35-阮帅-三维大地电磁反演初步研究

Vertical, low resistance target Kimberley pipes, rise steeply faults?
1) 2D case without topography is okay 2) 2D case with topography and non-unique near surface, 3) Remember, The 3D is the true situation
L08
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 528200
L12
51 49 47 45 43 41 39 37 35 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1 528400
Note: Even for a classical 2D inversion, we may lose information of this target if we use bigger lambda for inversion stabilizer.
Outlines
• Interest based on purpose, resolution or reliability, phenomena of EM on topographical area • Real case: Challenge for reliability on vertical low resistance target abnormities • Modeling AMT data analyzing: impedance phase invariant correction .vs. 1D & 2D inversion • 3D LBFGS Inversion of Real Data • Conclusions
L14
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 3 1 528600
L16
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 3 1 528800 ELV(m) 1030 1020 1010 1000 990 980 970 960 950 940 930 920 910 900 890 880 870 860 850
528200
528400
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528600
East(m)
East(m)
Impedance Phase Invariant correction, VS 1D Inversion L4:Zxy1DOCCAMINV L4:Zyx1DOCCAMINV
What? No Abnormally At All on Phase, But…
L00 L02
MA-MB:freq.=1000Hz
L04 L06 L08 L12 L14
L16
MA-MB:freq.=10Hz
L00
2981000
L02
L04
L06
L08
L12
L14
L16
degree
47.6 47.55 47.5 47.45 47.4 47.35 47.3
East(m)
Outlines
• Interest based on purpose, resolution or reliability, phenomena of EM on topographical area • Real case: Challenge for reliability on vertical low resistance target abnormities • Modeling AMT data analyzing: impedance phase invariant correction .vs. 1D & 2D inversion • 3D LBFGS-B Inversion of Real Data • Conclusions
2981000
2980800
2980800
North(m)
2980600
North(m)
2980600
47.25 47.2 47.15 47.1
2980400
2980400
47.05 47 46.95 46.9 46.85 46.8 46.75
2980200
2980200
527600
527800
528000
Challenge Kimberley case
L00
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
L02
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
2980400
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527600
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528600
East(m)
East(m)
3D modeling with FD using Yee’s grid, Impedance Phase Invariant correction MB:freq.=500Hz MA:freq.=500Hz
Applications of 3-D modeling & inversion technology in AMT exploration with a varied topography
阮帅,1，2，3, 王绪本1, 周军1, 汤吉2
1.Collage of Geophysics, Chengdu University of Technology 2.State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration 3. Hengda Century (BeiJing) Geophysics Technology Co.,Ltd
L02
L04
L06
L08
L12
L14
L16
2980800
2980800
2980600
North(m)
North(m)
2980600
Resistivity is based on 1D inversion on one site without static shift And Rock samples lab. measurement
resolution & reliability
resolution
Focus on geologic hazard: Railway Channels, Buildings Safety, Coal mining goaf…… paradox Care more on consequence Money for rebuild Even Human Life 1D & 2D Inversion may give you more detailed information Care more on spend Money for dry-wells???
2981000 1400 1300 2980800 1200 1100 1000
2980800
North(m)
North(m)
900 2980600 800 700 600 2980400 500 400 300 200 2980200 100 -0 527600 527800 528000 528200 528400 528600
2981000
About 1 km * 1 km 150m Elevation variation
2980800
2980600
???
527600 527800 528000
Limestone Fragmentized Dolostone
2980400
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527400
Kimberley pipes found before: Cracked, Contains Huge amount of Mica Lower the resistivity to 50~200 ohm.m Depth is about 300~500m beneath
3D modeling with FD using Yee’s grid, Impedance Phase Invariant correction MB:L04 MA:L04
MA:Elv=500m
L00
2981000
MA:Elv=0m
L16
L02
L04
L06
L08
L12
L14
L00
2981000
reliability
Focus on resources: Oil-gas exploration, Mining exploration, Geothermal……
1D & 2D Inversion may give you faked target abnormally
EM (AMT) & topography
L04
51 49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
L06
51 49 48 46 44 42 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
L00
2981000
L02
L04
L06
L08
L12
L14
L16
Ohm.m
600
2980800
550 500 450
2980600
400 350 300
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250 200 150
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100 50
527600 527800 528000 528200 528400 528600
2DRxy+Ryx+Pxy+PyxINV. ELV=500m
29wenku.baidu.com0600
2980400
2980200
East(m)
East(m)
Obv.IPI.on500Hz Well….. Data is not coherent with Inversion? 1D and 2D is totally different???
North(m)
1DRxyINV.ELV=500m
Outlines
• Interest based on purpose, resolution or reliability, phenomena of EM on topographical area • Real case: Challenge for reliability on vertical low resistance target abnormities • Modeling AMT data analyzing: impedance phase invariant correction .vs. 1D & 2D inversion • 3D LBFGS-B Inversion of Real Data • Conclusions
A simple 2D case consideration: Rxy is very sensitive of topography and near surface small abnormally, Static Shift, Really bad for 1D inversion, DC sounding have same phenomena The Impedance phase in 2D case, Pxy is not influence by that too much, But…. What about 3D case
Real Datas, 1D & 2D
2981000 59.5 59 58.5 58 57.5 57 56.5 56 55.5 55 54.5 54 53.5 53 52.5 52 51.5 51 50.5 50 49.5 49 48.5 527600 527800 528000 528200 528400 528600