293 Synthesis provide valuable data about subsurface materials. By acquiring and analyzing this data through specific geophysical surveys, we can better understand the subsurface properties and characteristics, offering important insights for exploring and managing subsurface resources and developing geotechnical engineering. Geophysical methods encompass various techniques, each designed to characterize specific properties. • Gravity and gravity-gradiometry are sensitive to density variations. • Magnetic methods respond to rock magnetization properties, including magnetic susceptibility and remanence. • Electrical and electromagnetic (EM) methods capture resistivity variations. • Seismic methods are influenced by both velocity and density variations. By measuring variations in the subsurface’s physical properties, geophysical surveys can provide valuable insights into geological features, helping to identify critical characteristics of geothermal systems before the costly process of drilling. Generally, no single geophysical method can characterize all the elements of a geothermal play. Each technique has unique strengths and limitations, responding to specific subsurface properties and functioning at different scales, depths, and spatial resolutions. Instead, multi-physics approaches combine several geophysical techniques, allowing experts to construct a more reliable picture of the subsurface. Geophysics for geothermal systems This book further illustrates the techniques and strategies that can be employed to investigate geothermal systems via geophysical methods. Surface geophysical methods enable the construction of a 2D or 3D geophysical model of the subsurface link to one or more physical parameters. Borehole methods help to investigate the nearby well and calibrate the models derived from the surface geophysical methods. As in any geophysical study, multi-physics approaches facilitate interpretation. By providing insights into the subsurface’s physical properties, geophysical methods help better understand, assess, and monitor geothermal resources. The goal is to enable engineers to optimize production, mitigate risks, and ensure the sustainability of the reservoir. Here is a selected list of the key information that geophysicists can contribute. • Identifying subsurface structures. • Mapping temperature distribution. • Characterizing rock types and reservoir properties. • Differentiating geothermal fluids. • Assessing fault activity. • Real-Time well steering during drilling.
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