AN ASSESSMENT OF BOREHOLE SEALING PERFORMANCE IN A SALT ENVIRONMENT

Design of plugs for abandonment of boreholes and shafts may be governe d by the bond strength between the plug and host rock. This paper pres ents the results of push-out tests on cement grout plugs in salt. Two types of expandable cement grouts have been tested. The average interf ace shear strengths ranged from 2 to 12 MPa (290 to 1740 psi). Peak sh ear stresses at failure, assuming an elastic stress distribution along the interface, were up to eight times higher. Standard deviations com monly reached 20%. Dissolution along the interface was observed, and m ay have been enhanced by clay inclusions in the salt. This dissolution appears to have reduced bond strengths. Application of the results to the design of plugs for larger openings (for example, shafts, drifts, or boreholes) is discussed.