First Hydraulic Stimulation in Fractured Geothermal Reservoir in Pohang PX-2 Well

Park, Sehyeok; Xie, Linmao; Kim, Kwang Il; Kwon, Saeha; Min, Ki‐Bok; Choi, Jaiwon; Yoon, Woon-Sang; Song, Yoonho

doi:10.1016/j.proeng.2017.05.250

Cited by 53 publications

(26 citation statements)

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“…In the previous stimulation in PX-1, the fracture opening pressure was determined to be between 15 MPa and 17 MPa wellhead pressure, which indicates shearing of pre-existing fractures rather than tensile hydraulic fracturing (Park et al 2017a, b). 17 MPa WHP was reached with an injection rate of l/s within less than an hour time.…”

Section: Short-term Cyclesmentioning

confidence: 86%

“…The granodiorite and granitic gneiss were accessed by the deviated well PX-1 and the vertical well PX-2 which reached a measured depth of 4362 m and 4348 m, respectively (Kim et al 2017). Multiple hydraulic stimulation treatments were performed at the site in 2016 and 2017 (Kim et al 2017;Park et al 2017a. The magnitudes of the largest seismic events during PX-1 and PX-2 stimulations were reported as 2.3 (Kim et al 2017) and 3.1 (Grigoli et al 2018), respectively.…”

Section: The Pohang Egs Projectmentioning

confidence: 99%

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Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

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Economic production of a variety of geological resources, such as shale gas, tight oil, coal bed methane and geothermal heat using enhanced geothermal systems (EGS), relies on hydraulic stimulation treatments. These are reservoir enhancement methods where fluid is injected into a reservoir to increase its productivity by a combination of developing new tensile and shear fractures, and tensile opening and shearing of pre-existing fractures. Stimulated fractures may stay open naturally through the self-propping effect or they have to be kept open artificially by proppants, such as sands or ceramics that are injected together with the stimulation fluid to achieve a permanent productivity enhancement. Details about hydraulic fracturing and other reservoir stimulation methods can be found in an abundance of textbooks and other publications (e.g., Bunger et al. 2013; Economides and Nolte 2000; Economides and Martin 2007; Huenges and Ledru 2010). While improving the hydraulic reservoir performance, hydraulic stimulation treatments also cause fluid-injection-induced seismicity. On the one hand, induced seismicity

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Section: Short-term Cyclesmentioning

confidence: 86%

Section: The Pohang Egs Projectmentioning

confidence: 99%

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

et al. 2018

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Section: Introductionmentioning

confidence: 99%

“…The first enhanced geothermal system (EGS) project was initiated in late 2010 in Pohang, South Korea (Park et al, 2017), where the highest geothermal gradient and heat flow are observed (Figure 1; Kim & Lee, 2007; Lee et al, 2010). Injection wells (denoted by PX‐1 and PX‐2) were drilled to depths of 4,362 and 4,341 m, respectively, and the first high‐pressure hydraulic stimulation began on 29 January 2016 (Hofmann et al, 2019; Park et al, 2017). Before the last fluid injection on 18 September 2017, an earthquake occurred on 15 April 2017 at or near the EGS site with a moment magnitude, Mw, of 3.2 (Kim et al, 2018; Korean Government Commission, 2019 [KGC, 2019, hereafter]; Woo et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

et al. 2020

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The 2017 Mw 5.5 Pohang earthquake in South Korea, the first reported and largest magnitude-induced earthquake, occurred near the enhanced geothermal power plant in Pohang on 15 November 2017. We compute the spatiotemporal changes in poroelastic stresses perturbed by injected fluid under various conditions to better understand the occurrences of the Pohang earthquake and the small-magnitude earthquakes preceding it. Space-time variation of the earthquakes that occurred before the Pohang earthquake correlates significantly with fluid injection history between January 2016 and September 2017. We attribute the timing in earthquake occurrence to slow fluid diffusion, making hydraulic diffusivity of bedrock the critical model parameter for representing this slow process. In this context, the delay between the injection and the Pohang earthquake requires diffusivity estimates within a range of 1 × 10 −4-5 × 10 −4 m 2 /s for damaged granodiorite at 4-5 km, corresponding to the depth range between the well and the focal depth. According to these estimates, the pore pressure and thus the Coulomb failure stress changes are further enhanced by each injection with minimum stress dissipation. We find fluid injection can result in a change of the Coulomb stress of up to 0.4-1.1 bar, exceeding those associated with the 2016 Mw 5.5 Gyeongju earthquake by 2 orders of magnitude.

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“…We also studied the relation between the seismic moment (M o~1 .7 × 10 17 N•m) of the mainshock (6) and the volume (V ) of fluid injected. Assuming that unreported injections are similar to initial stimulation (3), we estimated an upper bound to the total volume of~10,000 m 3 . The limitation of water supply and storage capacity of the EGS justifies our assumption.…”

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The November 2017 M _w 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

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Rinaldi

et al. 2018

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The moment magnitude () 5.5 earthquake that struck South Korea in November 2017 was one of the largest and most damaging events in that country over the past century. Its proximity to an enhanced geothermal system site, where high-pressure hydraulic injection had been performed during the previous 2 years, raises the possibility that this earthquake was anthropogenic. We have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks, constrain the geometry of this seismic sequence, and shed light on its causal factors. According to our analysis, it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities. Finally, we found that the earthquake transferred static stress to larger nearby faults, potentially increasing the seismic hazard in the area.

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First Hydraulic Stimulation in Fractured Geothermal Reservoir in Pohang PX-2 Well

Cited by 53 publications

References 2 publications

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

The November 2017 M _w 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

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First Hydraulic Stimulation in Fractured Geothermal Reservoir in Pohang PX-2 Well

Cited by 53 publications

References 2 publications

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

The November 2017 M w 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

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The November 2017 M _w 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea