Northwestern California’s stunning Mayacamas Mountain Range is home to the world’s largest geothermal field.
Since 1960, The Geysers region has continuously generated geothermal energy—heat generated by the Earth’s hot interior—by harnessing steam from deep underground wells. Steam is piped overland to a network of interconnected facilities that power turbines to produce clean, continuous electricity for Lake, Sonoma, and Mendocino counties.
“We’re extremely proud of what we’ve been doing over the last 60 years to produce the sustainable amount of clean, reliable base-load generation,” said Joe Greco, strategic origination director at Calpine Corp., which operates 13 power plants in The Geysers region.
Calpine partnered with Seequent, Bentley Systems’ subsurface company, to create a 3D model of the underground steam reservoir at The Geysers. Seequent’s Leapfrog subsurface software helps Calpine optimize geothermal energy production, efficiently plan new wells, and improve generation profiles at specific facilities.
The heat is on
Northwestern California’s stunning Mayacamas Mountain Range is home to the world’s largest geothermal field.Geothermal energy production supports the state of California’s ambition to achieve carbon neutrality by 2045. It’s also both renewable and reliable. Unlike weather-dependent sources like solar and wind, which generate intermittent power, geothermal generates always-on electricity.
Geothermal power generation utilizes wells to produce hot fluids from the reservoir and reinjects spent fluid back into the reservoir. At The Geysers, superheated steam is produced from hot permeable rocks and is converted into electricity. To support the ongoing operation of the resource, Calpine reinjects additional fluids to sustainably produce geothermal power from the steam.
“We’re required to buy our fuel upfront,” Greco said. “And what that means, different than other energy components, is we have to go and drill and explore to make sure we can accurately determine the amount of energy we can get from a specific resource.”
Next year’s model
Steve DeOreo, Calpine’s senior geologist, said the 3D modeling technology helps his team “get their arms around” the reservoir, which spans more than 40 square miles, by rendering surface and subsurface data.
“This is really valuable, not just in understanding the resource we have in our existing steam reservoir, but also in planning new geothermal wells to be drilled in the future,” he said. “The software model allows us to visualize, in great detail and with high accuracy, exactly where a new well will be situated in relation to surrounding wells.”
Single source of truth
Seequent software brings together and standardizes historical and real-time data from disparate sources into one “single source of truth” environment.
“With a 3D model of the reservoir, teams can understand how the resource will respond to changes in production and operation,” said Kathleen Gould, account executive at Seequent and a trained geologist. “It’s incredible the innovation and opportunity we can unlock when we understand the underground.”
Above ground, Calpine uses OpenFlows software from Bentley Systems to sustain its operations by modeling and monitoring an innovative wastewater recharge system.
“Seequent software brings the subsurface and surface together so they can talk to each other and help geologists, geophysicists, and engineers make the right decisions to preserve this resource for generations to come,” Gould said.
Under pressure
The Geysers power plants developed rapidly from the early-1970s to the late-1980s, quickly depleting the system’s steam supply. Declines in steam pressure hampered power production, threatening geothermal energy’s future in the region.
By the late 1990s, many operators had left, but Calpine continued to explore creative ways to optimize the resource. At the same time, nearby communities were struggling to find a responsible, weather-independent solution for wastewater disposal. Calpine’s solution: the world’s first wastewater-to-steam power project. Recycled water pumped from the city of Santa Rosa and Lake County is reinjected into hot rocks at The Geysers to maintain pressure in the reservoir and fuel turbines with steam.
“It was a revolutionary idea,” said Jody Batten, senior director of asset management at Calpine. “It’s the first and largest water injection solution of its kind, serving about 825,000 homes and businesses. This earth has given us a gift up here with the geothermal resource, and we’re committed to using it wisely.”
