In the early stages of geothermal explorationGeothermal exploration, geochemical surveysGeochemical survey are typically conducted prior to drilling, using silica and cation geothermometersCation geothermometer as summarized in Table 10.1. During the drilling phase, borehole temperature profilesTemperature profile can be categorized into six types, as illustrated in Fig. 10.5, with particular emphasis on fluid convection patterns inferred from geophysical anomaliesGeophysical anomalies associated with subsurface fractures. In addition, fluid inclusion analysis is recommended to improve the estimation of deep reservoir temperatures at this stage.