Anisotropic Probabilistic Imaging for the Seismic Characterisation of Earth's Subsurface

The exploration and responsible exploitation of geothermal resources requires accurately mapping and monitoring crustal fracture networks and fluids. Fractures provide the permeable pathways required for efficient energy production and knowledge of their subsurface distribution is necessary for optimal well placement. Locating supercritical fluids offer opportunities for enhanced energy production and identifying volcanic brines yield opportunities for the extraction of critical energy metals. Considering that drilling operations are the primary cost for geothermal projects, identifying such economically viable targets in advance of drilling activities is key to minimising financial risk. Fractures also play a significant role in induced seismic hazards as they decrease rock strength and provide hydraulic connections between fluid injection/extraction sites and faults that can be triggered by pore pressure perturbations. Clearly, characterising subsurface conditions is fundamental to geothermal exploration. To this end, seismic imaging is a well-established tool for constructing models of the subsurface. However, current methods face two important challenges/opportunities. (1) They neglect directionally-dependent material properties (i.e. anisotropy) created by the alignment of crustal fractures in response to the local stress field. This information is not only relevant for mapping fracture densities and fluid flow pathways but, if unaccounted for, can misguide interpretation of crustal properties. (2) Commonly applied imaging methods lack robust uncertainty quantification which hinders accurate model interpretation. My project, A-PISCES, addresses these issues by implementing a novel probabilistic approach to building seismic models of crustal reservoirs. This method will be developed and tested using data collected across the Hengill geothermal field (Iceland) providing a new view into geothermal fracture networks and their role in induced seismic hazards.