23.06.17 1 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 [email protected]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%
8
Embed
Advances in microseismic monitoring and understanding of … · 2017. 6. 27. · c) Grigoli et al. (2017) Reviews of Geophysics Earthquake rupture: ! nucleates where Coulomb stress
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
23.06.17
1
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
1982 USA, CaliforniaGeothermal energyMagnitude 4.6 2006 Switzerland, Basel
Geothermal energyMagnitude 3.5
Grigoli et al. (2017) Reviews of Geophysics
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
Year
0
50
100
150
200
250
300
Scientific articles on Induced Seismicity
Num
ber
of p
aper
s
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)
23.06.17
3
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
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
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
23.06.17
6
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
23.06.17
7
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)
23.06.17
8
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