Testing water next step in city’s geothermal project
The Aspen Times
With the drilling process on its geothermal well complete, the city of Aspen will soon embark on a series of tests that will help decide whether the water deep below the earth’s surface is conducive to consider the creation of a “geothermal utility district,” officials said Thursday.
The well — measuring 1,520 feet deep in a parking lot near Herron Park, the No Problem Bridge and Neale Avenue — was completed in the final week of June following a nearly two-year, off-and-on drilling process that made noise during the day and irritated some of the project site’s east Aspen neighbors.
Initial test results were positive in terms of pressure, geologic layer and temperature, according to Jeff Rice, the city’s utilities energy efficiency manager.
Rice said a preliminary estimate shows that water near the surface had a temperature ranging between 60 and 70 degrees while water at the bottom of the well was estimated around 90 degrees. Future tests, which won’t impact the neighborhood, will provide a more accurate assessment of temperature and chemical content of the water, he said.
“What our geothermal consultant figures is happening is that from 1,500 feet and coming upward, there is some heat exchange going on with the ground and the water at different levels that we came across,” Rice said. “So it’s cooling that water. What the consultant said is if we have these temperatures (60 to 70 degrees) at the surface, it’s highly likely we’ve got 90-plus-degree water at the bottom of the hole.”
For a geothermal heating system to work, “you really only need an eight- to 10-degree differential from whatever it is around you that you’re trying to heat up,” he said.”We need to have 90 to 95 degrees minimum at the bottom of the well. We would love to see something in the 100- to 120-degree range or better. We really won’t know until we actually drop a temperature gauge down to 1,500 feet.”
The well is completely cased, sealed and capped. It needs to settle before the testing can begin, Rice said, adding that the first round might start in late August.
The consultant, John Kaufman, said there were other surprises in addition to the high temperatures.
“The water level came in higher than we expected,” Kaufman said in a news release. “We expected the water level to be around that of the creek based on old mine maps but it actually came in artesian at the ground surface at 29 (pounds per square inch). Normal pressure in a household faucet is about 60 psi, so this means no pump is needed and the water is really clear. It’s a great benefit to the city.”
In addition to testing for temperature and chemical content, future tests will involve geophysical logging, which is a probe to determine what geologic layers the well has penetrated.
“We are so thankful to the neighbors for their patience and support during this project,” Rice said. “We ran into some difficult conditions and unforeseen challenges, which can happen when you are drilling to such depths.”
The city’s goal was to conduct a scientific test on something that’s the subject of anecdotal discussions for many years.
“There are stories from the mining days about possible conditions down there as well as talk from other drillers and consultants and the fact that this area is geothermally active, so it’s nice to have the tests to prove the hypotheses. It is exciting to know there could be another local renewable-energy option for Aspen,” Rice said.
So far, the project has cost the city a little more than $300,000, but $50,000 of the total was reimbursed through a state grant.
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