Reinjection of the CO_2 into the Reservoirs of the Geothermal Waters in the Continental Rift Zones of the Menderes Massif, Western Anatolia, Turkey

摘要

Turkey has high potential for exploitation of geothermal waters which are distributed with high temperatures up to 287 °C within the Menderes Massif intensively. The geothermal waters are associated with the faults that strike preferentially NW-SE and NE-SW and also located diagonal to the general strike of the rift zones of the Menderes Massif in western Anatolia, Turkey. These NW-SE and NE-SW striking faults were probably generated by compressional tectonic regimes which lead to deformation of uplift between two extensional rift zones of the Menderes Massif. The active geothermal waters of Kizildere, Bayindir and Salihli and Alasehir in the continental rift zones of the Buyuk Menderes, Kucuk Menderes and Gediz represent typical examples in the study area. The meteoric waters in the drainage areas of the rift zones percolate at NE-SW and/or NW-SE trending fault zones and permeable clastic sediments into the reaction zone of the roof area of a magma chamber situated in a probable depth of up to 4-5 km where meteoric fluids are heated by the cooling magmatic melt and ascend to the surface due to their lower density caused by convection cells. The volatile components of CO_2, SO_2, HCl, H_2S, HB, HF, and He out of the magma reach the geothermal water reservoir where an equilibrium between altered rocks, gas components, and fluids performs. Thus, the geothermal waters ascend in the tectonical zones of weakness at the continental rift zones of the Menderes Massif in terms of hot springs, gases, and steams. These fluids are characterized by high to medium CO_2, H_2S and NaCl contents. 2.0 percent of the production of the geothermal waters in the area of the Menderes Massif displays CO_2 emissions. In order to consider the geothermal waters as environmental and human friendly energy, CO_2 emissions must be reinjected into the reservoirs of each geothermal waters. As alternative to inhibitors, it can be taken in consideration a reinjection of the waste CO_2 quantities into the reservoir of the geothermal waters for adjust of pH values of geothermal fluids. Approximately 2.0 percent of CO_2 in the production of the geothermal waters is available for reinjection into the reservoirs. A small amount of this total mass might be attributed to a correction of pH value of 6-7 of geothermal fluids in a reinjection process. An acid reinjection pH value can decrease an arising oversaturation of calcite and aragonite by the pH effect of reinjected geothermal waters. However, there are difficulties. A superficial blow on of CO_2 into reinjection fluid leads to push of dissolved gases in reinjection well, because high CO_2 contents at high pressures can be dissolved in deeper spheres of reinjection well. Therefore, CO_2 gases should be conducted to the depth below the solution depth in a separate intern pipe and must be reinjected into the reservoir of geothermal waters. However, this assumes previous condensing of CO_2 gases, because die pressure in the total gas column must overstep die pressure in the mixing depth. The geothermal waters in the continental rift zones of the Menderes Massif have CO_2 contents of up to 2.0 percent which represent very important environmental problems. Therefore, these CO_2 emissions must be reinjected into the reservoirs at the achievement of the geothermal energy.