Buletin Sumber Daya Geologi

ANALISIS ALTERASI DAN MINERALISASI MENGGUNAKAN METODE XRD, PETROGRAFI DAN MINERAGRAFI DAERAH PROSPEK CIHAUR, SIMPENAN, KABUPATEN SUKABUMI

Nadya Finlandini — 2024-11-13

The research is located in Cihaur, Sukabumi, West Java, occupied by the Jampang Formation, located in the Sunda-Banda Arc. The magmatic activity and complex tectonic setting in the arc have the potential to cause mineralization, resulting in several types of ore deposits such as porphyry, epithermal and skarn. The objectives of this research are to identify alteration, mineralization, and ore deposit types in the research area. The research methodology includes exploration drilling, alteration mapping, and laboratory analysis using XRD, petrography, and mineragraphy methods. Alteration of the research area consists of argillic alteration (illite, kaolin, and smectite), propylitic alteration (chlorite, epidote, and calcite), marbellized (95% calcite), and skarnization (clinopyroxene, wollastonite, chlorite-skarn, and epidote-skarn). In the skarn there are indications of a prograde stage characterized by pyroxene and wollastonite minerals, and a retrograde stage characterized by epidote, calcite, and chlorite minerals. Mineralization of the research area consists of galena, sphalerite, pyrrhotite, pyrite, and chalcopyrite. The presence of pyroxene and wollastonite minerals, as well as galena and sphalerite indicate that the skarn formed in the intermediate to distal zone.

ASAL USUL FLUIDA MANIFESTASI PANAS BUMI DAN ESTIMASI TEMPERATUR RESERVOIR DENGAN PENDEKATAN ANALISIS ISOTOP PADA DAERAH DANAU RANAU, OGAN KOMERING ULU (OKU) SELATAN, SUMATERA SELATAN

Mochamad Malik Ibrahim — 2024-11-29

The geothermal potential of the Lake Ranau area comes from the remains of magmatic activity from Mount Seminung. The geothermal manifestation in this area is in the form of hot springs which are thought to arise through geological structures. The existence of geothermal fluid manifestations is very interesting to research, especially regarding the origin and estimation of reservoir temperature using the δ¹⁸O and δ²H isotope composition approach. It is important to know the origin of fluid manifestations to determine the potential of geothermal systems from surface manifestations fluid related to magmatic, evaporation or rock interactions. This research method uses isotope analysis to determine the origin of geothermal fluid manifestations and isotope geothermometer to estimate reservoir temperature. Isotope sampling in geothermal manifestation fluids in Kota Batu Village was 3 samples and Lombok Village was 3 samples. The results of isotope analysis on the relationship graph between δ¹⁸O and δ²H show that all isotope samples in geothermal manifestation fluids come from meteoric water. The local meteoric water line value equation has a difference in the deuterium excess (DE) value compared to the global meteoric water line value equation. This change in DE value is due to the interaction and mixing process between geothermal fluid and rock (connate water) with the source of evaporation and precipitation from Lake Ranau. The results of isotope geothermometer calculations based on the isotope fractionation factor, it is estimated that the reservoir temperature is around ± 270 ⁰C. Reservoir temperature estimates show that all isotope samples in geothermal manifestation fluids are classified as high temperatures.

KARAKTERISASI BATUAN INDUK HIDROKARBON DAN RESERVOAR NONKONVENSIONAL DI CEKUNGAN JAWA TIMUR BAGIAN UTARA

Feby Airlangga — 2024-11-29

The northern East Java Basin is one of the hydrocarbon producing basins in Indonesia with a thick source rock layer and is interesting to study as a potential unconventional reservoir in the future. In this research, integration of well data analysis and seismic inversion is used to identify the characteristics of the source rock in the studied area. Well data analysis can provide lithological information from the source rocks bearing formations, namely shale of the Prupuh Formation, dominant shale of the Kranji Formation, and limestone of the Ngimbang Formation. In addition, log data can provide information on predicting Brittleness Index (BI) and Total Organic Carbon (TOC) values in the target zone. The linear regression is used to propagate BI, porosity, and TOC on the seismic data. To assist the process of distributing TOC and BI values on seismic parameters, Acoustic Impedance (AI) inversion was carried out by using a model based hard constraint method to predict the AI distribution. The results of this study show that the target zone is a potential zone with a medium to potential category with a TOC distribution of 1.5%-2.2%, BI of 0.2-0.46, and porosity of 0.03-0.15. Moreover, seismic inversion data also helps the distribution of petrophysical parameters in good lateral conditions following the distribution of shale source rock horizons.

ALTERASI DAN MINERALISASI PADA DAERAH SUB-PROJECT S, BLOK A, PT SUMBAWA BARAT MINERAL, KABUPATEN SUMBAWA BARAT, PROVINSI NUSA TENGGARA BARAT

Ariel Dwiyanto Nugroho — 2024-11-30

The research area is located in the Mining Business License (IUP) owned by PT Sumbawa Barat Mineral located in Taliwang, West Sumbawa, West Nusa Tenggara, located on the Sunda-Banda Arc magmatic line which shows the potential for metal mineralization resulting from hydrothermal activity in the research area, the potential for mineralization spread in the research area is epithermal type. This research aims to determine the alteration, mineralization and type of depositethat develops in the research area. The methods used in this research are geological mapping with grid mapping method and grab sampling, XRF analysis by looking for elemental content, petrography analysis to determine the texture and structure of rocks and minerals, mineragraphy analysis to determine the kind of metallic minerals, and XRD analysis to identify alteration minerals in more detail. The results of this research show the presence of propylitic, argillic, advanced argillic, and silicified alteration. With mineralization of silver, copper, lead, zinc, arsenic, and manganese with the presence of covellite minerals, and dickite, the mineralization type of the research area is intermediate depth high sulfidation epithermal type.

THE POTENTIAL AND UTILIZATION OF GEOTHERMAL ENERGY ASSESSMENT FOR DIRECT UTILIZATION IN THE LELES PROSPECT, CIANJUR, WEST JAWA

Husin Nugraha — 2024-11-30

This research activity aims to estimate the potential and utilization of geothermal energy for direct use in Prospect Leles, Cianjur Regency, by applying technical instructions on calculating the potential and utilization of geothermal energy for direct use. The Leles prospect has eight heat sources for direct utilization of geothermal energy: five hot springs, one hot water drilled well, and two hot water bathing pools. Two pools are categorized as utilized, with the installed capacity of one hot spring with proven reserves. Meanwhile, the remaining five hot springs are still categorized as measurable resources. The total installed capacity of the two hot spring pools is 38.85 kW_t with an annual utilization of 1.23 TJoules per year or ~0.34 GW_hper year with an estimated capacity factor of 33.3%. With this capacity, the ratio of installed capacity to proven reserves is still very small, only 1.41%. Meanwhile, the total potential of the Leles Prospect is 3.3 MW_t with details of proven reserves of 2,592 kW_t and measured resources of 704 kW_t. The recommendation for direct use is to increase the utilization installation, either in parallel, a pool can be made for swimming, bathing, and a jacuzzi, and in cascading with aquaculture, such as shrimp or catfish.