Aromatic Biomarker From Brown Coal, Sangatta Coalfield, East Borneo of Middle Miocene to Late Miocene Age

Abstract

A section of the Sangatta coalfield in the Balikpapan formation located in Kutai Basin, East Borneo, Indonesia, is the Inul area, located North of Pinang Dome. This section of the coalmine has coals with low calories (ca. 4379 cal/g), which is why they cannot be used optimally yet. The reasons of using low calorie coals are besides from being used as a mixing ingredient for the blending process of high calorie coals, they are also used to diversify the coals through the process of coal liquefaction (coal to liquid). In order for the coal liquefaction to be processed correctly, there needs to be a study on the geochemistry organics through coal biomarker analysis, particularly on the hydrocarbon aromatic fractions, so that the origins of the coal organic compounds could be known. Biomarker analysis on the aromatic hydrocarbon fraction shows the existence of naphthalene compound groups with sesquiterpenoids skeleton, phenanthrene with diterpenoids, sesterpenoids skeleton and triterpenoids aromatic pentacyclic. The existence of cadalene compound, triterpene pentacyclic monoaromatic, -triaromatic, -tetraaromatic, -pentaaromatic and triterpenoid C-ring cleaved hydrocarbon with oleanane, ursane and lupane skeletons indicated that the source of coal organic compounds were derived from b-amyrin which were produced by Angiospermae plants. The coal biomarkers distribution, particularly the high abundance of triterpenoid pentacyclic triaromatic compound, confirmed the low maturity of the coals which is predicted to profit from the process of liquefaction due to the high contents of their aromatic fractions.

Paleoenvironmental and Maturity Indicator of Cepu Block Oil, Wonocolo Formation, East Java-Indonesia

“…The Miocene period was dominated by Angiosperm plants and few conifers [12,13,14]. This is proven by several previous studies which found aromatic hydrocarbons such as retene, tetrahydroretene, simonellite, and some tricyclic diterpenoids in oil and coal as coniferous organic material indication [13,15]. Naphthalene derivatives and sesquiterpenoid group such as cadalene were also found abundantly in some Miocene period oil and condensate samples.…”

“…The other naphthalene derivatives was identified as ionene based on m/z 159 fragmentogram [15,36,40]. The existence of this compound is not specific, because it could be formed through carotenoid [41] and labdane degradation which are the main components of conifers resin in the oxidative environment [42,43].…”

“…[26,39] as seen in Figure 9. Other compounds identified in Cepu oil were benzonaphtothiophene based on the m/z 234 fragmentogram and de-A-aromatic triterpenoid based on the m/z 306 fragmentogram [15,41,59]. One of the identified benzonaphtothiophene isomer is benzo(b)naphto(2,1-d)thiophene with a low intensity.…”

“…Naphthalene derivatives and sesquiterpenoid group such as cadalene were also found abundantly in some Miocene period oil and condensate samples. These biomarkers were used as indicators of high level terrestrial organic matter, especially Angiosperms [12,14,15,16]. Heterocyclic aromatic compounds such as dibenzothiophene, dibenzofuran and fluorene have been applied as indicators of terrestrial and marin depositional environments and the level of maturity deposited in the Early Miocene -Late Miocene period [17,18].…”