Detection of water flow available for geothermal power generation from component analysis of unfelt microtremors

Geothermal power generation is a type of renewable energy that has the advantage of stable power generation regardless of weather or time of day. However, in some geothermal power plants that have been in operation for many years, there is the issue that the quantity of hot water may gradually decay to a level less than that required for stable power generation.

One solution is to artificially inject water to the target location to replenish the hot water quantity, but care must be given to the possibility of inducing earthquakes. It is a challenge to understand the subsurface water flow that cannot be viewed directly. However, in order to generate sustainable geothermal power, it is important to understand the subsurface water flow in real time and to make appropriate use of geothermal resources.

Researchers in AIST developed a new technology monitoring a water flow in a geothermal field by detection of the changes in subsurface microtremors.

As part of efforts to monitor the subsurface environment during geothermal power generation, AIST has used a high sensitivity seismograph network to continuously observe microearthquakes in the Okuaizu Geothermal Field (Yanaizu Town, Fukushima Prefecture) since 2015. This study found that the magnitude ratio between the horizontal and vertical components of microtremors observed by the high-sensitivity seismometer installed at a depth of approximately 400 m changes in accordance with the subsurface water flow. By detecting these changes in real time, the water flow can easily be estimated, which is expected to contribute to a more effective development of geothermal resources. Furthermore, this technology also holds the potential for application to fields such as oil field development, underground storage of CO₂, and monitoring of deep fluid activity in areas with active seismicity and volcanic activity and is expected to develop into a new deep subsurface monitoring technology.

Provided by Advanced Industrial Science and Technology