Types of commercial deposits of thermal underground waters and some views on the assessment of their reserves

Abstract

All known ground thermal occurrences of the world may be grouped into the following main industrial types, based on geological and hydrodynamic conditions: 1. 1. Thermal water occurences of large artesian basins of platform areas. 2. 2. Thermal water occurrences of small artesian basins of intermontane areas and submontane troughs of the Alpine zone of folding. 3. 3. Thermal water occurrences of crystalline massifs connected with fissure-vein systems of recent tectonic disturbances. The first type of the above thermal water occurrences occur usually at a great depth and are notable for a high salinity. Thermal water occurrences of the second type are characterized by smaller areal distribution but their exploitation resources, as a rule, are greatly higher than those of the first type. Among the thermal water occurrences of this type a group of thermal water occurrences confined to the areas of late and recent volcanism is clearly singled out. According to the generating capacity of thermal energetic resources and economic effectivity of practical use, they are of the greatest industrial interest. Thermal waters and superheated waters of volcanic areas are different regarding their high temperature, small depth of occurrence and low salinity. The resources and areal distribution of thermal water occurrences of the third type are, as a rule, small. In accordance with initial and boundary conditions, which predetermine the character of the ground thermal water flow, each of the above types of thermal water occurrences is divided into two subtypes. Thermal water occurrences of the first subtype are confined to bed-porous, bed-fissure or fissure-vein systems. The second subtype, called «focuså, is characterized by a highly specific mechanism of interaction of ground-waters in bed or fissure systems with ascending deeper confined thermal water along separate rupture dislocations. The purpose and scope of prospecting-exploration works and the technique of estimating exploitation resources, as well as technico-economical conditions of thermal water exploitation, depend upon the type of thermal water occurrences. According to the character of carrying out exploration works thermal water occurrences of the «focuså subtype is of special complexity.