The Nevada–Texas–Utah Retort process (also known as NTU, Dundas–Howes or Rexco process) was an above ground shale oil extraction technology to produce shale oil, a type of synthetic crude oil. It heated oil shale in a sealed vessel (retort) causing its decomposition into shale oil, oil shale gas and spent residue. The process was developed in the 1920s and used for shale oil production in the United States and in Australia. The process was simple to operate; however, it was ceased from the operation because of a small capacity and labor extensiveness.