Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory: summary report 2007

Harrington, J.F.; Birchall, D.J.; Noy, D.J.; Cuss, R.J.. 2008 Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory: summary report 2007. Nottingham, UK, British Geological Survey, 87pp. (CR/07/211N) (Unpublished)

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The deposition hole was closed on the 1st February 2005 signifying the start of the hydration phase. Groundwater inflow through a number of conductive discrete fractures resulted in elevated porewater pressures leading to the formation of conductive channels (piping), the extrusion of bentonite from the hole and the discharge of groundwater to the gallery floor. This problem was addressed by drilling two pressure-relief holes in the surrounding rock mass. Artificial hydration began on the 18th May 2005 after 106 days of testing. Initial attempts to raise porewater pressure in the artificial hydration arrays often resulted in the formation of preferential pathways. These pressure dependent features were not focused in one location but occurred at multiple sites at different times in the test history. These pathways appear to be relatively short lived, closing when water pressure is reduced. It was determined that both pressure relief holes should remain open until the bentonite had generated sufficient swelling pressure to withstand the high water pressure in the system when these holes are closed. Packers were installed into the pressure relief holes on 23rd March 2006 and sections in them closed off over the period to 5th July 2006. There was no repeat of the formation of piping through discrete channels so, on 20th November 2006, pressures to the artificial hydration filters on the canister were increased to 2350 kPa.

Item Type: Publication - Report
Programmes: BGS Programmes > Chemical and Biological Hazards
Funders/Sponsors: SKB (Stockholm), BGS Science Budget, European Commission NF-PRO project
Additional Information. Not used in RCUK Gateway to Research.: This item made open by author December 2012. This item has been internally reviewed but not externally peer-reviewed
Additional Keywords: Lasgit, gas injection, bentonite, modelling, hydration, hydraulic, storage, gas entry pressure.
NORA Subject Terms: Earth Sciences
Date made live: 17 Dec 2012 13:33 +0 (UTC)

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