Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 4. A COMPARISON OF MICROSEISMIC MONITORING OF FRACTURE STIMULATION DUE TO WATER VERSUS CO 2 INJECTION Inclination (degrees from vertical) 130 120 110 100 90 80 70 60 50 180 190 200 210 220 230 240 250 260 270 Azimuth (degrees) Figure 4.14: Horizontal projection of splitting orientations and magnitudes during CO 2 injection, in the same format as Figure 4.12. 10 9 8 Number of events 7 6 5 4 3 2 1 0 0 20 40 60 80 100 120 140 160 180 Fast direction from vertical Figure 4.15: Histogram showing ψ (in degrees from qS V ) for the SWS results during CO 2 injection. deformational regime in this field is strike slip. As such, for S-waves travelling subhorizontally from a strike slip event, the orientation of the initial S-wave polarisation, θ S , will be subhorizontal. θ S is computed by SHEBA as part of the SWS analysis, and the results are plotted as histograms in Figure 4.16. During water injection θ S appears mainly to be orientated subhorizontally, consistent with the 68
4.5. INITIAL S-WAVE POLARISATION 6 10 9 8 7 6 5 4 3 2 1 0 0 20 40 60 80 100 120 140 160 180 S polarisation (degrees from vertical) (a) 5 4 3 2 1 0 0 20 40 60 80 100 120 140 160 180 S polarisation (degrees from vertical) (b) Figure 4.16: Histograms of initial S-wave polarisation for the successful splitting results during water (a) and CO 2 injection (b). The modal polarisation during water injection is subhorizontal, suggesting a strike-slip failure mechanism. The polarisations during CO 2 injection are much more scattered. above inferences, while during CO 2 injection the data has significantly more scatter, but shows the same trend. This raises a potential problem in that ψ and θ S are apparently very close (i.e., both are horizontal). In theory, if ψ and θ S are the identical, then splitting will not occur and null results will be produced by the splitting analysis (Wüstefeld and Bokelmann, 2007; Wüstefeld et al., 2010a). In reality, with real data that contain noise, if ψ and θ S are close then the SWS analysis may produce unreliable results. 4.5.1 Modelling the effects of θ S on splitting analysis In order to investigate this issue I developed synthetic tests to assess how close θ S and ψ can get before the results become unreliable. I assess the reliability of the SWS measurement while varying 3 parameters: the difference between θ S and ψ; the signal/noise ratio; and the time-lag between the fast and slow S waves, considered here as a non-dimensional parameter by multiplying by the dominant wave frequency. Time-lag δt Non-dimensional time-lag δt N (=δt × ω) 0.5s 0.075 1.0s 0.15 2.0s 0.30 3.0s 0.45 Table 4.2: Time-lags and equivalent non-dimensional time-lags for synthetic modelling of the effects of θ S on SWS analysis. 69
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Microseismic Monitoring and Geomech
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Abstract Capture of CO 2 produced a
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Author’s Declaration I declare th
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Acknowledgments There are many thin
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Table of Contents Abstract Author
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TABLE OF CONTENTS 5.4 Results . . .
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Preface ‘Research is not an end i
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6. D. Angus, J-M. Kendall, J.P. Ver
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1 Introduction A technology push ap
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1.2. CCS OVERVIEW Figure 1.2: CCS s
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1.3. THESIS OVERVIEW for CO 2 to be
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1.3. THESIS OVERVIEW as microseismi
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2 The Weyburn CO 2 injection projec
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2.2. WEYBURN GEOLOGICAL SETTING Fig
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2.2. WEYBURN GEOLOGICAL SETTING N F
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2.4. EVENT TIMING AND LOCATIONS 500
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Page 37 and 38: 2.4. EVENT TIMING AND LOCATIONS Nor
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Page 41 and 42: 2.5. DISCUSSION 500 1000 1100 North
Page 43 and 44: 2.6. SUMMARY 2.6 Summary • CO 2 s
Page 45 and 46: 3 Inverting shear-wave splitting me
Page 47 and 48: 3.2. INVERSION METHOD the additiona
Page 49 and 50: 3.2. INVERSION METHOD 1. P-wave inc
Page 51 and 52: 3.2. INVERSION METHOD 180 160 140 C
Page 53 and 54: 3.2. INVERSION METHOD 2800 2800 260
Page 55 and 56: 3.2. INVERSION METHOD Loop over γ,
Page 57 and 58: 20 10 5 5 1 20 30 40 80 100 60 40 1
Page 59 and 60: 3.4. SWS MEASUREMENTS AT WEYBURN th
Page 61 and 62: 3.4. SWS MEASUREMENTS AT WEYBURN ei
Page 63 and 64: 3.4. SWS MEASUREMENTS AT WEYBURN ξ
Page 65 and 66: 3.4. SWS MEASUREMENTS AT WEYBURN da
Page 67 and 68: 4 2 2 3.4. SWS MEASUREMENTS AT WEYB
Page 69 and 70: 1 1 1 1 1 1 1 1 1 1 3.5. DISCUSSION
Page 71 and 72: 3.6. SUMMARY 3.6 Summary • I have
Page 73 and 74: 4 A comparison of microseismic moni
Page 75 and 76: 4.2. EVENT LOCATIONS 2400 Velocity
Page 77 and 78: 4.2. EVENT LOCATIONS 200 150 Northi
Page 79 and 80: 4.3. EVENT MAGNITUDES Pressure (MPa
Page 81 and 82: 4.3. EVENT MAGNITUDES 160 140 120 N
Page 83 and 84: 4.4. SHEAR WAVE SPLITTING 50 −3 E
Page 85: 4.5. INITIAL S-WAVE POLARISATION In
Page 89 and 90: 4.5. INITIAL S-WAVE POLARISATION of
Page 91 and 92: 4.6. INTERPRETATION OF SHEAR WAVE S
Page 93 and 94: 1 1 5 5 30 4.6. INTERPRETATION OF S
Page 95 and 96: 80 4.6. INTERPRETATION OF SHEAR WAV
Page 97 and 98: 2 3 3.5 4 5 2 1.8 1.4 4 4.6. INTERP
Page 99 and 100: 4.7. DISCUSSION 4.7 Discussion The
Page 101 and 102: pressure, P fl σ ′ ij = σ ij
Page 103 and 104: 5.2. EFFECTIVE STRESS AND STRESS PA
Page 105 and 106: 5.3. NUMERICAL MODELLING 5.3.1 Flui
Page 107 and 108: 5.3. NUMERICAL MODELLING MORE FLUID
Page 109 and 110: 5.3. NUMERICAL MODELLING (a) (b) Fi
Page 111 and 112: 5.4. RESULTS 0 500 1000 Depth (m) 1
Page 113 and 114: 5.4. RESULTS 1 0.9 0.8 Soft Med Sti
Page 115 and 116: 5.4. RESULTS Overburden Extension i
Page 117 and 118: 5.4. RESULTS 1z:100x:100y 1z:100x:5
Page 119 and 120: 5.5. SURFACE UPLIFT 1 0.9 0.8 Soft
Page 121 and 122: 5.5. SURFACE UPLIFT Figure 5.17: Ma
Page 123 and 124: 6 Generating anisotropic seismic mo
Page 125 and 126: 6.2. STRESS-SENSITIVE ROCK PHYSICS
Page 127 and 128: 6.3. A MICRO-STRUCTURAL MODEL FOR N
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6.3. A MICRO-STRUCTURAL MODEL FOR N
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6.4. CALIBRATION WITH LITERATURE DA
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6.4. CALIBRATION WITH LITERATURE DA
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6.5. COMPARISON OF ROCK PHYSICS MOD
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6.5. COMPARISON OF ROCK PHYSICS MOD
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7 Forward modelling of seismic prop
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7.2. SEISMODEL c⃝ WORKFLOW time s
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7.3. RESULTS FROM SIMPLE GEOMECHANI
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7.4. SUMMARY 7.4 Summary • I have
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8 Linking geomechanical modelling a
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8.2. MODEL DESCRIPTION Layer Thickn
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8.2. MODEL DESCRIPTION Unit E (GPa)
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8.3. RESULTS Marl Vugg 0.8 0.8 Norm
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8.3. RESULTS 15 10 Injector Produce
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8.3. RESULTS 2000 15 2000 15 1500 1
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8.4. A SOFTER RESERVOIR 8.4 A softe
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8.4. A SOFTER RESERVOIR 2000 15 200
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8.4. A SOFTER RESERVOIR 2000 Max SW
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8.5. DISCUSSION pore-pressure being
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8.6. SUMMARY 8.6 Summary • I appl
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9 Conclusions Geological storage wi
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calibrate. This model has been cali
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9.1. NOVEL CONTRIBUTIONS techniques
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9.2. FUTURE WORK Finally, the compa
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Bibliography Abt, D. L., Fischer, K
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BIBLIOGRAPHY Gassmann, F., 1951. Ub
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BIBLIOGRAPHY Kendall, J.-M., Pilido
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BIBLIOGRAPHY Sayers, C. M., 2002. S
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BIBLIOGRAPHY White, D., 2009. Monit
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A List of Symbols The table below l
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B In Support of Carbon Capture and
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Both China and India are aggressive
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Utsira rock properties vary signifi
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Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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