Predictive reservoir modeling for CO2 sequestration in Kızıldere reservoir using multiple inter-well tracer tests

Date

2023-9-08

Author

Sevindik, Doğuhan Barlas

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Geothermal energy is generally considered a clean and sustainable energy source compared to fossil fuels. However, there exist geothermal fields in Turkey where a high amount of non-condensable gas (NCG) with 98% CO2 composition is co-produced with reservoir fluids. Thus, it is crucial to mitigate the co-produced NCG by re-injecting the captured gas back into the reservoir. In that regard, numerical reservoir models are significant tools for understanding the subsurface flow process and predicting the possible outcomes of the re-injection in the long term. In this study, a localized numerical reservoir model is developed centered across the pilot brine-CO2 injection well to characterize the flow paths of the Kızıldere geothermal reservoir to predict the impact of the injection. The natural state model of the field has been calibrated to obtain the initial conditions of the reservoir model with less than a 10 % error tolerance for the PT observations. To characterize the flow characteristics in the reservoir, chloride is assumed to be a conservative species for which the gradual enrichment of the chloride concentrations is matched across the observation wells. Furthermore, two slug tracer tests have been performed from the pilot injection well and from the northernmost injection well by using naphthalene-sulphonates for which the calibration across the possible flow paths in the Kızıldere reservoir is achieved accordingly. Consequently, a high degree of quantitative and qualitative characterization of the flow paths in the Kızıldere geothermal reservoir has been achieved. Based on the calibrated model, the impact of CO2-brine injection has been predicted under different injection scenarios which consist of varying injection rates and durations, and constant and varying pressure conditions. The results of the CO2-brine injection showed that approximately 20% of the injected CO2 reaches back into the production wells until 2030 ensuring a safe CO2 sequestration in the Kızıldere geothermal reservoir. Furthermore, under certain conditions, it has been estimated that a total of 200 Mt of CO2 can be stored in the Kızıldere reservoir by commencing all of the re-injection wells.

Subject Keywords

Tracers, TOUGH2, CO2 sequestration, Geothermal, Kızıldere

URI

https://hdl.handle.net/11511/105625

Collections

Graduate School of Natural and Applied Sciences, Thesis