A wellbore pressure - temperature (p-T) model for geothermal wells with multiple feed zones is presented. The flow rate, temperature and pressure may vary depending on the feed zones. The fluid considered is water containing low amount of CO2. Especially in Turkey, geothermal waters contain considerable amounts of CO2 dissolved in water. The presence of CO2 leads to two phase flow at higher pressure conditions than the vapor pressure of water. The wellbore model considers all these conditions. The model assumes that the flow is in steady state and Henry's law is valid for CO2's partial pressure calculations. The main inputs of the model are reservoir properties and the depths of the feed points. The main outputs are pressure and temperature profiles. If measured profiles of temperature and pressure are available then the model can be used to estimate the mass fraction of CO2.

Dynamic temperature profiles measured at some wells in Afyon Omer-Gecek geothermal field in Turkey showed multi-feed wellbore behavior. The multi-feed p-T wellbore model developed in this study was applied to analyze the p-T profiles of one of the wells, the well AF-21. There are two feed points in the wellbore, one of which is cooler. The field data from the AF-21 well was analyzed with the model and a good match between the calculated and measured data was obtained. Also the CO2 content was estimated from the match. This paper discusses the analysis procedure as well as the results obtained from the modeling approach.

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