Modelling Carbon Dioxide Content of a Liquid Dominated Geothermal Reservoir

Date

2023-12

Author

Tokel, Ali Berkay

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Geothermal energy is a renewable and clean energy source that can be used for electricity generation. The share of geothermal energy in the electricity production in Turkey has been increasing steadily with recent incentives imposed by the state. Geothermal reservoirs in Menderes and Gediz grabens of Turkey naturally contain significant amounts of carbon dioxide. Carbon dioxide content of a reservoir considerable effects the electricity generation due to its impact on flashing point of the brine. Although the carbon dioxide content in the reservoir may be beneficial for electricity generation, emission of carbon dioxide from these power plants has negative effect on the environment. For these reasons, some portion of the carbon dioxide produced from the Kızıldere Geothermal Field was reinjected back into reservoir to mitigate emissions as part of Geothermal Emissions COntrol (GECO) Project. To assess the safety and feasibility of the carbon dioxide reinjection, reservoir carbon dioxide levels and soil carbon dioxide fluxes were monitored. In this study, a lumped parameter model that can account for carbon dioxide content and soil carbon dioxide fluxes is developed. The developed model relates the soil fluxes to the carbon dioxide content of the reservoir by a parameter (θ). The model developed in this study is fine-tuned using field observations, including data on pressure, carbon dioxide content, and soil carbon dioxide fluxes. Through this calibration process, the parameter θ is established to be 10.8x10-6. The model is then utilized to forecast the carbon dioxide content in the pilot reinjection area over a period of five years under various carbon dioxide reinjection strategies. If the current operational parameters are maintained (no carbon dioxide reinjection), the carbon dioxide mass fraction in the study area is projected to decrease to 0.0115 over five years. For scenarios involving reinjection of water with 1 and 1.5 weight percent carbon dioxide, the predicted carbon dioxide contents after five years are 0.0121 and 0.0123, respectively.

Subject Keywords

Geothermal Energy, Lumped Parameter Modelling, Kızıldere, Soil Carbon Dioxide Flux

URI

https://hdl.handle.net/11511/110455

Collections

Graduate School of Natural and Applied Sciences, Thesis