Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

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CHAPTER 4. A COMPARISON OF MICROSEISMIC MONITORING OF FRACTURE STIMULATION DUE TO WATER VERSUS CO 2 INJECTION Depth (m) 2800 2820 2840 2860 2880 2900 2920 0 2 4 6 8 10 (a) Depth (m) 2540 2560 2580 2600 2620 2640 2660 0 2 4 6 8 10 (b) Figure 4.7: Histograms of event depths during (a) water injection and (b) CO 2 injection. The injection depths are marked by the dotted red line. There is a greater spread in event depths during CO 2 injection. injection pressures between 16 and 22 minutes during water injection correlates with a drop in event magnitudes. During CO 2 injection, the initial stepped increase in injection pressures matches the stepped increase in event magnitudes. This correlation between injection pressures and event magnitudes can be tested more directly by computing the correlation coefficients between magnitude and the injection pressure at the time the event occurs. The statistical significance of the correlations is computed using a t-test, with the null hypothesis that there is no correlation. I consider the water and CO 2 cases separately. If the magnitudes are independent of fluid properties, then combining the datasets should not decrease the correlation. Therefore I also compute correlation for all the data points together. The correlation coefficients and statistical significance of correlation are given in Table 4.1. In Figure 4.11 I plot the event magnitudes as a function of the injection pressure. The best linear fit lines are shown for water and CO 2 separately and for the overall dataset. The data are quite scattered, and the correlation coefficients are not particularly high. Nevertheless, during water injection, and for the combined data, the correlation is significant at the 99% level. The correlation coefficient for CO 2 injection is poorer, and lacks good statistical significance. From Figure 4.11 it appears that the events during CO 2 injection have slightly higher magnitudes than during water injection at the same pressures. Although no exact relationship should be inferred from this data, we suggest that larger event magnitudes should be expected during periods of higher injection pressures, regardless of the compressibility of the injection fluid. Above I have noted some differences between water and CO 2 injection. I also note that there is a greater temporal spread of events during water injection, while the majority of events during CO 2 injection occur during the first 25 minutes. However, the most striking observation is the similarity of the response from the two fluids. The injection rates and pressures used during both stages are similar, and the result is that event magnitudes and rates of seismicity are also similar. There is certainly no evidence to suggest that CO 2 - the softer hammer - has induced less seismicity than water. 62
4.3. EVENT MAGNITUDES 160 140 120 Northing (m) 100 80 60 40 20 Recording well Injection well 0 0 50 100 150 Easting (m) 2500 2550 Perf shots Geophones (a) Depth (m) 2600 2650 2700 2750 −50 0 50 100 150 200 Easting (m) (b) Figure 4.8: Map (a) and cross-section (b) views of event locations during CO 2 injection. The location of the recording well is at (0,0), and the injection well is shown. Error bars represent those calculated automatically by SeisPT c⃝ . The events fall along a trend at 120 ◦ , and some events occur at depths well above the injection depth. 63
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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
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
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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 and 60: 3.4. SWS MEASUREMENTS AT WEYBURN th
Page 61 and 62: 3.4. SWS MEASUREMENTS AT WEYBURN ei
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: 4.3. EVENT MAGNITUDES Pressure (MPa
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
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
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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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