Abstract: A ring seal packer is used for sealing the inside of a specified diameter of API tube. The cylindrical body of the ring seal packer has a pair of circumferential grooves and a pair of rigid seal rings are provided in each such groove. The two rings collectively occupy substantially the entire length of the groove, with no more than a small clearance at the ends for forming a small area orifice through which fluid may flow. Each of the rings has an outside diameter larger than the inside diameter of a specified size of API tube. A longitudinal slot in the ring permits it to collapse to a diameter that fits into the tube as it is pushed into the well. A tang and notch arrangement keeps the rings from rotating relative to each other so that the slots are kept out of alignment. The ring seal packer does not use any elastomeric sealing materials.