Significance of oleanane occurrence in shales of Opuama Channel Complex, Niger delta

Udo, Onkel; Ekweozor, C. M.

doi:10.1021/ef00021a006

Cited by 24 publications

(5 citation statements)

References 8 publications

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“…8; Table 5). On the m/z 191 mass chromatograms of oil shale samples, no oleanane was recorded, which also supports terrigenous organic matter input [25][26][27][28][29][30] (Fig. 9).…”

Section: Discussionsupporting

confidence: 64%

Organic Geochemical Characteristics of Miocene Oil Shale Deposits in the Eski̇şehi̇r Basin, Western Anatolia, Turkey

Şengüler¹,

Kara-Gülbay²,

Korkmaz³

2014

Oil Shale

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In the Eskişehir Basin, western Turkey, oil shale occurs in alternation with claystone, siltstone, conglomerate and coal (lignite) seams in lacustrine deposits of Early-Middle Miocene age. The thickness of oil shale seams drilled during the study varies between 20 and 30 m. Organic geochemical features of the shale were evaluated using TOC, pyrolysis, GC and GC-MS analyses. The Eskişehir oil shale is characterized by very high TOC contents (6.32-37.15 wt%), Hydrogen Index (HI = 392-777 mg HC/g TOC), Potential Yield (PY = 35.50-159.32 mg HC/g rock) and very low Oxygen Index (OI = 13-92 mg CO 2 /g TOC) values. Organic matter in the studied oil shale is of Type II kerogen and shows S 2 /S 3 ratio values between 5.49 and 56.79 and low T max (421-435 °C) and PI (0.01-0.05) values. Low Pr/Ph ratio of oil shale (0.17-0.96) is indicative of anoxic conditions. Dominant steranes are either C 27 or C 28. Normal steranes are more abundant than iso-and diasteranes and diasterane abundances as well as 20S/(20S + 20R) and ββ/(ββ + αα) sterane ratios are low. While oil shale samples in general have low tricyclic terpane (C 19-C 29) abundance, their C 30 (R + S) tricyclic terpane content is high. For all the oil shale samples studied C 29 /C 30 hopane, C 31 R homohopane/hopane and moretane/hopane ratios are high and Ts/(Ts + Tm) and C 29 Ts/(C 29 Ts + C 29 H) ratios are low. 22S homohopanes are recorded in lower quantities in comparison to 22R epimers and the 22S/(22S + 22R) homohopane ratio is low.

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“…8; Table 5). On the m/z 191 mass chromatograms of oil shale samples, no oleanane was recorded, which also supports terrigenous organic matter input [25][26][27][28][29][30] (Fig. 9).…”

Section: Discussionsupporting

confidence: 64%

Organic Geochemical Characteristics of Miocene Oil Shale Deposits in the Eski̇şehi̇r Basin, Western Anatolia, Turkey

Şengüler¹,

Kara-Gülbay²,

Korkmaz³

2014

Oil Shale

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“…18α(H)-oleanane is thought to be derived from pentacyclic triterpanes in certain angiosperms (Grantham et al 1983). There is a correlation between the abundance of higher-plant macerals and the oleanane index (Udo & Ekweozor 1990). The oleanane/hopane ratios of the Sagara oils, ranging from 0.69 to 0.92, are higher than the ratios of Niigata oils (Fig.…”

Section: Aromatics Saturatesmentioning

confidence: 99%

Geochemical characteristics of crude oils from the Sagara oil field, Shizuoka Prefecture, Japan

Katō¹,

Waseda²,

Nishita³

2006

Island Arc

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Six oil samples collected from the Sagara oil field, Shizuoka Prefecture, were geochemically analyzed. Unlike the Niigata oils, the Sagara oils: (i) are low‐sulphur light oils dominated by gasoline and kerosene fractions; (ii) have low values of environment index in light hydrocarbon compositions; (iii) have high Pr/n‐C17 and low Ph/n‐C18 ratios and high oleanane/hopane ratios; (iv) have high relative abundance of C29 and low relative abundance of C28 regular steranes; and (v) have ‘light’ stable carbon isotope compositions. These characteristics show that the source rocks of the Sagara oils contain mainly marine organic matter, but with more input of terrigenous organic matter deposited under more oxic conditions compared to those of the Niigata oils. The light carbon isotope compositions and the low relative abundance of C28 regular steranes of the Sagara oils suggest that their source rock is not Miocene, but probably Paleogene in age. The Sagara oils probably migrated along faults from deeper parts of the basin.

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“…A knowledge of the petroleum systems within a mature basin is important for future oil exploration activities. Previous studies have shown that there is a single petroleum system in the Niger Delta (Ekweozor et al, 1979;Nwachukwu and Chukwura, 1986;Bustin, 1988;Udo and Ekweozor, 1990;Akinlua et al, 2000;Eneogwe and Ekundayo, 2003;Akinlua et al, 2005). However, it is important to investigate the petroleum system in different parts of the delta, and to determine whether there are any subtle differences within different areas.…”

Section: Introductionmentioning

confidence: 99%

Geochemical Characterization of Central Niger Delta Oils

Akinlua¹,

Ajayi²

2009

Journal of Petroleum Geology

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Oil samples from six oilfields in the Central Niger Delta were analyzed for normal alkanes, aliphatic isoprenoid hydrocarbons, aromatic hydrocarbons and biomarkers using gas chromatography (GC) and gas chromatography‐mass spectrometry (GC‐MS). The study was carried out with the aim of assessing the origin and thermal maturity of the oils and the depositional environment of the organic matter from which they were derived, and to evaluate similarities (or differences) among the oils from the Central Niger Delta in comparison to those from other parts of the Delta. The ratios of n‐alkanes and aliphatic isoprenoids showed that Pr/nC17 ranged from 0.56 to 0.86 while Ph/nC18 ranged from 0.22 to 0.31 indicating that the oils were derived from organic matter of both terrestrial and marine origin. Pristane/phytane ratios ranged from 2.67 to 3.50, suggesting that the organic matter was deposited in generally oxidizing environments. The oleanane index, which ranged from 0.07 to 1.39, and other biomarker data also indicate contributions from both marine and terrestrial organic matter. Both saturated and aromatic hydrocarbon biomarker data indicate that the oils are thermally mature. The study showed that the Central Niger Delta oils have organic geochemical characteristics similar to those of oils from other parts of the Delta. However, there is a striking difference in the distribution of aromatic hydrocarbons, and this may in future be used as a tool with which oils from different parts of the Delta can be differentiated.

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Significance of oleanane occurrence in shales of Opuama Channel Complex, Niger delta

Cited by 24 publications

References 8 publications

Organic Geochemical Characteristics of Miocene Oil Shale Deposits in the Eski̇şehi̇r Basin, Western Anatolia, Turkey

Organic Geochemical Characteristics of Miocene Oil Shale Deposits in the Eski̇şehi̇r Basin, Western Anatolia, Turkey

Geochemical characteristics of crude oils from the Sagara oil field, Shizuoka Prefecture, Japan

Geochemical Characterization of Central Niger Delta Oils

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