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Advances in microseismic monitoring and

understanding of hydraulic fracturing: the contribution of the SHEER EU project.

T. Dahm, S. Cesca, J. A. Lopez Comino, S. Heimann, D. Kühn, S. Lasocki, B. Dost GFZ - German Research Center for Geosciences, Potsdam, Germany

NORSAR, Norway, Institute of Geophysics, Polish Academy of Sciences

KNMI The Royal Netherlands Meteorological Institute

torsten.dahm@gfz-potsdam.de

Transatlantic Knowledge Sharing Conference on Unconventional Hydrocarbons: Resources, Risks, Impact and Research Needs

Session 1: Induced seismicity from hydraulic fracturing and waste water management.

De Bazel Conference Centre, Amsterdam, 20-21 June 2017

European on-shore basins and their potential for shalegas/-oil

Gas production in UK dropped 1/3 since 2000. Shale exploration with strict regulations

70 shale gas licences

Wysin test site

Expected shalegas production in USA in 2040 (EIA, 2014): 53%

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EU  Projects  on  Shale  Gas  Environmental  Footprint  

Four projects under EU-LCE-16-2014 on impacts and risks of shale gas 1.  Fracrisk - Furthering the Knowledge Base For Reducing the

Environmental Footprint of Shale Gas Development 2.  M4ShaleGas - Measuring, Monitoring, Mitigating, Managing the

environmental impact of Shale Gas 3.  STX, ShaleXenvironmenT, Maximizing the EU shale gas potential by

minimizing its environmental footprint 4.  SHEER - SHale gas Exploration and Exploitation induces Risks 2015–18, 8 Partners/WPs, (AMRA, IFG PAS, KeU, GFZ, KNMI, UG, +Industry)

Objectives: •  Groundwater contamination by chemical contained in flow back and produced water

•  Air pollution by migration of methane & other gases through fractures

•  Induced seismicity by fracking and injection of waste water

Global aspects of induced and triggered earthquakes

2013 Spain, Gulf of ValenciaGas storageMagnitude 4.2

2005 South Africa, KlerksdorpMining operationsMagnitude 5.3

1967 USA, ColoradoWastewater injectionMagnitude 4.8

2003 Australia, Cooper basinGeothermal energyMagnitude 3.7

2013 Australia, New CastleMining operationsMagnitude 5.6

2008 China, ZipingpuWater impoundmentMagnitude 7.9

2011 USA, OklahomaWastewater injectionMagnitude 5.6

2010 UK, BlackpoolShale Gas extractionMagnitude 2.3

2016 USA, OklahomaWastewater injectionMagnitude 5.8

Magnitude1.5 < M ≤ 2.02.0 < M ≤ 3.03.0 < M ≤ 4.04.0 < M ≤ 5.05.0 < M ≤ 6.0

M > 6.0

Oil and GasGeothermalWastewater

Dams

Mining

Activity

2016 Canada, Fox CreekShale Gas extractionMagnitude 4.4

No. of events

47

8170

2113

2012 Netherlands, GroningenGas extractionMagnitude 3.6

1982 USA, CaliforniaGeothermal energyMagnitude 4.6 2006 Switzerland, Basel

Geothermal energyMagnitude 3.5

Grigoli et al. (2017) Reviews of Geophysics

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Scientific articles on Induced Seismicity

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2016

Main scientific challenges: a)  Understand and predict probability of larger earthquakes (EQ) b) Monitor small induced EQ and use them for characterization (e.g. traffic light)

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Mechanism of induced seismicity

Mining

operations (IV)

Hydrocarbons storage

and extractio

n (I)

Shale gas

exploitation (II)

CO2 sequestra

tion (V)

Dams (VI)

Geothermal energy

exploitation (III)

(a, b)(a,c)

(a,c)

(b)(a, b)

(a,b)

Main industrial activities which can "induce" or "trigger" seismicity a)

b)

c)

Grigoli et al. (2017) Reviews of Geophysics

Earthquake rupture: ü  nucleates where Coulomb stress exceeds fault strength ü  is driven by shear stress

Monitoring network Wysin

Wysin

Detection performance:

-  Synthetic catalogue -  Real data

2x11 stages in Jun/Jul 2016, 17E3 m3

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a) Potential triggered events? CHR1

Jun, 25 – 20:08:25 5 s

CHR2 CHR3 CHR4 CHR5 CHR6 CHR7 CHR8 CHRW GLO1 GLO2 GLO3 GLO4 GLO5 GLO6 GLO7 GLO8 GLO9 GLOD GW3S GW4S GWS1 PLA1 PLA2 PLA3 PLA4 PLA5 PLA6 PLA7 PLA8 PLAC SKRZ STEF SZCZ

CHR1 CHR2 CHR3 CHR4 CHR5 CHR6 CHR7 CHR8 CHRW GLO1 GLO2 GLO3 GLO4 GLO5 GLO6 GLO7 GLO8 GLO9 GLOD GW3S GW4S GWS1 PLA1 PLA2 PLA3 PLA4 PLA5 PLA6 PLA7 PLA8 PLAC SKRZ STEF SZCZ

Jul, 26 – 01:05:30 5 s

f) Long period signals

Detections during/after fracking operations

Borehole stations

CHRX

GLOX

PLAX

BB

ü  The most of local detections (M>0.4) corresponds to sources close to the surface. E.g. two EQ with Mw 1 and 0.5 likely occurred close to the surface.

ü  Weak EQ (M<0.4) associated with fracking operations detected only in the three borehole stations.

ü  The number of fracking induced high frequency events are (unusual) low. Instead, un-typical long period events were recorded

ü  Some transients / peaks in methane observed after fracking

ü  No ground water anomalies

New waveform detection/location approach June July August September

Wysin- 2H Wysin- 3H

Mw≈ 1.0. Near surface source (wave velocity = 400 m/s). Mc≈0.45

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Wysin- 2H Wysin- 3H

June July August September

New waveform detection/location approach

Mw≈ 0.5 (at completeness limit from surface stations)

peak in methane ≈6h after EQ

What happens at the fracture at the borehole ?

ü  Micro-earthquakes occur in shear mode at fracture tip ü  Opening of fractures generate long period transients (e.g. measured on tilt or broadband sensors) ü  Magnitude of events increases with injected volume and duration. Largest events often after stop of injection

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Sequence of mine-fracs using “frac-monitoring tool”

Packer Packer 0.5m

1.5m

AE sensor array

Injection interval

Frac sonde, see Manthei et al, 2003

Hydrofrac experiments in massive granite (Äspö, Sweden) Zang et al. (2017) GJI

50Hz-25kHz 1kHz-100kHz

60s-100Hz

Goals of the field experiment: - verify soft stimulation concepts - test hydraulic fracturing seismicity models

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Is seismicity controlled by pressure or by deformation ?

BB ground velocity - long period transients -

injection pressure HF2

high freq. microcracks event rate (MAE>1.25)

high freq. microcracks event magnitudes

Duration of fracture opening (Tr) is ≈1.6 x duration of injection (Td)

Dahm et al. (2012) JGR

large “gradient” small “gradient”

0.0 0.5 1.0 (t-t3)/(t4-t3)

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First results: MAE_max is controlled by fracture size (stress anomaly)

Note: - Mmax does not correlate to injection pressure - Event rate correlate with Pi

Äspö experiment

Summary ( Wysin / Äspö )

ü  Monitoring of M<0.5 EQ is challenging and needs borehole sensors

ü  Significant EQ (M>3) can be induced by fracking. Wysin experiment did not induce EQ with M>1

ü  Long period events have been recorded in Wysin – LP transients measured close to well (e.g. tilt) are associated with frac opening

ü  Fracture after-growth after stop of injection measured by tilt signals

ü  Frac tip EQ rate is controlled by injection pressure

ü  Frac-induced EQ magnitude is controlled by size and not pressure