automatic detection and location of microseismic events
DESCRIPTION
Automatic detection and location of microseismic events . Tomas Fischer. Outline. Why automatic How automatic Errors West Bohemia swarm 2000 Hydraulic stimulation in gas field in Texas. Why automatic processing?. Huge datasets Improve productivity Improve data homogeneity - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/1.jpg)
Automatic detection and Automatic detection and location of microseismic location of microseismic events events Tomas Fischer
![Page 2: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/2.jpg)
OutlineOutlineWhy automaticHow automaticErrors West Bohemia swarm 2000Hydraulic stimulation in gas field
in Texas
![Page 3: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/3.jpg)
Why automatic Why automatic processing?processing?Huge datasetsImprove productivityImprove data homogeneityReal time processing – alarms
![Page 4: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/4.jpg)
Utilization of automatic Utilization of automatic processingprocessingMeasurement of arrival times Measurement of amplitudesPhase-waveform extraction
Hypocentre locationSource parameters, focal mechanismsSeismic tomographyAttenuation studies…
![Page 5: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/5.jpg)
ApproachesApproachesClassical - stepwise:
(single station / network)1. Phase detection & picking2. Hypocentre location
Simultaneous (seismic network)– source scanning / back-propagation(Kao & Shan, 2003; Drew 2005)
![Page 6: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/6.jpg)
Classical approach – stepsClassical approach – stepsPhase detection – increased
signal energy, single station
Phase association – consistency betw. stations
Phase picking – identify phase onset
Location of hypocenters
![Page 7: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/7.jpg)
Phase detectionPhase detectionTransform 3C seismogram to a
scalar > 0, characteristic function CF (Allen, 1978)
Find maxima of CF S-wave energy detector
ENZ
–maximum eigenvalue of signal
covariance matrix
€
Σnini Σniei
Σniei Σeiei
⎛ ⎝ ⎜
⎞ ⎠ ⎟
in a running window
![Page 8: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/8.jpg)
Distinguishing P and S-Distinguishing P and S-waveswavesHierarchic approach First find S-waves (higher amplitude, horiz.
polarization) Then find P-waves (perpendicular
polarization)
![Page 9: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/9.jpg)
Distinguishing P and S-Distinguishing P and S-waveswavesEqual approach
evaluate horiz. & vert. polarization find consecutive intervals of perpendicular
polarization (ampl. ratio or hor/vert gives hint to which one is P and S)
![Page 10: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/10.jpg)
Phase associationPhase associationSimple kinematic (geometric) criteria
e.g. t2 < t1+t12
A-priori information on source position- plane wave consistency
Preliminary location- test the phase consistency by location residual
1 2
Source
![Page 11: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/11.jpg)
Phase pickingPhase pickingFind onset – abrupt
amplitude increaseSTA/LTA
(non-overlapping)
Higher statistic momentsKurtosis
Waveform cross-correlationSTA/LTA
Kurtosis
Horiz. Polarization
€
S4 =x i − X ( )
4
i=1
N
∑Nσ 4
![Page 12: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/12.jpg)
Automatic locationAutomatic locationNo special needs (each location
algorithm is automatic)Hydrocarbon reservoir stimulations
– linear array of receivers – besides arrival times also backazimuth (polarization) needed => modify the location algorithm to include also the fit to the polarization data
![Page 13: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/13.jpg)
Event locationEvent location2D array (Earth surface)
– P-waves sufficient (S-waves beneficial)
1
2
3
4 t1-t2
t3-t4
t2-t3
![Page 14: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/14.jpg)
Event locationEvent location
depth1
2
3
4
5
t1>t2>t3=t4<t5
1
Map viewDepth
view
1D array (borehole)both P and S-waves needed
![Page 15: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/15.jpg)
GoodnessGoodnessPicking success
◦Amplitude ratio @ pick◦Location residual
Location success◦Location residual◦Sharpness of foci image ?! Location residual – results from
◦ Unknown structure◦ Timing errors◦ Picking errors (Gaussian & gross)=> Residual is not a unique measure of
picking success
![Page 16: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/16.jpg)
Location residual calibration Location residual calibration (remove gross errors)(remove gross errors)Training dataset – if manual
processing availableLoc. error:
difference between manual and automaticlocations
6 samples
![Page 17: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/17.jpg)
Location residual calibration Location residual calibration (remove gross errors)(remove gross errors)Dataset to be processed
Limit for choice of good locations
![Page 18: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/18.jpg)
Swarm 2000 in West Swarm 2000 in West BohemiaBohemia
4 SP stations
0-20 km epicentral distance
synchronous triggered recording
![Page 19: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/19.jpg)
Swarm 2000 Automatic Swarm 2000 Automatic processingprocessingCharacteristic functionS: maximum eigenvalue of the covariance matrix in
horizontal plane (Magotra et al., 1987)
P: sum of the Z-comp. and its derivative (Allen, 1978)
Method1. S-waves, minimum interval>maximum expected tS-tP2. P-waves in a fixed time window prior to S3. Only complete P and S pairs processed
=> homogeneous dataset
)()( tzKtzCFP
2
4 22neeenneenn
neSCF
![Page 20: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/20.jpg)
Swarm 2000 in West Swarm 2000 in West BohemiaBohemiaResulting automatic picks
![Page 21: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/21.jpg)
Swarm 2000 in West Swarm 2000 in West BohemiaBohemia>7000 detected events, 4500 well located
Homogeneous catalog downto ML=0.4Location error: ±100 m horiz. and ±200 m vert. 24.4 .2001
psonset9.pas - N KC m aster(psons22.txt)
- 1 0 1 2 3M l
1
10
100
1000
10000
NAll events
R M S<8 sm pl
0 10 20 30 40 50residuum lokace, sm pl.
0
1000
2000
3000
4000
5000
6000
7000
N
![Page 22: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/22.jpg)
-600 -400 -200 0 200 400 600m eters
0
40
80
120
160ev
ents
-600 -400 -200 0 200 400 600m eters
Difference between manually and automately
obtained hypocentre locations
E-W coo., stdev 77 m
N-S coo., stdev 127 m
depth, stdev 127 m
-0.10 0.00 0.10 0.20 0.30 0.40secs
origin tim e, stdev 38 m s
Swarm Nový Kostel 2000
Automatic locations with RMS<8 smpl.Automatic locations with RMS<8 smpl.compared with 405 manually located eventscompared with 405 manually located events
![Page 23: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/23.jpg)
P1 a P2
1 2 3 4 5 6+7 8 9
Automatic locations of the 2000 swarm
![Page 24: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/24.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
![Page 25: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/25.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
8 3C geophonescontinuous recording
![Page 26: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/26.jpg)
Hydraulic stimulation in gas Hydraulic stimulation in gas fieldfieldS-wave picker Get the maximum eigenvalue tof the signal
covariance matrix
Find maxima of polarized energy
arriving at consistent delays j to vertical array (derived from expected slowness)
• Identify the S-wave onsets tS by STA/LTA detector in a short time window preceding the maxima of L(t)
• Measure S-wave backazimuth
• Array compatibility check by fitting hodochrone tS(z) by parabola, outliers repicked or removed
j
jj ttL
![Page 27: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/27.jpg)
Hydraulic stimulation in gas Hydraulic stimulation in gas fieldfieldP-wave picker• Search for signal s polarized in S-ray direction p.
We use the characteristic function
• Find maxima of P-wave polarized energy Cp(t) arriving at consistent slowness (similar as in S-wave detection)
• Identify the P-wave onsets tP by STA/LTA detector in a short time window preceding the maxima of Cp(t)
• Measure the P-wave backazimuth
• Use Wadati’s relation to remove tP outliers
ssps ...Pc
€
tS − tP = tS α − β( ) /β
![Page 28: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/28.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
![Page 29: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/29.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
![Page 30: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/30.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
![Page 31: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/31.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas field
![Page 32: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/32.jpg)
Hydraulic stimulation in Hydraulic stimulation in gas fieldgas fieldComparison of manual and auto picks
for 296 manually picked events
Fig. 3. Distribution of time differences between automatically and manualy obtained arrival times of test dataset.
PS
![Page 33: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/33.jpg)
Comparison of manual and auto Comparison of manual and auto locationslocations
![Page 34: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/34.jpg)
![Page 35: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/35.jpg)
ConclusionsConclusionsautomatic processing useful in case of
huge datasets & provides homogeneous results
two approaches◦classic – mimics human interpreter◦modern – direct search for the hypocentre
classic – network consistency beneficial
two case studies show successful implementation of polarization based picker
![Page 36: Automatic detection and location of microseismic events](https://reader038.vdocument.in/reader038/viewer/2022103007/56815e32550346895dcc936c/html5/thumbnails/36.jpg)
OutlinesOutlinesuse waveform cross-correlation
for picking