TINGKAT SULFIDASI FLUIDA PANAS BUMI DITINJAU DARI KANDUNGAN MINERAL SULFIDA DIDALAM KERAK SILIKA PADA PIPA SEPARATOR WELL PAD 7 LAPANGAN PANAS BUMI DIENG

Dieng Geothermal Field is located in Banjarnegara and Wonosobo, Central Java has been utilized for power generation totaling 60 MWe which is extracted from the geothermal energy. During the exploitation and production processes, there is silica scaling deposited, especially in the production pipe. It happens in the separator well pad 7, silica scaling rich-sulphide mineral is deposited inside the separator and reduce the fluid capacity of the pipe. There is a texture similar with quartz vein in the epithermal deposit, crustiform banded and colloform banded. Silica scaling mainly composed of amorphous silica, and also sulphide mineral and silicate mineral. The sulphide mineral of silica scaling are chalcopyrite, pyrite, sphalerite, galena and pyrrhotite. The silicate mineral of silica scaling are half-altered plagioclase, pyroxene, and quartz. The existence of pyrite is indication of an intermediate sulphidation deposit. The existence of pyrrhotite is indication of a low sulphidation deposit. According to the sulfiide mineral composition, the existence of pyrite and pyrrhotite can concluded that the sulphidation state is reducing from intermediate to low. So that, the sulphidation state of geothermal fluid based on the sulphide mineral composition of silica scaling is low-intermediete. Based on the mineragraphy analysis, the first formed of sulphide mineral is chalcopyrite, and then follow by pyrite, sphalerite, galena and pyrrhotite. Crustiform banded and colloform banded of the silica scaling indicate that the sulphide minerals deposited by the presipitation of hydrothermal fluid and the boiling process inside the separator