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All Journal IJOG : Indonesian Journal on Geoscience Journal of Engineering and Technological Sciences Jurnal Geologi dan Sumberdaya Mineral Jurnal GEOSAPTA Prosiding Temu Profesi Tahunan PERHAPI Indonesian Journal on Geoscience Indonesian Journal on Geoscience
Agus Haris Widayat
Research Group of Earth Resources Exploration, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jln. Ganesha 10, Bandung, 40132, Indonesia
Chemical Engineering, Chemistry & Bioengineering Earth & Planetary Sciences Education Energy Engineering Environmental Science

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Journal : Indonesian Journal on Geoscience

 1 
Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia Widayat, Agus Haris; Anggayana, Komang; Khoiri, Isra
Indonesian Journal on Geoscience Vol 2, No 3 (2015)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.2.3.185-197

Abstract

DOI: 10.17014/ijog.2.3.185-197Geochemical and petrographical analyses were carried out to investigate the occurrence of calcite in theformer Ombilin lacustrine lake. The study involves eight samples taken from a 56 m long drill core of Sangkarewangoil shale. Geochemical investigation showed that the samples consist of varied terrigenous input represented by Si, Al, K, and Ti, and autochthonous input represented by S, total organic carbon (TOC), and d13C of bulk organic matter. Along the drill core profile the abundance of autochthonous input decreases upwards, while that of terrigenous input oppositely increases upwards. Petrographical analysis revealed that calcite is a major mineral in the samples. In this study, the abundance of calcite could be represented by the abundance of Ca, as calcite is the only significant Ca containing mineral. Ca is abundant in the samples (8.4% in average) and its concentration varies similarly with those of S, TOC, and d13C, suggesting that the element as well as calcite incorporates the autochthonous input. Thevariation of calcite abundance in the drill core profile is considered to be related with primary productivity changes during the development of the former lake. Higher primary productivity represented by more positive of d13C value(-24.8‰) during the deposition of the lower part of the drill core profile promoted the higher amount of deposited organic matter. In such environment, the supersaturation of carbonate ion in lake water was also reached and significant precipitation of authigenic calcite occurred. As the lake developed, the primary productivity decreased as indicated by more negative of d13C value (eventually -26.8‰). This condition led to the decreases of deposited organic matterand calcite in the lake sediments.
Wireline Log Responses, Mudweight, Clay Mineralogy, and Implied Overpressure Condition: Insights from Aru Field, North Sumatra Basin Syaiful, Mohammad; Hutasoit, Lambok M.; Ramdhan, Agus M.; Widayat, Agus Haris
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.105-119

Abstract

DOI:10.17014/ijog.7.2.105-119This paper comprehensively discusses overpressuring in the North Sumatra Basin by using wireline log, drilling events and parameters, and clay mineralogical data. It shows an interesting phenomenon related to overpressuring in this basin, i.e. strong log reversals indicating high overpressure, yet the mudweight used during drilling was relatively low, indicating low overpressure with no significant drilling events noted in the final well report.The result of the study shows that wireline log is the best parameter to imply overpressure magnitude. Regarding low mudweight in the strong log reversal zone, it would be elucidated that the drilling in that zone was in underbalance condition with respect to shale pressure, but not to sandstone pressure. The sandstone pressure is interpreted to be lower than shale pressure due to lateral drainage process. By applying the Eaton’s method, the estimated maximum overpressure magnitude in the Baong Formation is in the range of 1,594 - 3,185 psi. or equivalent to the mudweight of 1.61 - 192 g/cm3. The analysis of wireline log in combination with clay mineralogical data shows that there are two compaction lines in the studied area, i.e. smectitic and illitic compaction lines. The cross-plot of density and sonic logs in shale section suggest that the cause of overpressure was loading mechanism. The scanning electron microscope (SEM) image confirms that in overpressure zone, grain to grain contact is still able to be observed fairly well, inferring that loading mechanism is really the cause of overpressure in the studied area.
Co-Authors Agus M. Ramdhan Andy Yahya Al Hakim Andy Yahya Al Hakim Anggayana, Komang Asep Suryana BASUKI RAHMAD Budi Sulistijo Denny Reza Kamarullah, Denny Reza Hutasoit, Lambok M. Isra Khoiri Isra Khoiri, Isra Khoiri, Isra Komang Anggayana Komang Anggayana Komang Anggayana Komang Anggayana Komang Anggayana Komang Anggayana Lambok M. Hutasoit Miqdam Furqany Mirza Dian Rifaldi Mohamad Nur Heriawan Mohammad Syaiful Mulyono Dwiantoro Ramdhan, Agus M. Sri Widodo Suhat, Boas Syafrizal Syafrizal Syaiful, Mohammad Teti Indriati Teti Indriati