SUBSURFACE GEOLOGY AND FLUID EVOLUTION OF THE CANGGA-PUMA GEOTHERMAL SYSTEM BASED ON WELL 50 AND 105R DATA, DOMPU REGENCY, WEST NUSA TENGGARA PROVINCE

• Main Author: Ilham Khudlori, Ayyubi
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/78819
• Institution: Institut Teknologi Bandung

The Cangga-Puma Geothermal System is located in the Hu'u District, Dompu Regency, West Nusa Tenggara Province. Several drillings have been conducted and have results yielded high-temperature wells (>200°C) and indications of alteration overprints. Geological maps and crosssections based on two wells have been created. But, to better understand the subsurface geology, needs data integration from several wells: wells that have been studied (82, 95, and 97) and the two focus research wells, namely well 50 and 105R in 3D model. The data used in this study include LiDAR, core description, hand specimen samples, and thin section analysis. To assist in distinguishing lithologic units and alteration zones, ASD-SWIR and ICP-OES data were employed. The results revealed 7 lithologic units: Kareo Andesite Lava Unit, Diatreme Breccia Unit, Crystal Tuff Unit, Maar Sediment Unit, Wawosigi Andesite Lava Flow Unit, Wawosigi Volcanic Breccia Unit, 1 st Pure Andesite Lava Flow Unit, and 2 nd Pure Andesite Lava Flow Unit. As for alteration zones, there are 8 zones: Quartz + Epidote + Calcite + Chlorite ± Anhydrite Zone, Quartz + Montmorillonite + Calcite + Chlorite Zone, Quartz + Sericite + Anhydrite + Calcite + Chlorite Zone, Pyrophyllite ± Alunite Zone, Dacite + Kaolinite + Quartz Zone, Quartz + Alunite Zone, Vuggy Quartz + Silicification Zone, and Montmorillonite + Kaolinite Zone. To understand the fluid history, fluid inclusions data (temperatur and sallinity), alteration mineral temperatures, and well temperatures were used. The results indicated a decrease in temperature in both research wells (50 and 105R). Meanwhile, the salinity analysis indicated the origin of the fluid to be magmatic fluid. Low resistivity (MT) anomaly related to clay mineral and diatreme. Whereas high resistivity anomaly related to Vuggy Quartz Zone.