The Effect of Temperature and pH on the Formation of Silica Scaling at Dieng Geothermal Field, Indonesia

Abstract

Dieng Geothermal Field has been long encountered with a severe production issue regarding to silica scaling, in which has also been a serious problem in many other water-dominated hydrothermal fields. This paper examines silica scaling occurence in the surface facilities of Dieng Geothermal Field, e.g. separator, brine pipeline, and weirbox, and thus most likely has affected adversely to the production activities of the field. Accordingly, the precipitation of silica is highly dependent on temperature and pH of fluid. In which, the estimation of silica precipitation at two representative production wells, Well A and Well B, was obtained by sampling of separator water and calculating the SiO2 concentration within the brine. The value of silica deposition was obtained by calculating the difference between the value of dissolved SiO2 with the solubility of amorphous silica curve in respect of the temperature and pH. The result of this research shows that the process of silica scaling formation at the surface facilities of Dieng Geothermal Field is controlled more by temperature and pressure change compared to pH. The solubility of amorphous silica increases significantly at pH more than 7 in both of separators in Well A and Well B, and pH more than 8 in both weirboxes.