U.S. Sen. Jon Tester is introducing a bill that would give loans to developers that risk exploration of unproven areas of geothermal energy and encourages co-leasing of land with oil and geothermal resources.

Tester says the Geothermal Exploration and Technology Act would increase the country's energy security and better utilize Montana's energy resources.

In the past, exploration for hot water or steam deep in the earth has occurred mostly in known areas of heat, fracturing and liquids, Tester's office said.

Tester's legislation encourages "enhanced exploration" in areas where there might be just two of those known components, which involves more of a risk because the return could be less.

"Montana needs to take advantage of every responsible energy opportunity across our state to create jobs and lead our nation toward energy independence," the Montana Democrat said in a statement. "My bill makes it easier for folks already working in this field to tap into the resources below our feet.

Tester's office said the bill would establish a direct loan program to encourage high risk geothermal exploration wells. In selecting applicants for loans, preference would be given for projects likely to lead to successful new development that leads to electricity production.

The bill also would streamline co-leasing of geothermal wells with oil and gas wells. Tester's office said some oil and gas wells could then be run off of geothermal power instead of diesel generators.

Geothermal currently makes up 0.4 percent of U.S. electricity generation, but generation is expected to increase as sites are developed, costs are reduced and technology increases, according to the U.S. Energy Information Administration. Geothermal power plants do not burn fuel, so emission levels are low.

At very high temperatures, water or steam can be used to generate electricity at power plants, just like coal or natural gas.

The bill also aims to improve heat pump technology and mapping.

Tester's office says Montana has more than 50 geothermal areas and at least 15 with high-temperature sites. Geothermal features in national parks such as Yellowstone are protected by law.

"There's a couple of areas in the state that are interesting but nobody's ever had the funding or bravery to go drill 'em," said state geologist John Metesh, director Montana Bureau of Mines and Geology.

The hottest known springs are located near Ennis and Anaconda, Metesh said. Other known geothermal sources are near Hot Springs, Whitehall, Boulder, south of Helena, Marysville and Warm Springs.

Some locations have boiling water, he said.

Gary Icopini, a Bureau of Mines and Geology hydro-geologist, said most geothermal development in the United States has occurred in areas where water or steam is extractable.

Enhanced recovery involves directional drilling and pumping water and steam into the ground to break up rock, Icopini said.

It's similar to the hydraulic fracturing process used to recover oil and gas, he said.

"There are hot rocks everywhere if you drill deep enough," Icopini said.

Montana has no geothermal power plants. Tester's office said there are plants in California and Nevada. In Montana, the Flathead Electric Cooperative is exploring the Hot Springs area for geothermal energy.

Data from all exploratory wells, even if unsuccessfully developed, would be useful in mapping national geothermal resources, Tester said.