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KMOU RESEARCH NEWS 게시판의 작성자 함혜주씨가 2020.12.04에 등록한 A Groundbreaking Way to Extract Geothermal Energy from Rocks without Inducing Earthquakes의 상세페이지입니다.
A Groundbreaking Way to Extract Geothermal Energy from Rocks without Inducing Earthquakes
Writer PR Team Date 2020.12.04

A Groundbreaking Way to Extract Geothermal Energy from Rocks without Inducing Earthquakes



Scientists compare various fluid injection schemes to increase rock permeability in enhanced geothermal systems


Scientists from the Korea Institute of Maritime and Ocean Technology compare different injection strategies for breaking rock samples using hydraulic pressure. Their findings will make enhanced geothermal systems safer and more efficient, facilitating their adoption as sources of renewable energy.



Geothermal energy―the internal heat of our planet contained in underground rocks―is a promising type of renewable energy that can be used to produce electricity. One way to harvest this energy is through enhanced geothermal systems (EGSs), in which water is poured through a hole four miles deep in the ground and the emerging steam is run through a turbine. For this method to work, however, the underground rocks must be highly permeable; that is, they must have many macro- and microscopic cracks that water can fill to achieve efficient temperature exchange.


A somewhat controversial technique called “hydraulic fracturing” is used to create these cracks, wherein a fluid is injected at a pressure so high that the rocks break. Although this method is useful for increasing rock permeability, it can induce “seismic activity,” or a sudden movement of the earth's crust―potentially leading to devastating earthquakes.


In an effort to find the safest and most effective injection scheme for hydraulic fracturing, a team of scientists at Korea Institute of Maritime and Ocean Technology compared different fluid injection strategies in cubic granite samples. Professor Kwang Yeom Kim, who led the study, explains their motivation, “Actual geothermal power projects in Basel, Switzerland, and Pohang, Korea, have been suspended because of induced seismicity or the unexpected shaking of the ground. We want to develop alternative methods of hydraulic stimulation to mitigate such risks in the future.


Using acoustic sensors to pinpoint the exact moments in which cracks formed, the scientists tested six different ways of injecting fluid into rocks and compared the resulting permeability values. Then, after cracking all the samples, they used X-ray computed tomography to observe the three-dimensional structure of the cracks and gain insight into how rock composition affects the breaking process.


Their findings showed that the two best injection strategies involve using cyclic injection, or increasing and decreasing pressure periodically. This maximizes the distribution of hydraulic energy while using lower pressure levels than in conventional methods. The result is a combination of good permeability and minimal seismic energy, which mitigates the risk of induced earthquakes. Excited about the results, Prof Kim explains, “We suggest a hydraulic stimulation method based on the distribution of hydraulic energy by alternating the pressurization and depressurization with an injection pressure lower than the usual stimulation pressure. This leads to a decrease in the induction of large seismic energy.”


Prof Kim is optimistic that the proposed hydraulic stimulation strategies could effectively prevent seismic events and ensure that EGSs reach a commercial stage. These “groundbreaking” findings could certainly make the adoption of geothermal energy easier―a key step toward a greener future.


DOI: 10.1007/s00603-020-02170-8

*Corresponding authors’ emails: kykim@kmou.ac.kr


About the author

Kwang Yeom Kim is an Associate Professor of the Department of Energy and Resources Engineering at Korea Maritime and Ocean University. He has been developing approaches to characterize the behavior of various types of rock mass through physical experiments and numerical simulations combined with microscopic observation using X-ray computed tomography (CT). He has suggested many novel assessment methods for solid materials, mostly rock materials, using his unique approach based on capturing three-dimensional internal structures via X-ray CT images. Before joining the Korea Maritime and Ocean University, he worked at the Korea Institute of Civil Engineering and Building Technology. He obtained a PhD in Geomechanics from Seoul National University in 2007.