Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 8. LINKING GEOMECHANICAL MODELLING AND MICROSEISMIC OBSERVATIONS AT WEYBURN Unit a 0 ξ 0 B N /B T Marly 0.0006 0.125 0.51 Vuggy 0.0006 0.02 1.0 Table 8.3: Inverted rock physics properties for the Marly and Vuggy samples described in Brown (2002). 3600 Marl 5500 Vugg 3400 3200 5000 Velocity (m/s) 3000 2800 2600 2400 2200 Velocity (m/s) 4500 4000 3500 2000 1800 3000 1600 0 5 10 15 20 25 30 Pressure (MPa) (a) 2500 0 5 10 15 20 25 30 Pressure (MPa) (b) Figure 8.3: Observed ultrasonic P (solid lines) and S (dashed lines) velocities (symbols) and back calculated values (lines) as a function of stress for the Marly (a) and Vuggy (b) units. shown in Figure 8.3, and I note an excellent match. The average mismatch between modelled and observed velocities is 0.5% - equal to the experimental errors in measurement (Brown, 2002). The crack density tensors as a function of the applied stresses are plotted in Figure 8.4. These inverted values are used in the subsequent section to model changes to P-wave velocity and shear wave splitting. No ultrasonic measurements on overburden materials are available, so generic values are used. 152
8.3. RESULTS Marl Vugg 0.8 0.8 Normalised crack density 0.6 0.4 0.2 Normalised crack density 0.6 0.4 0.2 0 0 −0.2 0 5 10 15 20 25 30 Pressure (MPa) (a) −0.2 0 5 10 15 20 25 30 Pressure (MPa) (b) Figure 8.4: Crack densities of the Weyburn Marly (a) and Vuggy (b) rocks inverted from velocity observations (symbols) and using stress-sensitive modelling (lines). The 2nd order tensor components (solid lines) and 4th order tensor diagonal (dashed lines) and off-diagonal (dotted lines) components are shown. 8.3 Results 8.3.1 Stress evolution and failure The total simulation run lasts 4 years - one year pre-production, two years of production, one year of injection. As in Chapter 5, the results I will now discuss are output by ELFEN at equally spaced, user defined timesteps. In Figure 8.5 I plot the vertical effective stress in the reservoir and overburden after injection. Around the injection wells there is a lower effective stress due to pore pressure increase, while there is a higher effective stress around the producing wells. In the overburden there is increase in effective stress above the injection wells, as the expanding reservoir pushes into the overburden, while the compaction of the reservoir reduces the effective stress above the production wells in the overburden. However, these stress effects in the overburden are small. To compute the fracture potential I use equation 5.22 and the values for cohesion and angle of friction measured from core samples by Jimenez Gomez (2006). These are given in Table 8.4. Of course, these values represent the strength of intact rock, and not the planes of weakness which would be the first places to experience shear failure. Therefore, the high value for cohesion found by Jimenez Gomez for the evaporite is probably unrealistic, so I use an arbitrarily reduced value. I am most interested in the change in f p , whether it increases or reduces, which is relatively insensitive to the values of χ and ϕ f , rather than absolute magnitudes of f p . Therefore the choice of these values is not particularly important. In Figure 8.6 I plot the evolution of fracture potential through time in the reservoir and overburden at the injection and production wells, while in Figures 8.7 and 8.8 I plot snapshots of the fracture potential before production begins (ELFEN output timestep 3), during production (timestep 8), after 153
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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
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 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: 8.2. MODEL DESCRIPTION Unit E (GPa)
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
Page 211 and 212: Utsira rock properties vary signifi
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