PERUBAHAN KARAKTERISTIK FLUIDA RESERVOIR DI LAPANGAN PANASBUMI PATUHA, JAWA BARAT BERDASARKAN ANALISIS GEOKIMIA FLUIDA

• Main Author: Florentina, Ayu
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/47069
• Institution: Institut Teknologi Bandung

Patuha Geothermal Field is a two-phase fluid system with vapor-dominated which associated with Quartenary Patuha Volcano. Patuha Geothermal Field has been exploited since 2014 through operations by PT Geo Dipa Energy. Developments that have been conducted for the last 5 years would cause changes in the geothermal reservoir itself, especially in the reservoir zone. Geochemical monitoring is conducted to observe changes in fluid characteristics of Patuha reservoir from 2014 to 2018 and identify the causes of it. This study uses secondary data from three production wells (SS-1, SS-2, and SS-7) consists of nine drilling cuttings, data measurements of pressure and temperature, and drilling mud log reports, while the chemical data of condensate water and gas derived from ten production wells (SS-1 to SS-10) taken at the wellhead. This study uses two methods, namely geological method such as megascopic and microscopic observations of drilling cuttings especially from reservoir zone to determine the lithology and hydrothermal alteration, and geochemical method such as geochemical analysis of geothermal fluid. The geochemical analysis result will be compared with geological data to examine whether the reservoir changes are due to natural factors or exploitation effect. Lithology in reservoir consists of andesite lava and pyroclastic. Alteration parageneses consists of chlorite, epidote, illite, quartz, calcite, and anhydrite. Results of fluid geochemical monitoring show that there is a decrease in gas/steam ratio and less soluble/more soluble gases ratio (e.g. CO2/H2S) in from SS-1 to SS-6 and from SS-8 to SS- 10, except SS-7 that show an increase in gas/steam ratio and less soluble/more soluble gases ratio.