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Hjerne, Calle; Ludvigsson, Jan-Erik; Harrstroem, Johan
Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)2013
Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)2013
AbstractAbstract
[en] A large number of constant head injection tests were carried out in the site investigation at Forsmark using the Pipe String System, PSS3. During the original evaluation of the tests the dominating transient flow regimes during both the injection and recovery period were interpreted together with estimation of hydraulic parameters. The flow regimes represent different flow and boundary conditions during the tests. Different boreholes or borehole intervals may display different distributions of flow regimes. In some boreholes good agreement was obtained between the results of the injection tests and difference flow logging with Posiva flow log (PFL) but in other boreholes significant discrepancies were found. The main objective of this project is to study the correlation between transient flow regimes from the injection tests and other borehole features such as transmissivity, depth, geology, fracturing etc. Another subject studied is whether observed discrepancies between estimated transmissivity from difference flow logging and injection tests can be correlated to interpreted flow regimes. Finally, a detailed comparison between transient and stationary evaluation of transmissivity from the injection tests in relation to estimated transmissivity from PFL tests in corresponding sections is made. Results from previous injection tests in 5 m sections in boreholes KFM04, KFM08A and KFM10A were used. Only injection tests above the (test-specific) measurement limit regarding flow rate are included in the analyses. For all of these tests transient flow regimes were interpreted. In addition, results from difference flow logging in the corresponding 5 m test sections were used. Finally, geological data of fractures together with rock and fracture zone properties have been used in the correlations. Flow regimes interpreted from the injection period of the tests are generally used in the correlations but deviations between the interpreted flow regimes from the injection and recovery period are also discussed. The observed discrepancies between the estimated transmissivity from difference flow logging and injection tests can in most cases be correlated to the interpreted flow regimes during the injection tests. In particular, for tests with apparent no-flow boundaries (NFB) during the injection period the estimated transmissivity from the injection tests was frequently much higher than the reported transmissivity of PFL, while tests with pseudo-spherical flow regime (PSF) or pseudo-steady state (PSS) often display rather similar values from injection tests and PFL. This fact is likely to depend on conceptual differences between the two test types. In KFM04A and KFM10A pseudo-radial (PRF) and pseudo-spherical flow regimes (PSF) were more common than in KFM08A while pseudo-linear flow (PLF) and apparent no-flow boundaries (NFB) were more common in KFM08A than in KFM04A and KFM10A. Tests displaying NFB or PLF are more common in sections with a lower fracture frequency and/or sections in located in fracture domains. PSF is more common to find in sections located in deformation zones and/or sections with an increased fracture frequency. No clear relationship between interpreted flow regimes and evaluated transmissivity or borehole length (and depth) could be found in the three studied boreholes
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Apr 2013; 56 p; ISSN 1402-3091;
; Also available from: http://www.skb.se/upload/publications/pdf/R-08-118.pdf; refs., figs., tabs.

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