Rotary separator turbine uses unique technology to separate oil, water and gas, while offering the opportunity to recover energy lost in conventional pressure letdown operations. A rotary-separator turbine is built with full flow capacity for a 500 F downhole temperature with 850,000 lbm/hr production rate. The preliminary design is for the 10-megawatt wellhead power plant for the Roosevelt type resource. This system shows a specific power of .0013 kW hr per lbm, which is 20 percent greater than an optimized wellhead single stage flash plant. This is 26 percent greater than a central plant of 20 to 50 MW capacity when consideration is given to steam-gathering system pressure drop between the wells and central plant.