Controlling fluid-induced seismicity during a 6.1-km-deep geothermal stimulation in Finland

Kwiatek, Grzegorz; Saarno, Tero; Ader, Thomas; Bluemle, F.; Bohnhoff, Marco; Chendorain, Michael; Dresen, Georg; Heikkinen, Pekka; Kukkonen, Ilmo; Leary, Peter; Leonhardt, Maria; Malin, Péter; Martínez‐Garzón, Patricia; Passmore, Kevin; Passmore, P. R.; Valenzuela, S. G.; Wollin, Christopher

doi:10.1126/sciadv.aav7224

Cited by 184 publications

(254 citation statements)

References 50 publications

(87 reference statements)

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“…The radiated seismic energy E 0 for each event is estimated from the seismic moment M 0 and stress drop ∆σ following Hanks and Kanamori () as

E_{0} = ∆ σ \frac{M_{0}}{2 G} η_{R},

where G is the shear modulus calculated as

G = ρ V_{s}^{2}

, with density ρ and shear wave velocity V s , and η R is the radiation efficiency. When available we used already calculated catalogs of radiated energy (Kwiatek et al, ; Kwiatek et al, ) or computed radiated energy using average stress drops available (Baisch et al, ; Charléty et al, ; Goertz‐Allmann et al, ; Jost et al, ) and assumed a median radiation efficiency of 0.46 (McGarr, ). The KTB data were corrected for the finite bandwidth applied in previous studies (Ide & Beroza, ).…”

Section: Methodsmentioning

confidence: 99%

Seismic Moment Evolution During Hydraulic Stimulations

Bentz

Kwiatek

Martínez‐Garzón

et al. 2020

Geophysical Research Letters

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Analysis of past and present stimulation projects reveals that the temporal evolution and growth of maximum observed moment magnitudes may be linked directly to the injected fluid volume and hydraulic energy. Overall evolution of seismic moment seems independent of the tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. Data suggest that magnitudes can grow either in a stable way, indicating the constant propagation of self‐arrested ruptures, or unbound, for which the maximum magnitude is only limited by the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection or not at all. Monitoring and traffic light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near‐real time and at high resolution for an immediate reaction in injection strategy.

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“…The radiated seismic energy E 0 for each event is estimated from the seismic moment M 0 and stress drop ∆σ following Hanks and Kanamori () as

E_{0} = ∆ σ \frac{M_{0}}{2 G} η_{R},

where G is the shear modulus calculated as

G = ρ V_{s}^{2}

Section: Methodsmentioning

confidence: 99%

Seismic Moment Evolution During Hydraulic Stimulations

Bentz

Kwiatek

Martínez‐Garzón

et al. 2020

Geophysical Research Letters

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“…Over 18,000 m 3 of water was recently injected at~6 km depth in Finland to stimulate flow for deep geothermal heat extraction [28]. Over 54,000 microearthquakes (−1 < M < 1.9) resulted from this stimulation, of which 6150 were located and characterized.…”

Section: Power Law Exponent Of Permeability From Microearthquake Distmentioning

confidence: 99%

Observational and Critical State Physics Descriptions of Long-Range Flow Structures

Malin

Leary²,

Cathles

et al. 2020

Geosciences

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Using Fracture Seismic methods to map fluid-conducting fracture zones makes it important to understand fracture connectivity over distances greater 10–20 m in the Earth’s upper crust. The principles required for this understanding are developed here from the observations that (1) the spatial variations in crustal porosity are commonly associated with spatial variations in the magnitude of the natural logarithm of crustal permeability, and (2) many parameters, including permeability have a scale-invariant power law distribution in the crust. The first observation means that crustal permeability has a lognormal distribution that can be described as κ ≈ κ 0 exp ( α ( φ − φ 0 ) ) , where α is the ratio of the standard deviation of ln permeability from its mean to the standard deviation of porosity from its mean. The scale invariance of permeability indicates that αϕο = 3 to 4 and that the natural log of permeability has a 1/k pink noise spatial distribution. Combined, these conclusions mean that channelized flow in the upper crust is expected as the distance traversed by flow increases. Locating the most permeable channels using Seismic Fracture methods, while filling in the less permeable parts of the modeled volume with the correct pink noise spatial distribution of permeability, will produce much more realistic models of subsurface flow.

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“…Hydraulic testing of small intervals in the open section of the borehole (e.g., individual fractures and faults intersecting the borehole) could significantly improve hydromechanical analyses, and would provide more detailed input data for numerical models. Although expensive, such a multi-stage approach was recently carried out in an EGS project in Finland (e.g., Kwiatek et al, 2019) and could potentially also be used for hydrothermal systems.…”

Section: Implications For Future Deep Hydrothermal Projectsmentioning

confidence: 99%

“…A striking example is the Enhanced Geothermal System (EGS) project in Basel, Switzerland, where seismicity was induced immediately below the city, which led to the suspension of the entire project (e.g., Giardini, 2009). Recent history clearly shows that the success of geo-energy, in particular geothermal projects, largely depends on the level at which we are able to control induced seismicity (Kraft et al, 2009;Kwiatek et al, 2019). There is an urgent need to communicate transparently with the public and employ methods that will safely keep the seismicity to a tolerable level (Giardini, 2009;Lee et al, 2019).…”

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confidence: 99%

Potential influence of overpressurized gas on the induced seismicity in the St. Gallen deep geothermal project (Switzerland)

Zbinden¹,

Rinaldi²,

Diehl³

et al. 2019

Preprint

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Abstract. In July 2013, the city of St. Gallen conducted a deep geothermal project that aimed to exploit energy for district heating and generating power. A few days after an injection test and two acid stimulations that caused only minor seismicity, a gas kick forced the operators to inject drilling mud to combat the kick. Subsequently, multiple earthquakes were induced on a fault several hundred meters away from the well, including a ML 3.5 event that was felt throughout the nearby population centers. Given the occurrence of a gas kick and a felt seismic sequence with low total injected fluid volumes (~ 1200 m3), the St. Gallen deep geothermal project represents a particularly interesting case study of induced seismicity. Here, we first present a conceptual model based on seismic, borehole and seismological data suggesting a hydraulic connection between the well and the fault. The overpressurized gas, which is assumed to be initially sealed by the fault, may have been released due to the stimulations before entering the well via the hydraulic connection. We test this hypothesis with a numerical model calibrated against the borehole pressure of the injection test. We successfully reproduce the gas kick and the temporal and spatial characteristics of the main seismicity sequence that followed the well control operation. The results indicate that the gas may have destabilized the fault during and after the injection operations and could have enhanced the resulting seismicity. This study may have important implications for future deep hydrothermal projects conducted in similar geological conditions.

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Controlling fluid-induced seismicity during a 6.1-km-deep geothermal stimulation in Finland

Cited by 184 publications

References 50 publications

Seismic Moment Evolution During Hydraulic Stimulations

Seismic Moment Evolution During Hydraulic Stimulations

Observational and Critical State Physics Descriptions of Long-Range Flow Structures

Potential influence of overpressurized gas on the induced seismicity in the St. Gallen deep geothermal project (Switzerland)

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