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Poellaenen, J.; Heikkinen, P.; Lehtinen, A.
Posiva Oy, Helsinki (Finland)2012
Posiva Oy, Helsinki (Finland)2012
AbstractAbstract
[en] To improve the understanding of processes associated with glaciation and their impact on the long-term performance of a deep geological repository of spent nuclear fuel, the Greenland Analogue Project (GAP) has been initiated collaboratively by SKB, Posiva and NWMO. The study site encompasses a land terminus portion of the Greenland ice sheet, east of Kangerlussuaq, and is in many ways considered to be an appropriate analogue of the conditions that are expected to prevail in much of Canada and Fennoscandia during future glacial cycles. The project began in 2009 and is scheduled for completion in 2012. In 2011, deep drillhole DH-GAP04 was drilled at the study site and Posiva Flow Log measurements were carried out in the drillhole. The Posiva Flow Log, Difference Flow Method (PFL DIFF) uses a flowmeter that incorporates a flow guide and can be used for relatively quick determinations of transmissivity and hydraulic head in fractures/fractured zones in cored drillholes. The aim of the measurements was to find high transmissive fractures, which would define the target for water sampling, i.e. the location for the packers in the drillhole. This report presents the principles of the method and the results of measurements carried out in drillhole DH-GAP04 in July 2011. The length of the flow guide in the flow logging measurements was 10 m (section length). Flow into the drillhole or from the drillhole to the bedrock was measured within the section length. The measurements were carried out in both pumped and natural (i.e. un-pumped) conditions. Calculations of the transmissivity (T) and the hydraulic head (h) of the fractures are shown in the results. Measurements were carried out in drillhole length interval 184 - 675 m without pumping. During pumping, measurements were conducted in drillhole length interval 274 - 675 m due to permafrost condition above this level. The risk for the drillhole freezing over in the permafrost area was remarkable. Due to lack of time, the upper part of the drillhole was not measured. The device used also includes a sensor for single point resistance (SPR). SPR was measured in connection with the flow measurements. The electric conductivity (EC) and temperature of the drillhole water were measured as well. (orig.)
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Jul 2012; 41 p; Also available in fulltext at www.posiva.fi or as a soft back edition from P; 3 refs.
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