DOE Geothermal Electricity Holds Promise for Older Oil Fields

October 22, 2008 // Published as a news service by IHS

The power is used in oil field operations.

The 12-month test began in September 2008 at RMOTC Naval Petroleum Reserve #3 (NPR-3) site. The power system is a commercial standard design Ormat Organic Rankine Cycle 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 kilowatts of power since it was started.

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-3's 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.

The unit at NPR-3 is the first using geothermal water from a producing oil field but it is similar to a 250 kilowatt Ormat unit that has been producing electricity from 210 degree Fahrenheit geothermal water at an Austrian resort for more than six years.

Similar units have also been in continuous commercial operation since the 1980s in Nevada and Thailand and have been field proven in 1,000 installations worldwide, said DOE.

There are a large number of oil and gas wells in the U.S. that produce hot water, as well as hydrocarbon products. These wells, which generally produce fluids at temperatures below 220 degree Fahrenheit, have been estimated as being capable of generating upwards of 5,000 megawatts of power.

In Texas, 8,000 similar wells have been identified and Ormat is now assessing the feasibility of utilizing these wells to support onsite power generation by employing its sub-megawatt geothermal power units.

"This project is unique in its production of onsite renewable power and has the potential to increase the productivity and longevity of existing U.S. oil fields," said Acting Assistant Secretary for Fossil Energy James Slutz. "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."

Source: U.S. Department of Energy (DOE) Office of Fossil Energy.