Sanyal Temperature Classification: High Temperature
Reservoir fluid between 230°C and 300°C is considered by Sanyal to be "high temperature."
"Above a temperature level of 230°C, the reservoir would be expected to become two-phase at some point during exploitation. The next higher temperature limit of 300°C is rather arbitrary; changing it by perhaps up to 20°C will not affect the classification. For this class of resource, as well as for classes 6 and 7, well productivity varies within an extremely wide range, depending on reservoir flow capacity as well as the extent of steam saturation in the reservoir, which, together with the relative permeability characteristics of the reservoir, determines the steam fraction in the mobile fluid phase. Individual well productivities as high as 50 MWe have been reported for fields in classes 5 through 7" (reference: http://www.geothermal-energy.org/pdf/IGAstandard/SGW/2005/sanyal1.pdf).