--> --> Geochemical Characterization and Petroleum Source-Rock Potential of Fika Formation Tuma-1 Well, Chad Basin, Nigeria

2018 AAPG International Conference and Exhibition

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Geochemical Characterization and Petroleum Source-Rock Potential of Fika Formation Tuma-1 Well, Chad Basin, Nigeria

Abstract

Recent studies have shown that Fika formation shale has required amount of organic matter which qualifies her to be a good candidate of hydrocarbon generation in Nigerian inland basins e.g. Benue trough and Chad (Bornu) basin. Thirty (30) shale samples (800 m to 2566 m) were analyzed within the Fika formation in Tuma-1 well. The biomarker contents and distribution of polycyclic aromatic hydrocarbons of soluble organic matter (SOM) contained in the samples was studied using Gas chromatography- Mass spectrometry (GC-MS) technique in order to evaluate the petroleum source-rock potential of Fika formation that penetrated this well. The n-alkane ranged from nC12- nC32 in most samples maximizing at nC20 which suggested that the organic matter are mainly derived from algae. Higher value of n-C31/n-C19 ratio (>0.4) with characteristics odd-over-even predominance in some of the samples supported presence of non-marine algae species e.g. Botryococcus braunii and suggested lacustrine signature in Fika formation. The Pr/Ph (0.40-1.12) ratio showed that the organic matter was deposited under anoxic to suboxic condition. The plot of Ph/nC18 vs. Pr/nC17 indicated that the organic matter was derived from Type II/III and Type III kerogen capable of generating oil and gas. The plots of C3122R homohopane/ C30 hopane vs. Pr/Ph ratio and ternary plot of sterane (C27-C29) showed that the organic matter was deposited in lacustrine to marine environment. The distributions of aromatic steroids, polycyclic aromatic hydrocarbons and (C0-C3) alkylated dibenzothiophenes to determine organic matter type and depositional environment were also discussed. Various maturity parameters computed from biomarker, polyaromatics, and heterocycles distribution as well as calculated vitrinite reflectance (sterane and methylphenanthrenes) showed that the samples were low mature to early oil window. Fika shale has ability to generate hydrocarbon with oil kitchen at the bottom of the formation (2285 m to 2566 m) and can therefore serve as petroleum source-rock in the Chad (Bornu) basin, Nigeria.