Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 7. FORWARD MODELLING OF SEISMIC PROPERTIES 500 5000 Max SWS =0.76267% 400 Max SWS =0.71441% 4000 Y (m) 300 200 Y (m) 3000 2000 100 1000 0 0 100 200 300 400 500 X (m) (a) 0 0 1000 2000 3000 4000 5000 X (m) (b) 5000 Max SWS =0.27657% 4000 3000 Y (m) 2000 1000 0 0 1000 2000 3000 4000 5000 X (m) (c) Figure 7.2: Shear wave fast direction and splitting magnitude for a vertically propagating wave through the simple, medium stiffness reservoir models. The edges of the reservoirs are marked in red, and the maximum splitting amounts are given. 142
7.3. RESULTS FROM SIMPLE GEOMECHANICAL MODELS 1.) In the center of the reservoir, the horizontal stresses increase equally. No anisotropy develops. 2.) The edges of the reservoir can push into the sideburden, opening cracks parallel to the edge. Anisotropy develops with fast direction parallel to the edge. 3.) Outside the reservoir, the force from the expanding reservoir closes cracks parallel to the edge. This leave cracks perpendicular to the edge. Anisotropy develops with fast direction perpendicular to the edge. Figure 7.3: Cartoon depicting the horizontal stress redistribution around an expanding reservoir, demonstrating the SWS patterns seen in Figure 7.2. The red dashes indicate the resulting SWS pattern. by the expansion of the reservoir, increasing the horizontal stress perpendicular to the reservoir edge. As a result, the fast direction is orientated perpendicular to the reservoir. The maximum splitting magnitude modelled here is below 1%. Even a splitting magnitude of 1% may be hard to detect given that the maximum raypath length for a vertical wave through the anisotropic region is 75m. Therefore the splitting modelled here is at the limits of detectability. Additionally, in Chapters 3 and 4 I found that when inverting for anisotropy using splitting from microseismic events it is difficult to resolve more than one anisotropic fabric. Therefore detecting different regions of anisotropy with orthogonally polarised fast direction will be very challenging. Nevertheless, in Chapter 6 (Figure 6.9) I noted that the rock physics model does tend to underestimate splitting. Furthermore, the presence of fractures could serve to amplify the amount of splitting induced by stress changes. Additionally, while splitting of microseismic events might not be able to resolve adjacent anisotropic fabrics, splitting of 9C controlled source seismic data, or Amplitude Variation with Offset and Azimuth (AVOA), may be able to image such fabrics. This SWS pattern has been generated because there is a discontinuous edge between where pressure is increasing and where it is not. Therefore, these prediction have a limited applicability, because in reality reservoirs are often not bounded in this manner. Nevertheless, a sealing vertical fault would generate the kind of edge around which the modelled splitting pattern could develop. Such a feature would be of great importance for storage security, as an undetected sealing fault would prevent the dispersion of both the injected CO 2 and also the pressure wave through the target reservoir. We have seen that small reservoirs (or the equivalent, such as a compartmentalised large reservoir) are prone 143
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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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2.4. EVENT TIMING AND LOCATIONS 500
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2.4. EVENT TIMING AND LOCATIONS Nor
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2.4. EVENT TIMING AND LOCATIONS Fig
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2.5. DISCUSSION 500 1000 1100 North
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2.6. SUMMARY 2.6 Summary • CO 2 s
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3 Inverting shear-wave splitting me
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3.2. INVERSION METHOD the additiona
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3.2. INVERSION METHOD 1. P-wave inc
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3.2. INVERSION METHOD 180 160 140 C
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3.2. INVERSION METHOD 2800 2800 260
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3.2. INVERSION METHOD Loop over γ,
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20 10 5 5 1 20 30 40 80 100 60 40 1
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3.4. SWS MEASUREMENTS AT WEYBURN th
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3.4. SWS MEASUREMENTS AT WEYBURN ei
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3.4. SWS MEASUREMENTS AT WEYBURN ξ
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3.4. SWS MEASUREMENTS AT WEYBURN da
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4 2 2 3.4. SWS MEASUREMENTS AT WEYB
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1 1 1 1 1 1 1 1 1 1 3.5. DISCUSSION
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3.6. SUMMARY 3.6 Summary • I have
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4 A comparison of microseismic moni
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4.2. EVENT LOCATIONS 2400 Velocity
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4.2. EVENT LOCATIONS 200 150 Northi
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4.3. EVENT MAGNITUDES Pressure (MPa
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4.3. EVENT MAGNITUDES 160 140 120 N
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4.4. SHEAR WAVE SPLITTING 50 −3 E
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4.5. INITIAL S-WAVE POLARISATION In
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4.5. INITIAL S-WAVE POLARISATION 6
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4.5. INITIAL S-WAVE POLARISATION of
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4.6. INTERPRETATION OF SHEAR WAVE S
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1 1 5 5 30 4.6. INTERPRETATION OF S
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80 4.6. INTERPRETATION OF SHEAR WAV
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2 3 3.5 4 5 2 1.8 1.4 4 4.6. INTERP
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4.7. DISCUSSION 4.7 Discussion The
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pressure, P fl σ ′ ij = σ ij
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5.2. EFFECTIVE STRESS AND STRESS PA
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5.3. NUMERICAL MODELLING 5.3.1 Flui
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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
Page 145 and 146: 6.4. CALIBRATION WITH LITERATURE DA
Page 147 and 148: 6.4. CALIBRATION WITH LITERATURE DA
Page 149 and 150: 6.5. COMPARISON OF ROCK PHYSICS MOD
Page 151 and 152: 6.5. COMPARISON OF ROCK PHYSICS MOD
Page 153 and 154: 7 Forward modelling of seismic prop
Page 155 and 156: 7.2. SEISMODEL c⃝ WORKFLOW time s
Page 157 and 158: 7.3. RESULTS FROM SIMPLE GEOMECHANI
Page 159: 7.3. RESULTS FROM SIMPLE GEOMECHANI
Page 163 and 164: 7.4. SUMMARY 7.4 Summary • I have
Page 165 and 166: 8 Linking geomechanical modelling a
Page 167 and 168: 8.2. MODEL DESCRIPTION Layer Thickn
Page 169 and 170: 8.2. MODEL DESCRIPTION Unit E (GPa)
Page 171 and 172: 8.3. RESULTS Marl Vugg 0.8 0.8 Norm
Page 173 and 174: 8.3. RESULTS 15 10 Injector Produce
Page 175 and 176: 8.3. RESULTS 2000 15 2000 15 1500 1
Page 177 and 178: 8.4. A SOFTER RESERVOIR 8.4 A softe
Page 179 and 180: 8.4. A SOFTER RESERVOIR 2000 15 200
Page 181 and 182: 8.4. A SOFTER RESERVOIR 2000 Max SW
Page 183 and 184: 8.5. DISCUSSION pore-pressure being
Page 185 and 186: 8.6. SUMMARY 8.6 Summary • I appl
Page 187 and 188: 9 Conclusions Geological storage wi
Page 189 and 190: calibrate. This model has been cali
Page 191 and 192: 9.1. NOVEL CONTRIBUTIONS techniques
Page 193 and 194: 9.2. FUTURE WORK Finally, the compa
Page 195 and 196: Bibliography Abt, D. L., Fischer, K
Page 197 and 198: BIBLIOGRAPHY Gassmann, F., 1951. Ub
Page 199 and 200: BIBLIOGRAPHY Kendall, J.-M., Pilido
Page 201 and 202: BIBLIOGRAPHY Sayers, C. M., 2002. S
Page 203 and 204: BIBLIOGRAPHY White, D., 2009. Monit
Page 205 and 206: A List of Symbols The table below l
Page 207 and 208: B In Support of Carbon Capture and
Page 209 and 210: 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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