US Patent 7726392 Removal of downhole drill collar from well bore

A drill string in a borehole can be cut at the drill collars. A torch is lowered into the drill string and positioned at a joint of the drill collar string. The joint has a pin component and a box component. The torch has one or more openings in the pattern of a vertical slot. The torch is ignited and the pin component is cut in a direction along the length of the drill string. The joint uncoupled, even though the box component need not be cut. The uncoupling of the joint effectively cuts the drill string at the joint.