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Journal : Jurnal Penelitian Pendidikan IPA (JPPIPA)

Karakterisasi Struktur Bawah Permukaan Menggunakan Inversi Data Gravitasi di Cekungan Ombilin Fitria; Haris, A.; Rinaldo
Jurnal Penelitian Pendidikan IPA Vol 11 No 8 (2025): August
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v11i8.11762

Abstract

The Ombilin Basin in West Sumatra is one of the oldest intermontane basins in Indonesia that has significant geological potential, especially in relation to coal content and possible petroleum systems. This study uses a three-dimensional gravity inversion method to model the distribution of subsurface density from a depth of 0 to 6000 meters. The purpose of this study is to examine the subsurface geological modeling in the Ombilin Basin and to be a reference in exploration geophysical studies in other basins in Indonesia that have similar characteristics. Corrected regional gravity data are used as input in the inversion process to reconstruct the relative density model of rocks. The inversion results show a low-density zone (Δg between -0.1995 to -0.0099 gr/cc) in the central and southwest parts of the basin associated with sedimentary deposits such as sandstone, shale, and coal. At depths of more than 4000 meters, a high-density zone is identified that reflects the presence of basement rocks or possible magmatic intrusions. This density distribution strengthens the understanding of the basin geometry and potential hydrocarbon traps. This study shows that the gravity inversion method is an effective and economical approach for subsurface geological interpretation, especially in areas with limited exploration data.
Bahasa Inggris Rinaldo; Haris, A.
Jurnal Penelitian Pendidikan IPA Vol 11 No 4 (2025): April
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v11i4.10911

Abstract

The North Sumatra Basin is one of the major sedimentary basins in Indonesia with significant hydrocarbon potential. However, exploration in this region faces challenges due to overpressure, which can increase operational risks such as blowouts. This study aims to analyze pore pressure and overpressure formation mechanisms in Well Al using the Eaton method and a crossplot approach between sonic and density data. The analysis results indicate that the top overpressure is identified at a depth of 8,500 ft in the Keutapang Formation and continues into the Baong, Bampo, and Parapat Formations. Wireline log evaluation indicates anomalies in the sonic, neutron, and density logs, which are consistent with disequilibrium compaction patterns. The Dutta crossplot results also confirm the dominance of smectite minerals without transformation into illite, reinforcing that the primary overpressure mechanism is loading due to disequilibrium compaction. Accurate pore pressure modeling is necessary to improve drilling safety and efficiency in this area.
Analisis Petrofisika dan Evaluasi Zona Overpressure sebagai Perangkap Hidrokarbon di Cekungan Jawa Timur Utara Anggi, Michael; Haris, A.; Rinaldo
Jurnal Penelitian Pendidikan IPA Vol 11 No 5 (2025): May
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v11i5.11199

Abstract

Errors in estimating pore pressure can cause blowouts during the drilling process, especially in overpressured zones. This study focuses on pore pressure estimation in the North East Java Basin using the approach, which is validated with field data. The well log data analyzed include resistivity, density, sonic velocity, and porosity, which are used to detect the presence of overpressure zones and identify reservoir potential. The results show that the overpressure zone begins at a depth of 4600 feet and lasts up to 9000 feet. The interval between 4800 to 7300 feet is identified as a potential reservoir, while seal rocks are found at 4000–4600 feet. The cross plot between sonic and density parameters shows the dominance of smectite minerals, indicating that perfect compaction has not occurred due to trapped fluids. This finding strengthens the suspicion that the overpressure formation mechanism is dominated by sediment loading. Precise pore pressure estimation is needed to reduce operational risks and optimize hydrocarbon exploration in this area.