Abstract: A method of manufacturing a heat absorbing element, the method comprising combining a first metal strip face-to-face with a second metal strip having a width greater than that of the first to form a composite strip wherein the side margins of the second strip extend laterally outwardly beyond the side edges of the first. The composite strip thus has a central portion extending longitudinally of the strip comprising a double thickness of strip and portions extending longitudinally of the strip on opposite sides of the central portion each comprising one less thickness of strip than the central portion. The central portion of the composite strip is then formed into a tube, and the tube is closed along a line extending longitudinally of the tube with the side portions of the composite strip extending outwardly away from the seam to form a pair of fins along the tube.

Abstract: Oil is recovered from an oil-bearing subterranean formation penetrated by an injection well and a production well by injecting into the formation via the injection well a solution of a normally solid polymerized methacrylate and oil displaced by the injected solution is recovered from the formation via the production well. Optionally, after the solvent solution has been injected, a hydrocarbon slug such as crude oil, petroleum distillate, a soluble oil composition, etc. may be injected and, if desired, this may be followed by injection of water.