Alteration Rocks Analysis of SR-1 Exploration Well Cutting for Geothermal System Identification in Sokoria – Mutubusa Geothermal Field, Ende Regency, Flores Island, East Nusa Tenggara

Abstract

In geothermal research, alteration rocks analysis is an analysis knowing subsurface condition from a geothermal field, such as temperature condition when the alteration mineral and hydrothermal fluid were formed and then from that parameters, can be identify the geothermal system of research area. The aim of this research is in order to identification the cutting’s sample to interpretation mineral formed temperature, geothermal fluid and alteration type, and then it can be made the geothermal system in research area. The method which is used in this research are descriptive method and analithic method. The descriptive method in accordance with megascopis, petrography and PIMA (Portable Infrared Mineral Analyzer) to recognizing the alteration mineral accured at cutting sample of research’s well. The analithic method are used such as; analysis of calsite contens, anlysis of clay characteristic, analysis of alteration intensity, analysis of alteration range and analysis of magnetism. Those analysis are supporting the descriptive method’s data. Lithology research’s well is determined onto three rocks unit, there are; altered skoria unit, altered andesite unit and altered tuff breccia unit. With the accurance of altered mineral; montmorilonite, illite, kaolinite, chlorite, calsite, secondary quartz, garnet, epidote, magnetite, paragonite, nontronite, ferro oxide and pyrite. Alteration intensity have variation depend on the accurance alteration mineral percentage with range from unaltered until strong altered. Alteration type of research’s well are; argilic type with mineral alteration kaolinite montmorilonite as cap rock zone and propyllite type with mineral alteration chlorite - calsite – kaolinite - epidote as reservoir rock zone. With range subsurface temperature when alteration mineral formed between 300 – 2400 C, meanwhile 300 – 187,60 C for temperature log measurement. The geothermal system of reaserch area is convective geothermal system water dominated.