Geysers are some of Earth’s most spectacular sights – created when intense pressure causes a hot spring to erupt, sending jets of water and steam into the air. Some geysers are more powerful than others, however, and in 2023, Utah FORGE’s Dr. Stuart Simmons (our Technical Expert on Geology and Geochemistry) spoke with Geohug about the geological wonder that is the Waimangu geyser. Follow along for some of the takeaways!

Active from 1900 to 1904, the Waimangu geyser is the most powerful geyser in history. It played in an area of hydrothermal activity approximately 20 kilometers southeast of Rotorua on the northern island of New Zealand. It erupted frequently for periods lasting roughly 6 hours within a 36 hour cycle. The geyser pool was 11,475 square meters large and individual eruptions jetted water, steam, rocks and mud up to 400 meters into the air! During these eruptions, the geyser created an estimated thermal output of 500 to 750 megawatts of energy – an output so high, no geysers today can compare. It’s no wonder that the geyser captivated such large tourist interest.

September 9, 2024

In April 2024, the production and injection wells were successfully stimulated by perforating the steel casing in the wells and pumping water into them under pressure. This process created the fracture network that forms the reservoir. The stimulation was followed in August 2024 by a successful commercial scale circulation test. During the nearly month-long test, a consistent rate of 420 gallons of water per minute was injected. More than 90% of the produced fluid was recovered and the temperature remained at approximately 370°F. 

The results provide positive indications of the long-term behavior of the reservoir and the amount of heat that can be extracted.

Several methods were implemented to delineate reservoir performance in addition to monitoring flow rates and temperatures. Tracers were injected to track fluid flow, geophones located in other wells were continuously monitored for microseismicity related to fracture formation, and fiber optic cables were monitored for microseismicity, temperature, strain, and pressure. Downhole surveys were also conducted in the wells to determine their condition.

Analysis of the data collected during the circulation test is currently underway. The results will be made available on the Geothermal Data Repository, that may also be found on the Data Dashboard.  Longer-term tests planned for the next phase of the project will allow for further evaluation of the reservoir’s performance and sustainability.