Experiences in drilling in extreme cold

March 1, 2021

by Matti Rautakoski, Business Manager at Oy Kati Ab Kalajoki

You need both equipment and know-how, to survive and even flourish in a cold environment. If you miss either, you are going to jeopardize the success of the entire project. You must understand the perils of the combination of snow, ice and darkness, the risks it produces and how to tackle them.

Factors to keep in mind to secure successful operations in extreme cold


While we were drilling in Northern Finland and Sweden, it was not so rare to have more than -40°C (-40°F) and on rare occasions even -50°C (-58°F). In such temperatures, it is essential to remember not to shut down any vehicles or machines, if you want to use them. If you shut them, it may be difficult to start them again until the weather gets warmer.

Once we had a tricky situation where only the drill rig and one single snowmobile were left running, all other machines were completely frozen in the -43°C cold (-45.4°F).

As usual, we would have driven the snowmobile from the rig to the parking area, which was on a lake shore, and then taken a car to our accommodation. In that instance, when we reached the cars, we found them frozen; we were stranded. We thought to give the cars a boost and warm them up with a generator. We started the generator inside the rig, as it was warm there, put it on the snowmobile sledge and set off on the eight km (5 mi) where our cars stood. It was so cold that even though the generator was running at the beginning, it stopped after a couple of kilometers. We drove the generator back to the rig and tried again and again, only to have the same issue.

In the end, we had to weather the whole way to the accommodations on the snowmobile.

We had a similar case with a geologist working for our client. He was also traveling to our rig by a snowmobile. His snowmobile fizzled out halfway and he had to walk several kilometers to the rig. When he finally appeared, he looked like a snowman, his beard all white and covered from head to toe in ice and frost. Our driller gave him a mug of hot coffee and the geologist was overjoyed by relief, as walking in the Arctic cold is one of the most unpleasant and dangerous experiences. His ill-fated snowmobile remained frozen until the weather got warm enough to start it again.


As we have four seasons during the year, it also means that we need to be aware when they change. For instance, we have to measure ice thickness both in early winter and in early spring to know when we can enter an area or assess whether it is time to leave while we still can.

After the darkest time of the year, there is plenty of daylight in March and April and also a lot of snow

Workplace and PPE

Equipment is another story. Due to the location of our projects, light is often of great importance. During the winter, it is dark for most of the day, so it is essential to have good general lights inside the rig and outside and equip each person with good headlamps.

We want to give our employees the best possible working conditions. This means that our rigs must be fully covered, allowing us to warm up the interior of the drill rig, and give pleasant inside working temperatures for the drillers.

One of the highest safety risks in winter conditions is slipping on icy terrain, which may result in serious injuries. We are using technical solutions to keep the rig floor free of ice.

Water is essential in core drilling, and we need to use it, which may cause problems in cold weather. Keeping the water pump running without even a minute break is important. Sometimes the waterlines happen to freeze and getting them to work again is not an easy task. In such cases, you must have some spare line to put into use and even then you will lose valuable time. The water line could be buried in snow to prevent freezing, as snow will isolate the line from cold air. However, if that is not possible, there are some heater solutions that can also help.

Sometimes if it is very cold and you have been working inside the rig, there might be humidity due to the handling of water. Clothing and safety gear are particularly important then, as when you go outside, your clothes may freeze instantly. Since there is a range of personal clothing and safety gear to choose from, one should pay attention to how they work in a cold climate.

Cold and snow are much more than just an issue to be solved: they make it possible to go for exploration in places not accessible otherwise. Such is the case with our contract with AA Sakatti Mining.

Drilling in the extreme cold near the Arctic Circle

Kati Oy hold a drilling contract with AA Sakatti Mining, a Finnish company owned by Anglo American Plc. This has been a long-standing project, running for over ten years now with some idle years in between due to permitting. It is the great cooperation between us and Anglo American that has helped our company grow. Every year, we have been able to use the innovations and ideas from this project on others, benefitting exploration drilling on all of our drill sites.

The AA Sakatti deposit has multiple minerals: copper, nickel, cobalt and PGE-metals. It is located in Northern Finland, about 150 km (93 mi) north of the Arctic Circle, meaning it is not possible to enter unless there is sufficient snow cover on the ground. In a usual drilling season (December-April) we drill about 25 000 m (82 000 ft) with six rigs with different sizes. The biggest can drill up to 2200 m (7218 ft) with N-size. Hole depths vary from several hundred meters up to over 1000 m (3281 ft). Hole sizes are N-size and H-size. About 50 people are involved in the project.

The extreme cold is only one of the challenges we face. The area has some significant characteristics, which must also be taken into account. It is a protected nature conservation, so it is of utmost importance that we don’t leave any traces, spills or other marks. This has forced us to carefully identify all the risks, process them and come up with good preventive solutions.

Drilling on top of a mountain in Norway

Drill sites and drill cuttings

The ground on each of the drill sites, where the rig can stay up to one or two months, is protected with sufficient snow cover and tarpaulins. We are using bio-degradable hydraulic oils, which have different properties than the standard ones and that is the negative side, as they require more frequent changing and more care when working in the cold.

Another matter which we have to take care of is drill cuttings. No cuttings are let to flow to the ground, everything has to be collected and transported out of the area. This is possible with our closed system equipment – solids removal unit (SRU), which we have designed and built by ourselves. The idea for designing something like this was born on this very project in 2010. Today the closed system is working excellently in arctic conditions and also helps us use drill additives efficiently.

Artificial snow

We can only enter the area when there is snow on the ground. Often we are forced to keep waiting eagerly at the start of the season for sufficient coverage. To solve that, we came up with an innovative approach, which buys us more drilling time over the period, allowed in the drilling permits. We have started to make artificial snow to get the routes and drill pads ready. This gives us several weeks more time to drill and speeds up the development of the whole exploration project. It has been a challenge for us to learn how to make snow efficiently and we are grateful to our client for their input and ideas.

Customizing the rigs

Our rigs make a comfortable space to work even in harsh winter weather, as they have full cover, heating, good lighting and work ergonomics. Thanks to the improvements in the newest ones, used in this project, we have reduced the amount of hydraulic oils by 50% and we take numerous measures to minimize the risk of leaks. The drill rigs are mounted on tracked vehicles, such as the Morooka carrier. They are designed to be as environmentally friendly as possible and leave fairly small traces to the ground.

The biggest Kati Oy rig working in -28°C (-18.4°F) with the SRU standing next to it

Plugging and surveying

We have developed a method for hole plugging in this project, which is an important factor in terms of controlling waters in the area, both on the surface and underground. We also do packer testing to create an understanding of the hydrogeological structure of the area. The testing provides valuable information for underground mine planning.

We have a dedicated measurements team and really helpful partners. The team does hole deviation surveying with real north-seeking gyro (Gyromaster) from Stockholm Precision Tools. Our partner companies Geovisor and Palsatech are also involved, doing other fieldwork for the project. Additionally, we are doing directional core drilling with Devico AS from Norway. This helps us achieve more drill meters at the locations which really are of interest, and also helps our drills hit the exact targets.

In 2021, drilling is moving as scheduled. With the help of artificial snow, possibly all of the projected meters shall be drilled during this drill season. We just completed a H-size hole with 950 m (3117 ft) depth. On that hole, we were able to go through a fault zone which has been of great interest geologically. This is the deepest H-size hole we have ever done and drilling was completed in 21 days.

About the company

Kati Oy is a Finnish private-owned drilling company. It was founded in 1980 as the first private exploration core drilling company in Finland. Kati Oy operates mainly in the Nordic countries. Rig fleet size is 16, revenue generated in 2019 was EUR 20 million. Clients are both junior exploration companies and mining companies like Anglo American, Rio Tinto, Boliden and LKAB. The Kati Oy way of working emphasizes smooth cooperation with clients, creating solutions to their needs, being a pioneer in eco-friendly drilling and a great place to work for the employees.

Learn more: www.oykatiab.com/en/