Drill cutting samples were collected from two boreholes drilled on the island Sollerön, Dalarna in conjunction with drilling for geothermal energy. The place is located at Sollerön in the Siljan area that was subjected by a meteorite impact 330 million years ago. The island Sollerön is located in the Siljan Ring, which mainly consists of sedimentary rocks. In one of the boreholes, oil -mixed water was found when drilling and in the same borehole geophysical measurements were performed, such as gamma radiation, seismic velocity and temperature. At the bottom of the borehole the gamma radiation increased, while the seismic velocity was continuously low in the interval. The purpose was to determine which rock types the both boreholesconsisted of, what the cause of the low seismic velocity was in borehole two, could it be the oil observed during drilling that was the cause. The method used to identify the mineralogy in both the boreholes was X-ray powder diffraction (XRD), but in borehole two Raman spectroscopy and scanning electron microscopy (SEM) was also used. To see if organic carbon was present, the stable isotope mass spectrometry method was used. The result from the XRD showed that both borehole one and two consisted of shale, but in borehole two limestone was also present. The XRD results for borehole two could be strengthened by the other methods and also the gamma radiation measurements. The low velocity at the bottom of borehole two is probably caused by oil that has been seeping up from the shale overlaid by limestone, where the organic matter has transformed into hydrocarbons because of the heat that was produced during the impact.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-384249 |
| Date | January 2019 |
| Creators | Lindén Magnusson, Lovisa, Löfgren, Josefin |
| Publisher | Uppsala universitet, Institutionen för geovetenskaper, Uppsala universitet, Institutionen för geovetenskaper |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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