A massive hydraulic stimulation for enhanced geothermal system (EGS) development in Korea had been conducted in the PX-1 well of 4,217 m depth in Pohang EGS site from December 2016 to January 2017. Stimulation operation followed the planned programs composed of test stimulation, main stimulation and post-stimulation test as well as the traffic light system for induced seismicity management. Treatment histories of injection rate, wellhead pressure and corresponding induced seismicity data were obtained during the stimulation operation upon the 313 m of open-hole section at the bottomhole. Compared to the last and the first hydraulic stimulation at Pohang PX-2 well, wellhead pressure was significantly lower in PX-1 well. Injectivity index and reservoir transmissivity were evaluated from the stimulation data of PX-1 well, and those were compared with the case of PX-2 well. The critical fluid pressure for hydroshearing was estimated based on the joint and in-situ stress conditions of Pohang reservoir, and it showed a reasonable agreement with the pressure peaks observed in the first day of stimulation.
The first enhanced geothermal system (EGS) development project in Korea was launched at Pohang in December 2010. Drilling of PX-1 and PX-2 wells were finished with final depths of 4,217 m and 4,348 m as true vertical depths, respectively. The first large-scale hydraulic stimulation in the Pohang EGS site had been conducted in PX-2 well from January to February 2016. After the stimulation in PX-2 well, PX-1 well had been stimulated from December 2016 to January 2017. 3,907 m3 of water had been injected into the reservoir through 313 m long open hole section located at the bottom of PX-1 well.