Effect of Carbon Dioxide Content on the Well and Reservoir Performances in the Kizildere Geothermal Field

Abstract

The Kizildere geothermal field is located on the Buyuk Menderes Graben in the Denizli and Aydin Provinces of Aegean region, Turkey. The field was discovered in 1968 and production for power generation has started in 1984. Bottomhole temperatures as high as 245 C have been recorded. The installed capacity of the initial power plant was 17 MWe. In 2013, an additional 80MWe power plant was installed. Plans to expand the power generation capacity of the field to 260 MWe are under way. One of the main features of the Kizildere geothermal field is the carbon dioxide content which is measured at various wells to be between 1 to 3.5% by mass. Carbon dioxide in geothermal reservoirs can have a considerable effect on the production behavior. The main effect of carbon dioxide is that even small amounts dissolved in the geothermal water can raise the flashing point of water and subsequently affects the production well performance significantly. In this study we present models for analyzing the production well behavior for geothermal reservoirs with dissolved carbon dioxide. Mixing of the reinjection water with the reservoir water causes drop in CO2 content of the produced water and this leads to drop in wellhead flowing pressure and temperature. Some of the production wells nearby the reinjection region in the Kizildere geothermal field clearly showed this behavior. This paper discusses the effect of CO2 in production wells´ wellhead performance and presents the actual well data. We also assess the overall performance of the carbon dioxide behavior in the reservoir and present future predictions of how the dissolved amount of carbon dioxide changes in the field.