Today we assembled the multi-sensor core logger. Only the source for the gamma attenuation measurement is missing, traveling somewhere throught the wild Swedish woods in a separate packet.
Snow showers in Åre area. The GFZ BugLab and ICDP equipment (core scanner, multi-sensor core logger and on-line gas monitoring OLGA) arrived at the drill site today.
Last week a second observation drill hole was drilled to about 50 m depth only a couple of metres away from the first one. The two holes will form a single observational entity equipped with 3-component geophones. The shallower (second) hole to 50 m depth, and the deeper (first) hole to 100 m depth contain together 9 geophones with a spacing of 10 m in depth. Two holes were used since a single drill hole was considered too risky for the number of geophones being employed since each geophone is connected to its own cable. Yesterday and today, the two geophone chains were installed and cemented at 100 m, 90 m 80 m, 70 m and 60 m in the deep hole and at 50 m, 40 m, 30 m and 20 m in the shallower hole. The geophones will be connected to a recording system when power is installed on-site next Spring. The purpose of the observation system is threefold (i) to investigate if it is possible to record useful drill-bit noise from the drilling of COSC-1, (ii) to passively record potential local earthquakes and (iii) to act as calibration sensors for future VSP measurements in COSC-1 after drilling is completed. (Photo: Christopher Juhlin)
Scientific drilling light: Bjarne Almqvist drills samples from outcrops in the Lower Seve Nappe for petrophysical studies. A database with his results will then be available for comparative studies that will include the COSC-1 drill.
Today we put up an information board at the drill site. It explains scientific drilling and the COSC project in a popular scientific way and has enough detail for the geoscientifically interested reader. Let's hope the poles are long enough to keep the board above the snow during winter time, and the fundaments heavy enough to withstand the winter storms.
Today we logged the COSC-1 geophone drill hole (COSC-1G): temperature, fluid electric conductivity, electric resistivity, full waveform sonic and natural gamma. Logger's depth of COSC-1G is 102,3 m. For comparison, we run a natural gamma log inside the conductor casing of the COSC-1 drill hole, where the cuttings were sampled. At 83,5 m logger's depth we encountered the plug from cementing the casing. The distance between the two drill holes is only about 20 m, but the highly strained rocks can vary considerably over short distances and we have to wait for the processed data to see whether a correlation is possible.
In mid-August, the construction of the COSC-1 drill site started. Leif and Jan-Erik worked hard with the permissioning and organisational issues during spring and early summer. Also, the positive attitude of the authorities towards scientific drilling prevails. Now a c. 30 x 40 m large patch is cleared from trees and a stable substratum was built from macadam. A geotextile is underlying the drill site as protection. The drill site is located on the road from Åre Björnen to Huså, about 100 metres southeast of the junction to Fröå Gruva (mine) http://kartor.eniro.se/m/nO8uG
In early 2013, our plan was to use an existing parking lot at the Fröå mine museum as drill site and begin drilling in 2013. However, we discovered that we wouldn't get access to the drill site before late in the summer. Thus, in March this year, Leif Bjelm and Jan-Erik Rosberg (technical project management), Stellan Larson (driller) and Henning Lorenz (coordinator; on-site science) went to Åre and met representatives from the Fröå mine museum and the local authorities. It was nice to discover that all parties are positive to scientific drilling, and an alternative drill site was found only a few hundred meters to the south of the first site. The new site needs to be inspected from a geotechnical point of view and it will be necessary to construct a solid substrate for the rig. Also, the permission process with authorities and road owners is more complicated as when drilling on an existing parking lot. Jan-Erik and Leif take care of these issues. But already now a lot of science connected to the COSC project is going on: EM measurements along the seismic profiles, new gravity spot measurements, planning of a VSP survey, geological fieldwork around the drill site, on Åreskutan, and the Lower Seve Nappe in general.
