The results of the joint research by scientists of Empress Catherine II Saint Petersburg Mining University, Saint Petersburg, Russia and Department of Petroleum Engineering, Shiraz University, Shiraz, Iran have been published in International Journal of Engineering. It is published by the Materials and Energy Research Center (Iran).
Petrothermal energy (heat from dry rock formations, a type of geothermal energy) is available on almost the entire surface of the Earth. However, it is difficult to achieve acceptable profitability for such power plants. The main problem is high capital costs, including drilling. Meanwhile, according to experts’ estimates, there are about 30 million depleted oil and gas wells worldwide. These can be used to access geothermal resources.
A Russian-Iranian research group investigated the possibility of organizing geothermal energy production using carbon dioxide (CO₂) injection technology into depleted formations of oil and gas fields at the final stage of their development.
A model of an energy system has been obtained, which includes injection and production wells 2800 meters deep, a geothermal reservoir, and a power unit. The circulating energy carrier is carbon dioxide. The system requires its cyclic use as a working fluid in a closed-loop for the power plant. In this case, the environmental effect is coupled with the economic one.
Optimal operating parameters for the station have been found: CO₂ flow rate, tubing diameters, and the thermodynamic conditions of the process. The simulation results, in particular, showed that increasing the tubing diameter reduces pressure losses and improves thermal power generation.
The considered power level for the microturbine power unit is in the range of up to 200 kilowatts. This corresponds, for example, to the electricity needs of a construction site or a shopping mall. If the number of injection and production wells is increased and a corresponding amount of carbon dioxide is provided, the energy system can be scaled up.
