A wellbore intervention system for repairing a wall failure within a wellbore includes a fluid conduit installed to an outer surface of a casing string within the wellbore. The fluid conduit includes a tube to which a remedial substance is delivered, multiple ports arranged along a length of the tube for communicating the remedial substance to the wall failure in a cement region along the wellbore, and a one-way valve for preventing a reservoir fluid at the wall failure from flowing in an uphole direction through the tube.