Thermal Maturity Assessment and Charcterization of Crude Oils from exxonmobile Joint Venture area in the Estaern Niger Delta,Nigeria.
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Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Obafemi Awolowo University
Abstract
Seventeen crude oil samples from producing Oil Wells in the Eastern Niger Delta were analyzed for their thermal maturity status. This was with a view to establishing maturity trends across the area and identifying maturity parameters that could reliably be used for maturity assessment of the area.
Open Column Liquid Chromatography (OCLC) was used to separate the crude oil samples into saturate, aromatic and Nitrogen, Sulphur and Oxygen (NSO) compounds using n-hexane, methylene chloride and mixture of methanol and methylene chloride solvents respectively. The whole oil analysis with no prior preparation of the crude oil was done using gas chromatography (GC) with internal standard and helium (He) as carrier gas. Gas chromatography mass spectrophotometry (GC/MS) was used to evaluate compounds from saturate hydrocarbon such as tricyclic terpanes, pentacyclic terpanes, steranes and diasteranes. Also from the aromatic hydrocarbon, napthalenes, phenanthrenes and dibenzothiophenes as well as mono- and triaromatic steroids compounds were identified. Identification of each compound class was carried out using respective m/z values of 170, 191, 212, 217, 220, 231 and 253.
The value of pristine/phytane (Pr/Ph) ratio ranged from 2.3-5.1. Carbon Preference Index (CPI) value ranged from 1.03 to 1.09 with an average of 1.06. The average CPI value of 1.06 indicated that the oils were thermally mature. The values of 20S/(20S+20R)C27 and ββ/(ββ+αα)C29, ranged from 0.23-0.47 and 0.20-0.24 respectively, while Tm/Ts ratio in the crude oil samples ranged from 1.33 to 2.23. Triaromatic-TA(I)/TA(I+II) ratio ranged from 0.03-0.20, while monoaromatic-MA(I)/MA(I+II) ratio ranged from 0.1-0.3. The value of methyl phenanthrene index- 3 (MPI-3) ranged between 0.9-1.0.The results showed that Sterane and hopane based maturity parameters were unreliable for oil maturity assessment.
The study concluded that the maturity of crude oils was found to increase from east to west in the study area. It also established new thermal maturity parameters for the correlation of oil samples.
Description
xvii,114
Keywords
Thermal Maturity Assessment, Crude Oils, Exxomobilemobile Joint venture, Eastern Niger Delta, Nigeria
Citation
Omotoye Sunday Joseph(2015)Thermal Maturity Assessment and Charcterization of Crude Oils from exxonmobile Joint Venture area in the Estaern Niger Delta,Nigeria.