By comparison, U.S. geothermal capacity grew by roughly the same amount between the six-year period 2006-2012 as it did between the 20-year period 1960-1979, which is considered to be a solid growth period for the industry, Gawell noted.
Robertson-Tait reflects that as the industry has grown, so has the ability to interpret reservoir information. After data is gathered, the next step is accurate integration and interpretation, a skill that takes training and experience to develop a robust conceptual model of the geothermal system and the controls on permeability and fluid flow. She and her counterparts at GeothermEx (operating as part of Schlumberger, the global oilfield services conglomeration, since its 2010 purchase) bring this type of analysis to the table, deciphering multi-disciplinary data sets to characterize geothermal resources. Using that experience they identify specific R&D activities that can improve the development of both EGS systems and conventional geothermal systems.
Getting accurate temperature readings at various depths, which requires drilling, is the most fundamental component of any geothermal project because they reveal much about the flow of hot fluids. “The only way we’re currently able to measure temperature accurately is by poking holes in the ground,” said Robertson-Tait. But this may not be the case in the future: “The geothermal ‘holy grail’ would be methods that reveal subsurface temperatures without having to drill deep, expensive wells.”
Already, scientists measure wavelengths to create images of a geologic area; while the results of using this seismic profiling technology can improve drilling targets, it is more costly than solely using geophysical methods. Developers have to make difficult decisions on whether to de-risk the drilling by spending more money upfront.
While the cost is significant now, this could ultimately decrease costs as well as improve readings.
“Because of the terrains that are involved [in the U.S.], I think we’re going to see a resurgence of the use of seismic techniques to better understand geothermal resources,” says Robertson-Tait. “Chevron is coming back into the geothermal game in the United States, and I would bet they’re going to be using seismic methods to gain a better understanding of subsurface structure. They recognize the cost-benefit of this approach.”
Robertson-Tait also noted that Lockheed Martin and others have developed innovative airborne exploration methods to a new level through the use of “gravity and magnetic gradiometry” -- meaning – “the difference in gravity or magnetic field from place to place,” a method that is quick to implement and provides broad coverage of an area, yielding additional insights into the geologic variations in the subsurface, testing the geologists’ concepts of the geothermal reservoir and its surroundings.
Geothermal Innovators Cross-fertilize with Related Industries
Geothermal developers are pros at using existing ideas in new ways. One such project received credit from the industry through the GEA Honors Technological Advancement award.
Robertson-Tait was on the committee that selected it. “Enel [Green Power North America]’s combined solar and geothermal project [is] a great example of how marrying two technologies actually yields something that’s bigger than the sum of the parts,” she said. “When I looked at the nominees, I immediately thought that this was something that should be recognized for technical innovation. Neither the geothermal piece nor the solar piece was “new” in terms of the technology, but putting the two together was a very clever thing.”
Enel’s hybrid project happened in stages in the hot Nevada desert: first the binary geothermal plant, then the solar field. In the hot summer months, the solar field will offset the use of water for cooling the geothermal plant.
Geothermal can also take some plays from the oil and gas book, such as the use of seismic surveys and utilizing some of that industry’s drilling and completion concepts. Geothermal developers routinely gather data from old wells – particularly that precious temperature data, and there is increasing interest in utilizing the heat in co-produced geothermal waters in some oil and gas fields.
“I like that kind of cross-fertilization, and I think it’s important for the industry to recognize that it’s happening,” said Robertson-Tait. On the other side of it, oil and gas developers have used techniques from EGS to create big flow paths in tight gas shelves. “Although there are important differences, there is more overlap between the two technologies than people may realize,” she said.
New Study Shows Deep Potential in Geothermal-savvy Nevada
“Nevada continues to make valuable contributions to the geothermal community and shows immense promise in terms of both geothermal energy and economics,” Gawell said leading up to the recent GEA Geothermal Energy Expo in Reno.
Commenting on the GEA Expo in a letter, Majority Leader of the U.S. Senate Harry Reid (D-NV), a longtime proponent of geothermal and other renewable energy sources, highlighted Nevada’s continued clean energy efforts. “Clean energy development has already created thousands of jobs in Nevada, and continued investment will help to drive our economy forward. Clean energy innovators like those at the Expo will provide the solutions that Nevada and the rest of the country need to maintain its momentum as a leader in clean energy development,” Reid said.
In fact, four of the seven geothermal plants that came online in the past year are located in Nevada, including Tuscarora and McGinness Hills by Ormat Technologies; San Emidio by U.S. Geothermal; and Beowawe 2 by Terra-Gen and TAS Energy. In the most recent industry-wide survey on geothermal projects in development, conducted this past April by the GEA, developers confirmed that 59 of a total 147 geothermal projects-in-development in the U.S. are located in Nevada. These 59 have the combined potential to account for more than 2,000 MW of geothermal capacity.
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