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Jurnal Geosaintek
Published by Institut Teknologi Sepuluh Nopember Surabaya
ISSN : 24609072     EISSN : 25023659     DOI : https://doi.org/10.12962/j25023659
Core Subject : Science,
Earth & Planetary Sciences
Jurnal Geosaintek mempublikasikan dan menerbitkan hasil kajian, penelitian, penerapan ilmu pengetahuan serta teknologi di bidang kebumian
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Ilmu Bumi dan Planet (Lain-Lain)
Articles 223 Documents
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MINERALOGY AND MICROSTRUCTURE OF RANTAU DEDAP'S GEOTHERMAL RESERVOIR: HYDROTHERMAL ALTERATION INSIGHTS Welayaturromadhona Welayaturromadhona; Firman Sauqi Nur Sabila; Mauliate Agustinus Hamonangan Sihotang; Luthfi Rindra Salam; Fifi Izzati
Jurnal Geosaintek Vol. 11 No. 3 (2025)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v11i3.8982

Abstract

The Great Sumatra Fault controls the Rantau Dedap geothermal system in South Sumatra. It is a high-temperature volcano-tectonic system. This study presents a comprehensive mineralogical and microstructural examination of core samples from three deep wells (UJ-A1, UJ-B1, and UJ-C1) at depths ranging from 1,840 to 2,313 m, aiming to elucidate hydrothermal alteration and its impact on reservoir quality. X-ray Diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) analyses demonstrate a distinct propylitic alteration zonation correlated with increasing depth and temperature. UJ-A1 (1840 m) is mainly made up of oligoclase, microcline, and quartz. UJ-B1 (2142 m) is mainly made up of oligoclase-quartz. UJ-C1 (2313 m) is mainly made up of anorthite-quartz with more iron. Anorthite, a calcium-rich plagioclase that stays stable above 280 °C, is found at greater depths. This means that the area is close to a major upflow zone. SEM microstructural analysis reveals hydrothermal breccia textures, characterized by angular fragments within a matrix of secondary minerals, and indicates secondary porosity resulting from mineral alteration. These characteristics suggest that hydraulic brecciation resulting from tectonic activity is essential for the creation and preservation of reservoir permeability. The reservoir's potential is enhanced because it lacks smectite-type clays, which typically block pores. In general, these results indicate that Rantau Dedap is a structurally controlled upflow zone characterized by deep mafic lithologies. The anorthite-quartz assemblage stands out as a key sign for future high-temperature geothermal exploration.
ANALISIS SEKATAN SESAR PADA SEGMEN ZONA SESAR LEMATANG CEKUNGAN SUMATERA SELATAN: IMPLIKASI TERHADAP MIGRASI HIDROKARBON Shinta Ayu Puspita; Benyamin Sapiie; Indra Gunawan; Aveliansyah Aveliansyah
Jurnal Geosaintek Vol. 11 No. 3 (2025)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v11i3.8985

Abstract

Sesar Lematang merupakan salah satu struktur utama di Cekungan Sumatera Selatan yang berperan penting dalam mengontrol pola deformasi, sedimentasi, dan sistem petroleum. Sesar Lematang berfungsi sebagai batas morfotektonik aktif yang terbentuk sejak fase ekstensional Eosen–Oligosen dan mengalami reaktivasi pada fase kompresi Miosen–Plio-Plistosen. Penelitian ini bertujuan untuk mengidentifikasi kerangka struktur dan mengevaluasi kemampuan sekatan (fault sealing capacity) Sesar Lematang berdasarkan integrasi data seismik 2D, data sumur, dan analisis petrofisika. Metode yang digunakan meliputi interpretasi seismik struktural untuk menentukan bidang dan geometri sesar, analisis petrofisika untuk menghitung kandungan lempung (Vshale), serta perhitungan Shale Gouge Ratio (SGR) guna menilai kemampuan sekatan sesar. Hasil perhitungan menunjukkan nilai SGR berkisar antara 47–61% dengan rata-rata sekitar 54%. Kombinasi kedua parameter tersebut. Implikasi hasil penelitian ini menunjukkan bahwa segmen-segmen Sesar Lematang berpotensi membentuk perangkap bertipe fault-bounded dan perangkap kombinasi stratigrafi-struktural yang baik bagi akumulasi hidrokarbon. Oleh karena itu, pemahaman terhadap kerangkas struktur dan perilaku sekatan Sesar Lematang menjadi aspek penting dalam strategi eksplorasi dan pengembangan migas di Cekungan Sumatera Selatan
SEISMOTECTONIC STUDY OF THE SIBOLANGIT, NORTH SUMATRA REGION BASED ON DOUBLE-DIFFERENCE RELOCATION Nesia S. Marbun; Aulia A. Aisjah; Anne M. M. Sirait; Yusran Asnawi; Hendro Nugroho; Andrean V. H. Simanjuntak
Jurnal Geosaintek Vol. 11 No. 3 (2025)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v11i3.8986

Abstract

Sumatra is one of the most seismically active regions in the world due to the oblique convergence between the Indo-Australian and Eurasian plates, where strain is partitioned between the Sunda megathrust and the Great Sumatran Fault (GSF). While most seismicity in North Sumatra occurs along mapped strands of the GSF, several damaging earthquakes have occurred outside known fault zones, raising critical questions about hidden seismogenic structures. This study investigates the seismotectonic framework of the Karo region, with a focus on the 2017 Karo earthquake (Mw 5.6), using the double-difference relocation method. A dataset of local earthquakes recorded by the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) was analyzed to refine hypocenter locations, reduce uncertainties, and identify seismic clusters. Relocation results significantly improved spatial resolution, reducing average location errors to less than 3 km, and revealed clustered seismicity along a northwest–southeast trending structure offset from the Renun Fault. Depth cross-sections indicate brittle faulting within the upper crust (5–12 km), and the aftershock alignment suggests the presence of an unmapped subsidiary fault accommodating dextral shear. Comparisons with similar studies across Sumatra and Java confirm that off-fault seismicity is a common but often overlooked contributor to regional hazard. These findings underscore the importance of integrating relocated seismicity into national hazard models to account for hidden faults. By providing improved fault geometry and seismotectonic insights, this study enhances the understanding of earthquake sources in North Sumatra and supports future efforts in seismic hazard mitigation and disaster risk reduction in one of Indonesia’s most vulnerable regions.

Page 23 of 23 | Total Record : 223

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