Technologies of geothermal resources development in South of Russia

Abstract

A technology has been proposed for the integrated development of low-temperature geothermal resources for using their thermal and water potentials for various purposes. The possibility is substantiated for efficient development of geothermal resources by construction of binary geothermal power plants (GeoPP) using idle oil and gas wells that will significantly reduce capital investments for their building. The East Ciscaucasian artesian basin situated in the South European part of Russia has a number of fields with idle wells that can be converted to thermal water production. Involving the entire fund of idle wells will make it possible to obtain up to 300 MW of summary net capacity at a geothermal power plant. This work proposes a deployment of hybrid technology of geothermal power plant coupled with combined cycle plant of gas turbine type (further GCP) for the effective utilization of medium-temperature thermal waters (80–100 °C). These technologies are shown to be promising for using such water for electricity generating with high efficiency. A comparative analysis was carried out for GeoPP and GCP operating on medium-temperature water, which has shown the advantage of the latter. According to the calculations, the implementation of hybrid technology at the Thernair field in Makhachkala town will make it possible to get a power plant capacity of up to 60 MW. The prospects of integrated processing of high-temperature geothermal brines are shown. The technological diagrams are presented where the electricity generated at a binary GeoPP is used in the unit for the chemical components extraction. The estimated parameters for the Berikey geothermal field are given. The proven reserves of the Berikey field thermal brines are shown to be promising for output more than 2000 tons of lithium carbonate annually. The prospects of integrated processing of high-temperature geothermal brines in the Tarumovka geothermal field have been presented. The thermal energy of the geothermal brine can be converted into electricity in a binary geothermal power plant using a low-boiling working agent. The Rankine thermodynamic cycles have been considered realized in the secondary circuit of the GeoPP at different temperatures of evaporation of the working agent isobutane. The most effective in terms of maximum power generation is a supercritical cycle, close to the so-called “triangular” cycle with an evaporation pressure pe = 5.0 MPa. The spent brine with a low temperature from the GeoPP will go to a chemical plant, where the main chemical components, namely, lithium carbonate, magnesia, calcium carbonate and sodium chloride will be extracted according to the developed by us technology for the integrated utilization of hydrothermal brines. For the production of valuable inorganic materials, the electricity generated at the GeoPP may be applied. The need is shown in the priority integrated processing the associated highly saline brines of the Yuzhno-Sukhokumsk group of oil and gas wells in Northern Dagestan. At present, the associated brines with a radioactive background exceeding permissible standards are dumped onto surface filtration fields. Technological solutions for their decontamination and development have been proposed.