E-vib as an innovative seismic source in hard rock mineral ...
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E-vib as an innovative seismic source in hard rock mineral exploration in Ludvika Mines (Sweden)Sweden) Tatiana Pertuz*, Alireza Malehmir, Bojan Brodic and Ding Yinshuai, Uppsala University; Jordan Bos, Seismic Mechatronics; Paul Marsden, Nordic Iron Ore AB Objectives Introduction Conclusions Acknowledgements Results Methods This study was carried out within the Smart Exploration project. Smart Exploration has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 775971. Authors wish to thank NIO, Seismic Mechatronics, and Uppsala University students for the collaboration in the study. WWW.SMARTEXPLORATION.EU E-mail: [email protected], Department of Earth Sciences, Geophysics Program,Uppsala University, Villavägen 16, Uppsala-Sweden CONTACT: 2. 3. 4. 5. » Iron-oxide deposits in Blötberget match the strong amplitude reflections in the data, both, unmigrated and migrated stacked sections. g » A clear and long crosscutting reflection appears to intersect the mineralization and project to the surface towards the southern end of the profile. g » Acquisition with the E-vib source added up output frequencies to the low and high end of the spectrum and permitted deeper wave penetration. g » The broadband processing flow allowed enhancement and preservation of target reflections into the final stacked section with a reasonable quality without modifying the bandwidth of the data severely. 1. » Test the prototype E-vib (electromagnetic based, electrically driven) broadband seismic vibrator in hard rock and mineral exploration seismic surveys. » Enhance seismic imaging while taking advantage of the broadband signal nature generated by the E-vib in this challenging hard rock setting by a tailored broadband processing flow. Phase Step Process Parameter Pre-stack 1 Data input SEGY file 2 Merged Cable system and wireless 3 Trace edit Kill Null and noisy traces 4 First break picking Automatic and manual 5 Refraction static 2-layers model using surface elevation, shot positions, first breaks 6 Gapped deconvolution Gap: 13-22 ms Length: 80-150ms 7 Median filtering Velocity: 2149 and 2244 m/s 8 Airwave Attenuation at velocity 330 m/s 9 Trace muting Mute above first breaks 10 Residual statics Surface-consistent 11 NMO 50% stretch and taper 20 ms 12 Stack Unity Post- stack 13 FX-deconvolution Filter length: 19 ms Window length: 100 ms 14 f-k filtering Surgical muting on selected CDPs 15 Migration Phase shift Table 2. Broadband processing parameters applied in the workflow to the 2D seismic section at Blötberget mine. Acquisition type Cable system Wireless Survey parameters Receiver-line direction SN Number of receivers 425 128 Receiver interval (m) 5 Maximum offset (m) 2753 Source Storm (E-vib) Frequency range (Hz) 2-180 Sweep rate Linear Sweep length (s) 14, 16, 18, 20 Recording parameters Record length (ms) 3000 Sampling rate (ms) 1 Table 1. Parameters designed and used for the 2D seismic acquisition at Blötberget site. N R e c e i v e r s Receivers Source (Evib) Source (Evib) Blötberget 5 m a) b) Figure 2. Field photos displaying northern portion of the profile towards the mine shaft. (a) Storm E-vib source in operation, and (b) wireless recorders placed on the southern section of the » P-wave (vertical-type) electromagnetic vibrator, electrically driven (E-vibe), which produce a full drive frequency range of 2-180 Hz. » Uses a linear synchronous motor (LSM) to avoid intrinsic limitations to add up output frequencies. Easting (m) Northing (m) 502.5 503.5 504.5 505.5 506.5 502.5 503.5 504.5 505.5 506.5 507.0 6662.0 6663.0 6664.0 6665.0 6666.0 Borehole depth (m) 1000 750 500 250 6661.5 6662.0 6663.0 6664.0 6665.0 6666.0 (nT) Airborne magnetic (TMI) Blötberget mine Wireless recorders 502.5 6661.5 6662.0 P1 P1 P2 6659500 628 10˚ 20˚ 30˚ 40˚ 60˚ 65˚ 70˚ Ludvika Mines 49500 52300 49700 49800 49850 49900 BB12004 BB14001 BB14001 BB14002 BB14002 BB14005 BB14005 BB14008 BB14008 BB70-001 BB70-001 BB73-001 BB73-001 BB14004 BB14004 P1 P1 P2 Easting (m) Northing (m) 502.5 503.5 504.5 505.5 506.5 504.5 505.5 506.5 6663.0 6664.0 6665.0 6663.0 6664.0 6665.0 6666.0 6662.0 BB14005 Blötberget mine BB14001 BB14002 BB70-001 BB73-001 BB14004 BB12004 BB14008 Wireless recorders Borehole depth (m) 1000 750 500 250 6662.0 6666.0 Figure 1. Study area, Blötberget, Ludvika Mines (Sweden). (a) Aerial photo showing the seismic profile and existing boreholes. (b) Total-field aeromagnetic map showing the pronounced maganetic signature of the Blötberget deposits towards the northern end of the profile (dark blue line). Light blue line: wireless stations, and dark blue line: cabeled stations. a) b) a) 0.0 0.1 0.2 0.3 0.4 0.5 Time (s) 1001 1092 1183 1274 1365 1456 1547 Receiver Location Raw Shot N S 50 100 150 200 Frequency (Hz) 0 -60 -40 -20 0 Power (dB) 0 -60 -40 -20 0 Power (dB) 50 100 150 200 Frequency (Hz) b) 0.0 0.1 0.2 0.3 0.4 0.5 Time (s) 1001 1092 1183 1274 1365 1456 1547 Receiver Location Gap deconv. N S 50 100 150 200 Frequency (Hz) 0 -60 -40 -20 0 Power (dB) 0 -60 -40 -20 0 Power (dB) 50 100 150 200 Frequency (Hz) c) 0.0 0.1 0.2 0.3 0.4 0.5 Time (s) 1001 1092 1183 1274 1365 1456 1547 Receiver Location N S Median filter 50 100 150 200 Frequency (Hz) 0 -60 -40 -20 0 Power (dB) 0 -60 -40 -20 0 Power (dB) 50 100 150 200 Frequency (Hz) Figure 4. (a) Average amplitude spectrum for receivers of every 10th shot with natural frequency of 4.5 and 10 Hz recorded. (b) An example of raw shot gather showing clear reflections interpreted to be from the mineralization. (c) After gapped deconvolution, and (d) median filter as part of broadband processing steps, which is displaying enhacement of the reflections coherency as indicated by red arrows. Figure 5. (a) Unmigrated stacked and (b) migrated sections visualized with the known deposits showing their correlations and possible depth extent. The crosscutting reflection is interpreted to be from a fault system likely terminating the mineralization and controlling its geometry at depth. Inset figure in (b) is the migrated section wihtout the deposit models. Acquisition » Weight of 1650 kg with a peak force of 7kN.I » Its design and dimensions enable it to be attached to locally available vehicles (tractors, skid-steer loaders, etc.) Processing Seismic source. » The mining industry is constantly challenged by a number of internal and external factors demanding refinement of the deep exploration technologies, also environmentally friendly. » Raw materials have good physical property contrasts compared to their host rocks, and hence, their direct targeting is possible even within a complex 3D geological setting. » Blötberget, iron deposit mine, belongs to the Bergslagen mineral district, one of the three major mineral districts in Sweden. » Rocks are dominantly Svecofennian (1.91 to 1.88 Ga) felsic meta-volcanics. » High quality apatite iron-oxide mineralization is distributed in sheet-like horizons, skarn-type iron-oxide deposits and apatite-rich iron oxide deposits. POST-STACK PRE-STACK Final section Migration Balance Stack Median Filtering Gapped deconvolution Residual static FK- filtering FX- deconvolution Trace edit/QC Refraction static NMO AGC Merged FDU Wireless Velocity analysis Figure 3. Broadband processing workflow applied to the seismic data from the Blötberget mine. NW 10 20 30 40 50 60 70 80 1001 1140 1280 Time (ms) Source Location 10 20 30 40 50 60 70 80 Time (ms) 1001 1190 1380 Source Location Drophammer 2015+2016 E-Vib 2019 Drophammer 2015+2016 Frequency (Hz) E-Vib 2019 1050 1100 1150 1200 1250 1100 1200 1300 Source Location Source Location 4 3.5 3 2.5 2 1.5 1 0.5 7 6 5 4 3 1 2 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Frequency (Hz) 50 100 150 200 250 300 350 400 450 500 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Normalized amplitude spectrum E-Vib 2019 Source Nr. 280 Source Nr. 140 Source Nr. 001 50 100 150 200 250 300 350 400 450 500 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Normalized amplitude spectrum Frequency (Hz) Source Nr. 380 Source Nr. 190 Source Nr. 001 Drophammer 2015+2016 a) b) c) d) e) f) Frequency (Hz) Amplitude Amplitude Figure 6. window around the first breaks for the 2019 (E-Vib) and 2016 (drophammer) seismic datasets to analyse the frequency band. (a) Stronger amplitudes and broader bandwidth frequency from the E-Vib source, (d) while the drophammer presents limited bandwidth. (b and e) Extracted wavelets displaying also a smaller side-lobe and hence better resolution for the E-Vib than the drophammer. (c and f) The amplitude spectra for the seismic datasets.
Transcript of E-vib as an innovative seismic source in hard rock mineral ...
E-vib as an innovative seismic source in hard rock mineral exploration in Ludvika Mines (Sweden)Sweden)
Tatiana Pertuz*, Alireza Malehmir, Bojan Brodic and Ding Yinshuai, Uppsala University; Jordan Bos, Seismic Mechatronics; Paul Marsden, Nordic Iron Ore AB
Objectives
Introduction
Conclusions
Acknowledgements
ResultsMethods
This study was carried out within the Smart Exploration project. Smart Exploration has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 775971. Authors wish to thank NIO, Seismic Mechatronics, and Uppsala University students for the collaboration in the study.
WWW.SMARTEXPLORATION.EUE-mail: [email protected], Department of Earth Sciences, Geophysics Program,Uppsala University, Villavägen 16, Uppsala-SwedenCONTACT:
2.
3. 4.
5.» Iron-oxide deposits in Blötberget match the strong amplitude reflections in the data, both, unmigrated and migrated stacked sections.g
» A clear and long crosscutting reflection appears to intersect the mineralization and project to the surface towards the southern end of the profile.g
» Acquisition with the E-vib source added up output frequencies to the low and high end of the spectrum and permitted deeper wave penetration.g
» The broadband processing flow allowed enhancement and preservation of target reflections into the final stacked section with a reasonable quality without modifying the bandwidth of the data severely.
1.» Test the prototype E-vib (electromagnetic based, electrically driven) broadband seismic vibrator in hard rock and mineral exploration seismic surveys.
» Enhance seismic imaging while taking advantage of the broadband signal nature generated by the E-vib in this challenging hard rock setting by a tailored broadband processing flow.
Phase Step Process Parameter
Pre-stack 1 Data input SEGY file
2 Merged Cable system and wireless
3 Trace edit Kill Null and noisy traces
4 First break picking Automatic and manual
5 Refraction static 2-layers model using surface
elevation, shot positions, first breaks
6 Gapped deconvolution Gap: 13-22 ms
Length: 80-150ms
7 Median filtering Velocity: 2149 and 2244 m/s
8 Airwave Attenuation at velocity 330 m/s
9 Trace muting Mute above first breaks
10 Residual statics Surface-consistent
11 NMO 50% stretch and taper 20 ms
12 Stack Unity
Post- stack 13 FX-deconvolution Filter length: 19 ms
Window length: 100 ms
14 f-k filtering Surgical muting on selected CDPs
15 Migration Phase shift
Table 2. Broadband processing parameters applied in the workflow to the 2D seismic section at Blötberget mine.
Acquisition type Cable system Wireless
Survey parameters
Receiver-line direction
SN
Number of receivers 425 128
Receiver interval (m) 5
Maximum offset (m) 2753
Source Storm (E-vib)
Frequency range (Hz) 2-180
Sweep rate Linear
Sweep length (s) 14, 16, 18, 20
Recording parameters
Record length (ms) 3000
Sampling rate (ms) 1
Table 1. Parameters designed and used for the 2D seismic acquisition at Blötberget site.
N
ReceiversReceivers
Source (Evib)Source (Evib)
Blötberget
5 m
a)
b)
Figure 2. Field photos displaying northern portion of the profile towards the mine shaft. (a) Storm E-vib source in operation, and (b) wireless recorders placed on the southern section of the
» P-wave (vertical-type) electromagnetic vibrator, electrically driven (E-vibe), which produce a full drive frequency range of 2-180 Hz.
» Uses a linear synchronous motor (LSM) to avoid intrinsic limitations to add up output frequencies.
Easting (m)
Nor
thin
g (m
)
502.5 503.5 504.5 505.5 506.5
502.5 503.5 504.5 505.5 506.5507.0
6662
.066
63.0
6664
.066
65.0
6666
.0
Borehole depth (m)
1000
750
500
250
6661
.566
62.0
6663
.066
64.0
6665
.066
66.0
(nT)
Airborne magnetic (TMI)
Blötberget mine
Wireless recorders
502.56661
.566
62.0
P1
P1
P2
6659
500
62810˚ 20˚ 30˚
40˚
60˚
65˚
70˚
Ludvika Mines
4950
0
5230
0
4970
0
4980
0
4985
0
4990
0
BB12004
BB14001BB14001BB14002BB14002
BB14005BB14005BB14008BB14008
BB70-001BB70-001
BB73-001BB73-001
BB14004BB14004
P1
P1
P2
Easting (m)
Nor
thin
g (m
)
502.5 503.5 504.5 505.5 506.5
504.5 505.5 506.5
6663
.066
64.0
6665
.0
6663
.066
64.0
6665
.066
66.0
6662
.0
BB14005 Blötberget mine
BB14001BB14002
BB70-001
BB73-001
BB14004BB12004
BB14008
Wireless recorders
Borehole depth (m)
1000
750
500
250
6662
.0
6666
.0
Figure 1. Study area, Blötberget, Ludvika Mines (Sweden). (a) Aerial photo showing the seismic profile and existing boreholes. (b) Total-field aeromagnetic map showing the pronounced maganetic signature of the Blötberget deposits towards the northern end of the profile (dark blue line). Light blue line: wireless stations, and dark blue line: cabeled stations.
a) b)
a)0.0
0.1
0.2
0.3
0.4
0.5
Tim
e (s
)
1001 1092 1183 1274 1365 1456 1547Receiver Location
Raw Shot
N
S
50 100 150 200Frequency (Hz)
0−60
−40
−20
0
Pow
er (d
B)
0−60
−40
−20
0
Pow
er (d
B)
50 100 150 200Frequency (Hz)
b)0.0
0.1
0.2
0.3
0.4
0.5
Tim
e (s
)
1001 1092 1183 1274 1365 1456 1547Receiver Location
Gap deconv.
N S
50 100 150 200Frequency (Hz)
0−60
−40
−20
0
Pow
er (d
B)
0−60
−40
−20
0
Pow
er (d
B)
50 100 150 200Frequency (Hz)
c)0.0
0.1
0.2
0.3
0.4
0.5
Tim
e (s
)
1001 1092 1183 1274 1365 1456 1547Receiver LocationN S
Median filter
50 100 150 200Frequency (Hz)
0−60
−40
−20
0
Pow
er (d
B)
0−60
−40
−20
0
Pow
er (d
B)
50 100 150 200Frequency (Hz)
Figure 4. (a) Average amplitude spectrum for receivers of every 10th shot with natural frequency of 4.5 and 10 Hz recorded. (b) An example of raw shot gather showing clear reflections interpreted to be from the mineralization. (c) After gapped deconvolution, and (d) median filter as part of broadband processing steps, which is displaying enhacement of the reflections coherency as indicated by red arrows.
Figure 5. (a) Unmigrated stacked and (b) migrated sections visualized with the known deposits showing their correlations and possible depth extent. The crosscutting reflection is interpreted to be from a fault system likely terminating the mineralization and controlling its geometry at depth. Inset figure in (b) is the migrated section wihtout the deposit models.
Acquisition
» Weight of 1650 kg with a peak force of 7kN.I
» Its design and dimensions enable it to be attached to locally available vehicles (tractors, skid-steer loaders, etc.)
Processing
Seismic source.
» The mining industry is constantly challenged by a number of internal and external factors demanding refinement of the deep exploration technologies, also environmentally friendly.
» Raw materials have good physical property contrasts compared to their host rocks, and hence, their direct targeting is possible even within a complex 3D geological setting.
» Blötberget, iron deposit mine, belongs to the Bergslagen mineral district, one of the three major mineral districts in Sweden.
» Rocks are dominantly Svecofennian (1.91 to 1.88 Ga) felsic meta-volcanics.
» High quality apatite iron-oxide mineralization is distributed in sheet-like horizons, skarn-type iron-oxide deposits and apatite-rich iron oxide deposits.
POST-STA
CKPR
E-STAC
K
Final section
Migration
Balance
Stack
MedianFiltering
Gappeddeconvolution
Residualstatic
FK-�ltering
FX-deconvolution
Traceedit/QC
Refractionstatic
NMO
AGC
Merged
FDU Wireless
Velocityanalysis
Figure 3. Broadband processing workflow applied to the seismic data from the Blötberget mine.
250 mNW
10 20 30 40 50 60 70 80
1001
1140
1280
Time (ms)
Sour
ce L
ocat
ion
10 20 30 40 50 60 70 80Time (ms)
1001
1190
1380
Sour
ce L
ocat
ion
Drophammer 2015+2016
E-Vib 2019
Drophammer 2015+2016
Freq
uenc
y (H
z)
E-Vib 2019 1050 1100 1150 1200 1250
1100 1200 1300
Source Location
Source Location
4
3.5
3
2.5
2
1.5
1
0.5
7
6
5
4
3
1
2
0
50
100
150
200
250
300
0
50
100
150
200
250
300
Frequency (Hz)50 100 150 200 250 300 350 400 450 5000
0.1
0.2
0.30.4
0.5
0.6
0.7
0.8
0.91
Nor
mal
ized
am
plitu
de s
pect
rum
E-Vib 2019
Source Nr. 280Source Nr. 140Source Nr. 001
50 100 150 200 250 300 350 400 450 5000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.80.9
1
Nor
mal
ized
am
plitu
de s
pect
rum
Frequency (Hz)
Source Nr. 380 Source Nr. 190 Source Nr. 001
Drophammer 2015+2016
a) b) c)
d) e) f)
Freq
uenc
y (H
z)
Am
plitu
deA
mpl
itude
Figure 6. window around the first breaks for the 2019 (E-Vib) and 2016 (drophammer) seismic datasets to analyse the frequency band. (a) Stronger amplitudes and broader bandwidth frequency from the E-Vib source, (d) while the drophammer presents limited bandwidth. (b and e) Extracted wavelets displaying also a smaller side-lobe and hence better resolution for the E-Vib than the drophammer. (c and f) The amplitude spectra for the seismic datasets.
