Assessing California’s Population of Low-Temperature Geothermal Wells for Plugging and Abandonment: Research and Analysis on Long-Term Idle Wells

California is the number one producer of geothermal energy in the United States, according to the 2021 Energy Information Administration, Power Plant Operations Report. Geothermal energy provides many benefits to Californians, including as a source of reliable baseload electricity generation, supplying hot springs for resorts throughout the state, and providing the heat for district heating projects concentrated in small rural communities.  

Low Temperature Geothermal Wells (LTGWs) were drilled and completed in California, mostly during the 1980s, for direct use in applications such as water and space heating. The California Department of Conservation, California Geologic Energy Management Division (CalGEM) regulates the geothermal industry and issues permits for these LTGWs.  

Wells that remain unused for years can pose a threat to groundwater and be a safety hazard. These long-term, idle LTGWs should be safely plugged and abandoned in accordance with CalGEM’s geothermal regulations.  

The California Energy Commission (CEC) contracted with CalGEM to provide technical assistance for the Geothermal Grant and Loan Program. The purpose of this project was to develop plans to plug and abandon identified, unused, and/or deserted LTGWs in California.  

CalGEM assessed 30 wells, resulting in 10 wells being targeted as eligible for plugging and abandonment. The corresponding well owners and/or operators may use the information in this report to solicit bids from contractors to plug and abandon the wells. 

Additional funding to properly plug and abandon the 10 unused wells would benefit all Californians by providing a safer environment. Six wells were not found, and resources should be allocated to conclusively determine their status and location. Six wells are still in use.  

Eight wells still exist in viable geothermal resource areas and should be explored to see what means are available to assist in their development.