| Abstract |
Natural heat loss from geothermal systems is commonly assessed by measurements of individual discharge features (surface manifestation method). Results can be affected by systematic errors due to overestimation of surface steam losses and under-estimation of concealed outflows. For systems discharging neutral pH chloride waters, such errors can be detected by the balance method if reliable data for the equivalent upflow rate of deeper fluids are available (chloride flux studies). Recently, heat losses have also been determined by simulation studies, i.e. modelling of fluid flow in the natural state. Application of the balance method for the Yangbayain Field (Tibet) shows that too large values (between 215 and 485 MW) have been obtained by the surface method whereas the balance method indicates a total loss of about 90+30 MW, similar to that obtained by an independent simulation study (about 70 MW). Discrepancies are also indicated for the 1951/52 and 1954 surveys of the Tauhara and Wairakei Fields (NZ) where the balance method indicates total losses of about 350+70 MW whereas a significantly higher value (530 MW) was obtained by the surface method. |