8 Geophysics in Geothermal Exploration Chapter 7 • Seismic inversion and characterization applied to geothermal energy 223 R. Baillet, T. Chrest, T. Defreminville and E. Masse 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 Chapter 8 • Seismic anisotropy applied to geothermal prospection 241 R. Baillet, N. Desgoutte, V.Thomas and J. Caudroit 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
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