First field application of cyclic soft stimulation at the Pohang Enhanced Geothermal System site in Korea

Hofmann, Hannes; Zimmermann, Günter; Farkas, Márton Pál; Huenges, Ernst; Zang, Arno; Leonhardt, Maria; Kwiatek, Grzegorz; Martínez‐Garzón, Patricia; Bohnhoff, Marco; Min, Ki‐Bok; Fokker, P.A.; Westaway, Rob; Bethmann, Falko; Meier, Peter; Yoon, Kern Shin; Choi, Jin Woo; Lee, Tae Jong; Kim, Kwang Yeom

doi:10.1093/gji/ggz058

Cited by 115 publications

(97 citation statements)

References 61 publications

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“…Zang et al (2019) have demonstrated this approach for experimental-scale injection tests. However, the results from application to an industrialscale project (Hofmann et al, 2019) are more ambiguous, as the Pohang geothermal project, South Korea, at which this method was applied, went on to experience one of the largest injection-induced events ever recorded (Grigoli et al, 2018). Moreover, for shale gas hydraulic fracturing applications, it is not clear that such a low-rate injection program would result in effective proppant placement into a shale formation.…”

Section: Using Microseismic Data For Decision-making To Mitigate Indumentioning

confidence: 99%

“…It is therefore desirable to manage and mitigate induced seismicity in real time, as operations proceed. For example, injection volumes or pressures could be reduced (e.g., Kwiatek et al, 2019), or stimulation can be directed away from areas showing fault reactivation. Here we show a successful example of managing HF-IS with a recently acquired dataset from a shale gas operation in the UK.…”

Section: Introductionmentioning

confidence: 99%

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Real‐Time Imaging, Forecasting, and Management of Human‐Induced Seismicity at Preston New Road, Lancashire, England

Clarke¹,

Verdon

Kettlety

et al. 2019

Seismological Research Letters

103

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Earthquakes induced by subsurface fluid injection pose a significant issue across a range of industries. Debate continues as to the most effective methods to mitigate the resulting seismic hazard. Observations of induced seismicity indicate that the rate of seismicity scales with the injection volume and that events follow the Gutenberg–Richter distribution. These two inferences permit us to populate statistical models of the seismicity and extrapolate them to make forecasts of the expected event magnitudes as injection continues. Here, we describe a shale gas site where this approach was used in real time to make operational decisions during hydraulic fracturing operations.Microseismic observations revealed the intersection between hydraulic fracturing and a pre‐existing fault or fracture network that became seismically active. Although “red light” events, requiring a pause to the injection program, occurred on several occasions, the observed event magnitudes fell within expected levels based on the extrapolated statistical models, and the levels of seismicity remained within acceptable limits as defined by the regulator. To date, induced seismicity has typically been regulated using retroactive traffic light schemes. This study shows that the use of high‐quality microseismic observations to populate statistical models that forecast expected event magnitudes can provide a more effective approach.

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Section: Using Microseismic Data For Decision-making To Mitigate Indumentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real‐Time Imaging, Forecasting, and Management of Human‐Induced Seismicity at Preston New Road, Lancashire, England

Clarke¹,

Verdon

Kettlety

et al. 2019

Seismological Research Letters

103

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“…in Basel and St. Gallen, Switzerland (e.g. Giardini, 2009;Diehl et al, 2017) or most recently in Pohang, South Korea (Hofmann et al, 2019;Ellsworth et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Seismicity during and after stimulation of a 6.1 km deep Enhanced Geothermal System in Helsinki, Finland

Leonhardt¹,

Kwiatek²,

Martínez‐Garzón³

et al. 2020

Preprint

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Abstract. In this study, we present a high-resolution dataset of seismicity framing the stimulation campaign of a 6.1 km deep Enhanced Geothermal System (EGS) in Helsinki suburban area and discuss the complexity of fracture network development. Within St1 Deep Heat project, 18 160 m3 of water was injected over 49 days in summer 2018. The seismicity was monitored by a seismic network of near-surface borehole sensors framing the EGS site in combination with a multi-level geophone array located at ≥ 2 km depth. We expand the original catalog of Kwiatek et al. (2019) and provide the community with the dataset including detected seismic events and earthquakes that occurred two month after the end of injection, totalling to 61 163 events. We relocated events of the catalog with sufficient number of available phase onsets and moment magnitudes between Mw −0.7 and Mw 1.9 using the double-difference technique and a new velocity model derived from a post-stimulation vertical seismic profiling campaign. The analysis of the fault network development at reservoir depth of 4.5–7 km is one primary focus of this study. To achieve this, we investigate 191 focal mechanisms of the induced seismicity using cross-correlation based technique. Our results indicate that seismicity occurred in three spatially separated clusters centered around the injection well. We observe a spatio-temporal migration of the seismicity during the stimulation starting from the injection well in northwest (NW) – southeast (SE) direction and in northeast (NE) direction towards greater depth. The spatial evolution of the cumulative seismic moment, the distribution of events with Mw ≥ 1 and the fault plane orientations of focal mechanisms indicate an active network of at least three NW–SE to NNW-SSE orientated permeable zones which is interpreted to be responsible for migration of seismic activity away from the injection well. Fault plane solutions of the best-constrained focal mechanisms as well as results for the local stress field orientation indicate a reverse faulting regime and suggest that seismic slip occurred on a sub-parallel network of pre-existing weak fractures favorably oriented with the stress field, striking NNW-SEE with a dip of 45° ENE, parallel to the injection well.

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“…Then, such forecasts can be used in an optimization schedule to support decision making. Fact‐based decision making is required in many circumstances—some examples being the warranting of wellbore stability, the design of reservoir stimulation, and the minimization of induced seismicity …”

Section: Introductionmentioning

confidence: 99%

“…Fact-based decision making is required in many circumstances-some examples being the warranting of wellbore stability, the design of reservoir stimulation, and the minimization of induced seismicity. 5,6 Quality decisions must be based on quality knowledge. Crucial in such knowledge is its quantified reliability, or uncertainty.…”

mentioning

confidence: 99%

A semianalytic time‐resolved poro‐elasto‐plastic model for wellbore stability and stimulation

Fokker

Singh

Wassing

2020

Num Anal Meth Geomechanics

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Summary Wellbore stability problems and stimulation operations call for models helping in understanding the subsurface behaviour and optimizing engineering performance. We present a fast, iteratively coupled model for the flow and mechanical behaviour that employs a time‐sequential approach. Updates of pore pressure are calculated in a timestepping approach and propagated analytically to updates of the mechanical response. This way, the spatial and temporal evolution of pressure and mechanical response around a wellbore can be evaluated. The sequential approach facilitates the incorporation of pressure diffusion and of time‐dependent plasticity. Also, it facilitates the implementation of permeability evolving with time, due to plasticity or stimulation. The model has been validated by means of a coupled numerical simulator. Its capabilities are demonstrated with a selection of sensitivity runs for typical parameters. Ongoing investigations target geothermal energy operations through the incorporation of thermo‐elastic stresses and more advanced plasticity models.

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First field application of cyclic soft stimulation at the Pohang Enhanced Geothermal System site in Korea

Cited by 115 publications

References 61 publications

Real‐Time Imaging, Forecasting, and Management of Human‐Induced Seismicity at Preston New Road, Lancashire, England

Real‐Time Imaging, Forecasting, and Management of Human‐Induced Seismicity at Preston New Road, Lancashire, England

Seismicity during and after stimulation of a 6.1 km deep Enhanced Geothermal System in Helsinki, Finland

A semianalytic time‐resolved poro‐elasto‐plastic model for wellbore stability and stimulation

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