Did You Know … the largest geothermal power plant is over a century old?

(Image Credit: Blog.bently.com. “Notes From The Underground: How Seequent’s Subsurface Software Helps Keep World’s Largest Geothermal Complex Powering Full Steam Ahead” by Jay Moye. https://blog.bentley.com/insights/notes-from-the-underground-how-seequents-subsurface-software-helps-keep-worlds-largest-geothermal-complex-powering-full-steam-ahead/)

The Geysers Geothermal Field is the largest geothermal power plant complex in the world, covering over 45 square miles in northern California. In 2018, The Geysers accounted for 50% of California’s geothermal power generation and 7% of all clean energy generation in the state. This potential is thanks in part to the area’s easily accessible reservoirs of steam and high geological activity. In fact, electricity has been generated using The Geyser’s steam since 1922, when well No. 1 was drilled in the canyon. While this is not nearly as effective as the modern wells we have today (which were also pioneered at The Geysers), it paved the way for global development of geothermal technologies.

Well No. 1 was “the world’s first successful geothermal well drilled for electrical power generation outside of Larderello Geothermal Field in Tuscany, Italy” (Hodgson, 1997,. According to 17-year-old rig operator Glen Trutt, when it was first drilled at a shallow depth of 200 feet, “Everything came flying up – mud, tools, rocks, and steam. After things settled down, there was just clean steam. But the noise was loud enough to hear all over the valley” (Hodgson, 1997, p. 22). After being attached to an old steam engine harvested from the Foppiano Winery in Healdsburg, CA, they had enough power to begin a larger scale drilling process. By 1926, the field had 88 geothermal wells. Proprietor John D. Grant contracted to sell 112 Megawatts of electricity to the nearby city of Healdsburg. However, that contract was cancelled in 1934 by Healdsburg in favor of a nearby oil-fired electricity plant.

After the era of health research, The Geysers region lost prominence. The nearby water was harvested and bottled as “Geyser Water,” sold to workers building the Panama Canal and across America for its high mineral content and positive health impacts. Only one electricity-producing well remained, nicknamed “Whistling Annie.” With little optimism for its future, Unocal Corporation had the resort razed in its 129th year of operation. As the era of tourism and commercial product development ended, Magma Power Company purchased leases for 3,300 acres of land in the region.

The Geysers’ landscape was unique for its deep history, which played a pivotal role in the emergence of more contemporary technologies. “In 1955, Magma drilled well Magma No. 1, the first modern well … about halfway between John Grant’s wells No. 1 and [Whistling Annie], not far from the Witches’ Cauldron” (Hodgson, 1997, p. 39). Even as history was replaced with modern electricity generation, The Geysers remained for the leader in geothermal energy. Magma and Thermal Power Company worked together to drill five additional wells over the next 2 years, the deepest of which reached 1,400 feet.

With the electricity generation reaching an all-time high, Pacific Gas & Electric Company (PG&E) signed a contract with the Magma-Thermal team; this was the first example of geothermal power being contracted for commercial use. This expansion increased over the next several decades, thanks to a 1966 discovery of generation viability outside of an area with surface manifestations. In 1968, power capacity totaled about 82 MW.

One drawback of these expansions was that with so many production wells, the pressure of the steam reservoir decreased from 500 psi to 200 psi. This was a sign that these companies had to remain conservative when extracting this natural resource. Almost every electricity company signed on to ecology-friendly rules to ensure continuity and safety of the reservoir. They replaced old topsoil to grow new vegetation and plugged/covered wells after steam extraction in that area had been completed.

Since geothermal electricity production was still a fairly new energy source, many questions were raised regarding the ownership of these resources. The Geothermal Steam Act of 1970 clearly identified that geothermal resources were not water resources (as they had originally been defined); instead, they were “embraced in the reservation of minerals by the state and federal governments in instruments granting title of public lands” (Hodgson, 1997, 41). This meant that companies had to lease both the land and the minerals, rather than just the land and whatever was beneath it. This legislative focus on geothermal resources paved the way for a burgeoning era of power generation for The Geysers.

After these advancements, The Geysers once again rose to be the largest geothermal electricity generators in the world. It is also serving as one of the forefront producers of EGS electricity generation. As of 2017, Calpine Corporation has been producing steam from an EGS well in the northwest region. They are also conducting tests for induced seismicity, consistent production, and steam generation. Calpine (with financial assistance from the DOE) also opened a Geothermal Visitor Center that has been active for over 24 years.

As of 2022, The Geysers Geothermal Field “can generate 725 megawatts of electricity, enough to power a city the size of San Francisco” (Pratt, 2022, para. 4). That valley has been a staple of natural geothermal expressions for over 12,000 years, and it has also been spearheading geothermal electricity for over one hundred years. The geothermal industry owes many of its greatest advancements to The Geysers, even as it continues to erupt into the future.