The geochemical methods described in Chapter 6 allow investigators to develop a description of the thermal and chemical properties of possible geothermal reservoirs. They also support the development of geological and hydrological models that allow conceptualization of the physical framework within which a geothermal reservoir exists. Taken together, the shape, ow eld, stage of development, location of high-temperature zones, and possible drilling targets can be approximately delineated. However, rening these models to a higher spatial resolution is required before serious consideration is given to whether a resource is a good candidate for further development. To obtain this higher resolution, geophysical methods are employed to better dene the resource.