Study on Injecting Low Temperature Geothermal Brine

Abstract

The injection capacity of wells in the Otake Hatchobaru geothermal fields decreases several tons percent a year. When the low temperature geothermal brine, which was utilized for binary cycle power generation or others by using of heat exchanger, is injected to underground, it is presumed that the deposition rate of silica scale and decrement in injection ability of wells are accelerated. Then, brine transmission test was carried out to know the behavior of scale deposition under various conditions by using of the equipment which is composed of five columns connected to each other in series and packed with some materials to simulate a injection zone. From the above test, it is found that the scale deposition is occurred remarkably in the upper part of the first column and that the decreasing rate of permeability is conspicuous in that part. On the other hand, when pH of geothermal brine was adjusted to about 5, the clogging in the vessel became very scarce. From these results, the condition to prevent the decrement of the injection capacity of wells is found.