Kajian Skaling Silika dan Sulfida di Lapangan Panas Bumi Dieng, Jawa Tengah
The study of silica and sulfide scaling of Dieng Geothermal Field, Central Java, was done by analyzing the water, rocks, and scales chemistry at seven production wells at Dieng, i.e. HCE-7B, 7C, 28A, 29, 30, 30A, dan 31. The objectives of the research were to investigate the silica scaling formation process at the surface facilities, and the sulfide scaling within the production wells‟ casings.
The methods that has been used in this study include the analysis of the water and base metals (Pb, Zn, Cu) geochemistry, XRD, and SEM-EDS. Regarding to the analysis calculations and results, the silica scaling formation on the surface facilities at each production well was affected and controlled by the change of temperature, pressure -that induced flashing to occur, and the solute pH. The deposition rate of silica scaling was strongly affected by the SiO2 concentration within the fluid and the mass flowrate.
The sulfide scaling occurred due to the change of casing diameter and boiling/flashing, the significant change of temperature gradient (from 200 to 100oC), and the change of pressure control, from lithostatic to hydrostatic pressure.
The type of sulfide minerals formed at Well HCE-7B were galena and sphalerite. Galena dominated the composition of sulfide scaling. While at Well HCE-7C, sulfide minerals consisted of galena, sphalerite, and chalcopyrite. Sphalerite dominated the composition of sulfide scaling.