USE OF COMPUTER MODELLING FOR THE KHANKALA GEOTHERMAL WATERS SUSTAINABLE EXPLOITATION

Abstract

The relevance of the research is caused by the need of achieving sustainability in exploitation of geothermal waters. Temperature drop of geothermal reservoir during the re-injection of used fluid is the most important problem of long-term operation, the forecast of which is possible with the help of computer modelling. The main aim of the research is to forecast the temperature changes during the Khankala field exploitation, consider various development scenarios and propose possible solutions to achieve sustainability in field operation. Objects of the research are the Khankala field; doublet circulation system of the Khankala geothermal station. Methods: computer modelling of temperature changes of the geothermal resource; assessment and analysis of possible variants for periodic exploitation of the field; calculation of the total heat generation and the final temperature of the geothermal reservoir at the time of shutdown for various operating options. Results. Temperature drop in a production well will start after 6–7 years of exploitaion in the planned mode at the Khankala field. Periodic short-term operation and shutdown (10-year cycle, 100 years in total) allows more heat to be generated compared with longer operation (50-year cycle, 100 years in total), while the second variant makes it possible to achieve a higher temperature recovery in the production well. In the case of a significant decrease in temperature after a certain period of the XIII layer exploitation, periodic use of various productive layers (IV–VII, XVI or XXII) is proposed to ensure the sustainability of the geothermal station. Development of the XIII layer is possible after a period of stopping due to the relatively high rate of temperature recovery. Wells should be placed parallel to the two main faults of the Khankala field, with the productive well in the south and the injection well in the northern part, since the natural flow of groundwater can slow down the expansion of the cold front to the productive well. The installation and periodic use of two or more circulation systems can provide the greatest stability in long-term operation. However, the rationality of this method, which requires large additional costs at the initial stage of project implementation, is a complex issue. The choice of operating mode requires consideration of hydrogeological, geothermal, economic and technical aspects with the joint participation of hydrogeologists, geothermal specialists, technologists and economists.

Keywords

• renewable energy resources
• geothermal waters
• sustainable exploitation
• doublet
• modelling
• khankala field