| Abstract |
Good reservoir engineering practice is a must for making accurate future performance predictions in geothermal fields. Accurate performance predictions lead to good reservoir management. In almost all fields, a reservoir model is of necessity for providing good reservoir engineering practice. The model must be calibrated to all kind of data available. When future performance predictions are concerned, it becomes extremely important to integrate production data. Production data may consist of flow rates, wellbore pressures, wellhead pressures, average reservoir pressure and tracer data in geothermal reservoirs. Collecting wellbore pressures may not be possible at all times since a gauge needs to be lowered into the well. Wellhead pressures, although easy to obtain, may not be always be useful since they also contain all kinds of wellbore phenomena. Average reservoir pressures are very useful but is extremely hard to obtain and usually require observation wells to be used. Tracers give a good idea about inter-well connectivity but are applied seldom. Carbon dioxide exists in most geothermal reservoirs, especially the ones in Turkey. Usually the concentration of carbon dioxide is a function of depth. The deeper the wells, the more carbon dioxide content there is. With production this carbon dioxide is also produced. However, the reinjection water on the other hand does not contain any carbon dioxide. Hence when this water is reinjected, the concentration of carbon dioxide is changed and decreases with time and space. Sooner or later, the water with the decreased carbon dioxide content reaches the production wells causing a decrease in the carbon dioxide content at the production wells. Measuring the carbon dioxide content at the production wells is a very easy process and can be repeated whenever necessary. In this study, a model is constructed to simulate the behavior of the carbon dioxide content for geothermal reservoirs. Using the model, the carbon dioxide data is treated as if it were a tracer and leads to a better characterization of the reservoir. Furthermore, we also make use of existing models developed for tracers and for thermal applications for further characterization of a geothermal field. From the carbon dioxide data, connectivity between regions of injection wells and production wells can be quantified. However, at this point it is important to note that the models used in this study and the applications given are valid for liquid dominated geothermal reservoirs. |