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All Journal IJOG : Indonesian Journal on Geoscience Journal of Engineering and Technological Sciences Jurnal Ilmu Kebumian Teknologi Mineral (JIK TekMin) Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources) Jurnal GEOSAPTA Prosiding Temu Profesi Tahunan PERHAPI INDONESIAN MINING PROFESSIONALS JOURNAL Indonesian Journal on Geoscience Indonesian Journal on Geoscience Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)

Agus Haris Widayat

Earth Resource Research Group, Faculty Of Mining And Petroleum Engineering, Institut Teknologi Bandung,

Author-ID : 415184

Aerospace Engineering Chemical Engineering, Chemistry & Bioengineering Chemistry Earth & Planetary Sciences Education Energy Engineering Environmental Science

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Depositional Cycles of Muara Wahau Coals, Kutai Basin, East Kalimantan Anggayana, Komang; Rahmad, Basuki; Widayat, Agus Haris
Indonesian Journal on Geoscience Vol 1, No 2 (2014)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.v1i2.183Fifteen samples were taken ply by ply from a 33 m thick drill core of Muara Wahau coal seams for interpretation of depositional environments. Generally, lithotype variation in the bottom part of the coal seams has a lower frequency than in the upper part. Petrographical analysis was performed to determine the maceral composition, groundwater index (GWI), and gelification index (GI). The samples from lower sections show much higher GWI-GI values and lower variation frequency than from the upper section. This characteristic is interpreted as the result of development of mesotrophic to ombrotrophic peats during the deposition of lower to upper parts of the section, respectively. During the development of the mesotrophic peat, water was more abundant and relatively stable in budget. However, during the development of ombrotrophic peat, water was less abundant and relatively not stable in budget. The latter is related to the water supply depending only on rain, resulted in the more sensitive water table in the om- brotrophic peat. The unstable water table is thought as the reason of higher variation frequency of lithotype, GWI, GI, as well as maceral composition in the upper part of the core. Unstable water table would lead to moist condition in the uppermost layer of the ombrotrophic peat, favoring fungi to grow. This is confirmed by the higher abundance of sclerotinite maceral in samples from the upper part of the coal core.

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

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(-24.8â€°) 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 -26.8â€°). 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

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 Eatonâ€™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 Andi Zulkarnain, Andi Andrew Harryanto Sinaga Andy Yahya Al Hakim Asep Suryana Basuki Rahmad Basuki Rahmad Basuki Rahmad BASUKI RAHMAD Budi Sulistijo Denny Reza Kamarullah Denny Reza Kamarullah, Denny Reza Hakim, Andy Yahya Al Heriawan, Mohamad Nur Hutasoit, Lambok M. Indriati, Teti Isra Khoiri Isra Khoiri, Isra Khoiri, Isra Komang Anggayana Komang Anggayana Komang Anggayana Komang Anggayana Lambok M. Hutasoit Luthfi Hafizh Azhar Miqdam Furqany Mirza Dian Rifaldi Mohamad Nur Heriawan Mohammad Syaiful Mulyono Dwiantoro Putra, Jovian Addo Ramdhan, Agus M. Solly Aryza Sri Widodo Suhat, Boas Syafrizal Syafrizal Syaiful, Mohammad Teti Indriati

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