Petroleum system, filling history and age appraisal of source rocks of the Niger Delta Basin: Fingerprinting of pentacyclic triterpenoids

IF 3.6

Energy Geoscience Pub Date : 2025-03-14 DOI:10.1016/j.engeos.2025.100399

Timothy Chibuike Anyanwu , Bassey Offiong Ekpo

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Abstract

Gas chromatography-mass spectrometry (GC-MS) was used to analyze the pentacyclic triterpenoid distributions, specifically hopane and oleanane fingerprints, in 24 crude oil samples from the Niger Delta depobelts, with the aim of defining the petroleum system, filling history, and the age of source rock producing these oils. The results indicate that the Niger Delta oils belong to a single fluvio-deltaic petroleum system, reflecting similar source organic facies and depositional environments. Geochemical parameters, including C₂₉/C₃₀ hopane ratios, oleanane index, Ts/Tm, (Ts/(Ts + Tm)), moretane/C₃₀ hopane ratios, and C₃₂ 22S/(22S + 22R) ratios, suggest oxic conditions during source rock deposition and thermal maturity of the oils. The presence of terrigenous organic matter and complex filling history are also evident and influenced by multiple phases of sedimentation, and petroleum generation. A comparative plot of geologic time (Paleogene-Neogene age) and oleanane percentage composition show that the crude oils are constrained to the chronostratigraphic ages of their respective depobelts, demonstrating the potential of oleanane-derived parameters for relative dating of hydrocarbon sources, complementing traditional index fossil methods.

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尼日尔三角洲盆地烃源岩含油气系统、充填史及年龄评价：五环三萜指纹图谱

采用气相色谱-质谱联用技术（GC-MS）分析了尼日尔三角洲沉积带24个原油样品中五环三萜的分布特征，特别是藿烷和齐烷指纹图谱，旨在确定油气系统、充注历史和产油源岩的年龄。结果表明，尼日尔三角洲油气属于单一的河流-三角洲油气系统，反映了相似的烃源岩相和沉积环境。C29/C30藿烷比值、齐墩烷指数、Ts/Tm、（Ts/(Ts + Tm)）、多烷/C30藿烷比值、C32 22S/(22S + 22R)比值等地球化学参数反映了烃源岩沉积时的氧化条件和油的热成熟度。陆源有机质的存在和复杂的充填历史也很明显，并受到多期沉积和生烃的影响。地质年代（古近系-新近系）和齐墩烷百分比组成对比图表明，原油受各自沉积带的年代地层年龄限制，表明齐墩烷衍生参数在烃源相对定年方面的潜力，是传统指数化石方法的补充。

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来源期刊

Energy Geoscience

CiteScore

8.20

自引率

0.00%

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