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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.

Depositional Environment of the Sangkarewang Oil Shale, Ombilin Basin, Indonesia Anggayana, Komang; Widayat, Agus Haris; Widodo, Sri
Journal of Engineering and Technological Sciences Vol 46, No 4 (2014)
Publisher : ITB Journal Publisher, LPPM ITB

Five samples from 56 m long drill core of lacustrine Sangkarewang oil shale have been studied by means of petrography and organic geochemistry to investigate the organic matter composition and depositional environments of the shale. The organic matter consists of abundant lamalginite (30%, v/v) and very limited amount of vitrinite, suggesting aquatic depositional environments with minor terrestrial influence. Organic geochemical analysis exhibits the dominance of pristane, phytane, and generally n-alkanes compounds. These compounds might originate mostly from aquatic photosynthetic organisms. The oil shale was likely deposited in anoxic lake environments, suggested by the presence of framboidal pyrite (6%, v/v) and preserved organic matter with total organic carbon (TOC) about 4.9%. The pristane/phytane ratio is relatively high about 3.9 and thought as source sensitive rather than redox sensitive. Hopanoid and aryl isoprenoid compounds are present in minor amounts. The latter compounds are interpreted to be derived from green sulfur bacteria dwelling in anoxic and the presence of H2S in bottom water.

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.

Methane Adsorption Characteristics of coals from Sambaliung area,Berau, East Kalimantan and Sawahlunto area, West Sumatra, Indonesia Anggayana, Komang; Kamarullah, Denny Reza; Suryana, Asep; Widayat, Agus Haris
Jurnal Geologi dan Sumberdaya Mineral Vol 18, No 4 (2017): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (295.918 KB)

Investigation of methane adsorption capacity has been performed in Sambaliung Area, Berau, East Kalimantan (Latih Formation) and Sawahlunto Area, West Sumatra (Sawahlunto Formation). The study involves some analyses: methane sorption, petrography, and proximate. Adsorption isotherm analysis reveals storage capacity of Sambaliung and Sawahlunto coals about 113 to 269 scf/ton (daf) and from 486 to 561 scf/ton (daf), respectively. The adsorption capacity of the coals is thought to be related with formation pressure represented by depth as well as coal rank. The Sambaliung coal rank is low as indicated by the lower vitrinite reflectance (Rr about 0.38%) and higher total moisture (TM about 31%, ar). The Sawahlunto coal rank is higher as indicated by higher Rr (about 0.72%) and lower TM (about 6%, ar).

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.

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

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

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

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.

STUDI KARAKTERISTIK BEBERAPA BATUBARA INDONESIA UNTUK MENDUKUNG PROSPEK PEMANFAATANYA Suhat, Boas; Widayat, Agus Haris; Anggayana, Komang
Prosiding Temu Profesi Tahunan PERHAPI 2020: PROSIDING TEMU PROFESI TAHUNAN PERHAPI
Publisher : PERHAPI

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36986/ptptp.v0i0.133

Batubara merupakan hasil tambang yang memiliki beragam manfaat. Pada umumnya, batubara di Indonesia dimanfaatkan sebagai bahan bakar yang biasa disebut batubara uap atau sebagai bahan baku industri baja yang biasa disebut batubara kokas. Baik batubara uap maupun batubara kokas memiliki spesifikasi kualitas yang berbeda satu sama lainnya sesuai dengan kebutuhan dari proses pemanfaatanya masing-masing. Agar batubara dapat dimanfaatkan sesuai dengan kualitasnya, perlu dilakukan pengujian kualitas terhadap sampel-sampel batubara. Pada penelitian ini dipilih contoh batubara yang berasal dari beberapa formasi geologi pembawa batubara, yaitu Formasi Batu Ayau dan Formasi Tanjung di Cekungan Barito, Formasi Balikpapan di Cekungan Kutai, dan Formasi Muara Enim di Cekungan Sumatera Selatan. Pengujian yang dilakukan meliputi pengujian proksimat, pengujian ultimat, pengukuran nilai kalori, dan pengujian FSI (Free Swelling Index). Hasil dari pengujian-pengujian tersebut akan mencerminkan proses pembatubaraan yang telah dialami oleh batubara. Batubara yang telah mengalami pembatubaraan hingga peringkat Subbituminus dengan tipikal Gross Calorific Value di kisaran 5000 kcal/kg (ar), kandungan air di bawah 36 % (ar), kandungan abu di bawah 15% (adb), kandungan zat terbang di kisaran 40% (adb), dan kandungan sulfur di bawah 0,9% (adb) lebih cocok untuk dimanfaatkan sebagai batubara uap. Sedangkan batubara yang telah mengalami pembatubaraan hingga peringkat bituminus dengan tipikal kandungan air di bawah 15% (ar), kandungan abu di bawah 12% (adb), kandungan belerang di bawah 1% (adb), dan FSI di atas 6 lebih cocok untuk dijadikan batubara kokas.

Depositional Environment of the Sangkarewang Oil Shale, Ombilin Basin, Indonesia Komang Anggayana; Agus Haris Widayat; Sri Widodo
Journal of Engineering and Technological Sciences Vol. 46 No. 4 (2014)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2014.46.4.6

Five samples from 56 m long drill core of lacustrine Sangkarewang oil shale have been studied by means of petrography and organic geochemistry to investigate the organic matter composition and depositional environments of the shale. The organic matter consists of abundant lamalginite (30%, v/v) and very limited amount of vitrinite, suggesting aquatic depositional environments with minor terrestrial influence. Organic geochemical analysis exhibits the dominance of pristane, phytane, and generally n-alkanes compounds. These compounds might originate mostly from aquatic photosynthetic organisms. The oil shale was likely deposited in anoxic lake environments, suggested by the presence of framboidal pyrite (6%, v/v) and preserved organic matter with total organic carbon (TOC) about 4.9%. The pristane/phytane ratio is relatively high about 3.9 and thought as source sensitive rather than redox sensitive. Hopanoid and aryl isoprenoid compounds are present in minor amounts. The latter compounds are interpreted to be derived from green sulfur bacteria dwelling in anoxic and the presence of H2S in bottom water.

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