small packers to close or constrict the perforations the tools 151 152 are mounted on telescopic arms 153 which extend from the tool body 11 to the opening 13 of a perforation and if required into the perforation there are also shown pads 17 which can in operation been extended against the casing to provide a counterforce and or anchor the tool body in the wellbore the extendable devices arms 153 17 18 are hydraulically operated or use electric actuators for extending positioning and retraction into the tool body the tool includes electronic devices 19 to control the downhole operation of the tool and to communicate measurements to the surface and to receive instructions from a surface operator a more detailed view of a perforation intervention tool for sand control purposes is shown in fig1 b retaining the numerals used in fig1 a for identical or similar elements the intervention tool inserts a tube 151 shown cutaway into the perforation tunnel 13 and a coaxial piston 154 then pushes a sand control plug 155 into the tunnel as the tube withdraws the plug is made of an elastic mesh that springs open as it is released from the tube together with an elastic fishbone structure that provides some support to the mesh and also locks it within the tunnel in fig2 the tool of fig1 is shown again retaining the numerals used in fig1 a for identical or similar elements.