Processing and analysis of acoustic borehole data from the Sunnfjord area and the Oslo region for evaluation of fracturing and possible water movements in the rock.

The knowledge of the distribution of fractures in a certain area can help to understand possible groundwater movements in the rock. In the investigated area, the Sognfjord area, lineament structures are situated and was a goal of the project to discuss whether a model for such a lineament (Braathen & Gabrielsen 1998) is right or not. The analysis of the Follevåg boreholet that is drilled directly through such a lineament structures covers a bigger area than assumed in the model. The boreholes from Holmedal should be outside the lineament structures but they show also a trend of orientation of the fractures and they are also oriented parallel to the lineaments. But this is not clear because of many lineaments in this area, which could influence the results too. Furthermore interpretation and analysis was made with data from a borehole in the Oslo region (Bærum). There was little background information available. The amount of fracture is high in the lower part of the boreholes but the fractures are not oriented. It may be a fracture network that enables a good ground water flow in the area. So the borehole is well suitable for heat production because of the great surface of the rock, which enables an efficient heat exchange between the rock and the injected water. Image logs of the acoustic televiewer data are not presented in this report. These data are available at NGU.

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