One of the most consequential decisions in planning a mineral exploration programme is choosing the right drilling method for the geology, the exploration stage, and the budget available. Aircore and reverse circulation (RC) drilling are two of the most commonly used methods in Australian exploration – and while they’re sometimes discussed as if interchangeable, they serve genuinely different purposes and produce different quality and cost outcomes depending on the application.
Bostech Drilling has over 25 years of experience delivering exploration drilling programmes across Western Australia. Here’s an honest comparison of the two methods, and how to think about which is right for your project.
How Aircore Drilling Works
Aircore drilling uses a dual-wall drill string with compressed air to lift drill cuttings to the surface through an inner tube, keeping the sample isolated from contact with the borehole walls. This produces a clean, representative sample with minimal contamination – an important consideration for accurate geochemical analysis. Aircore rigs are typically lighter and more mobile than RC rigs, capable of drilling relatively shallow holes (generally up to around 100 to 150 metres, depending on ground conditions) efficiently and cost-effectively.
Aircore is widely used for regional-scale, first-pass exploration – testing broad areas quickly and affordably to identify zones warranting more detailed follow-up. It performs well in unconsolidated to moderately consolidated ground, including regolith and weathered rock, which makes it particularly suited to exploration in areas with significant weathering profiles – common across much of Western Australia.
How RC Drilling Works
Reverse circulation drilling uses a similar principle of returning samples through an inner tube isolated from the borehole walls, but employs a more powerful hammer-based drilling mechanism suited to harder, more consolidated rock. RC drilling can penetrate significantly deeper than aircore, often several hundred metres and performs reliably in fresh, unweathered rock that aircore struggles to penetrate efficiently.
RC is typically used for more advanced-stage exploration, where a target has already been identified through earlier-stage work (such as aircore) and the objective is to test that target in more detail, at greater depth, and with sample quality suitable for resource definition work.
Comparing Cost and Efficiency
Aircore drilling is generally faster and less expensive per metre than RC drilling, largely because of the lighter equipment, faster penetration rates in suitable ground, and lower operating costs. This makes it the logical choice for early-stage, wide-area exploration where the goal is covering ground efficiently to identify targets rather than characterising a known target in detail.
RC drilling costs more per metre but delivers samples and depth capability that aircore cannot match in harder ground. For exploration companies with defined budgets, understanding this cost differential, and matching the method to the actual exploration objective is one of the most important planning decisions in a drilling programme.
When to Use Each Method
As a general guide: aircore suits regional reconnaissance, broad-area geochemical sampling, and testing shallow to moderate-depth targets in weathered ground. RC suits detailed target testing, deeper penetration into fresh rock, and situations where more precise sample definition is required to advance a project toward resource estimation.
Many successful exploration programmes use both methods sequentially – aircore first to identify prospective zones across a broad area, followed by targeted RC drilling once specific targets have been narrowed down. This staged approach optimises both cost efficiency and data quality across the life of the programme.
Getting the Right Advice for Your Ground
The right method for your project depends on your specific geology, exploration stage, budget, and objectives, and getting this decision right from the outset can significantly affect both the cost-efficiency and the scientific value of your programme. Bostech’s team has over 25 years of experience matching drilling method to exploration objective across WA’s diverse geological terrain.
To discuss the right drilling method for your exploration programme, contact Bostech Drilling Australia at bostech.com.au and speak with our experienced team.