Developing Systematic Workflow From Field Work to Quantitative 3D Modeling for Successful Exploration of Structurally Controlled Geothermal Systems

摘要

Ongoing research has shown that structurally controlled geothermal systems are associated with specific structural settings, such as terminations of major normal faults, accommodation zones, pull-aparts in strike-slip faults, displacement transfer zones, or step-overs in range-front faults. The structural framework of each of these principal structural settings is innately complex, and the permeable and productive areas are commonly spatially discrete, limited in some cases to a single part of an individual fault zone. Successful development of these systems relies on accurately defining these permeable up-flow zones in 3D space for precise well targeting and resource estimation. However, there is no single tool that can both define the detailed structural framework of a geothermal area and also define the individual parts of which faults currently host the geothermal fluids. Through recent and ongoing detailed studies of over 20 systems in the Great Basin region, we have been developing a systematic workflow that integrates multiple geologic and geophysical data sets. The workflow is centered on constructing an accurate and detailed 3D geologic map while using the same conventional geologic reasoning as is used in constructing 2D geologic cross-sections and maps of the ground surface. The 3D geologic map is then used to run quantitative 3D models, consider discrete geothermal indicator data sets relative to the entire 3D map, define a conceptual fluid-flow model, and select well targets.