Reinjection Problems in Overpressured Geothermal Reservoirs

Abstract

As known, geothermal systems have developed in highly fractured media and therefore, they have low formation pressures by their nature; especially vapor dominated systems have abnormally low pressure without any operational problems for the field management s. In several cases encountered in the literature, reinjection is conducted by gravity since formation pressures are low and water levels in the wells remain below the surface.

In Turkey, most geothermal systems are slightly overpressured by either topographically forced terrain convection or high gas partial pressures due to high dissolved CO2 content of geothermal fluids or both. Reinjection in this type of geothermal systems is difficult because it requires high wellhead injection pressures increasing both investment and operational costs substantially.

In this study, field reinjection experiments in overpressured geothermal systems prior to and after exploitation and are reported. The results of modeling studies for the prediction of behavior of geothermal systems under reinjection are presented. Possible solutions, some of tham field specific; for this problem are also given.