QUANTITATIVE ANALYSIS OF EARTHQUAKE ENERGY INDUCED BY WATER INJECTION FOR HOT DRY ROCK POWER GENERATION

Abstract

High water utilization efficiency is important as well as high generation efficiency when implementing Hot Dry Rock power generation (HDR). In addition, hydraulic fracturing performed to create reservoirs requires suppressing induced earthquakes. However, the relation between conditions of hydraulic fracturing and the magnitude of the induced earthquake has not been clarified. We showed the relationship between the injection energy of hydraulic fracturing and the induced earthquake energy.
We selected 6 sites with injection point depth of 1000 to 5000 m; Hijiori, Ogachi, Newberry, Soultz, Cooper Basin, Basel. The injection energy was calculated from wellhead pressure, flow rate and operating time of injection water and the induced earthquake energy was calculated using the Gutenberg-Richter equation.
As a result, the ratios of the total energy of induced earthquakes to the injection energy at Hijiori and Ogachi sites were as low as 0.1% or less, but the ratios at Cooper Basin and Basel sites were as high as about 5%. The ratios at Newberry and Soultz sites were in between. The ratio of the induced earthquake energy greatly varies depending on the difference in underground structure.
The evaluation method from the viewpoint of the injection energy and the induced earthquake energy is useful for selection of HDR site and planning of effective operation conditions.