Geophysics in Geothermal Exploration

Cover I
Contents 5
Prefaces 11
Foreword 13
J.-L. Mari and G. Paixach 13
The authors 15
Introduction 25
J.L. Mari and G. Paixach 25
The Role of Geophysics in Geothermal Energy 25
Glossary of Geothermal Energy 26
Geothermal Energy in France 28
Book content 28
Reference 29
1. Overview of the different geothermal systems: role of geophysics in exploration and production 31
G. Paixach, H. Traineau, F. Bugarel, E. Lasne and C. Maïlhol 31
1.1 What is geothermal energy? 31
1.2 What are the main geothermal systems? 37
1.3 The role of geophysics 43
References 49
2. Surface geophysical methods 51
J.-L. Mari and G. Paixach 51
2.1 Physical properties of rocks and pore space properties 55
2.1.1 Porosity 57
2.1.2 Permeability 58
2.2 Geophysical methods 61
2.2.1 Gravity method 63
2.2.2 Magnetic method 68
2.2.3 Electrical and EM methods 69
2.2.4 Seismic methods 80
Conclusion 107
References 108
3. Borehole geophysical methods 115
J.L. Mari 115
3.1 Conventional logging methods 116
3.2 Hydrogeological methods 120
3.3 Full waveform acoustic methods 123
3.4 Borehole seismic method 129
Conclusion 140
References 141
4. Towards a revisited geothermal conceptual model in the Upper Rhine Graben 145
A. Genter, C. Baujard, C. Glaas and V. Maurer 145
4.1 Geothermal development in the Upper Rhine Graben 146
4.2 Evolution of the geothermal concept during the SsF adventure 148
4.3 Pre-exploration phase 153
4.4 Optimizing borehole design according to the geological knowledge of the reservoir 159
Conclusion and perspectives 160
Acknowledgments 161
References 161
5. DEEP ERT/IP for geothermal exploration and de-risking 165
A. Rosselli, C. Truffert, F. Barsuglia, F. Fischanger, A. Coletti, G. Morelli and S. Del Ghianda 165
5.1 Context 165
5.2 Why electrical resistivity tomography is useful? 166
5.3 Deep electrical resistivity tomography for geothermal exploration – an Italian example 166
5.3.1 Unconventional ERT data acquisition 167
5.3.2 Acquisition methodology 169
5.3.3 Acquisition layout 170
5.3.4 Current transmissions 172
5.3.5 Quality control 173
5.3.6 Processing of resistivity and chargeability measurements 175
5.3.7 Results 177
Conclusion 180
6. The use of passive seismic methods for Geothermal exploration and monitoring 181
T. Kremer, J. M. Ars, T. Gaubert-Bastide, K. Khazraj and C. Voisin 181
Introduction 181
6.1 Methods 185
6.1.1 Seismological analysis 185
6.1.2 Ambient noise seismic interferometry (ANSI) 189
6.1.3 Tomography 190
6.1.4 Monitoring 191
6.2 Passive seismic methods for geothermal exploration 193
6.2.1 Seismological analysis 194
6.2.2 Ambient noise seismic interferometry (ANSI) 204
6.2.3 Integration into the geothermal exploration workflow 206
6.3 Geothermal monitoring 208
6.3.1 Seismological analysis monitoring 208
6.3.2 Ambient noise seismic interferometry monitoring 210
Concluding remarks 214
References 216
7. Seismic inversion and characterization applied to geothermal energy 223
R. Baillet, T. Chrest, T. Defreminville and E. Masse 223
Introduction 223
7.1 Technical background 224
7.1.1 Seismic gathers and partial stacking 224
7.1.2 The subsurface as an isotropic elastic medium 225
7.1.3 Convolution and resolution 226
7.2 Seismic inversion 228
7.2.1 About seismic conditioning 228
7.2.2 Wavelet extraction and optimization 228
7.2.3 Construction of a low-frequency model 229
7.2.4 Performing a seismic inversion 230
7.3 Introduction to seismic characterization 232
7.3.1 Exploring well response through a petro-elastic model building 232
7.3.2 Seismic attributes related to faults and fractures 234
7.3.3 Characterization empowered by machine learning 235
7.4 Example: identification of lithology, good porosity and fractured areas through a seismic inversion study 237
Conclusions and perspectives 239
References 239
8. Seismic anisotropy applied to geothermal prospection 241
R. Baillet, N. Desgoutte, V.Thomas and J. Caudroit 241
Introduction 241
8.1 Technical background 242
8.1.1 The HTI and VTI models for anisotropy models 242
8.1.2 Azimuthal stacking and required processing 243
8.2 Velocity versus Azimuth (VVAz): a shift detection methodology 244
8.3 Amplitude versus Azimuth (AVAz): an inversion methodology 245
8.4 Ellipse fitting on properties to estimate the anisotropy 245
8.5 From anisotropy to fracture attributes 247
8.6 Case study: Fracture characterization through azimuthal inversions to prospect the geothermal potential of Geneva basin 248
8.6.1 Processing, conditioning, shift detection 248
8.6.2 Model-based inversions 250
8.6.3 Results and way forward 251
Conclusions and perspectives 254
References 254
9. Defining high enthalpy geothermal drilling target with multi-physics integrated exploration program. Mayotte’s Petite-Terre Island case study 257
A. Stopin, C. Dezayes and T. Farlotti 257
Introduction 257
9.1 Integration of magnetotelluric data 260
9.2 Electric profile integration 264
9.3 Gravimetric data integration 267
9.4 Final model 268
9.5 Choice of the drilling target 271
References 272
10. Feasibility of monitoring cold fronts of geothermal doublets using 4D active electromagnetic techniques – a field trial in the Dogger play in the Paris Basin 275
F. Dubois, A. Stopin, F. Bretaudeau and P. Wawrzyniak 275
Introduction 276
10.1 Context 277
10.2 Acquisition 278
10.3 Receiver conception 281
10.4 Survey 282
10.5 Data processing 284
10.6 Detectability of the cold front 287
Conclusions 288
References 290
Synthesis 291
G. Paixach and J.L. Mari 291
A range of geothermal systems 291
A range of geophysical techniques 292
Geophysics for geothermal systems 293
From resource exploration to drilling project de-risking and asset monitoring 295
Conclusion 297
J.L. Mari and G. Paixach 297

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