A method for forming substantially lateral boreholes from within an existing elongated shaft includes positioning a drilling unit within the existing shaft, bracing the drilling unit against a wall surrounding the existing shaft to transmit forces between the drilling unit and the medium surrounding...http://www.google.fr/patents/US5425429?utm_source=gb-gplus-shareBrevet US5425429 - Method and apparatus for forming lateral boreholes
Method and apparatus for forming lateral boreholes
