Driving along the Büyük Menderes valley between Aydın and Denizli, you can spot steam plumes and cooling towers from the highway. The fields around Germencik, İncirliova, Salavatlı, Sultanhisar and Kuyucak have made Aydın one of the Turkish provinces with the largest number of geothermal power plants. One of the factors that most strongly shapes the output of these plants is the chemistry of the fluid coming up from below.
The Büyük Menderes Graben: why is it so hot?
Western Anatolia is a region where the Earth’s crust is being stretched in a north–south direction. This extension creates fault-bounded basins known as grabens, and the Büyük Menderes Graben is one of the largest. The faults act as natural pathways: rainwater percolates to depth, heats up and rises again. On its way it dissolves minerals from the rock and accumulates in the reservoir. Fields such as Germencik are among Turkey’s high-temperature geothermal reservoirs.
The fluid’s signature: high CO₂
The defining feature of Büyük Menderes fluids is the carbon dioxide they carry in solution as non-condensable gas. Its sources are the carbonate rocks (marble and limestone) around the reservoir and gases rising from depth. High CO₂ has two separate consequences for operators:
- Calcite scaling: as the fluid rises in the well and pressure drops, boiling (flashing) starts and CO₂ escapes into the gas phase. The pH rises, calcium carbonate becomes insoluble and deposits rapidly just above the flash point. Within a few months this scale can narrow the well bore and cut flow.
- Corrosion: CO₂ that stays in the liquid forms carbonic acid and accelerates corrosion of carbon-steel casing, separators and pipelines. The risk rises further if H₂S is present.
The same chemistry has an environmental side too: because most of the non-condensable gas is CO₂, work on gas reinjection and reduction is under way in the region. This does not change the chemical programme directly, but it does call for more holistic monitoring of the fluid.
Different problems in flash and binary plants
Flash and binary (ORC) technologies operate side by side in Aydın, and where problems appear depends on the plant type:
- Production wells: calcite scale around the flash point is the most common issue. See our guide to calcite scaling.
- Binary heat exchangers: as the brine is cooled, silica and metal silicates precipitate, heat transfer falls and net plant output drops. See heat exchanger and ORC fouling.
- Reinjection lines: silica in the cooled brine can cause injectivity loss in lines and wells. See reinjection line.
- Surface equipment: corrosion driven by CO₂ and oxygen ingress. See geothermal corrosion.
A short checklist for operators
- Refresh the full fluid analysis (Ca, alkalinity, silica, pH, gas content) regularly; field conditions change over time.
- Recalculate the flash depth from wellhead pressure and the temperature profile; the scale inhibitor must be delivered below this depth. See downhole dosing.
- Track calcium and alkalinity at the wellhead, approach temperature at the heat exchangers and injectivity at reinjection wells.
- Measure corrosion rates with coupons or probes, and evaluate the scale and corrosion programmes together.
What Biyopol Kimya offers the region
Our plant in Menderes, İzmir, is a short drive from the Aydın fields, which makes site visits, sampling and supply fast. With BiyoGeo CS scale inhibitor, BiyoGeo CI corrosion inhibitor and BiyoGeo HX heat exchanger conditioner, developed in a TÜBİTAK-supported R&D project, we build each programme around the field’s own fluid analysis. Read about our regional approach on the Aydın geothermal fields page, and see all solutions on geothermal power plant chemicals.
Looking for a fluid analysis and trial programme for your field? Contact us through the quote and sample request form.