April 4, 2022
The geological conditions at the Čukaru Peki copper mine near Bor in Eastern Serbia, are not exactly ideal for exploration drilling. The ground consists of complex formations, mostly andesite and quartz, mixed with various types of clay and sand, intersected throughout by fractures and faults.
Furthermore, the material is hard – between 7 and 9 on the Mohs scale – and notoriously porous, especially in holes more than 2000 m deep. All this makes exploration drilling a daunting task, but not for Geomag DOO.
This company, which is one of the region’s top core drilling contractors, is proving that extreme conditions can be overcome with the right equipment and technology.
Based in Belgrade, Geomag has some 80 employees, a fleet of 10 drill rigs and operations throughout the country. It also numbers some of the world’s biggest mining companies among its clients such as Rio Tinto and ZiJin.
For several years, the company has been using Epiroc Christensen CS14 exploration drill rigs and more recently has added the larger, more advanced Epiroc Christensen CT20 to its fleet.
Since it came on stream in 2017 this unit has been at work all year round and every year in the Čukaru Peki sites and Bor areas. To date it has taken a total of around 30 000 meters of cores and is currently averaging 50 m per day, with three operators rotated on two shifts per 24 hours, and drilling at a hole range of 800-1400 meter.
Ivan Rakić, Executive Director and Project Manager for deep-shallow drilling programs, explains why the company uses the Epiroc Christensen CT20.
"We needed another deep hole drill rig for future projects and we also wanted to be more competitive on the market. But primarily we wanted a rig that had more than enough pulling and drilling power to be able to tackle the demanding conditions we are working in."
Another reason, he continues, was that the company is impressed with the all-round capabilities of its Epiroc Christensen CS14 rigs.
“We have five Christensen CS14 rigs and use them all the time,” adds Ivan Rakić. “They are small but strong machines and can complete most tasks, from geotechnical drilling to exploration holes up to one thousand two hundred meters deep.
“The bigger Christensen CT20 will pull nine-meter strings. It’s very quiet, which was the first thing we noticed and is good for the working environment, and it’s easy to track the wireline. The winding feature of the wireline winch works great as it helps to place the wire evenly on the drum and reduce wear.”
On shallow-hole projects (up to 1000 m), a less experienced drilling crew can manage just fine and easily operate the Epiroc Christensen CT20 given that the basic system is very similar to that of the Epiroc Christensen CS14. However, on deep-hole projects (1500 – 2300 m) more experienced drilling crews will be deployed. Geomag’s model also has a CE certificate.
Another important motivation to stay with Epiroc technology, Rakić says, was its close relationship with the “very good service and maintenance team” set up by Epiroc in Bor.
The company drills all diameters – PQ, HQ, NQ – and uses SQ rods for casing. The deepest hole achieved over the years is 2300 m deep.
In general, it takes Geomag approximately one month to complete a 1000 meter deep hole, including deviation monitoring (using an Axis ChampGyro camera), replacing rods and casings and cementation of the hole. Deeper holes, around 2000 meters, usually take approximately three months to complete.
Concludes Rakić: “The deeper the hole the more challenges we need to overcome. But at the same time, we know we can succeed and that makes us proud to work on these projects.”