Relating to well abandonment

A method for removing a section of well tubing comprising the steps:

• a) providing a work string with a hydraulic tensioning device and a section mill mounted below the hydraulic tensioning device, the hydraulic tensioning device operating over a stroke length between a fully extended position and a fully retracted position;
• b) selecting a desired rate of progress and calculating a pump flow rate to create a back pressure in the hydraulic tensioning device to maintain the hydraulic tensioning device between the fully extended position and the fully retracted position;
• c) lowering the work string into tubing to be milled;
• d) pumping fluid through the work string to actuate the section mill and extend cutter blades;
• e) rotating the section mill to mill the tubing with the cutter blades;
• f) pumping fluid at the calculated pump flow rate through the work string and actuating the hydraulic tensioning device to position the lower end of the hydraulic tensioning device between the fully extended position and the fully retracted position while milling the tubing;
• g) maintaining the calculated pump flow rate while raising the work string at the desired rate of progress to continuously mill the tubing;
• h) in the event that the rate of milling is lower than the desired rate of progress and the lower end of the hydraulic tensioning device moves downwards away from the work string towards the fully extended position, auto-correcting the hydraulic tensioning device to return to a position between the fully extended position and the fully retracted position by increasing a load on the section mill to thereby speed up the rate of milling;
• i) in the event that the rate of milling is higher than the desired rate of progress and the lower end of the hydraulic tensioning device moves upwards towards the work string towards the fully retracted position, auto-correcting the hydraulic tensioning device to return to a position between the fully extended position and the fully retracted position by decreasing a load on the section mill to thereby slow down the rate of milling;
• j) repeating steps (h) and (i) as required while performing step (g) to remove a longitudinal section of the tubing.