration: heavy rigid (HR) licence for truck-mounted rigs, or medium rigid (MR) for smaller trailer-mounted units. Additionally, you should complete recognised drilling operator training covering rig systems, drilling techniques, geological interpretation, and safety procedures. While no nationally mandated high-risk work licence exists specifically for drilling rig operation, many employers require competency-based training and assessment demonstrating practical skills. If drilling operations involve confined space entry for sample collection or equipment retrieval, confined space entry training is required. Operators working near overhead power lines should complete electrical safety awareness training. First aid certification is beneficial given remote work locations and injury potential. Employers must verify operator competency before allowing unsupervised drilling operations and maintain training records documenting completed courses and assessments. Given the specialist nature of drilling work and equipment-specific operational differences, manufacturer training for specific rig models provides valuable knowledge of system capabilities, limitations, and maintenance requirements.

How can I prevent drill string breakage during operations?

Preventing drill string failures requires systematic inspection, correct makeup procedures, and appropriate operational practices. Before each use, inspect drill rod threads visually checking for damage, corrosion, elongation, or unusual wear indicating fatigue. Use thread gauges verifying dimensions within tolerance, rejecting any rods with damaged threads. Clean threads thoroughly removing old thread compound and debris before rod makeup. Apply fresh manufacturer-approved thread compound providing lubrication and preventing corrosion. Make up rod connections using calibrated torque wrenches achieving specified torque values - insufficient torque permits joints loosening during operation while excessive torque damages threads. Verify proper shoulder engagement after makeup with no visible gaps. During drilling, monitor torque indicators watching for unusual increases suggesting developing problems. Avoid exceeding manufacturer rotation speed and feed pressure limits as excessive parameters stress connections accelerating fatigue. When drilling in corrosive groundwater, flush drill string with clean water after completion and apply corrosion inhibitor to threads. Track drill rod usage hours marking rods approaching service life limits (typically 2000-5000 hours) for detailed inspection or retirement. Consider magnetic particle or ultrasonic testing on high-time rods detecting internal cracks before catastrophic failure. Maintain detailed drill string inventory records enabling proactive replacement before failures occur rather than reacting to breakages.

What should I do if the borehole starts to collapse during drilling?

If borehole collapse begins indicated by increasing rotation torque, difficulty moving drill string, or reduced fluid returns, take immediate action to prevent string entrapment. First, reduce feed pressure and penetration rate minimising disturbance to unstable formations. Increase drilling fluid circulation attempting to stabilise hole walls with increased fluid pressure and viscosity. Add bentonite or polymer to drilling fluid creating more effective wall support. If collapse continues, stop drilling and carefully trip drill string from hole before becoming firmly stuck. Work string gently up and down during extraction using short movements avoiding sudden jerks while maintaining maximum fluid circulation. If string becomes difficult to move indicating partial collapse around it, cease upward pulling to avoid breaking string and apply jarring impacts if hydraulic jar tools available. For formations showing consistent instability, install steel or PVC casing promptly after drilling providing mechanical support preventing further collapse. Size casing to fit inside borehole with adequate clearance while preventing passage of collapsed material. Cement casing in place if permanent installation required creating seal between casing and formation. In extremely unstable formations, consider abandoning current hole and relocating drill position to more stable ground. Document all collapse incidents and formation types involved in drilling log enabling better planning for future holes in same geological conditions.

How do I safely handle confined aquifer zones during drilling to prevent blowouts?

Managing confined aquifer drilling requires research, preparation, and careful monitoring for early warning signs. Before commencing drilling, research geological conditions using existing bore logs and government geological databases identifying known confined aquifer depths and formation pressures in area. When approaching known pressure zones, increase drilling fluid density using barite (barium sulphate) or other weighting materials attempting to balance anticipated formation pressure. Calculate required mud weight based on estimated formation pressure and depth. Install blowout preventer (BOP) equipment at surface before penetrating high-risk zones enabling rapid hole closure if flow begins. Test BOP functionality confirming closure times meet requirements. Watch for early warning signs of approaching pressure zones including increased penetration rate as formation changes, gas bubbles appearing in drilling fluid returns, or formation cuttings showing characteristics associated with seal layers overlying aquifers. If these signs observed, stop drilling immediately and increase mud weight before proceeding. Maintain full drilling fluid circulation during all rod changes in pressure zones preventing pressure differential developing. Have cement plugging materials prepared and ready for rapid deployment if circulation lost allowing emergency sealing. If flow begins from hole despite mud weight, activate BOP closing annular space around drill string. Monitor pressure at surface planning controlled bleeding of pressure if necessary. Never attempt to cap flowing holes without proper well control equipment and procedures as this creates extreme blowout risk.

What are the health effects of whole-body vibration from drilling operations?

Long-term whole-body vibration exposure from drilling equipment operation is associated with multiple chronic health conditions affecting career longevity and quality of life. The primary concern is lower back pain and degenerative disc disease as vibration transmitted through spine causes micro-trauma to intervertebral discs. This cumulative damage develops over months and years of exposure presenting as chronic pain, reduced flexibility, and eventual structural disc degeneration visible on medical imaging. Hand-arm vibration syndrome can develop affecting circulation in fingers and hands, though this is more associated with hand-held equipment than whole-body exposure. Digestive system disturbances have been reported in workers with high vibration exposure. Increased fatigue during and after shifts affects alertness creating safety risks. The magnitude of health effects relates to vibration intensity, frequency characteristics, duration of daily exposure, and total years of exposure. To minimise effects: use equipment with vibration-dampened operator platforms or seats, limit continuous drilling periods to 2-hour maximum followed by breaks, rotate between drilling and other duties reducing individual exposure time, maintain equipment in good condition as worn components increase vibration, seek medical attention early if back pain develops rather than working through symptoms. Current exposure limits under workplace regulations establish action and limit values requiring employers to implement controls when exposures exceed thresholds, but even exposure below these limits creates health risk with long-term exposure making vibration reduction important throughout career.

How should hydraulic hoses be maintained to prevent injection injuries and hose whip?

Preventing hydraulic hose failures requires systematic inspection and proactive replacement before failures occur. Inspect all visible hydraulic hoses daily before operations checking for surface cracking, bulging indicating internal breakdown, abrasion wear from contact with drill components, and leaking at couplings suggesting seal degradation. Pay particular attention to hoses experiencing repeated flexing during rig operation as these develop fatigue cracks in rubber layers. Use infrared thermal imaging identifying hot spots in hydraulic systems indicating internal restrictions or developing failures. Replace hoses at maximum 4-year service life intervals regardless of visual appearance as internal deterioration occurs from temperature cycling, pressure fluctuations, and fluid contamination effects not visible externally. Route hoses avoiding sharp edges, excessive bending beyond minimum radius limits, and contact with rotating drill strings causing accelerated wear. Install protective sleeves on hoses in high-wear areas. Mark installation dates on hoses using permanent marker or tags enabling tracking of service life. Train operators to identify hydraulic leaks using cardboard or paper held near suspected leak areas never using hands as even pinhole leaks produce invisible high-velocity jets penetrating skin causing injection injuries requiring emergency surgery. Always shut down hydraulic systems completely and relieve pressure before attempting hose replacement or repairs. Install hose burst containment sleeves on critical circuits limiting fluid spray and whip energy if failures occur. Document all hose replacements and inspection findings in equipment maintenance log enabling pattern recognition if particular circuits experiencing repeated failures requiring system redesign or operational changes.

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Borehole Drilling Methods, Geotechnical Requirements, and ARPANSA Obligations for Radioactive Tracers

Vehicle-mounted borehole drilling for geotechnical investigation, environmental monitoring, groundwater assessment, and mineral exploration uses a range of drilling methods selected based on the investigation objectives, required sample quality, drilling depth, and ground conditions. Rotary mud drilling uses a rotating drill string with tri-cone or PDC drill bits and circulating drilling fluid (water-based or polymer mud) to advance the borehole and remove cuttings; it provides the highest drilling rates in hard rock but recovers disturbed samples unsuitable for detailed soil characterisation. Cable tool (percussion) drilling uses a weighted bit repeatedly raised and dropped by a spooled cable to break soil and rock; it provides good sample recovery from soft soils and shallow borehole investigation requirements common in geotechnical site investigation. Continuous Flight Auger (CFA) drilling uses hollow-stem augers advanced by rotation without drilling fluid, providing undisturbed or minimally disturbed soil samples in cohesive soils for Atterberg limit and compaction testing. Geotechnical investigation boreholes for infrastructure projects must comply with AS 1726:2017 Geotechnical Site Investigations, which specifies minimum standards for investigation program design, sampling methods, laboratory testing requirements, and reporting format. AS 1726 requirements for sample types at specified depth intervals—undisturbed tube samples, standard penetration test (SPT) values, and field vane shear tests in soft soils—must be implemented correctly to produce investigation data suitable for foundation design. The geotechnical engineer directing the investigation must be present or represented at the borehole during drilling to confirm sample collection, record observations, and make real-time decisions about additional testing requirements based on what is encountered. Groundwater monitoring borehole installation must comply with the relevant state or territory groundwater management authority requirements. Most states require a Water Bore Drillers Licence for anyone drilling groundwater bores; in some states, this licence extends to monitoring boreholes even where groundwater extraction is not the purpose. Construction of monitoring bores must use materials specified in authority guidelines—typically slotted casing in the screened interval, solid casing above, and appropriate grout seal above the screened interval to prevent surface water contamination of the monitored aquifer. Well completion records (bore completion reports) must be submitted to the authority within specified timeframes after borehole completion.

Mechanical Hazards, Drilling Fluid Management, and Working at Height on Drill Rigs

Vehicle-mounted drilling rigs present multiple severe mechanical hazards concentrated at the drill mast, rotary head, and rod handling zone. The rotary head—the power head that rotates the drill string—can generate torque values of 1,000–10,000 Nm depending on rig size, and any loose clothing, hair, personal items, or body parts within reach of the rotating drill rod can be instantly entangled with catastrophic consequence. All workers within the mast zone must wear snug-fitting high-visibility clothing without loose ends, and long hair must be tied back and under a hardhat. Drill rod connections—adding rods as the borehole advances—require careful hand positioning relative to the rotating head and must be performed strictly according to the driller's specific procedure for that rig model. Working in close proximity to rotating drill rods during rod connection and disconnection is the highest injury risk activity in borehole drilling operations. Drilling fluid management during rotary mud drilling requires containment of drilling fluid and cuttings within a sump system to prevent ground contamination. Water-based drilling mud is generally environmentally benign, but polymer muds and foam drilling fluids may require specific disposal arrangements. The sump must have adequate capacity for the drilling fluid volume, and overflow containment must prevent mud from entering drainage systems, adjacent waterways, or sensitive ecological areas. Decontamination of drilling equipment between boreholes at contaminated sites prevents cross-contamination—equipment used in a contaminated borehole must be cleaned before drilling in an uncontaminated location. Investigation of contaminated sites requires specific contamination management protocols including protective PPE for drillers handling contaminated soil samples and drilling fluids. Working at height on drilling mast structures is required for rod handling on deep boreholes, mast adjustment, and equipment maintenance. The mast structure extends 5–15 metres above ground level on typical vehicle-mounted rigs, and activities at mast height—attaching lifting slings, adjusting mast angle, maintaining cathead winch systems—require fall protection under WHS working at height requirements. The rig design should incorporate fall arrest anchor points at positions where worker access to height is required; where designed anchor points are absent, engineering assessment of alternative anchor locations must be performed before any elevated work commences.

Underground Service Protection, Groundwater Control, and Borehole Abandonment

Borehole drilling creates a direct penetration through surface ground to potentially considerable depth, passing through all subsurface features including underground services, buried foundations, contaminated soil layers, and multiple aquifer levels. Underground service location is mandatory before any drilling commences—even small-diameter monitoring boreholes of 50–100 mm diameter can sever undetected services. Dial Before You Dig enquiry, electromagnetic service location, and GPR scanning provide pre-drill service location information, but potholing by hand or vacuum excavation at the exact drilling location provides definitive confirmation before the drill rod is advanced. Multiple borehole locations require service verification at each individual location, not just a single verification for the site. Groundwater artesian pressure presents a significant hazard when drilling intersects confined aquifers. An artesian aquifer is one where groundwater is under pressure sufficient to cause water to flow to the surface unaided. Drilling into an artesian aquifer without pressure control equipment can result in an uncontrolled blowout—a fountain of water, drilling fluid, and potentially gas that can prevent drill rod extraction, flood the drilling area, damage the drilling rig, and in extreme cases involving gas-bearing formations, create explosion risk. Aquifer pressure assessment from geological data and nearby bore records before drilling allows appropriate casing and pressure control planning. Drilling contractors should discuss artesian aquifer risk with the supervising engineer before mobilising to sites in known artesian pressure areas such as the Great Artesian Basin region. Borehole abandonment procedures are required when investigation or monitoring boreholes reach the end of their useful life. An abandoned open borehole left without proper sealing creates a direct hydraulic connection between the surface and subsurface aquifers, potentially contaminating deep clean aquifers with surface-derived pollutants. State groundwater authority regulations specify grouting requirements for borehole abandonment, typically requiring a cement-bentonite grout column from the base of the borehole to the surface. Abandonment records must be submitted to the groundwater authority. The obligation for proper borehole abandonment falls on the bore owner and the drilling contractor; improper abandonment constitutes an environmental offence under water resource legislation in all Australian jurisdictions.

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