Journal of Earth Sciences and Geotechnical Engineering

Fracking - Prevention of Leakage of Oil and Gas from Abandoned Holes in Consolidated Rock

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• Abstract

  Fracking of deep shales is used in the US for making otherwise unavailable gas and oil in dense rock exploitable but can cause problems by leakage to the ground surface or shallow aquifers of such matter and of water contaminated by chemicals used for release of the precious substances. The issue is primarily boring disturbance causing a high-permeable annulus around boreholes that interacts hydrologically with natural fracture zones, and secondarily, malfunctioning concrete liners. A novel approach for new holes is to eliminate leakage by constructing long-lasting linings, and chemically stable concrete plugs where permeable fracture zones are intersected. The vertical parts of abandoned holes can be sealed by construction of concrete plugs where such zones are intersected and by installing clay seals in between. For holes to be abandoned, long-term sealing is provided by installing very dense smectitic clay plugs that are chemically compatible with the concrete.