PALEOENVIRONMENTAL AND MATURITY INDICATOR OF CEPU BLOCK OIL, WONOCOLO FORMATION, EAST JAVA-INDONESIA

Biomarkers identification of aromatic hydrocarbon fraction of Cepu oil samples was carried out to determine the ancient depositional environment, the source of origin and indicators of the maturity of the old well of the Cepu Block oil, Wonocolo Formation, East Java Indonesia. Biomarkers was identified through the Gas Chromatography-Mass Spectroscopy (GC-MS) method. The distribution of aromatic hydrocarbon biomarkers indicates the presence of naphthalene compounds and their derivatives, sesquiterpenoids, diterpenoids and heterocyclic aromatic groups. The presence of identified biomarkers indicates the source of the oil organic compound coming from higher plants Angiosperms. The presence of methyl phenanthrene and aromatic heterocyclic biomarkers such as dibenzothiophene and dibenzofuran , as well as fluorene shows that Cepu Block oil was deposited not only in the terrestrial environment, but also lacustrine and marin under oxidic precipitation conditions. The presence of methyl phenanthrene with MPI value of 0.86 and isocadalene abundance higher than cadalene indicates moderate to high maturity of the Cepu Block oil analyzed. Keywords: Cepu Block oil, aromatic hydrocarbon, biomarker, paleoenvironment, GC-MS analysis.

Origin and Maturity of Biomarker Aliphatic Hydrocarbon in Wondama Coal Indonesia

Organic geochemical characterization of Wondama coal samples from the Lengguru Folding Belt has been carried out through the study of its aliphatic hydrocarbon biomarkers. This study is to determine the origin, depositional environment and maturity of coal which is useful for determining the use of coal as an energy source. Aliphatic hydrocarbon biomarkers were identified by using gas chromatography-mass spectroscopy methods which showed the presence of n-alkane homologs (n-C15 - n-C33), which was dominated by n-C31. This indicates that the organic material originates from Angiosperms of terrestrial higher plants. The ratio of pristane to phytane (Pr/Ph) with value of 3.74 indicates that the Wondama coal is buried in an oxic depositional environment. The Carbon Preference Index (CPI) value of 7.82 and the C31αβS/(S + R) ratio of 0.27 indicate low maturity of Wondama coal and is classified into a sub-bituminous coal ranks.

Aliphatic hydrocarbon biomarkers of Sekar Kurung Gresik crude oil

Characterization of petroleum biomarker from Sekar Kurung Gresik, was carried out to investigate its organic composition, depositional environment and oil maturity. The oil sample was extracted and fractionated using column chromatography to derive aliphatic hydrocarbon fraction. The aliphatic hydrocarbon compounds were analyzed using gas chromatography-mass spectrometer (GC-MS). The GC-MS analysis shows that n-alkanes compound (C14-C28), isoprenoid alkanes (iC15 iC16 and iC18-iC20), a bicyclic sesquiterpene, eudesmane, cadinane, hopane, bicadinane, gammacerane and diasterane were observed. The identified compounds show that the crude oil compounds were derived from terrestrial higher plants, the contribution of bacterial activity and the oxic deposition environment (Pr/Ph = 5.3 (<1)). The oil analyzed is a mature oil.

Hydrocarbon biomarkers and isotopic composition of carbon from bitumoids and oils of Mesozoic sediments in the western part of the Yenisei-Khatanga oil and gas region

Based on analyzes of carbon isotopic composition, distribution and composition of hydrocarbon biomarkers of oils and bitumoids from source rocks of the Mesozoic sediments in the western part of the Yenisei-Khatanga oil and gas region and the northeast of the West-Siberian plate, two groups of oils and bitumoids are identified, genetically associated with organic matter, mainly sapropel type (I group) and mainly humus type (II group). The genetic correlation of oils and bitumoids has been made. Possible foci of generation, which participated in the formation of hydrocarbon deposits, have been determined.

Geochemical research of asphaltite formation in the Orenburg region

The results of the studies of the physicochemical properties and genesis of asphaltites from the deposits of the Orenburg region are considered. Based on the data of a study on the distribution of hydrocarbon biomarkers (n-alkanes, isoprenanes, steranes, and terpanes), it was found that deposit formation occurred in carbonate layers under reducing conditions. The distribution of steranes and terpanes confirmed a sufficient maturity of the asphaltite. The C28/C29 sterane ratio of 0.31 corresponds to Silurian age according to Grantham or to Silurian–Devonian age according to the pregnane coefficient (a ratio of the sum of C21–C22 pregnanes to the sum of C21–C22 pregnanes and C27–C29 regular steranes) of 9.0%. Thus, it is likely that asphaltites from the Ivanovk deposit in the Orenburg region were redeposited in Silurian/Devonian source rock formations.