Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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40 1 40 30 CHAPTER 3. INVERTING SHEAR-WAVE SPLITTING MEASUREMENTS FOR FRACTURE PROPERTIES 330° 0° 30° Anisotropy [%] 5 300° 60° 4 3 270° 90° 2 240° 120° 1 210° 180° 150° 0 (a) 0.2 0.18 100 80 60 80 100 0.2 0.18 200 100 80 100 0.16 0.14 100 60 40 0.16 0.14 60 40 30 20 60 80 0.12 0.12 5 10 5 γ 0.1 100 80 30 20 30 40 60 δ 0.1 100 80 80 0.08 0.06 0.04 0.02 100 100 60 80 0 0 20 40 60 80 100 120 140 160 180 Fracture Strike (α) 20 10 30 5 1 5 10 30 40 20 60 80 100 0.08 0.06 0.04 0.02 60 80 100 80 60 40 30 20 0 0 20 40 60 80 100 120 140 160 180 Fracture Strike (α) 10 80 60 40 20 30 60 (b) 0.2 30 (c) 0.18 200 40 30 40 80 0.16 0.14 100 80 60 20 10 5 20 60 0.12 40 30 30 δ 0.1 20 1 10 40 0.08 0.06 0.04 0.02 10 5 30 40 20 5 10 60 80 100 30 40 20 60 0 0 0.05 0.1 0.15 0.2 γ (d) Figure 3.7: Inversion results for the third synthetic example, with oblique arrivals, in the same format as Figure 3.5. The initial elastic model is still the same. There is still some trade-off between γ and δ, but both are better constrained than in Figure 3.6. 80 100 60 80 42
3.4. SWS MEASUREMENTS AT WEYBURN eigenvalue minimisation analysis. Cluster analysis is performed to chose the best cluster of results, from which the best result is selected. To conduct the analysis I use the SHEar-wave Birefringence Analysis (SHEBA) algorithm developed by Teanby et al. (2004b). Figure 3.8 shows the results for an example event from the dataset. In panel (a), the seismograms are rotated into the ray frame. There should be no P-wave energy on the Sv and Sh components. Panel (b) shows the S-wave components rotated into radial and transverse components with respect to the initial source polarisation, both before and after the splitting correction. After correction, the transverse component should be minimised. Panel (c) shows the S-wave particle motion before and after correction, and the fast and slow waveforms before and after correction. The particle motion should be linearised after the splitting correction, and the fast and slow waveforms should be similar. Panel (d) shows a contour plot of the energy on the transverse component after correction as a function of ψ and δt stacked for each of the 100 picked splitting analysis windows. An F-test is used to normalised this surface such that a value of 1 represents the 95% confidence interval. The cluster analysis is also displayed to the right of this panel. The upper cluster analysis panel shows the results (ψ and δV S ) of the splitting measurement for each of the splitting analysis windows. The lower cluster analysis panel maps the results for each window in ψ-δV S space, highlighting the clusters identified by SHEBA. Teanby et al. (2004b) provide a number of requirements that must be fulfilled if a splitting result is to be deemed reliable: • Well defined S-wave and successful rotation, with all the P-wave energy on the ‘c’ component ((quasi-)parallel to the raypath), and S-wave energy on the ‘a’ and ‘b’ components (perpendicular to ‘c’). • Energy minimised on the transverse component after correction. • Linear S-wave particle motion after correction. • Good match between fast and slow waveforms. • Unique solution, with a well defined and small error ellipse. If a splitting measurement fulfils all of the above criteria then it is graded class A. Should it fulfil all but one of the above requirements it is graded class B. If it fails to satisfy two or more of these criteria, it is classed as C and considered to be unreliable. 3.4.2 Splitting results for Weyburn Of the 688 possible splitting measurements (86 events × 8 receivers) only 72 provided class A and B results. This is a very low success rate for SWS analysis (compare with, for e.g., Al-Harrasi et al., 2010). There are two probable reasons for this. Firstly, the data generally has a very poor signalto-noise ratio. Secondly, many of the events are located close to the array (
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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
Page 9 and 10: Acknowledgments There are many thin
Page 11 and 12: Table of Contents Abstract Author
Page 13 and 14: TABLE OF CONTENTS 5.4 Results . . .
Page 15 and 16: Preface ‘Research is not an end i
Page 17 and 18: 6. D. Angus, J-M. Kendall, J.P. Ver
Page 19 and 20: 1 Introduction A technology push ap
Page 21 and 22: 1.2. CCS OVERVIEW Figure 1.2: CCS s
Page 23 and 24: 1.3. THESIS OVERVIEW for CO 2 to be
Page 25 and 26: 1.3. THESIS OVERVIEW as microseismi
Page 27 and 28: 2 The Weyburn CO 2 injection projec
Page 29 and 30: 2.2. WEYBURN GEOLOGICAL SETTING Fig
Page 31 and 32: 2.2. WEYBURN GEOLOGICAL SETTING N F
Page 33 and 34: 2.4. EVENT TIMING AND LOCATIONS 500
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Page 37 and 38: 2.4. EVENT TIMING AND LOCATIONS Nor
Page 39 and 40: 2.4. EVENT TIMING AND LOCATIONS Fig
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: 3.4. SWS MEASUREMENTS AT WEYBURN th
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 and 86: 4.5. INITIAL S-WAVE POLARISATION In
Page 87 and 88: 4.5. INITIAL S-WAVE POLARISATION 6
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
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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
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6.2. STRESS-SENSITIVE ROCK PHYSICS
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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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