The U.S. Department of Energy's (DOE) Office of Fossil Energy's Rocky Mountain Oilfield Testing Center (RMOTC) and Ormat Technologies Inc. have produced the first successful generation of electricity using geothermal hot water from a producing oil well in Wyoming, they said last week. The power can be used in oil/gas production, reducing costs and freeing capacity on the power grid.
"This project is unique in its production of on-site renewable power and has the potential to increase the productivity and longevity of existing U.S. oil fields," said James Slutz, acting assistant secretary for Fossil Energy at the DOE's Fossil Energy Office. "Harnessing hot water produced during oil production to power the oil field could lead to more economical access to reserves, especially in older, depleted fields."
The 12-month test began in September 2008 at RMOTC's Naval Petroleum Reserve #3 (NPR-3) site just north of Casper, WY. The power system being used is a commercial standard design Ormat Organic Rankine Cycle (ORC) power plant. The binary power unit uses hot water from a producing oil well as the heating fluid for a heat exchanger in the Ormat Energy Converter (OEC). In the heat exchanger a secondary working fluid -- an organic fluid with a low boiling point -- is vaporized. That vapor is then used to spin a turbine coupled to a generator to produce electricity. Output is connected to the field electrical system to power production equipment, and the produced energy is metered and monitored for both reliability and quality. It has been producing 150-250 gross kW since it was started in early September.
"In the past 20 years, Ormat's ORC power technology has optimized the range of exploitable geothermal resources from low to moderate temperatures previously discarded" said Ormat Chairman Lucien Bronicki.
The cooled geothermal fluid from power production can be re-injected into the reservoir or discharged, depending on the location. Currently, the 190-degree Fahrenheit water produced from NPR-3s Tensleep sandstone formation is treated before being safely discharged into an adjacent stream. The OEC captures the water's heat and makes use of it before the water is treated and discharged.
"With Ormat's advancement in binary turbine technology and the increased drilling for oil and gas exploration, the U.S. is primed for additional geothermal development," according to Dr. David Blackwell of Southern Methodist University.
The unit at NPR-3 is the first using geothermal water from a producing oil field but it is similar to a 250 kW Ormat unit that has been producing electricity from 210 degrees Fahrenheit geothermal water at an Austrian resort for more than six years. Additionally, there are similar units in Nevada (700 kW) and Thailand (300 kW) that have been in continuous commercial operation and without overhaul, since 1984 and 1989, respectively, Ormat said.
There are a large number of oil and gas wells in the United States that produce hot water, as well as hydrocarbon products, RMOTC said. These wells, which generally produce fluids at temperatures below 220 degrees Fahrenheit, have been estimated as being capable of generating upwards of 5,000 MW of power. In Texas alone, some 8,000 similar wells have been identified and Ormat is now assessing the feasibility of utilizing these wells to support on-site power generation by employing its sub-megawatt geothermal power units.
The RMOTC is a 10,000-acre DOE facility located within NPR-3 -- also known as Teapot Dome Oil Field.
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