Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 8. LINKING GEOMECHANICAL MODELLING AND MICROSEISMIC OBSERVATIONS AT WEYBURN 2000 Max SWS =0.079693% 1500 Y (m) 1000 500 0 1500 2000 2500 3000 X (m) (a) 2000 Max SWS =0.087055% 1500 Y (m) 1000 500 0 1500 2000 2500 3000 X (m) (b) Figure 8.9: Modelled shear wave splitting in the Weyburn reservoir (a) and in the evaporite caprock (b) after 1 year of injection. Tick orientations mark the fast direction, tick lengths mark the splitting magnitude, and the maximum splitting values are given. 158
8.4. A SOFTER RESERVOIR 8.4 A softer reservoir For the updated model, I reduce the Young’s modulus of the reservoir to 0.5GPa, while keeping all the other properties the same as for the first model. Therefore this model has a reduced reservoir:overburden stiffness ratio. The stress evolution for this model is plotted in Figure 8.10. The trends are the same as for the stiffer model (Figure 8.5). However, because in this case the reservoir is softer in comparison to the overburden, more stress can be transferred from the reservoir to the overburden (as demonstrated in Chapter 5). As a result, the changes in effective stress in the reservoir are reduced, while the changes in stress in the overburden are increased. 2000 17 2000 18 1500 16 1500 17.8 15 17.6 Y 1000 Y 1000 14 17.4 500 13 500 17.2 0 1500 2000 2500 3000 X 12 0 1500 2000 2500 3000 X 17 (a) (b) Figure 8.10: Vertical effective stress in (a) the reservoir and (b) the overburden of the softer Weyburn model after injection. The locations of the vertical injection wells (triangles) and horizontal producers (lines) are marked. The fracture potentials for the softer model are computed as for the first model, using the values in Table 8.4. The results are shown evolving through time in Figure 8.11, with snapshots across the reservoir and overburden in Figures 8.12 and 8.13 respectively. As with the stiffer reservoir, the fracture potential increases during production. However, the behaviour in the overburden is different once injection begins. The fracture potential at the producing wells is relatively unchanged. However, the onset of injection leads to a sharp increase in f p in the overburden above the producing wells. After an initial increase in f p in the overburden, the rocks around and above the injection well experience a decrease in fracture potential, returning to values similar to what they were before production had begun. This provides a much better match with observations made in Chapter 2, where events occur in the reservoir and overburden near the horizontal production wells, but few if any events are found near the injection well. In particular, this model shows how stress transfer into the overburden, which is promoted by a reservoir that is softer in comparison to the overburden (as noted in Chapter 5), can generate increases in shear stress, and therefore a greater likelihood of microseismicity, above the horizontal production wells. 159
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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
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5.3. NUMERICAL MODELLING (a) (b) Fi
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5.4. RESULTS 0 500 1000 Depth (m) 1
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5.4. RESULTS 1 0.9 0.8 Soft Med Sti
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5.4. RESULTS Overburden Extension i
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5.4. RESULTS 1z:100x:100y 1z:100x:5
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5.5. SURFACE UPLIFT 1 0.9 0.8 Soft
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5.5. SURFACE UPLIFT Figure 5.17: Ma
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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 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: 8.3. RESULTS 2000 15 2000 15 1500 1
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
Page 211 and 212: Utsira rock properties vary signifi
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Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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