Exploration Drilling Rigs: 6 Types by Sample and Cost

Exploration drilling rigs: six types and what each is for

Exploration drilling rigs come in six working types: surface diamond core rigs, compact core rigs, portable core rigs, reverse circulation (RC) rigs, aircore and rotary air blast (RAB) rigs, and multi-purpose rigs that combine RC and core. The choice follows from the sample you need. Core rigs recover a solid cylinder of rock. Makers rate them from 815 m for a compact rig to 3,360 m for the deepest surface rigs; for example, Epiroc lists N-size ratings for the Christensen CT14 and CT20 of 1,200 m and at least 2,450 m. RC and air rigs return chips, drill faster and cost less per metre, and suit the first passes through soft or weathered ground.

This guide is for licence and claim owners, consultants and company staff who must brief a drilling contractor or decide whether to buy a rig. It compares the six types on sample, depth and cost, explains why a depth rating changes with core size, covers tools, fluids and water, and ends with a calculator that turns holes and depth into rig days and a budget. Depths are in metres (1 m is 3.28 ft). Costs are base rates from one published glossary, so ask contractors for a quote on your ground before you plan around any figure here.

Cost figures are the average base rates, in an unstated currency, listed by Novo Resources, which notes that consumables, slow penetration, standby, mobilisation and water cartage often bring the final all-inclusive cost to double the base rate. Depth guides are maker ratings in N-size core. Epiroc states that its figures are for vertical holes and are guidelines, not guarantees; Sandvik gives 815 m N-size without stating the hole angle. The RC Drilling guide puts RAB at about 100 m in unconsolidated ground.

How to choose an exploration drill rig: five checks

Answer these in order and the rig type usually picks itself.

1. What must the sample prove? Geochemistry and rough geology can come from chips. Structure, true widths, rock strength and metallurgical tests need core. A conference comparison by Hapugoda and Manuel (AusIMM, 2010) compares diamond, aircore, RC and RAB on sample size, representativity, recovery and contamination for this reason.
2. How deep is the target? Shallow oxide or weathered targets suit aircore or RAB. Mid-depth targets suit RC, and deep or structurally complex targets suit core.
3. What is the ground like? Soft, broken or wet ground changes both the rig and the fluid plan (see the sections on core size and water below).
4. How will the rig get there? Truck-mounted rigs need tracks. Crawler carriers cross rougher ground, skid or compact rigs are moved in pieces, and portable rigs are flown or carried in modules.
5. Hire or buy? Most small explorers hire a contractor by the metre. Buying makes sense only for steady, multi-year metreage, because you also take on crews, spares and downtime.

Diamond core rigs: surface, compact and portable

A diamond core rig spins a hollow bit set with industrial diamonds and brings up a solid column of rock inside the rod string. Geologists log the core, record how much came back as recovery (for example 8 ft of core from a 10 ft run is 80% recovery) and split it for assay, as described by Earth Science Australia. Core is the most expensive sample per metre, but it carries the structural and rock-strength information that chips cannot.

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One deep-core rig, three core sizes

Rated depth of the Boart Longyear LF350e, metres

Truck and crawler core rigs

Epiroc rates its Christensen CT14 at 0 to 1,200 m and its CT20 at 0 to at least 2,450 m (the maker’s current table may list a higher calculated maximum), both in N-size for vertical holes and both as guidelines (Epiroc specifications as listed by Geotechpedia). In its 2018 fleet announcement, Boart Longyear described the LF350e as reaching 3,360 m with NQ rods, 3,050 m with HQ and 1,800 m with PQ (Global Mining Review, 2018). Mounting matters on rough ground: a truck needs a road or a graded track, while a crawler carrier can follow a narrower track and so needs less earthwork.

Compact, skid-mounted and underground core rigs

Compact rigs trade depth for size. Sandvik’s DE100 series of compact core drills covers surface and underground work, and the DE130x is rated to 815 m N-size (Sandvik, 2012 product release). A compact rig makes sense when the pad is small, when holes are drilled upwards or sideways from a drift, or when the rig must be broken down and moved by hand.

Portable rigs for highlands and roadless ground

Where no truck or crawler can reach, drillers use demountable rigs that are flown by helicopter in modules or carried in on foot. Expect shallower holes and smaller core than a surface rig, a higher cost per metre once the fly-in is counted, and a camp that must be supplied by air. Ask any supplier for the heaviest module weight, because it sets the helicopter you need, and for the depth rating at your core size.

Soft ground and multi-function rigs

Soft, broken or fractured ground loses core. Larger core sizes such as HQ and PQ are specified when the ground needs a larger borehole for stability, according to the DCDMA size summary by a drill rod maker. A common cost-saving answer is a multi-purpose rig that drills an RC pre-collar through the soft upper ground and then continues with core, either in one hole or by returning to a promising RC hole (RC Drilling guide).

Core size decides how deep a rig can drill

A rig’s depth rating always belongs to a core size. The same rig that reaches 3,360 m with NQ rods is rated for 1,800 m with PQ, because wider rods weigh more per metre. When a supplier quotes one number, such as a 530 m core rig, ask which core size and which hole angle it describes. Epiroc states that its ratings refer to N-size and to vertical down drilling.

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Core diameter by standard size

Diameter of the core recovered, millimetres

The letters name the core you recover. Under the DCDMA standard sizes, AQ core is 27.0 mm across, BQ 36.5 mm, NQ 47.6 mm, HQ 63.5 mm and PQ 85.0 mm (a drill rod maker’s summary of DCDMA sizes). ASTM D6032 confirms 36.5 mm for BQ, 47.5 mm for NQ and 85 mm for PQ, and names NQ as an optimal size for measuring rock quality designation, a standard core-logging measure (ASTM D6032). Smaller core costs less per metre; bigger core gives more sample for metallurgical tests and better stability in poor ground.

Reverse circulation rigs

An RC rig forces compressed air down the outer wall of a double-wall rod. A hammer at the bit shatters the rock, and the chips rise through the inner tube to a cyclone at surface. Earth Science Australia notes that this needs much larger equipment than core drilling, including a high-capacity compressor, and that samples are usually collected over 5 ft intervals, then split to about one eighth in a Jones splitter. Structural detail is lost because there is no solid rock to measure.

RC penetrates faster and is usually 25 to 40% cheaper than diamond drilling on all-up cost (its example is A$120 a metre for RC against A$200 for diamond), according to the RC Drilling guide. Base rates per metre in the cost chart below show a wider gap, so rely on a quote for your ground. Water is the main limit on sample quality. A hammer bit works well above the water table and in dense, hard rock, while a tricone bit copes better in wet or soft ground (Earth Science Australia). In a 1991 paper on Chimney Creek, Nevada, Gold Fields reported visible contamination of RC samples drilled below the water table, although RC holes defined mineralised zones almost as well as diamond holes (SME paper abstract).

Aircore, RAB and RC compared for shallow ground

RAB uses a rotating blade bit on single-tube rods and is cheap and quick, but its samples are poorer because of downhole contamination. Aircore improves on RAB by returning the sample through an inner tube, which limits cross-contamination. Novo describes aircore as capable of boring unconsolidated or weathered material only, with depth limited by the machine’s air pressure, so it is traditionally used in first-pass exploration. RC gives more reliable samples than either, at higher cost.

A practical sequence in weathered terrain is aircore or RAB to map the regolith (the loose weathered cover above fresh rock), RC to test anomalies, and core to confirm structure and grade. Treat the figures in the table as ranges for planning, and replace them with real quotes.

Drilling tools: bits, rods, barrels and hammers

Drilling tools for mineral exploration depend on the method. Core drilling needs diamond bits, core barrels, rods and a wireline system (a cable that hauls the inner core tube up through the rods), since the inner core tube is winched to surface on a cable at the end of each run. RC needs hammer or tricone bits and double-wall rods. Blade bits and single-tube rods serve RAB. Consumables are a real cost: the RC Drilling guide notes that diamond consumables are more expensive because they are made to suit the rig.

Water and drilling fluids: the part buyers skip

Core bits are lubricated and cooled with water or mud. In fractured rock, fluid can escape down the hole, so drillers inject mud, sawdust or other plugging material (Earth Science Australia). A rig package for dry country should therefore include a water source, a pump, a settling tank and a sump so that fluid is recirculated and not discharged. Ask contractors whether recirculation, solids control and a water truck are in the rate or priced separately, since Novo lists water cartage as a cost that raises the base rate.

When a programme crosses the water table, RC sample quality and rig choice change, as the Chimney Creek study shows. Where permits restrict water use or discharge, build the fluid plan into the contract before mobilisation, not after.

Directional drilling from one parent hole

Directional core drilling steers branches, called daughter holes, off one parent hole, which cuts the metres drilled from surface. IMDEX’s Devico DeviDrill system recommends an average turn of 9 degrees per 30 m, which gives a radius of about 200 m, and rates its productivity at 50 to 75% of conventional wireline drilling. The same page credits the technique with saving 23,997.6 m, or about US$12 million, on the Alpala programme (IMDEX, DeviDrill). These are manufacturer figures, so ask for a trial on your own geology. The method suits programmes that need many intercepts of one deep body from few pads.

How much drilling is happening

Australian explorers drilled 3,461.6 km in the June quarter of 2026 on the original series, of which 2,639.8 km was on existing deposits and 821.8 km on new ones, according to the Australian Bureau of Statistics. The seasonally adjusted figure was 3,170.3 km, up from 2,646.3 km a year earlier. Contractor and rig availability tighten when drilling is busy, so book early in an upswing.

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Australian mineral exploration drilling, June quarters

Thousand metres drilled, seasonally adjusted

What a metre costs by rig type

Base rates climb steeply from RAB to core. Novo lists RAB at $12 to $20 a metre, aircore at $18 to $30, RC at $30 to $55 and diamond drilling at $110 to $250, noting that RC and diamond costs increase with depth and that diamond cost also rises with core diameter. Government rebate schedules give a second reference point: Newfoundland and Labrador caps claimable diamond drilling at C$200 a metre in its 2024 guide, all-inclusive of standby, moves and consumables, in its Junior Exploration Assistance guide. That cap is a program ceiling, not a market price. For a Canadian view of permits, seasons and quotes, see diamond drilling companies in Canada, and for underground against surface costs, see diamond drilling costs per metre.

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Base cost per metre by drilling method

Dollars per metre, average base rate before consumables, standby, mobilisation and water

Rig manufacturers, suppliers and contractors

Three groups sell into exploration. Rig makers build the machines: Epiroc supplies the Christensen core range and the Schramm truck-mounted line, Sandvik builds the DE-series compact core rigs, and Boart Longyear builds the LF-series core rigs. Tooling suppliers sell bits, rods, core barrels and hammers to fit the rig. Drilling contractors own fleets and sell metres with crews, and they are the right first call for most claim owners. When you compare suppliers, ask for the depth rating by core size, the heaviest module weight for portable rigs, the compressor capacity for RC, spares support in your country and the safety record of the crew.

Check the rating basis on every quote. The Epiroc figures quoted here are for vertical N-size holes and the Sandvik figure is for N-size core, and angled holes, larger core or poor ground reduce reachable depth. For a wider look at methods and how to plan holes, see exploration drilling methods, costs and hole planning.

Permits and land disturbance before a rig moves

Drilling usually needs approval before a rig mobilises. On United States public land managed by the Bureau of Land Management, an operator must submit a notice 15 calendar days before exploration that causes surface disturbance of 5 acres or less of public land not yet reclaimed, and a series of small notices cannot be used to avoid a plan of operations (43 CFR 3809.21). Canada and Australia run provincial and state systems; for Ontario, see the steps from licence to drill permit. Keep pads small, plan access tracks to avoid wet ground, and budget for reclamation and fluid disposal.

Check the ground before you move a rig

A hole in the wrong place costs the same as a hole in the right one. Satellite imagery cannot see a deposit, but it can map rock colour, clay and iron minerals, and structure from space, so you can rank targets before paying for pads and tracks. Farmonaut maps a claim or licence from a KML or polygon and returns ranked exploration targets in 5 to 20 business days, as targets that sit ahead of a resource estimate. See our satellite mineral detection service or request a quote, or contact the team.

▶ Farmonaut explainer: why a hole in the wrong place costs as much as one in the right place, and how satellite screening helps pick where to drill. · 4:26

Plan a drill programme: metres, rig days and cost

Work out metres first, then rig days, then money. Metres are holes times depth. Rig days are metres divided by what the rig drills in a day, which depends on method, ground and shift pattern. Money is metres times the rate, plus mobilisation, pads and contingency. Contractors vary widely on daily metres, so use their number. Where a programme has many targets, rank them first so that the best-supported holes are drilled while budget remains; for survey-first sequencing on a first season, see induced polarization survey sequencing.

▶ Farmonaut explainer: how satellite targets are ranked into a drill order. · 2:19

Frequently asked questions

What is an exploration drilling rig?

It is a drill used to sample rock below the surface to find or measure a mineral deposit. It takes a solid core (diamond rigs) or chips (RC, aircore and RAB rigs), which are logged and assayed to show grade and geology.

What are the main types of exploration drill rigs?

Diamond core, reverse circulation, aircore and rotary air blast are the main families, built on truck, crawler, skid or portable carriers. Multi-purpose rigs do RC and core in one machine.

How deep can an exploration core drilling rig drill?

Rated depths run from a few hundred metres for compact rigs to over 2,000 m for large surface rigs, such as at least 2,450 m N-size for the Christensen CT20. The number always depends on core size, hole angle and ground, so ask for it by core size.

RC drilling or diamond drilling: which should I choose?

Choose RC to test many targets quickly and cheaply. Choose diamond core when you need structure, rock strength or metallurgical samples. Many programmes use RC first and core to follow up the best intercepts.

What is the difference between aircore and RC drilling?

Aircore uses a blade bit and returns the sample through an inner tube, and suits unconsolidated or weathered ground. RC uses a hammer, handles harder rock and gives more reliable samples, at higher cost.

How does RAB compare with RC drilling?

RAB is cheaper and quicker but gives poorer samples because of downhole contamination, and it is used at the early stages. RC samples are more reliable and the hole can go deeper.

Which rig works best in mountains or highlands?

Crawler-mounted rigs follow narrow tracks that trucks cannot use, and portable rigs fly in as modules where there are no tracks at all. Both reduce earthwork, but check depth by core size and the heaviest module weight.

What drilling tools are used in mineral exploration?

Core drilling uses diamond bits, core barrels, rods and a wireline; RC uses hammer or tricone bits and double-wall rods; RAB uses blade bits. Tooling is matched to the rig and the ground.

How much does exploration drilling cost per metre?

Novo lists base rates of $12 to $20 for RAB, $18 to $30 for aircore, $30 to $55 for RC and $110 to $250 for diamond core, and says final costs can reach double the base rate. Always get a quote for your site.

Who supplies exploration drilling rigs?

Major makers include Epiroc, Sandvik and Boart Longyear. Many other manufacturers sell smaller and portable rigs, so compare depth rating by core size, support and spares before buying.

Is a blasthole drill the same as an exploration drill?

No. Blasthole rigs drill many shallow, wide holes in a pattern to hold explosives and are built for production drilling and not for recovering exploration core or deep chip samples. Exploration rigs drill fewer, deeper holes to recover samples.

Can satellite data replace drilling?

No. Satellite screening ranks where to drill and can cut the number of holes placed in the wrong spot, but only drilling measures grade at depth.