Drilling

Setting records while adhering to strict environmental regulations

by Cory Ibbotson, Director at Alton Drilling

Alton Drilling (Alton) is a New Zealand-based drilling company, and we are making a name for ourselves by embracing innovation and versatility in our approach to drilling and rig manufacturing. We are committed to delivering customized solutions for clients with complex drilling needs, including heli-portable rigs for remote and hard-to-reach locations, as well as drilling in sensitive environments.

Our partnership with OceanaGold started when we were tasked to supply drilling services and expertise to the Wharekirauponga (WKP) project. This got some serious legs in 2015, and our work continues to this day. Primarily the project is based on a two-week on, one-week off roster with our exploration team accommodated in our Alton Drilling-built and serviced heli-camp and facilities with all day-to-day supplies and consumables flown in when weather permits. We are excited to be a part of the underground target and the challenges it brings.

The WKP project

The WKP project is situated within the Coromandel region on the northeast coast of the North Island. The project has varied terrain and environment, characterized by rugged mountains, steep valleys, and dense native forests and is beneath a forest park administered by New Zealand’s Department of Conservation. The prospect hosts a high-grade epithermal gold/silver deposit. It is planned to access the deposit by tunneling in from OceanaGold-owned land, therefore minimizing any impact on flora and fauna.

The operational areas must be no larger than 150 m2 (492 ft2) - sites are only granted in areas after extensive site ecological surveys to mitigate impacts to a range of flora and fauna and particularly to locate and avoid any native frogs. Thus, all drilling and other equipment is installed by a helicopter onto large, raised platforms built above ground usually from 8 x 8 in- and 6 x 2 in-timber. This allows us to work with the undulating ground and gives the luxury to recycle; that together limits our impact.

Many of our clients now have a no-dig policy due to environmental regulations, meaning that sumps are no longer an option for water retention and reticulation. To assist with keeping our drilling footprint as minimal as possible, we are developing new systems with our Solid Recovery Units (SRUs) and running multiple-stage pump systems for remote high-altitude sites.

Another recent challenge was to extract water samples at depth. There was nothing on the world market, so our team set to and designed and manufactured an overshot water sampler tool for both H-size and N-size. This tool runs on conventional wireline drilling equipment and provides uncontaminated water samples to be extracted at specified depths for geochemical analysis. We have settled on the modified heli-portable SC11 drill rigs for their small footprint. We opted for these rigs because they have the ability to drill up to P-size, can drill at low angle mast setups to -20° off horizontal and have rod handling capability.

Our hole depths are achieved through careful planning and mitigation of the day-to-day challenges. P-size is used to case off the top several hundred meters, while target depths are then achieved with H-size. This is due to the unexpected nature and ground conditions in New Zealand. It is not uncommon to run PWT casing down to depths of 60–100 m (197–328 ft). All drilling is orientated triple tube drilling. With this in mind, a recent company milestone was achieved when Rig 82 SC11 completed a heli-supported exploration hole, drilling over 1308 m (4291 ft) at -20° angle from a timber platform, utilizing pumpup equipment and a heli-portable SRU for solids recovery.

Another success on the WKP project was the completion of a sizeable heli-supported geotech program where one of the holes was drilled to 458 m (1503 ft) at -25 degrees and five vibrating wire piezometers were installed then fully stage grouted to the surface.

About the company

Established in 1983, Alton Drilling is a proudly Kiwi-owned and operated company. We provide quality, professional service with a friendly business approach. Continual research and using and developing the latest drilling equipment and technology, combined with a wide range of experience, Alton Drilling is at the forefront both in New Zealand and globally.

Alton Drilling’s rig manufacturing business is built with the same values. The company’s rigs are designed to be modular and portable, with minimal electronics, highly interchangeable parts, and the ability to be broken down into components weighing no more than 500 kg (1102 lb). This allows exploration in previously unreachable zones.

Alton Drilling’s commitment to innovation and versatility is reflected in the success of the company’s operations. The company’s rigs have been sold globally, and they continue to build on their turn-key packages including new rigs, downhole consumables, muds, supply pumps, rig spare parts, hyd motors, concept to design and more. With their ongoing investment in people, infrastructure, and stock levels, Alton Drilling is well-positioned to meet the increasing demand for exploration and geotechnical drilling both surface and underground. C

Visit: www.altondrilling.co.nz or call: +64 508 425 866

↓ Drilling on a heli-portable supported site from a wooden platform setup on a -20 degree angle has its own challeneges. Our Waihi surface crew also were faced with testing ground conditions. A great team effort for successfully reaching a depth of 1308 m (4291 ft) exceeding expectations.

↑ Rig 82 setup on a low angle and positioned on the 12 x 12m-timber platform keeping everything contained within the operational parameters. The site is careful selected to minimize any tree disturbance, native trees and step terrain surround the site.

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