Pipe joint separation

Method to loosen a screw connection of a pipe conduit in a bore hole comprising:

• (a) applying an unscrewing torque to the portion of the pipe above the screw connection, and
• (b) subjecting said screw connection while under that torque to at least one shock wave generated inside of said pipe conduit at or near said screw connection, by providing two electrodes with an arc space between them inside of said pipe and causing an electrical current arc between the two electrodes such as to cause said shock wave in the essential absence of generation of any additional gas in the pipe.