Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 8. LINKING GEOMECHANICAL MODELLING AND MICROSEISMIC OBSERVATIONS AT WEYBURN (a) (b) Figure 8.2: Map views of (a) pressure (in bar) and (b) gas saturation at the top of the reservoir after one year of injection computed by the fluid flow simulation of Weyburn. The vertical injection wells are marked by the blue stars, the horizontal producing wells by red lines. Reflective symmetry along the x axis means that I can model only half the reservoir, and use symmetry arguments to complete the model. 150
8.2. MODEL DESCRIPTION Unit E (GPa) ν ρ (kg/m 3 ) Φ Layer top (m) Layer base (m) Overburden 5.0 0.25 2000 0.2 0 1210 Watrous 14.0 0.23 2000 0.1 1210 1410 Marly Evaporite 24.0 0.34 2700 0.05 1410 1430 Reservoir 14.5 0.31 2200 NA 1430 1470 Frobisher Evaporite 24.0 0.34 2700 0.05 1470 1490 Underburden 20.0 0.25 2500 0.1 1490 2490 Table 8.2: Material parameters for the units of the Weyburn geomechanical model. All layers are saturated with water with K=2.2GPa and ρ=1100kg/m 3 , except the reservoir, whose porosity and saturation are determined by the fluid-flow simulation. coarsening away from the wells. The different reservoir units are too thin to model separately, because as the aspect ratios of the elements become too high, so the solutions become unstable. One solution would be to reduce the mesh spacing in the x and y directions, allowing for a reduction in mesh spacing in the z direction. However, this would significantly add to the computation time of the models. Average material values across the reservoir are used instead. The top of the reservoir is at 1430m. The overburden is modelled to the surface, the underburden is modelled to a depth of 2480m. The non pay rocks are divided into 4 units: the evaporite units bounding the reservoir, the overlying Watrous shale, while the remainder of the overburden above the Watrous, and the underburden below the Frobisher evaporite are modelled with uniform representative properties. 8.2.3 Material properties The material properties for each unit are given in Table 8.2, based on core sample work by Jimenez Gomez (2006) and Chalaturnyk (pers. comm. 2007 ). The boundary conditions are set as for all the models in Chapter 5, where the top of the model is a free surface. The planes at the sides and base of the model are prevented from moving in a direction normal to the boundary, although they are free to move within the plane of the boundary (i.e. at the x − z boundary, nodes can move vertically and horizontally in the x direction, but not in the y direction). 8.2.4 Rock physics properties To predict the changes in seismic properties as outlined in Chapters 6 and 7 the crack density and aspect ratio parameters must be calculated using ultrasonic velocity measurements. The data that I use are taken from Brown (2002), who performed ultrasonic velocity measurements on Vuggy and Marly core samples with variations in the applied hydrostatic stress (Figure 8.3). Brown (2002) only makes measurements along one axis, so it is only possible to invert for an isotropic rock. I use the method outlined in Chapter 6 to invert these measurements for the rock physics parameters, given in Table 8.3. The values fit comfortably within the global trends identified during calibration with literature samples given in Chapter 6. A comparison between modelled and observed velocities is 151
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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
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 163 and 164: 7.4. SUMMARY 7.4 Summary • I have
Page 165 and 166: 8 Linking geomechanical modelling a
Page 167: 8.2. MODEL DESCRIPTION Layer Thickn
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
Page 211 and 212: Utsira rock properties vary signifi
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