Hmmm, you did state that you are "extracting pipe from a shallow well", to me that would be a vertical run of pipe. A 1 1/2" pipe that is 18 feet into the ground sounds like a pretty good grip. What kind of ground comes to mind. This idea comes to mind as it is only 18 feet deep. Could you make up a pipe, even PVC may work, with a "jetter" on the end, and start feeding it down along side of the pipe you want to save so that this "jetter" softens the dirt somewhat? IF, and I state IF, there are threads on the exposed end could you make up some type of attachment so as to screw it onto the 1 1/2" pipe really secure, attach a chain to that, and the chain to a backhoe and use the previously stated suggestion of putting some pulling force on it and just wait a bit? I do understand you wanting to save those expensive points. Keep us posted on this one, Good Luck, David