Geothermal resource assessment aims to determine the condition of reservoir as well as to estimate production capacity of a geothermal field. The assessment is conducted by collaborating the available data, such as surface exploration data (geological, geochemical, and geophysical data), exploration and production drilling data, as well as monitoring data. The completeness and quality of available data are the main components to be confirmed at the beginning, since they are very important to understand the geothermal system and to provide recommendations for further development strategies. since it will be used for economic analysis which will then influence important decisions on the development of a geothermal field.

A conceptual model is describing the main physical features of the geothermal reservoir, such as estimation of the boundary, thickness, depth (TOR), and temperature. Another primary geothermal system informations such as possible heatsource, fault controlled, hydrogeology, and development constraint (acidity & scalling), will also be reconstructed based on evaluation of the available data. This conceptual model has an important role as the basis of well targeting, reservoir modeling and assessment, as well as development planing.