Induced Earthquake by Hot Dry Rock Power Generation - Influence of Injection Energy and Underground Structure -

Abstract

It is important to suppress induced earthquakes by hydraulic fracturing to create artificial reservoirs for hot dry rock power generation. The relationship between the magnitude of the induced earthquake and the conditions of hydraulic fracturing has not been clarified. We analyzed the relationship between the water injection energy of hydraulic fracturing and the induced earthquake energy and obtained useful information for the design of hot dry rock power generation. Data of 6 sites (Hijiori, Ogachi, Soltz, Newberry, Basel and Cooper Basin) were used for our investigation. For reference, the cases of wastewater injection and CCS (CO2 Capture and Sequestration) were also analyzed. The water injection energy was calculated by product of injection water pressure, flow rate and time, and the induced earthquake energy was calculated by the Gutenberg-Richter formula. The ratio of the induced earthquake energy to the water injection energy varied in a wide range from 0.1% or less to 4% or more depending on the underground structure. The maximum magnitude of the induced earthquake was closely related to the natural fracture density. The methodology from the viewpoint of water injection energy and induced earthquake energy will be useful for the selection of the site of hot dry rock power generation and setting of hydraulic fracturing conditions.