The Kittilä mine is a gold mine located app. 150 km north of Rovaniemi, Finland. The nearest little town is Kittilä which has an airport with connection to Helsinki.
Exploration in the area started in 1986. The Geological Survey of Finland initiated exploration which resulted in a discovery of gold minerali-zation. Agnico-Eagle is now the owner and operator of the mine and the open pit mine was opened in May 2009. In 2010 they started underground operations and open pit mining completed in 2012. The mine is extracting one of the largest known gold resources in Europe. They are processing approximately 3,000 tonnes of ore per day and producing an estimated amount of 4250 kg of gold in 2013.
The mine was found within the Kittilä Greenstone belt, beneath mafic, volcanic and sedimentary rocks. The major rocks are aligned vertically and trend towards north to north-east. Iron and magnesium-rich volcanic rocks are found at the west and east of the belt. Between these two categories of rocks, there is a transitional zone that has a thickness of 10m to 50m.
Referred to as the Surrikuusikko Trend, the zone has a distinctive shape and is composed of several shear zones. It is also characterised by heavy gold mineralisation and a change in mineralogy caused by hydrothermal fluids.
Devico started working in Kittilä March 2009. Agnico-Eagle drilled more than 100 000 meter that year, where at least 33 000 meter was focused on deep exploration. Agnico-Eagle had two commercial alternatives available for steering boreholes; mud motors (Navi drilling) and DeviDrill. With previous experience that mud motors did not work very efficiently in the Lapland rock, they went for the DeviDrill.
One Devico team was soon increased to two teams. During 2009 more than 2200 meter with directional core drilling was done in 56 corrections. Agnico-Eagle gave later that year a presentation at the Fennoscandian Exploration and Mining conference, where they presented their experience with Devico. Compared to traditional drilling they had saved 41 % in meters (23,600 meter reduced) and 29 % in time when they just looked at the direct drilling cost. They reported additional savings related to logging and logistics, and they reported excellent drilling accuracy. This numbers repeated in 2010. 2011 and 2012 didn’t have the same cost saving results due to more sparse profile exploration drilling layout, but the accuracy stayed the same.
During the next few years more than 2000 meters in average has been drilled with the DeviDrill. In November 2011 Agnico-Eagle wrote a long term contract with Devico to ensure that Devico would be there for at least three more years.
In 2011 Devicos steering accuracy was tested. A 200 meter borehole for fuel was needed from the surface and down to the mine. The target was approximately 3x3 meter. With one DeviDrill correction, the target was hit successfully thus demonstrating the excellent steering capabilities of the DeviDrill.
Most of Devicos corrections have been done between 500 – 750 meters towards targets at 600 – 1000 meters depth. The directional drilling has normally taken place in volcanic – sedimentary unit where lithologies varies from intensively altered tholeiitic volcanites to sulphide and graphite rich interflow sediments. The new corrections have been started either with a steel wedge placed in the borehole or with the Devico cut-the-curve method. The length has varied, but many corrections have been around 60 – 80 meter to obtain 20 to 25 degrees deviation.
Devico has cooperated with several different drilling companies in this project. Devico has contracted directly with Agnico Eagle, which gives them flexibility to hire drilling companies depending on the amount of drilling to be done. Kati Oy, Arctic Drilling and Protec have all been in the project and worked in cooperation with Devico.
The climate in northern Finland is cold and this has been one of the challenges in this project. Normal procedure before the DeviDrill is run down the borehole is to do a water test to check that all vital parts are working. The Devico technicians in Kittilä have successfully developed new procedures for winter testing, to avoid that the water is freezing inside the DeviDrill before it is going into the borehole.
Info from www.agnico-eagle.com and FEM