Geochemical Characterization of Central Niger Delta Oils

Abstract

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.

Quantitative diamondoid analysis indicates oil cosourcing from a deep petroleum system onshore Niger Delta Basin

“…Sterane isomerization parameters show that the Niger Delta oils are of relatively low thermal maturity (heavily biodegraded oils above level 5, as described in Peters and Moldowan, 1991, were not included) in comparison to the thermally mature North Sea oil (Figures 10, 11). This result is consistent with the work of Sonibare et al (2008) and Akinlua and Ajayi (2009).…”

High-Efficiency Microwave-Assisted Digestion Combined to in Situ Ultraviolet Radiation for the Determination of Rare Earth Elements by Ultrasonic Nebulization ICPMS in Crude Oils

“…Recent studies have pointed out that information related to crude oil origin, maturity, migration, and correlation of oil to source rock, among others parameters, could be properly obtained by the knowledge of concentration of rare earth elements (REE), , and a major part of the works concerning this issue was only published in the last 8 years. − In addition, the determination of REE is important because some of these elements could be indicators of environmental pollution by crude oil refineries. − , However, despite the relevance of REE determination in crude oil, only a few works have been reported in literature − and most of them refer to light crude oils, lubricating or diesel oils, , or crude oils with relatively low contents of heavy compounds or sulfur or high content of saturated hydrocarbons. , Heavy and extraheavy crude oil are considered as complex matrixes because generally they contain high concentration of asphaltenes and resins that makes difficult achieving effective digestion or suitable solutions to be analyzed by spectrometric techniques. Moreover, REE determination could be considered as an important analytical challenge mainly due to the low levels that these elements are currently found in crude oils.…”

“…R ecent studies have pointed out that information related to crude oil origin, maturity, migration, and correlation of oil to source rock, among others parameters, could be properly obtained by the knowledge of concentration of rare earth elements (REE), 1,2 and a major part of the works concerning this issue was only published in the last 8 years. 2−7 In addition, the determination of REE is important because some of these elements could be indicators of environmental pollution by crude oil refineries.…”

“…2−7 In addition, the determination of REE is important because some of these elements could be indicators of environmental pollution by crude oil refineries. [1][2][3]8 However, despite the relevance of REE determination in crude oil, only a few works have been reported in literature 2−8 and most of them refer to light crude oils, lubricating or diesel oils, 3,4 or crude oils with relatively low contents of heavy compounds or sulfur or high content of saturated hydrocarbons. 5,7 Heavy and extraheavy crude oil are considered as complex matrixes because generally they contain high concentration of asphaltenes and resins that makes difficult achieving effective digestion or suitable solutions to be analyzed by spectrometric techniques.…”

Using aromatic biological markers as a tool for assessing thermal maturity of source rocks in the Campano-Maastrichtian Mamu Formation, southeastern Nigeria

“…According to Tissot and Welte (1984), aromatization of C-ring steroid hydrocarbons occurs in mature oils. With an increase in thermal maturation, there is a conversion of C-ring monoaromatic steroid hydrocarbons to ABCring triaromatic steroid hydrocarbons (Akinlua and Ajayi, 2009). The TAS/ (TAS+MAS) and TAS 28/ (TAS 28+MAS 29) ratios ranged from 0.22 to 0.59 and 0.39 to 0.88, respectively (Table 5), indicating an immature to marginally mature status of the rock extracts.…”